S3 Lec 11: Orthomyxovirus and Paramyxovirus by Dr. Madrid November 17, 2010

ORTHOMYXOVIRUS

Highly infectious viral illness Epidemics reported since at least 1510 at least 4 pandemics in the 19th century First isolated in 1933

4 Genera: Influenza A, B, C and Thogotoviruses (found in mosquitoes, ticks and banded mongoose)

IMPORTANT PROPERTIES OF ORTHOMYXOVIRUSES

Orthomyxovirus

Influenza Viruses Type A, B and Co Subtypes due to antigenic variations of surface

glycoprotein’s hemagglutinin (HA) and neuraminidase (NA)

Paramyxoviruses

Parainfluenza and Respiratory Syncytial Virus (RSV)

Influenza Virus Structure

Genome :o Influenza A & B- 8 individual segments; o Influenza C – 7 segments

Each segment encodes a different viral protein

Viral Proteins and Function

RNA Protein Function

1—3 Pol B2, B1, A RNA synthesis, core

4 Hemagglutinin Attachment

5 Nucleoprotein RNA synthesis, Core receptor

6 Neuraminidase Release of virus

7 M-1, M-2 Scaffolding, ion channel

8 NS-1, NS-2 Regulates mRNA splicing

Influenza Virus – Surface Spike: GLYCOPROTEINS HA & NA

High frequency of variations, caused by HA & NA Variations result in the spread of new serologic types Hemagglutinin

o Binds to receptor (a trisaccharide of sialic acid, galactose & glucose on host cells)

o Sialic acid fits into pocket on top of HA; pocket highly conserved but the rest of HA is not

o HA is the target of neutralizing antibodies

Neuraminidaseo A “square-topped, mushroom-like projection”o Important for release of virion from cells

STRUCTURE

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N i n a I a n J o h n “ G ” R a c h e l M a r k J o c e l l e E d o G i e

A FRIENDLY NOTE FROM THE NEW AND IMPROVED MICROBIOMAN:

To facilitate you in studying this trans, enclose in textbox (like this) were lifted from Jawetz. Hope this helps.

Legend:RT- Respiratory tractHAI- hemagglutin inhibitionIF- Immunofluorescence

Happy Aral!

Virion: Spherical, pleomorphic, 80–120 nm in diameter (helical nucleocapsid, 9 nm)

Composition: RNA (1%), protein (73%), lipid (20%), carbohydrate (6%)

Genome: Single-stranded RNA, segmented (eight molecules), negative-sense, 13.6 kb overall size

Proteins: Nine structural proteins, one nonstructural

Envelope: Contains viral hemagglutinin (HA) and neuraminidase (NA) proteins

Replication: Nuclear transcription; capped 5' termini of cellular RNA scavenged as primers; particles mature by budding from plasma membrane

Outstanding characteristics: Genetic reassortment common among members of the same genus

Influenza viruses cause worldwide epidemics

VIRUS REPLICATION

Virus binds & enters cell (1) Endosome fuses with lysosome Acid stimulates HA fusion activity Replication begins ~1 hour later Nucleus is important in replication: does NOT occur in enucleated cells 5’ ends of nuclear transcripts used as viral mRNA Polymerase A & NP bind to RNA; stop polyadenylation & capping Uncapped RNA makes genome RNA Proteins associate with cell membrane Virus is released as it forms – no fully formed virions inside cells

Host Range

Influenza A: humans and other species (swine, horses, birds) Influenza B and C only: humans Influenza C has only one strain Influenza A & B have multiple strains based on

variation of HA and NA Type, host origin, geographic origin, strain # &

year isolated Antigenic descriptions (HA and NA) 3 subtypes of HA (H1-H3) and two subtypes of

NA (N1 and N2). Examples:o A/Hong Kong/03/68 (H3N2)o A/swine/Iowa/15/30 (H1N1)

