HIV-exposed uninfected infants: new global challenges in the era of paediatric

HIV elimination

Ceri Evans1,2, Christine E Jones3, Andrew J Prendergast1,2,4

1Blizard Institute, Queen Mary University of London, London, UK

2Zvitambo Institute for Maternal and Child Health Research, Harare, Zimbabwe

3Paediatric Infectious Diseases Research Group, Institute for Infection and Immunity,

St George’s, University of London, London, UK

4Department of International Health, Johns Hopkins Bloomberg School of Public

Health, Baltimore, MD, USA

Corresponding author: Dr Andrew J Prendergast, Centre for Genomics and Child

Health, Blizard Institute, Queen Mary University of London, 4 Newark Street,

London, E1 2AT, UK

Tel: +44 207 882 2269

Fax +44 207 882 2195

a.prendergast@qmul.ac.uk

Short title: HIV-exposed uninfected infants

Word count: 4997

Abstract: 152

References: 160

Key words: HIV, infant, Africa, immune activation, mortality, infections, growth

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ABSTRACT

With scale-up of interventions to achieve elimination of paediatric HIV infection, the

number of HIV-infected infants is declining, but the number of uninfected infants

exposed to maternal HIV is increasing. Interest in the health outcomes of HIV-

exposed uninfected (HEU) infants has grown over the last decade, with several

studies suggesting increased mortality, infectious morbidity and growth failure

compared to HIV-unexposed infants. However, heterogeneous results may reflect the

inherent challenges in studies of HEU infants, which require large populations with

appropriate, contemporaneous comparison groups and repeat HIV testing throughout

the period of breastfeeding. Here we review the effects of HIV exposure on mortality,

morbidity and growth, discuss the immunological abnormalities so far identified, and

provide an overview of interventions that may be effective in this vulnerable

population. As the number of HIV-infected infants declines, the health needs of HEU

infants should be prioritised further, to ensure that post-2015 Sustainable

Development Goals are achieved.

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INTRODUCTION

Mother-to-child transmission is one of the great tragedies of the HIV epidemic,

particularly in sub-Saharan Africa, where 90% of new infections occur. Although the

global target to eliminate paediatric HIV by 2015 has not been attained, there has

been huge progress in reducing the number of HIV-infected infants through scale-up

of prevention of mother-to-child transmission (PMTCT) programmes. In the pre-

antiretroviral therapy (ART) era, up to 40% of infants acquired HIV from their

mothers,1 but with increasing availability of effective PMTCT interventions,

transmission rates close to 1% are possible among breastfeeding populations in

developing countries,2 and <1% among non-breastfeeding populations.3 The current

public health approach to PMTCT is initiation of lifelong ART for all pregnant and

breastfeeding women (so-called Option B+)4 to eliminate new HIV infections among

children and keep their mothers alive.5 As PMTCT coverage expands, therefore, the

number of HIV-infected infants is declining, but the number of HIV-exposed

uninfected (HEU) infants is increasing (Figure 1). As progress towards elimination of

paediatric HIV infection accelerates, a potentially vulnerable population of HEU

infants, with uncertain health needs, is growing. In this Review, we summarise the

evidence regarding mortality, infectious morbidity, immune function and growth of

HEU infants, and highlight research gaps that need addressing to better define

interventions for this growing population.

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MORTALITY AND MORBIDITY

The observation that infants exposed to HIV, but not infected, might have increased susceptibility

to infections first emerged in 1992 when HEU infants in Kenya were found to have a high

incidence of measles.6 In 1993, HEU infants in Zaire were noted to have a greater risk of persistent

diarrhoea than HIV-unexposed infants;7 HEU infants were highlighted as a priority group, as few

management options were available for HIV-infected infants at that time. However, despite many

subsequent studies, the precise impact of vertical HIV exposure on child health outcomes remains

unclear. Interpretation of published findings is complicated by several factors: first, early studies

lacked HIV testing, making the impact of HIV exposure difficult to separate from infant HIV

infection; second, follow-up testing of HIV-uninfected mothers and infants to ensure accurate HIV

status is often lacking; third, HIV-unexposed comparison groups have either not been included, or

are not demographically comparable; fourth, HEU and HIV-unexposed infants often differ in

breastfeeding uptake and/or duration; and fifth, contemporary studies cannot distinguish the

relative contributions of HIV and ART exposure. Despite these limitations, several large studies

suggest that HEU infants have increased mortality and morbidity in early life.

Mortality in the pre-ART era

The largest HEU cohort (ZVITAMBO), which prospectively followed 14110 infants in Zimbabwe

prior to availability of ART, found 3-fold higher mortality among HIV-exposed compared to HIV-

unexposed infants through 2 years of follow-up; this mortality risk was higher in the first

compared to the second year of life (Table 1). Infants and mothers had regular HIV testing, and

sensitivity analyses showed that elevated mortality was not due to unascertained postnatal HIV

transmission.8 A study from Uganda reported significantly higher mortality among HEU infants at

18 months of age, but not at 12 or 24 months.9 A Zambian study, which prospectively assessed

infants from 9 months to 3 years of age, demonstrated 3-fold higher mortality in HEU compared to

HIV-unexposed children (95%CI 0·7-14·0).10 Statistical power in these latter studies may have

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been limited by relatively small sample sizes. Studies with longer follow-up report mixed results.

HEU children in Rwanda had no increase in mortality through 5 years,11 but in The Gambia, HIV-

1- and HIV-2-exposed uninfected children surviving beyond 4 months of age had increased

mortality through median 6 years compared to HIV-unexposed children.12

Mortality in the ART era

Where infants were exposed to limited PMTCT (single-dose nevirapine/zidovudine monotherapy),

results have been heterogeneous. A large South African study showed no difference in 12-month

mortality between HEU and HIV-unexposed groups; the majority of infants in both groups were

exclusively breastfed, which may have partially mitigated differences.13 A smaller South African

study, where HEU infants were less likely than HIV-unexposed infants to breastfeed beyond 12

weeks, showed no difference in mortality through 36 weeks,14 although approximately one-third

were recruited from a wealthier area where formula feeding may have been safe. HEU infants

exposed to single-dose nevirapine and 6 months of zidovudine for PMTCT in the Mashi trial in

Botswana had 4-fold higher mortality than HIV-unexposed infants through 24 months.15 In a large

trial in Malawi, Tanzania and Zambia, HEU infants had 50% higher 12-month mortality despite

single-dose nevirapine and co-trimoxazole prophylaxis.16A small study from Mozambique, in

which HIV-exposed infants received co-trimoxazole prophylaxis, single-dose nevirapine and 4

weeks of zidovudine, found a trend towards increased mortality in HEU infants (OR 3·74, 95%CI

0·41-34·3).17 In a small Ugandan study, HEU infants exposed to PMTCT and receiving co-

trimoxazole prophylaxis had almost 14-fold increased mortality (OR 13·7, 95%CI 1·12-167·3),

but breastfeeding duration was significantly shorter than for HIV-unexposed infants.18

Studies comparing mortality in middle- and high-income-countries are lacking, but there is a need

to determine the impact of HIV exposure in these settings, particularly in the current ART era.