Antigenic Variation

Antigenic DRIFT- selection of mutants less susceptible to most common antibodies

Antigenic SHIFT -new antigenic type unrelated to earlier typeso Occurs infrequently and only with Influenza A o Influenza A - major shifts:

H1N1 (1918) H2N2 (1957) H3N2 (1968)

H1N1 (1976)

UNIQUE PROPERTIES OF ORTHOMYXOVIRUSES

division into 8 separate segments facilitates development of new strains by mutation and reassortment of the gene segments between different human and animal strains of virus o responsible for the animal influenza epidemics

influenza epidemics (mutation : drift) and periodic pandemics (reassortment : shift) of influenza infection worldwide

Enveloped virion with a genome of 8 different (-) RNA nucleocapsid segments

The hemagglutinin (H) glycoprotein is the VAP, fusion protein, and elicits neutralizing, protective antibody responses

mutation-derived changes in H causes antigenic changes of minor(drift) or major(shift) degree

Shift o MAJOR change o Results to new subtypeo Caused by exchange of gene segment o pandemic

e.g. Antigenic Shift H2N2 1957-67 H3N2 1968

Drifto MINOR changeo same subtypeo caused by point mutation in geneo epidemic

e.g. Antigenic drift 1997- A/Wuhan/359/95

(H3N2) 1997 to 1998-

A/Sydney/5/97(H3N2) NEURAMINIDASE (N)

o hydrolyze the protective mucous coating on the respiratory tract

o assist in viral budding and releaseo prevent viruses from sticking together o participate in host cell fusion

Influenza transcribes and replicates its genome in the target cell nucleus but assembles and buds from the plasma membrane

The antiviral drugs inhibit an uncoating step and most likely target the M2 protein

The segmented genome promotes genetic diversity caused by mutation and reassortment of segments upon infection with 2 different strains

ORTHOMYXOVIRUS PANDEMICS

Year Subtype

1890 H2N2

1900 H3N8

1918 H1N1(Spanish)

1957 H2N2 (Asian)

1968 H3N2 ( Hong Kong)

1977 H3N2 + H1N1

1990 H3N2 + H1N1

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NOMENCLATURE

host of origin/geographical origin/ strain number/ year of isolation/ antigenic description of hemagglutinin and neuraminidase

e.g. A/swine/Iowa/3/70(H1N1)A/Scotland/42/89 (H3N2)

ORTHOPARAMYXOVIRUS

H 15 ; N 9 H1-H3 ; N1-N2

o found in epidemic/pandemic viruses from humans

1997 outbreak in Hong Kong o avian strain H5N1 , transmit directly from

chickens to humans

INFLUENZA VIRUS EPIDEMIOLOGY

Influenza outbreaks occur every year, extent and severity vary with antigenic composition

Influenza A outbreaks most common, Influenza B outbreaks less extensive and less severe

Influenza C infrequently associated with human disease – Antibodies against influenza C present in serum, asymptomatic infection

Epidemics – when non-immune/partially immune are infected

Epidemics occur most often during winter # of US citizens killed during 1918 pandemic – 548, 452 # of US citizens killed during WWI – 53,513 (10x fewer) India 12.5 million, world wide 20 million Infects many vertebrates species including mammals and

birds Co-infection with animal and human strains of virus –

generate different strains by genetic reassortment

Transmission Inhalation of small aerosol droplets (coughing and

sneezing) Confined populations – nursing homes, classrooms, ships

Physical Characteristics

Withstands slow drying at room temp based on articles Demonstrated in dust after an interval of 2 weeks Survive for several weeks at 4oC when contaminated in

infected tissue immersed in glycerol saline survive in seawater preserved for long periods at –70oC inactivate after exposure to heat for 30 min at 56°C : 90

min inactivated by 20% ether in the cold, phenol,

formaldehyde, salts of heavy metals, detergents, soaps, halogens

Disease Mechanism

Virus can establish infection of URT/LRT Systemic symptoms are due to the interferon and

lymphokine response to the virus. Local symptoms are due to epithelial cell damage, including ciliated and mucus secreting cells