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All-cause morbidity and hospitalisation

Prior to the availability of ART, HEU infants in the ZVITAMBO trial had more hospitalisations

during the neonatal period and more all-cause sick clinic visits throughout infancy, compared to

HIV-unexposed infants, particularly for pneumonia and oral thrush.19 In the ART era, a large

South African study found no difference in late-onset sepsis, and a slightly lower incidence of

early-onset sepsis, in HEU infants during the neonatal period. However, HEU infants receiving

single-dose nevirapine and 6 months of zidovudine for PMTCT in the Mashi trial in Botswana had

over 2-fold higher hospitalisation compared to HIV-unexposed infants through 24 months.15

Among infants surviving to 20 months of age in Malawi, there were no differences in

hospitalisation between HEU and HIV-unexposed infants, although this study may have been

limited by survival bias.20 One small study from South Africa showed that, while the frequency of

infections in HEU and HIV-unexposed infants was similar, HEU infants had a trend towards more

hospitalisations (RR 2·74, 95%CI 0·85-8·78).21 HEU infants in Mozambique receiving co-

trimoxazole prophylaxis, single-dose nevirapine and 4 weeks of zidovudine, had fewer outpatient

clinic attendances than HIV-unexposed infants at 12 months, and similar hospitalisation rates.17

The most common infections in HEU infants are skin infections, lower respiratory tract infections

and oral thrush, in sub-Saharan Africa,19 Latin America and the Caribbean.22 There are reports of

unusual infections in HEU infants, including invasive group A streptococcal disease, haemorrhagic

varicella and recurrent oral candida. HEU infants also appear to have more severe infections and a

greater risk of treatment failure, especially for pneumonia,21,23-26 and higher rates of surgical

complications.27

Pneumonia

Pneumonia was more common in HEU infants through 6 months of age in Zimbabwe; in

sensitivity analyses including only those surviving to the end of the interval, HEU infants had over

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3-fold more hospitalisations for pneumonia during the neonatal period (OR 3.4, 95%CI 1.9-6.0).19

HEU infants in South Africa had increased incidence of invasive pneumococcal disease compared

to HIV-unexposed infants, before and after introduction of pneumococcal conjugate vaccine.28,29

Several studies have described pneumonia caused by an unusually broad range of organisms in

HEU infants, including Staphylococcus aureus; 24 E. coli; Pseudomonas aeruginosa and other

Gram-negative bacteria;24,30 cytomegalovirus and other viruses;24,30,31 and Pneumocystis

jirovecii.24,25,32-36 Differences in outcome may therefore be partly due to a different spectrum of

causative organisms, which are not treated by standard first-line antimicrobial regimens, or altered

pathogen-specific immune responses.

Tuberculosis

HEU infants in developing countries may be at greater risk of tuberculosis (TB). In a South

African series, four of eight infants with congenital TB were HEU infants; a further two were

HIV-exposed but did not undergo virological testing.37 Compared to HIV-unexposed infants in

Uganda, HEU infants had a 2·6-fold increased odds of TB infection, diagnosed by tuberculin skin

testing or interferon-gamma release assay.38

Diarrhoea

Studies from sub-Saharan Africa comparing the incidence of diarrhoea between HEU and HIV-

unexposed infants may partly be confounded by feeding practices, due to changes over time in

breastfeeding recommendations for HIV-infected mothers. A comparison between formula-fed

HEU infants and breastfed HIV-unexposed infants in Uganda demonstrated a 6-fold higher risk of

severe diarrhoea in HEU infants at 6-11 months of age,18 whilst in Mozambique, HEU infants had

less diarrhoea and a similar frequency of diarrhoea-related hospitalisation as HIV-unexposed

infants, despite a shorter duration of breastfeeding.17 Other studies not reporting breastfeeding rates

had mixed results, with some showing a higher frequency of diarrhoea23 or persistent diarrhoea,24

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and others showing no differences.24,30 After adjusting for feeding practices in South Africa, there

were no significant associations between HIV exposure and acute, persistent or overall diarrhoea

to 6 months of age,13 and in the ZVITAMBO trial, where almost all HEU infants were breastfed,

HEU infants did not have more acute diarrhoea than HIV-unexposed infants.19

Morbidity in developed countries

Fewer studies have assessed morbidity among HEU infants in developed countries, where routine

ART exposure, lower background infectious morbidity and a lack of appropriate HIV-unexposed

control groups from similar socioeconomic backgrounds make the impact of HIV exposure harder

to determine. Despite these limitations, several studies suggest elevated infectious morbidity

among HEU infants. In a French study of 7638 HEU infants, a high proportion (9·3%) required

hospitalisation for serious infections during the first year of life;39 however, no HIV-unexposed

control group was assessed and there was potential for hospitalisation bias. The most common

bacterial infection was pneumonia caused by encapsulated organisms (Streptococcus pneumoniae

and Haemophilus influenzae); the risk was inversely associated with maternal CD4 count for

serious bacterial, but not viral, infections. In a Belgian cohort, HEU infants had almost 20-fold

increased incidence of invasive group B streptococcal disease compared to unexposed infants in

the first month of life (RR 19·6, 95%CI 7·5-51·7), although the absolute number of cases was

small.40 HEU infants remained at risk of infection over the first year of life, with a 13-fold

increased odds of invasive group B streptococcal disease and 4-fold increased odds of invasive

pneumococcal disease compared to HIV-unexposed infants.41 HEU infants born in the ART era

had almost 3-fold higher morbidity that those born prior to ART availability (adjusted HR 2·93,

95%CI 1·07-8·05), whether or not mothers actually received ART. A Danish study reported

increased hospitalisation among HEU compared to HIV-unexposed children over the first four

years of life; however, this increase was related to haematological disorders rather than infectious

diseases.42

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Opportunistic infections

Pneumocystis jirovecii pneumonia (PCP) is an opportunistic infection of HIV-infected infants, but

was reported in two 7-week-old HEU infants from Texas in 1997;32 in each case, infection was

associated with a transient drop in CD4 count. Further cases of PCP pneumonia in HEU infants

below 6 months of age have been reported from France,39 South Africa24,25,43 and the USA.36 In

South Africa, over half of children admitted to hospital with acute hypoxic pneumonia had PCP

detected using molecular techniques; HIV exposure and malnutrition were risk factors among

HIV-uninfected children.13 Infants in this study were thoroughly investigated, meaning the burden

of PCP in HEU infants elsewhere may be higher than previously recognised.

Causes of excess mortality and morbidity

Despite heterogeneity in the literature, the body of evidence from multiple settings indicates

increased morbidity and mortality among HEU infants, and a risk of severe, unusual and

complicated infections, compared to HIV-unexposed infants. The causes of excess morbidity and

mortality are likely multifactorial, and may be partly driven by adverse environmental and socio-

economic conditions. However, morbidity and mortality differences remain after adjustment for

socio-economic status,8,19,44 and findings are not driven purely by differences in maternal care-

taking capacity due to ill health;44,45 duration of breastfeeding45 and quality of breast milk;15 or

colonisation46 or vertical transmission47 of pathogens. Several studies report associations between

HEU infant mortality and maternal HIV disease severity, assessed either by maternal CD4

count,8,44,45,48-50 viral load44,48,49,51 or mortality44,45,48-50 (Supplementary Table 1). Incidence of

respiratory tract infection has also been associated with severity of maternal HIV disease in several

studies.19,22,52,53 In Zimbabwe, increased infectious morbidity remained even at maternal CD4

counts >500 cells/uL, and only disappeared with CD4 >800 cells/uL.19 HEU infants have evidence

of immunological abnormalities that may at least partly explain their poor health outcomes.

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IMMUNE DYSFUNCTION

A recent review provides an excellent overview of the immunology of HEU infants.54 Here, we

summarise the likely causes of immune dysfunction in HEU infants and discuss additional recent

studies.

Immune activation

Chronic immune activation is the hallmark of HIV infection, and is driven by multiple factors,

including HIV itself, chronic co-infections, and intestinal microbial translocation.55 HEU infants

are therefore born to mothers who have high levels of pro-inflammatory cytokines and activated T-

and B-cells during pregnancy.56 There is similarly evidence of immune activation in both innate

and adaptive immune cells of HEU infants compared to HIV-unexposed controls. In a recent study

of Zimbabwean infants, a more pro-inflammatory milieu (indicated by raised C-reactive protein)

was evident in HEU, compared to HIV-unexposed, infants at 6 weeks of age, and was still evident

at 6 months of age.57 HEU infants born to ART-treated women with undetectable viral loads had

significantly higher concentrations of pro-inflammatory cytokines (IL-1β and IL-8) than HIV-

unexposed controls.58 In HEU compared to HIV-unexposed infants, stimulated monocytes and

dendritic cells secrete higher concentrations of pro-inflammatory cytokines,59 dendritic cells have

greater up-regulation of the activation markers CD80 and CD86,60 and natural killer (NK) cells

have higher expression of the activation markers CD38(bright) and CD69.61 T-cells show a shift

towards memory (CD45RA-) and away from naïve (CD45RA+) phenotypes,62,63 have higher

expression of the activation markers CD154 and CD38,63-66 and demonstrate greater proliferation

but reduced polyfunctionality (i.e. produce fewer different cytokines) upon stimulation.67

Compared to HIV-unexposed controls, CD4 T-cells show higher expression of inflammatory

response-related chemokine receptors (in particular CCR3 and CCR8), and in vitro stimulation

results in up-regulation of CCR8 expression and TNF-α.58,68 These findings suggest an immune-

10

priming role of HIV exposure; activated cells are more susceptible to HIV infection in vitro, and

potentially other intracellular infections.58

T-cell number and function

HEU infants have lower absolute numbers of CD4 T-cells, which may be due to more apoptosis;69

HEU infants at 10 weeks of age in Malawi had similar CD4 counts to HIV-infected infants.62 In

Mozambique, the CD4 percentage was 3% lower, and CD8 percentage 1·15-fold higher in HEU

compared to HIV-unexposed infants in multivariate longitudinal analysis.17 Thymic dysfunction70

may account for high levels of circulating ‘double negative’ (CD4-/CD8-) T-cells in HEU

infants.65 HEU infants have evidence of HIV-specific T-cell responses,71 even in the context of

maternal ART, suggesting that exposure to HIV antigens occurs in utero.

Humoral immunity and vaccine responses

At birth, HEU infants in developing and developed countries have lower concentrations of specific

antibody to vaccine-preventable infections compared to HIV-unexposed infants.72-76 Lower

concentrations of specific antibodies in HIV-infected mothers, compounded by reduced

transplacental transfer of antibody from mother to infant, appears to account for the paucity of

antibody in newborn HEU infants,73,74,77-80 although there is no association between maternal CD4

count or viral load and transplacental transfer of antibody.73

However, responses to primary vaccination in HEU infants are similar (for diphtheria, tetanus,

Haemophilus influenzae B, and BCG),68,73,76,81-83 or even increased (for pertussis, pneumococcal

capsular polysaccharide and measles),73,75,76,81,84,85 compared to HIV-unexposed infants (Table 2;

Supplementary Table 2), and HEU infants have good serological evidence of protection following

combined measles, mumps and rubella (MMR) vaccination.86 Furthermore, the fold-increase of

antibody concentration from pre- to post-vaccination is higher among HEU infants compared to

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HIV-unexposed infants.73 An explanation for this is reduced interference of maternally acquired

antibody on infant B-cell response to vaccination, which has been reported for multiple vaccines.

Although the mechanism in humans is unknown, in animal models this appears to be due to cross-

linking of the B-cell receptor with the regulatory receptor FcγRIIB.87 Where the concentration of

pre-vaccination antibody is increased in HEU compared to HIV-unexposed infants, lower

concentrations are observed post-immunisation.76,85 The functionality of vaccine-specific antibody

is similar in HEU and unexposed infants.72,79 These factors support the hypothesis that differences

in vaccine responses are driven by the concentration of maternally derived antibody pre-

vaccination, rather than differences in infant B-cell function.

BIRTH, GROWTH AND DEVELOPMENT

Long-term nutritional and neurodevelopmental outcomes are influenced by environmental factors

during the first thousand days – the period from conception to 2 years of age

(www.thousanddays.org). HIV exposure during this period may therefore critically impact birth,

growth and development. In developing countries, HEU newborns may be more likely to be small

for gestational age (SGA) or low birth weight (LBW) compared to HIV-unexposed newborns

(Table 3; Supplementary Table 3). LBW among HEU infants is associated with 2·5-12-fold

increased mortality,45,49,88,89 particularly due to pneumonia.53 In HEU infants, preterm birth, LBW,

and SGA were each associated with at least 6-fold increased neonatal mortality, and at least 2-fold

increased mortality up to 1 year of age.51

Data on postnatal growth in HEU infants is heterogeneous (Supplementary Table 3). Before the

availability of ART (Table 3), the largest study (ZVITAMBO) showed that HEU infants had more

stunting, wasting and underweight than HIV-unexposed infants throughout infancy.90 Length-for-

age remained lower through 24 months of age in Zimbabwe90 and Malawi91 (Table 3). Stunting

(linear growth failure) has been associated with maternal disease severity in some92,93 but not all90

12

studies. Impaired growth in HEU infants was not seen in several, mostly smaller, studies, although

many showed non-significant trends towards poorer growth (Supplementary Table 3). A large

study from South Africa, where nevirapine was used for PMTCT and most infants were

exclusively breastfed, did not find a difference in weight-for-age Z-scores over the first 24

months.94 In Zambia, breastfed compared to formula-fed HEU infants had better weight-for-age,

but not length-for-age, Z-scores to 15 months of age.95 Large, well-designed studies in the context

of fully suppressive maternal ART are required to determine the effect on growth in the current

era.