Interferon and Cell mediated immune (CMI) response (NK and T cell) are important for both immune resolution and immunopathogenesis

Infected individuals are predisposed to bacterial superinfection because of the loss of these natural barriers and induction of bacteiral adhesion to epithelial cells

Antibody is important for future protection against infection and is specific for defined epitopes on H and N

The H and N of influenza A can undergo major (reassortment,shift) and minor (mutation,drift) antigenic changes to ensure the (+) of immunologically naïve, susceptible individuals

Influenza B undergoes only minor antigenic changes

Clinical Infections

Symptoms appear suddenly 1-2 days after exposure Major symptoms: rapid rise in body temp, to 102°F,

myalgias and on occasion sore throat, headache, cough and nasal congestion

Other symptoms: mark lassitude, moderate anorexia Epithelial cells of upper and lower respiratory tract Influenza A incubation period: 1-4 days (2 days average)

o Adults : sudden onset of fever, malaise, headache, myalgia, anorexia, sore throat, dry cough

o Children : higher fever, GI symptoms (abdominal pain, vomiting), OM , myositis, croup

Influenza B: >milder 3 day febrile illness with predominantly systemic symptoms; more GIT involvement “gastric flu”

Influenza C: afebrile URTI; confined to young children

Complications

Pneumonia – primary influenza viral pneumonia (rare, depending on strain)

Secondary bacterial pneumonia or mixed viral and bacterial pneumonia (pneumococci – S. pneumoniae, staphylococci – S. aureus, H. influenza)

Myositis and cardiac involvement Neurological syndromes

o GBSo encephalopathy o encephalitiso Reye’s syndrome

Reye’s Syndrome

Sequelae of Influenza Exclusively in 2-6 y/o, mostly with influenza B, less

common with INF A, VZV, measles, rubella & poliovirus Symptoms: encephalitis, mental status changes (ranging

from lethargy to coma, including delirium and seizures), hepatomegaly, increased levels of blood ammonia and bilirubin (moderate, so no jaundice), hypoglycemia

Fatty liver changes associated with aspirin treatment and Viral infection

Decreased incidence since warnings of aspirin use in children with acute viral respiratory infections; mortality rate initially ~40%, now<10%

Immunity

Depends on immunity to previous variant circulating in population and on relatedness of the two variants

Most epidemics due to antigenic shifts that produce subtypes distantly related to previous types

IgA, serum IgG and cellular immunity important Particular subtype of infecting virus is of long duration Related to the amount of local Ab (IgA) in the mucous

secretion of the RT + specific IgG serum Ab concentration Immunity to infection (type A) subtype specific

Diagnosis

Test What it detects?

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Cell culture in PMK or MDCK Virus

Hemadsorption to infected cells Hemadsorbing virus

Ab inhibition of hemadsorption Virus, type strain

IF, ELISA Virus antigens

HI Virus, type and strain

Serology: HI, HAI, ELISA, IF, CF seroepidemiology

Treatment

Amantadine o ineffective against Influenza B and Influenza C;

it is relatively nontoxic, but might stimulate CNS; dizziness & insomia, particularly in elderly.

Rimantadine o block ion channels in the envelope

preventing the pH changes that precede the membrane fusion step essential for nucleocapsid release (Influenza A)

Amantidine & Rimantidine are weak organic bases; block uncoating of INF A & prevent viral replication

M2 Matrix protein binding; resistance is due to mutations in genes encoding M2

Relieves symptoms only (doesn’t alter disease course)