There is emerging interest in the impact of impoverished environments on poor linear growth, so

the cleaner environments of developed countries may mitigate growth concerns. However, results

have been heterogeneous. HEU infants in the UK had normal length and weight compared to HIV-

unexposed controls at 3 years.96 Compared to formula-fed HIV-unexposed controls, formula-fed

HEU infants in Italy had similar weight-for-length and weight-for-age Z-scores, but poorer length-

for-age Z-scores at 18 and 24 months of age.97 In the USA, ART-exposed HEU newborns had

lower weight and length at birth than matched HIV-unexposed controls, but growth accelerated

during infancy, such that anthropometric measurements were similar by 10 months.98

The impact of HIV exposure on neurodevelopment remains uncertain. A systematic review from

2012 identified mostly studies with methodological shortcomings from high-income settings

without control groups.99 The authors concluded that, once confounders were accounted for (in

particular, maternal substance misuse), there was unlikely to be developmental delay up to 2 years

of age in HEU infants. More recent studies from Malawi20 and Colombia100 reported no significant

developmental differences at 20 and 24 months of age, respectively. Six- to eight-year-old

Zimbabwean children did not have more cognitive impairment than HIV-unexposed controls (OR

1·32, 95%CI 0·69-2·52).101 However, HEU Zambian children showed poorer mathematics, but not

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English, grades at 6-12 years of age than HIV-unexposed children after adjusting for

socioeconomic status.102 After adjusting for plausible confounders, including carer education, HEU

children aged 2-12 years in Thailand had poorer verbal IQ, full-scale IQ and Binet-Bead Memory

scores compared to HIV-unexposed controls, although differences were small and their clinical

significance remains questionable.103 A Thai study comparing HEU with HIV-unexposed children

at a mean age of 10·3 years, showed no difference in neuroanatomy or brain integrity measured by

magnetic resonance imaging with diffusion tensor imaging, after adjusting for socioeconomic

status.104

MECHANISMS UNDERLYING ADVERSE OUTCOMES IN HEU INFANTS

Multiple factors may contribute to the excess risk of morbidity, mortality and growth failure that

has been reported for HEU infants.

Family environment

There is a high risk of orphanhood in HIV-affected households; over 17 million children are

estimated to have lost at least one parent to AIDS since the beginning of the HIV epidemic.105 For

each woman dying of AIDS in Africa, an average of two children are orphaned.106 Maternal

mortality is associated with poor infant outcomes regardless of the cause of death,107 because

mothers who are sick may have impaired capacity to care for their offspring, and orphaned

children are subject to extreme poverty and homelessness.108 However, the death of a mother with

advanced HIV may exacerbate immune abnormalities in her offspring, compounding the morbidity

risk in HEU infants109 (see below). Even among mothers who survive, HIV infection has far-

reaching consequences for families. HIV-infected parents are at risk of poverty because of

inability to work, which may affect food security and access to healthcare for the household. HEU

children may adopt caregiver roles for infected family members, or may be neglected when other

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children in the family are HIV-infected. Furthermore, HEU infants may be brought up in an

environment with greater exposure to pathogens, including tuberculosis.110

Immune activation

Immune activation and systemic inflammation may lead to infection susceptibility and growth

failure. Each may be explained by in utero and postnatal exposure to HIV. Immune activation may

result from exposure to a pro-inflammatory fetal environment or from exposure to coinfections

(such as CMV111) or HIV itself; HEU infants have evidence of HIV-specific T-cell responses,71

suggestive of in utero HIV exposure.112 Maternal bacterial translocation, which causes immune

activation in HIV infection,56 may directly affect the developing immune system during fetal life,

although further studies are needed to explore this hypothesis. Postnatal exposure to HIV through

breastfeeding may disrupt the intestinal mucosal barrier; in vitro experiments found impaired tight

junction function within 2-4 hours of intestinal epithelial cell exposure to HIV, and this

dysfunction was associated with bacterial translocation.113

Antiretroviral therapy

Prolonged exposure to ART during the developmentally sensitive period from conception to the

end of breastfeeding could be associated with risks. A detailed discussion of these issues is beyond

the scope of this Review, but ART may be associated with preterm birth114 and mitochondrial

toxicity115. Associations between ART and congenital abnormalities are reported in some

studies116,117 but not others.118,119 Although an association was shown between antenatal tenofovir

and postnatal growth failure in one US study, similar results have not been reported from sub-

Saharan Africa.119 A recent analysis from Botswana showed that HEU children exposed to

maternal combination ART had significantly lower length-for-age and weight-for-age Z-scores at

24 months than those exposed to zidovudine monotherapy.120

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INTERVENTIONS FOR HEU INFANTS

HEU infants are a vulnerable population who may benefit from additional monitoring and

interventions. Here we review the evidence behind existing interventions and consider the

potential benefits of additional management approaches.

Antiretroviral therapy

Since lifelong ART for pregnant and breastfeeding women is an essential component of the efforts

to eliminate paediatric HIV infection, the benefits outweigh currently reported risks of antenatal

ART exposure. Few studies have compared health outcomes of HEU infants exposed or

unexposed to maternal ART, although one study reported an 81% reduction in mortality to 10

years of age (aHR 0·19, 95%CI 0·06-0·59) among infants exposed to maternal ART and receiving

co-trimoxazole, compared to those without interventions.121 With expansion of PMTCT Option

B+, more women will conceive on ART, and maternal virological suppression and CD4

reconstitution before pregnancy should have positive impacts on the health of HEU infants.

Longitudinal studies of well-characterised cohorts in sub-Saharan Africa are required to determine

whether maternal ART normalises immune function, growth and health in HEU infants, or

whether additional interventions are required.

Co-infections

Whether HEU infants would benefit from additional interventions to reduce PCP, TB and vaccine-

preventable infections is unclear. WHO recommends co-trimoxazole prophylaxis for all HEU

infants from 4-6 weeks of age until cessation of breastfeeding,122 because of the ongoing risk of

HIV transmission and rapid disease progression among infected infants. Although side-effects

have been noted17 co-trimoxazole is generally well tolerated in HEU infants, and safety data for

antenatal123 and postnatal124 co-trimoxazole support its use as a universal intervention. In a study

from Mozambique, HEU infants receiving co-trimoxazole had fewer clinic attendances than HIV-

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unexposed infants not receiving co-trimoxazole (incidence ratio 0·79, 95%CI 0·63-0·99),17

although in trial data from Malawi, Zambia and Tanzania, HEU infants receiving co-trimoxazole

had 12-month mortality of 7·2% compared to 4·8% among HIV-unexposed infants.16 In a non-

randomised comparison of infants in the Malawian BAN trial, co-trimoxazole was associated with

short-term protection from malaria, but had no impact on a combined endpoint of severe illness or

death through 36 weeks of age.125 However, subsequent analysis found that co-trimoxazole was

associated with reductions in pneumonia, serious febrile illness, diarrhoea, growth faltering and

malaria throughout the first year of life.89 Although protection from malaria is commonly

reported,89,125-127 not all studies have shown reductions in diarrhoea and pneumonia among HEU

infants receiving co-trimoxazole, and it has been argued that the risks of co-trimoxazole may

outweigh benefits.128 To address this uncertainty, two randomised trials of co-trimoxazole in HEU

infants are currently underway in Botswana (ClinicalTrials.gov identifier NCT01229761) and

South Africa (Pan-African Clinical Trials Registry identifier PACTR201311000621110).

Interventions to prevent TB have been unsuccessful; isoniazid preventive therapy did not reduce

TB infection among HEU infants in South Africa.129

Vaccinations

Vaccine responses appear broadly similar in HEU and HIV-unexposed infants, highlighting the

importance of timely and complete vaccination. However, there remains a paucity of clinical data

on vaccine effectiveness in this group.130 Vaccine strategies which may mitigate the risk of

infectious morbidity early in life include antenatal immunisation, neonatal vaccination and earlier

commencement of vaccine schedules. However, antenatal vaccination in the context of HIV may

be associated with reduced maternal immunogenicity and therefore reduced transplacental transfer

of antibody to the infant,131 especially in increased maternal disease severity.132 Earlier infant

vaccination may be more efficacious, although the feasibility of delivering such a programme in

developing countries has not been evaluated, and is likely to be a major barrier. In HIV-prevalent

17

settings, BCG should be delayed until infant HIV status has been confirmed to avoid vaccinating

HIV-infected infants, who are at risk of disseminated BCG disease.133

Infant feeding

Early cessation of breastfeeding reduces HIV transmission but increases morbidity and mortality

from other causes in developing countries.13,49,134-139 In Zambia, shortening the duration of

breastfeeding increased infant mortality,44 even if weaning occurred in the second year of life.49 In

Uganda, mortality was 6·2-fold higher in HEU infants breastfed for fewer than 6 months

compared to those breastfed for longer (95%CI 1·4-27·0).137 A Malawian trial found an association

between breastfeeding cessation and mortality and morbidity among HEU infants from 6-15

months of age.138 Most140-142 but not all50 studies comparing breastfeeding with replacement feeding

from birth report increased morbidity or mortality in formula-fed infants. Compared to breastfed

HEU infants, formula-fed HEU infants in South Africa had twice the frequency of illness in the

first two months of life (OR 2·02, 95%CI 1·16-3·51).141 In a trial from Burkina Faso, Kenya and

South Africa, HEU infants who were formula-fed from birth had 6-fold more serious infections

than those who were breastfed (adjusted OR 6·0, 95%CI 2·2-16·4).142 After adjusting for infant

growth and maternal disease status, breastfeeding among HEU infants in Kenya was associated

with 47% lower risk of pneumonia compared to never breastfeeding (HR 0·53, 95%CI 0·39-

0·73).140 However, causative organisms among HEU infants with diarrhoea or pneumonia did not

differ by feeding strategy in a recent analysis from the Mashi trial in Botswana.30

Although replacement feeding is recommended within PMTCT programmes in developed

countries, it is only recommended in developing countries if it is acceptable, feasible, affordable,

sustainable and safe.143 Breast milk of HIV-infected women has similar levels of innate immune

factors and specific immunoglobulins as HIV-uninfected women.15,144 Breastfeeding in the context

of Option B+, where women are on lifelong ART, leads to low levels of HIV transmission.

18

CONCLUSIONS

As progress is made towards elimination of paediatric HIV infection, there is a growing interest in

the health needs of HEU infants. The population remains challenging to study because of the

confounding effects of ART exposure and feeding modality, difficulties in confirming HIV status

and lack of comparable, contemporaneous control groups. However, the largest study, which

followed over 3000 well-characterised HEU infants before availability of ART in Zimbabwe,

demonstrated increased mortality,8 infectious morbidity19 and growth failure,90 in line with several

other well-designed, but smaller, studies.9,15,16,28,29,91,145,146 A South African study undertaken in the

pre-ART era with high exclusive breastfeeding rates found no differences in mortality13 or

growth94 of HEU and HIV-unexposed infants, meaning uptake of exclusive breastfeeding may at

least partly mitigate adverse outcomes.

Reports from developed countries suggest that, despite maternal ART, HEU infants remain at

increased risk of infections.39-41 Immunological abnormalities have been reported in HEU infants

from both developing and developed countries. These may persist despite maternal ART, although

prospective studies of appropriate cohorts are needed to determine the relative importance of

immune function, feeding practices and family environment in mediating poor outcomes of HEU

infants (Panel 1). Further detailed immunological analyses using modern laboratory techniques are

required, particularly in well-characterised cohorts from sub-Saharan Africa. Reassuringly, HEU

infants mount robust responses to vaccination; timely vaccination is vital to reduce the risk of

vaccine-preventable infections. HEU infants should remain in clinical follow-up after early infant

diagnosis at 4-6 weeks of age, with repeat HIV testing after complete cessation of breastfeeding.

Although breastfeeding increases the risk of HIV acquisition, transmission rates in the context of

fully suppressive maternal ART are low (approximately 0·2% per month147) and prolonged

breastfeeding reduces mortality in settings where formula feeding is unsafe.

19

Prevention of mother-to-child transmission of HIV is an evolving success story, although several

challenges remain in the quest to eliminate paediatric HIV. Integration of PMTCT into broader

maternal, newborn and child health services would fulfil the objective of improving child and

maternal survival together.148 However, as the number of HIV-infected infants declines, the health

needs of HEU infants should be prioritised further, to ensure that post-2015 Sustainable

Development Goals are achieved.

20

Search strategy and selection criteria

We searched PubMed using the terms (HIV or human immunodeficiency virus[MeSH Terms]) AND

(expos* or uninfected or maternal or affect*[MeSH Terms]) AND (child* or infant* or fetus or fetal or

foet* or neonat*[MeSH Terms]) for English language papers from January 1983- November 2015. We

reviewed citation lists of included studies and screened abstracts from relevant conference proceedings.