Neuraminidase inhibitors: (A and B) Zanamivir

o poor bioavailabilityo inhalation 2x a day for 5 dayso Relenza inhaled, improvement if taken within 2

days of flu symptoms Oseltamivir

o oral. 2x a day for 5-7 days o Tamiflu (not for infants) inhibits NAo OTC analgesics helps reduce headache,

fever/myalgia Active against Both Influenza A and Influenza B

Prevention

Vaccines: inactivated virus produced in eggs; ~70% effective (lack of local IgA, cell-mediated responses)

Complications: hypersensitivity reactions in persons with egg allergies; Guillain-Barré Syndrome

Strain of virus important; antigenic variation makes vaccines obsolete, WHO surveillance teams look for new variants (best guess)

Immunity is of short duration: 1-3 years Mild tenderness/redness in 30% of vaccines, fever & mild

systemic symptoms in up to 5% of vaccinees Additive protective effect of vaccine & amantidine

CONTROL

Immunization – 3 virus strains

2 type A + 1 type B Provoke a good local (IgA) antibody response

Recommended for:

Elderly (> 50 yrs) > 6 mos with chronic illness Residents of long term care facilities / health care providers Employees of long term facilities Household members of high-risk persons Providers of essential community services Pregnant women Persons 6 mos to 18 yrs – receiving ASA treatment Chronic illnesses:

o pulmonary diseaseo Heart diseaseo Metabolico Renal dysfunctiono Hemoglobinopathieso Immunosuppression (HIV)

Foreign travelers Students Anyone who wishes to reduce the likelihood of becoming ill from

influenza

PARAMYXOVIRUSES

IMPORTANT PROPERTIES OF PARAMYXOVIRUSES

3 Generao Paramyxovirus

Parainfluenza 1-4 Mumps Newcastle disease Virus (NDV) Simian virus 5 (SV5)

o Morbillivirus Measles Canine distemper virus Rinderpest –equine; several strains of seals,

dolphins and porpoises o Pneumovirus

Respiratory Syncytial virus (RSV)

HISTORY

1990s: Hendra and Nipah

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Virion: Spherical, pleomorphic, 150 nm or more in diameter (helical nucleocapsid, 13–18 nm) Diameter: Range: 100 – 800 nm; Average: 125 – 250 nmComposition: RNA (1%), protein (73%), lipid (20%), carbohydrate (6%)

Genome: Single-stranded RNA, linear, nonsegmented, negative-sense, noninfectious, about 15 kb

Proteins: Six to eight structural proteins

Envelope: Contains viral glycoprotein (G, H, or HN) (which sometimes carries hemagglutinin or neuraminidase activity) and fusion (F) glycoprotein; very fragile

Replication: Cytoplasm; particles bud from plasma membrane

Outstanding characteristics: Antigenically stable

Particles are labile yet highly infectious

o discovered in Australia and SEAo animal viruses occasionally transmitted in man

Proteins

Enveloped may contain 2 glycoproteins: HN – hemagglutinin and neuraminidase (mumps) activity F – hemolytic and cell fusion activity M – matrix, inner layer of envelope NP – nucleoprotein L – large protein P – polymerase

Unique Features

Large virion consisting of a (-) RNA genome in a helical nucleocapsid surrounded by an envelope containing a VAP

o HN- paramyxovirus; H- morbillivirus G: pneumovirus) and a fusion glycoprotein (F) leading to syncytia formation

The 3 genera can be distinguished by the activities of the VAP : o HN of paramyxovirus has hemagglutinin and

neuraminidase activityo H of morbilluvirus has hemagglutinin activityo G of pneumovirus lacks these activities

Virus replicates in the cytoplasm Virus penetrates the cell by fusion with the plasma

membrane Viruses induce cell-cell fusion, causing multinucleated

giant cells Transmitted in respiratory droplets and initiate infection in

the respiratory tract CMI causes many of the symptoms but is essential for

control of infection Easily deformed by external forces May assume a variety of shapes Break up more easily

REPLICATION

Entry into cell: Attachment to host cells via the hemagglutinin (HN)

protein F protein involved in fusion

Replication: Occurs in cytoplasm of cell Viruses have RNA-dependent RNA polymerase Release is by budding from the cell surface

Fate of host cell: Syncitium formation common Cytoplasmic eosiniphilic inclusions: site of viral synthesis;

contain nucleocapsids and viral proteins (RSV & Measles) Usually minimal effects on host cell metabolism, unless

extensive cell fusion occurs

MEASLES VIRUS

Epidemiology

Transmission : inhalation via large droplet aerosol Contagion period precedes symptoms Host range is limited to humans Only 1 serotype Immunity is lifelong

Disease Mechanism

Infects epithelial cells of RT Spreads systemically in lymphocytes and by viremia Replicates in cells of the conjunctiva, Respiratory tract,

GIT, Urinary tract, lymphatic system, blood vessels and CNS

Rash is caused by T-cell response to virus infected epithelial lining in the capillaries

CMI is essential to control of infection, antibody not sufficient due to measles ability to spread cell to cell

Sequelae in the CNS may result from immunopathogenesis (postinfectious measles encephalitis) or development of defective mutants (subacute sclerosing panencephalitis, SSPE)

Clinical consequences

Disorder SymptomsMeasles Koplik's spots, rash extends to the body and extremitiesAtypical measles Rash prominent in distal areasSSPE CNS manifestations: personality, behavior, memory

changes, myolonic jerks, spasticity, blindness

Complications

Laryngitis Otitis media Encephalitis – 7 to 10 days after onset Pneumonia

o giant cell pneumonia without rash o (-) CMI

Clinical Diagnosis

Clinical specimens: RT secretions, urine, blood, brain tissues Stain: Multinucleated giant cells with cytoplasmic and inclusion

bodies SSPE:

o high levels of measles antibody in the blood and CSFo eosinophilic inclusion bodies in the brain

Treatment: Supportive; Vitamin A

Prevention Live attenuated measles vaccine (+) exposure Ig within 6 days of exposure

PARAINFLUENZA VIRUS

Epidemiology

Transmission – respiratory secretionso person to persono respiratory droplet

Primary infection : < 5 yrs (+) reinfection Closed populations including young children are at risk Type 3 is most prevalent serotype Parainfluenza – cause human respiratory disease

throughout the year, but especially during Fall and Winter

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Antigenicity

Four major serotypes, based on HN, F and NP protein antigens

Types 1, 2 and 3 related, type 4 not related Most adults have circulating Ab’s necessary to prevent

primary infection Reinfection by same type is common despite presence of

Ab against it

Disease Mechanisms

4 serotypes Infection is limited to RT with URTI being the most

common, but significant disease can occur upon LRTI NOT systemic and do not cause viremia Diseases:

o Cold like symptoms, bronchitis, bronchiolitis, croup

o Parainfluenza 1, 2, or 3 in: Infants – more severe, appearing as

bronchiolitis, pneumonia, croup (Laryngotracheobronchitis - LTB)

Older children and adult: milder infections

Infection induces protective immunity of short duration

Clinical Syndromes

Variety of syndromes, primarily in infants and young children

LTB (croup) – sore throat, hoarseness, watery discharge and cough. o Severe cases – fever persists, with worsening

discharge and sore throat Bronchiolitis and pneumonia – associated with serotype 3,

infects infants less than 1 year old. Common cold in subclinical form – usual result of adult

infection with any type

Diagnosis

Isolation from nasal washings and respiratory secretions IF, HI

Treatment : mostly supportive

Upper respiratory tract illness – symptomatic therapy only Sinusitis, otitis, bacterial bronchitis – appropriate

antibiotics for post-viral bacterial infection No specific antiviral therapy – ribavirin has activity against

parainfluenza viruses in vitro and is being tested No effective vaccines available

MUMPS

Acute inflammation of parotid glands

Epidemiology

Transmission o person to persono respiratory droplets

Present in respiratory secretions x 7 days before illness One serotype Infects only humans