Articles were selected if infants were diagnosed as HIV-exposed uninfected. A systematic review was

beyond the scope of this article. Larger, better quality, and more recent studies with contemporaneous

comparison groups were preferentially selected, as were systematic reviews/meta-analyses of previous

data. Studies were preferentially included if direct comparisons between HIV-exposed and HIV-

unexposed groups were used. Studies were excluded if the HIV status of infants was not established

with virological testing.

21

TABLESTable 1: Studies comparing mortality in HEU and HIV-unexposed infantsCountry

N (HEU)

N (HUU)

HIV testing Feeding Outcome Result Comments

Pre-ART

Zimbabwe8

3135

9510

Mothers and infants tested at each visit

EBF at 3mo:HEU 10.5% vs. HUU 9.3% (NS)

Predominant BF at 3mo:HEU 30.6% vs. HUU 31.9% (NS)

Mixed BF at 3mo:HEU 58.9% vs. 58.9% (NS)

12mo mortality aHR 3.9 (95%CI 3.15-4.78)(aHR 2.5 on sensitivity analysis)

Very large number of HEU and HIV-unexposed infants Comparable, contemporaneous and demographically similar comparison group Most infants in both groups did not exclusively breastfeed Regular HIV testing undertaken Sensitivity analysis supported primary findings

24mo mortality aHR 2.0 (95%CI 1.2-3.5)(aHR 2.0 on sensitivity analysis)

Uganda9

269

3183

Infants tested several times; mothers not re-tested

98% breastfed

Duration/exclusivity not reported

12mo mortality RR 1.08 (NS) Small number of HEU infants Infants rested regularly – HEU group unlikely to be contaminated with postnatally infected infants Mothers not retested – unexposed group possibly contaminated with HEU or HIV-infected infants

18mo mortality RR 1.16, P<0.05

24mo mortality RR 1.29 (NS)

Zambia10

292

197

Infants tested several times; mothers not re-tested

Not stated 9mo-3yr mortality

HR 3.2 (95%CI, 0.7-14.0), P=0.13

Small number of HEU and HIV-unexposed infants Not followed from birth Period of highest morbidity and mortality not captured (birth-6mo) Hazard ratios not adjusted for confounders Mothers not retested – unexposed group possibly contaminated with HEU or HIV-infected infants Feeding modality not stated

Rwanda11

138209

Mothers and infants tested several times

Majority breastfedMedian of 18mo breastfeedingExclusivity not reported

5yr mortality HR 0.4 (95%CI 0.1-1.6), P= 0.20 Small number of HEU and HUU infants Hazard ratios not adjusted for confounders Long follow-up, but without breakdown into different time periods

The Gambia12

HIV-1N=64

HIV-2 N=194

HUU=448

Infants re-tested several times; mothers not re-tested

Not stated

Median 6yr mortality

HIV-1 HR 1.6 (95%CI 0.81-3.3) P=0.18

Small number of HEU infants HIV-1 and HIV-2 exposed uninfected infants included Infants without HIV test classified as unknown Unclear how missing results were treated – possibility that HEU group contaminated with

undiagnosed postnatally infected infants Feeding modality not stated More accurate HIV status when findings conditioned on survival to 4mo or 18mo

HIV-2 HR 1.2 (95%CI 0.70-2.0) P=0.5

Median 6yr mortality conditional on survival to 4mo

HIV-1 HR 2.7 (95%CI 1.3-5.6)

HIV-2 HR 2.0 (95%CI 1.1-3.6)

Median 6yr mortality conditional on survival to 18mo

HIV-1 HR 3.6 (95%CI 1.6-8.1)

HIV-2 HR 2.2 (95%CI 1.1-4.4)

Single dose nevirapine for PMTCT

22

South Africa13

936

1155

Infants tested monthly; mothers not re-tested

Never BF:HIV-infected mothers vs. 1.5% HIV-uninfected mothers

6-8w EBF:HIV infected mothers 81.4% vs. HIV-uninfected 92.9%

3-4mo EBF:HIV-infected mothers 61.8% vs. HIV-uninfected 72.6%

12mo mortality aHR 0.77 (95%CI 0.49-1.21), P=0.253

Large number of HEU and HUU infants HAART available before the end of the study (unclear how many mothers received HAART) Only those with available feeding data were included Very high rates of EBF Mothers not retested – unexposed group possibly contaminated with HEU or HIV-infected infants Data on missing test results unavailable

South Africa14

543218

Infants tested several times; mothers not re-tested

12wk EBF:HEU 54.7% vs. HUU 9.4% 9mo mortality HR 0.7 (95%CI 0.3-1.5)

65% of those born to mothers who died not included in analyses – most at-risk infants possibly excluded

Small number of HUU infants Mothers not retested – unexposed group possibly contaminated with HEU or HIV-infected infants

Single dose nevirapine and 6 months infant zidovudine for PMTCT

Botswana15

534

137

Infants tested several times; mothers not tested

Median BF duration:HIV-infected mothers 5.8mo vs. HIV-uninfected mothers 9.0mo

5mo EBF:HIV-infected mothers 17.5% vs. HIV uninfected mothers 9.5%

6mo mortality HEU 3.6% vs. HUU 0.8%, P=0.01

HIV-infected mothers breastfed for less time, but significantly more were exclusively breastfeeding at 5 months

Small number of HUU infants HAART available before the end of the study (unclear how many mothers received HAART) Mothers not retested – unexposed group possibly contaminated with HEU or HIV-infected infants Infants lost to follow-up censored at last HIV negative test/last study visit

24mo mortality HEU 6.7% vs. HUU 1.6%, P=0.002

Co-trimoxazole prophylaxis (HEU infants only) and single dose nevirapine for PMTCT

Malawi/Tanzania/Zambia16

1573

131

Infants tested several times; mothers not re-tested

Possibility of HEU group including postnatally infected inftants

Not stated 12mo mortality HEU 7.2% vs. HUU 4.8% (no statistical test performed)

Large number of HEU infants Infants lost to follow-up/died without recent testing not included Breastfeeding not stated Small number of HUU infants No statistical comparisons undertaken Mothers not retested – unexposed group possibly contaminated with HEU or HIV-infected infants Possibility of HEU group including postnatally infected inftants

Co-trimoxazole prophylaxis (HEU infants only) and single nevirapine and 4 weeks zidovudine for PMTCTMozambique17

158160

Not clear if PN included in analysis

Similar feeding until 6moHUU breastfed for longer100% of HUU breastfed to 12mo

12mo mortality OR 3.74 (95%CI 0.41-34.26), P= 0.195

Not primary trial outcome Small number of HEU and HUU infants

Co-trimoxazole prophylaxis (HEU infants only)Uganda18

186

389

Infants tested at several time points; mothers not re-tested

Breastfeeding at 6mo:84.4% vs. 99.7%, P<0.001

Breastfeeding at 12mo:28.7% vs. 98.9%, P<0.0001

Breastfeeding at 24mo:0% vs. 24%, P<0.0001

24mo mortality13.7 (95%CI 1.12-167.3), P=0.04

Dedicated study clinic Recruited from 4mo of age; period of highest morbidity and mortality not captured (birth-4mo) Adjusted for age, malaria prophylaxis, breastfeeding and wealth index

HEU=HIV-exposed uninfected; HUU=HIV unexposed uninfected; PN=postnatally HIV infected; N=number included; ART=anti-retroviral therapy; HAART=highly-active anti-retroviral therapy; PMTCT=prevention of mother-to-child transmission; wks=weeks; mo=months; yrs=years; (a)HR=(adjusted) hazard ratio; RR=relative risk; NS=not statistically significant.

23

Table 2: Comparison of vaccination responses between HEU and HIV-unexposed infants

Country HEU infants (n)

HUU infants (n)

Main findings (HIV-exposed vs. HIV-unexposed) Summary

Diphtheria

South Africa76 120 114 No difference in antibody concentration or proportion of infants protected Brazil149 19 112 No difference in antibody concentration or proportion of infants protected Tetanus

South Africa73 38 55 No difference in antibody concentration South Africa76 120 114 No difference in antibody concentration or proportion of infants protected South Africa81 27 28 No differences in antibody concentration post-primary DTP, but higher concentration post-booster response in HEU infants. No

differences in proportion protected

South Africa82 120 60 No difference in antibody concentration or proportion of infants protected Brazil149 19 112 Lower concentrations of specific antibody in HEU infants, but no difference in seroprotection. Uganda150 Not

stated, approx. 129

Not stated, approx. 1304

Reduced IFN-γ, IL-5 and IL-13 responses to tetanus toxin in HEU infants

Kenya151 8 (3mo)26 (12 mo)

8 (3 mo)17 (12 mo)

No differences in response to TT antigens at 3 months. At 12 months, lower CD4 IL-2 response and dual IL-2 /TNF- response to TT antigens in HEU infants

Pertussis (PT & FHA)

South Africa73 38 55 Higher antibody concentration in HEU infants, higher fold increase pre- to post-vaccination South Africa76 120 114 Higher PT antibody concentration in HEU infants, but similar FHA antibody concentration. Increased proportion of HEU infants with 4-

fold increase in PT antibody concentration, but no difference between HEU and HUU infants for FHA antibody

South Africa81 27 28 Higher antibody concentration in HEU infants post primary and pre-booster vaccines, no difference post-booster. Higher proportion of seropositive HEU infants at 6 months

South Africa82 120 60 Higher antibody concentration in HEU infants at 24 weeks, but no difference at 14 and 52 weeks. Higher proportion of seropositive HEU

infants at 24 weeks

Hib (PRP)Uganda (HEU) & USA (HUU)72

57 14 Higher antibody concentration in HEU infants at 48 weeks, but no difference in avidity South Africa73 38 55 No difference in antibody concentration after 3 vaccine doses at 16 weeks, but higher fold increase pre- to post-vaccination South Africa76 120 114 No difference in antibody concentration or SBA GMT South Africa81 27 28 No difference in vaccine responses South Africa82 120 60 Higher antibody concentration in HEU infants at 14 and 24 weeks, but no difference at 52 weeks. Higher proportion of HEU infants with

protective immunity

Denmark83 19 7 No difference in vaccine responses 24

Pneumococcal capsular polysaccharide

South Africa73 38 55 Higher antibody concentration in HEU infants, higher fold increase pre- to post-vaccination South Africa84 120 114 No differences in GMC for ST4, 9V, 14, 18C, 19F, higher GMC for ST 6B and 23F in HEU infants after 3 doses of PCV. No difference

in seroprotection, except for ST 6B. Similar results in OPA

South Africa152 121 116 No differences in GMC for ST 6B, 9V, 14, 18C, 19F, 23F, higher GMC for ST 4 in HEU infants after 2 doses of PCV. No difference in seroprotection, except for ST 4Similar results for most ST in OPA

Hepatitis B

South Africa76 120 114 Lower antibody concentration in HEU than HUU infants. No difference in seroprotection South Africa81 27 28 No difference in vaccine responses South Africa82 120 60 Lower antibody concentrations in HEU infants at 14 and 52 weeks, no difference at 24 weeks. No differences in proportion protected Brazil149 45 112 Increased proportion of HEU infants with high responses, similar proportion with very low responses. Measles

South Africa81 27 28 No difference in vaccine responses post-primary or post-booster measles vaccine South Africa85 116 112 Post-primary vaccine: Greater vaccine responses; no difference in seroprotection rates

Post-booster vaccine: No difference in vaccine responses; no difference in seroprotection ratesAt 2 years of age: Poorer vaccine responses in HEU infants; fewer HEU infants with seroprotection

Oral polo vaccine

Zambia153 133 397 Lower mean antibody titre in HEU infants, but no difference when breastfeeding adjusted for BCG

South Africa67 46 46 No difference in BCG-specific T-cell proliferation at 6 weeks; higher frequency at 14 weeks in HEU infant; decreased cytokine polyfunctionality in HEU infants

South Africa68 47 62 No difference in BCG-specific T-cell proliferation, intracellular cytokine expression, polyfunctional T cells or secreted cytokines Uganda150 Not

stated, approx. 136

Not stated, approx.1370

No difference in responses to crude culture filtrate proteins of Mycobacterium tuberculosis

Kenya151 16 (3mo)29 (12 mo)

9 (3 mo)17 (12 mo)

No differences in frequency of responders to PPD antigens at either time point. At 3 months, increased frequency of IL-2/TNF- dual positive PPD-specific CD4 T cells in HEU infants. Alterations in memory T cell subsets at 3 months of age in response to PPD stimulation.

South Africa154 94 12 No significant differences in BCG-specific release of IFN-γ, measured by ELISA South Africa155 25 23 No difference in BCG-specific CD4 T cell cytokine response or polyfunctional cells Brazil156 58 38 Delayed BCG responses in HEU infants – by 18.1-26.3mo HEU had similar responses to HUU infants aged 7.0-8.7mo HUU= HIV-unexposed uninfected, GMC=Geometric mean concentration, PT=Pertussis toxin, FHA=filamentous hemagglutinin, PRP=polyribosyl-ribitol phosphate, SBA=serum bactericidal assay, OPV=oral polio vaccine, DTwP=diphtheria, tetanus toxoid, cellular pertussis vaccine, BCG=Bacille Calmette-Guerin, Hib=Haemophilus

25

influenzae type b, HBV=hepatitis B vaccine, ST=serotypes, mo=months better results in HEU infants, poorer results in HEU infants, similar results between HEU and

HUU infants.