Antigenicity

Much like parainfluenza virus, surface HN glycoprotein, a surface F gp, and an internal NP

Single antigenic type (MMR)

Clinical Syndromes

Incubation period 16-18 days followed by bilateral or unilateral parotitis

Other organs may be involved (meninges, pancreas, ovaries, testes or heart)

Orchitis: 20-30% of affected adolescent males - lining surrounding testes does not allow for swelling, sterility can occur

Disease Mechanism

Infects epithelial cells of RT spreads systemically by

viremia Systemic infection, specially of parotid gland, testes, and

CNS Principal symptom is swelling of parotid glands because

of inflammation CMI is essential for control of infection and responsible for

a portion of the symptoms. Antibody is not sufficient due to mumps ability to spread

cell to cell

Clinical Diagnosis

Recovered from saliva, urine, pharynx, secretions from Stensen’s duct, CSF

(+) saliva x 5 days after onset of symptoms and in urine x 2 weeks

cytopathic effect : multinucleated giant cells Active infection (+) 4 fold rise in virus specific antibody

level Mumps specific IgM antibody HI, ELISA, IF

Treatment: Supportive

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GOD IS CRAZY ABOUT YOU

There are many reasons God saved you: To bring glory to himself, to appease his justice, to demonstrate his sovereignity. But one of the sweetest reasons God saved you is because he is fond of you. He likes having you around. He thinks you are the best thing to come down the pike in quite a while.

If God has a refrigerator, your picture would be on it. If He had a wallet, your photo would be in it. He sends you flowers every spring and sunrise every morning. Whenever you want to talk, he’ll listen. He can live anywhere in the universe, and he chose your heart.

Face it friend, HE IS CRAZY ABOUT YOU!

From Max Lucado’s A gentle thunder

Prevention: Live attenuated vaccine – Jeryl Lynn strain

RESPIRATORY SYNCYTIAL VIRUS (RSV)

Major cause of lower respiratory tract disease in infants and young children, especially in closed situations. Adults show mild or no symptoms; does not spread in older children and adults

Epidemiology Contagion period preceded symptoms and may occur in

the absence of symptoms Transmission : inhalation of droplet aerosols Peaks in December Yearly worldwide epidemics in infants and young children

o Major impact is during first 6 months of life, ~30% develop Ab’s in first year, 95% by 5 years

o Initial site of virus multiplication is epithelium of upper respiratory tract then spreads to lower tract (bronchi, bronchioli, lung parenchyma)

Cell fusion and aspiration may be involved in spreading

Antigenicity

Three minor types with high degree of cross-reactivity Immunity is short lived and dependent upon secretory IgA

in nasal secretions, not on circulating IgG concentrations

Disease Mechanism

Localized infection of RT Does not cause viremia or systemic spread Pneumonia results from cytopathic effect of virus

(including syncytia) Bronchiolitis most likely mediated by host’s immune

response Narrow airways of young infants readily obstructed by

virus-induced pathology maternal antibody does not protect infant from infection natural infection does not prevent reinfection vaccination increases severity of subsequent disease

Clinical Infections

Bronchiolitis – difficulty of breathing with evidence of obstructed airway (can be distinguished from asthma), noisy breathing

Pneumonia – pulmonary infiltrates are more prominent, can involve swelling of alveolar lining cells and interstitial inflammation

Respiratory failure can occur Bronchiolitis in childhood may be linked to chronic lung

disease later in lifeDiagnosis

Human and simian cell cultures Syncytia formation in culture Difficult to isolate in cell culture IF, EIA

Prevention: No vaccine availableTreatment: Ribavirin via inhalationControl: Standard precaution

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Ang nag-uumapaw sa impormasyon na trans na ito ay inihahandog ng:

MICROBIOMAN

(From L to R): Paulfie, Turay, Edo, Nina, Teacher

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