Table 3: Fetal and postnatal growth of HEU infants in developing countries before the availability of ARTNS=not significant, OR=odds ratio, LAZ=length for age Z-score, WAZ=weight for age Z-score, WLZ=weight for length Z-score, SGA=small for gestational age, w=weeks, m=months, SD=standard deviation, SE=standard error, IQR=inter-quartile range*Significantly poorer outcome of HEU compared to HIV-unexposed infants**Significantly poorer outcome of HIV-unexposed compared to HEU infants

Country HEU infants (n)

HIV-unexposed comparison group (n)

Follow-up period Main findings (HIV-exposed vs. HIV-unexposed)

Birth weight

Zimbabwe8 3135 9510 Mean birth weight (SD): 2·94kg (0·46) vs. 3·00kg (0·45), p<0·05*;Percentage low birth weight: 15·3% vs. 12·1%, p<0·05*; odds ratio for underweight at birth: 1.12 (95%CI 0.97-1.29)

Malawi91 270 686 Significant difference in mean birth weights*Democratic Republic of

Congo157 190 256 Mean birth weight (SE): 2·95kg (0·35) vs. 3·04kg (0·32)* (P value not stated)Mean z-score at birth (SE): +0.20 (0·07) vs. -0·47 (0·07) (P value/comparison not stated)

StuntingMalawi91 270 686 24 months Lower mean LAZ to 24mo*

Democratic Republic of Congo157 190 256 20 months No difference in mean LAZ scores to 20mo

Kenya158 155 139 18 months Mean LAZ scores: -0·48 vs. -0·19, p<0·05* at 1·5mo only, otherwise similar

Rwanda159 140 207 48 months Lower mean LAZ scores only at 6mo,* not throughout rest of 48mo follow-upZimbabwe90 3135 9510 48 months 6w OR 1·24, (95%CI 1·10-1·40)*, 6mo OR 1·25 (95%CI 1·09-1·42)*, 12mo OR 1·22 (95%CI 1·08-1·38)*, 18mo NS; 24mo NS

Uganda160 200 400 4-6mo (cross-sectional) Adjusted OR for stunting at median age of 5.2mo: 2.23, p=0.005*

UnderweightMalawi91 270 686 24 months Lower mean WAZ to 24mo*

Democratic Republic of Congo157 190 256 20 months No difference in mean WAZ scores to 20mo

Rwanda159 140 207 48 months No difference in mean WAZ scores to 48moZimbabwe90 3135 9510 24 months 6w OR 1·54 (95%CI 1.29-1·83)*, 6mo OR 1·53 (95%CI 1·26-1·84)*, 12mo OR 1·38 (95%CI 1·16-1·65)*, 18mo NS; 24mo NS

Uganda160 200 400 4-6mo (cross-sectional) Adjusted OR for underweight at median age of 5.2mo: 1.73, p=0.09

WastingDemocratic Republic of

Congo157 190 256 20 months No difference in mean WLZ scores to 20mo

Kenya158 155 139 18 months Mean WLZ at 6mo: 0·45 vs. 0·10, p<0·05**Mean WLZ at 18mo: 0·16 vs. -0·73, p<0·05**

Zimbabwe90 3135 9510 24 months 6w OR for wasting 1·60 (95%CI 1·22-2·10)*, 6mo OR 1·39 (95%CI 1·04-1·87)*, 12mo (OR 1·55, 95%CI 1·21-1·99)*, 18mo NS; 24mo NS

Malawi91 270 686 24 months Lower mean WLZ to 24mo*Uganda160

200 400 4-6mo (cross-sectional) Adjusted OR for wasting at median age 5.2mo: 3.29, p=0.02*

26

 

27

Panel 1: Suggested areas for future research in HEU infantsAssess mortality and growth of HEU infants in the ART era

Clarify deleterious effects of ART exposure Better understand whether poorer outcomes of HEU infants persist in the current era, comparing HEU

infants exposed to ART, with appropriate HIV-unexposed groupsDetermine the causes of infection susceptibility

Discern the relative impacts of immunological abnormalities, maternal caretaking capabilities, exposure to opportunistic infections, and feeding methods

Explore the relationship between inflammation and infection susceptibility/growth of HEU infantsBetter characterise the immune function of HEU infants

Evaluate ontogeny of the innate and adaptive immune system in HEU infants Define functional immune defects in HEU infants using modern immunological techniques Determine the effect of HIV exposure on immune activation beyond infancy and early childhood

Evaluate the mechanisms of immune activation, inflammation, and T-cell abnormalities Explore the contributions of maternal/infant enteropathy, maternal/infant microbial translocation, maternal

CD4 count, exposure to HIV in utero or through breastfeeding, maternal/infant co-infections, maternal/infant malnutrition, and exposure to ART

Assess the impact of immunological abnormalities on mortality/morbidity outcomes of HEU infants Correlate markers of immune dysfunction with clinical outcomes Better understand the time-course of immune defects and interventions that may be beneficial Determine the long-term impact of immune activation on health outcomes

Evaluate the impact of co-trimoxazole Evaluate the impact of co-trimoxazole on immune activation, HIV transmission, growth and health of HEU

infants

Infection prophylaxis and vaccination strategies Explore the role of additional antimicrobial prophylaxis to prevent co-infections, including CMV, TB, PCP Explore the protection provided by antenatal immunisation, neonatal vaccination or accelerated vaccination

schedule to young infants and the potential for modulation of the infant’s own response to vaccination

Identification of novel techniques to reduce the transmission of HIV during breastfeeding Breastfeeding may ameliorate some of the risks associated with HIV exposure, but HIV transmission is still

possible

28

FIGURES

Fig 1: Reduction in perinatally HIV-infected infants with increasing PMTCT coverageThe number of pregnant women living with HIV in low-income and middle-income countries declined slightly between 2005 and 2013, from 1.64 million to 1.45 million (chart plots, Source: http://www.who.int/hiv/data/arvpmtct2014.png.)  Over the same period, the proportion of HIV-infected pregnant women receiving effective PMTCT interventions increased from 13% in 2005 to 72% in 2013 (grey shaded areas, Source: http://www.who.int/hiv/data/arvpmtct2014.png), leading to a striking reduction in the number of HIV-infected infants (line plots, Source: UNAIDS Fact Sheet 2015).  The number of HIV-exposed uninfected (HEU) infants is therefore increasing.PMTCT=prevention of mother-to-child transmission

2005 2006 2007 2008 2009 2010 2011 20120

200000

400000

600000

800000

1000000

1200000

1400000

1600000

0

100000

200000

300000

400000

500000

13%22%

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29

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