INTERNATIONAL JOURNAL OF LEPROSY^ Volume 59, Number I

Printed in the U.S.A.

On the Value of Sequential Serology with aMycobacterium leprae-specific Antibody Competition

ELISA in Monitoring Leprosy Chemotherapy'Vinita Chaturvedi, Sudhir Sinha,

Bhawneshwar K. Girdhar, and Utpal Sengupta 2

The incidence of treatment failure in lep-rosy, due to reasons such as irregular treat-ment, drug resistance and persisters ( 22), hasbeen alarmingly high in the era of dapsonemonotherapy. Although this fear has beengreatly reduced with the advent of multi-drug therapy (MDT) for leprosy ( 9 ' 21 ), care-ful monitoring of the patients is still nec-essary, not only for the detection oftreatment failures at an early stage but alsofor further rationalization of treatmentschedules so as to avoid longer-than-nec-essary treatment ( 10).

A variety oflaboratory methods have beendeveloped for monitoring responses to an-tileprosy treatment, some of which are moretime consuming, sophisticated, and .cum-bersome than others. However, only bac-terial index (BI) determination ( 15) and, tosome extent, viability testing in foot padsof normal mice ( 17 ) have gained widespreadacceptance. The BI determination tech-nique has several inherent limitations, suchas the lack of standardization, susceptibilityto sampling and subjective errors, and theinability to distinguish between live anddead bacilli ( 26). The mouse foot pad tech-nique, besides being expensive and timeconsuming, is not highly sensitive due toimmune-mediated spontaneous killing ofsmall numbers of viable bacilli present in alarge pool of dead bacilli ( 5). A major lim-itation with most of the presently availablemonitoring methods is that they dependupon biopsies or samples from arbitrarilyselected site(s) of the skin, which is neither

I Received for publication on 9 May 1990; acceptedfor publication in revised form on 15 November 1990.

2 V. Chaturvedi, Ph.D.; S. Sinha, Ph.D.; B. K. Gir-dhar, M.D.; U. Sengupta, Ph.D., Central JALMA In-stitute for Leprosy (ICMR), P.O. Box 31, Taj Ganj,Agra 282001, India.

Reprint requests to Dr. Sinha.

uniformly infected (even in lepromatousleprosy patients) nor the only site of infec-tion ( 25 ).

Assays for Mycobacterium leprae -specificantibodies ( 17) have been used for monitor-ing leprosy treatment on the premise thatantibody titers would reflect the antigen loadin the whole body. Nonetheless, most of theprevious studies, including our own ( 18),

have been cross-sectional in nature withwide individual variations in the BI, andantibody titers within the same class of pa-tients have compromised the analysis andinterpretation of the data. Longitudinalstudies are likely to be more informative indetermining the role of serology in this con-text, as evident from some recent reportsbased on extensive data ( 4, "). The majorityof the published studies have dealt mainlywith serology for M. leprae-specific anti-bodies directed against the disaccharide ep-itope of phenolic glycolipid-I (PGDS-ELISA) ( 1-4, 11, 12). We report here on thepotentials of sequential serology with amonoclonal-antibody-based competitionELISA ( 19) for specific antibodies against the35-kDa M. leprae antigen (8. 20

) in monitor-ing treatment. Serial determinations ofPGDS-ELISA levels, the BI and clinical ac-tivity scores were also done simultaneouslyin leprosy patients subjected to this study.

MATERIALS AND METHODSStudy subjects. Twenty-six leprosy pa-

tients, 20 lepromatous (LL/BL) and 6 tu-berculoid (TT/BT) according to Ridley-Jopling criteria ( 16), were included in thestudy. All patients were registered with theclinics of Central JALMA Institute for Lep-rosy (CJIL), Agra, India, and were put onmultidrug therapy (MDT; dapsone, clofa-zimine and rifampin), with the exception ofone patient. A total of 70 serum samples

32

59, 1^Chaturvedi, et al.: Serology to Monitor Chemotherapy^33

were collected prospectively from these pa-tients at specified intervals over a period of19 months. One LL patient who was ex-amined and asked to collect medicine thenext day turned up for treatment only after9 months, and thus remained untreated overthis period.

Sera from 82 nonleprosy subjects (healthyIndian = 32; healthy European = 30; pul-monary tuberculosis Indian = 20) served ascontrols for deciding the cut-off points whenanalyzing the antibody assay results ( 18). Allsera were stored at — 20°C until used.

Bacterial index (BI). Four slit-skinsmears (from both earlobes and at least twoactive sites, generally on the arm and back)were used for serial determinations of theaverage BI in each patient, according toRidley's logarithmic scale ( 1 s).

Clinical scoring. The clinical scoring andcharting of the patients was done at specifiedintervals according to the method proposedby Ramanujam ("): the human body is di-vided into seven areas (head, trunk, but-tocks, 2 upper and 2 lower extremities) anda clinical score (1 to 4) is given to each area,depending on the activity in skin lesionsover it, and all scores are added up. For thepresent study, clinical improvement was ar-bitrarily graded as: mild improvement =1+, a reduction in overall score by 5points; moderate improvement = 2+, a re-duction of 5 to 10 points; marked im-provement = 3+, a reduction of > 10 points;and complete regression = 4+, zero score.

Serum antibody competition test (SACT).A SACT was performed according to theinhibition ELISA procedure reported by us( 19), which is an adaptation of the RIA tech-nique described earlier ( 20). Briefly, ELISAplates (Immunoplate I or II; Nunc, Den-mark) were coated with soluble antigen (2.5ktg/50 p1/well, at 4°C, overnight) ofM. leprae(of armadillo origin; a kind gift fromIMMLEP provided by Dr. R. J. W. Rees).After removing the antigen, the plates wereblocked (2 hr, ambient temperature) with1% skimmed milk powder (Anikspray; Lip-ton India Ltd.) in Tris-buffered saline (0.01M Tris, 0.15 M NaCI, pH 7.4) containing0.05% Tween 20 (TBST). Antigen wells (induplicate) were incubated (60 min, 37°C)with serial tenfold dilutions (in 1% milk-TBST) of each serum (25 ill/well). The in-cubation was continued for a further 120

min (37°C) after the addition of a 1:1000dilution (in 1% milk-TBST) of peroxidase-conjugated monoclonal antibody MLO4(25 Al/well). The plates were washed (withTBST) and color was developed witho-phenylenediamine (Sigma) substrate so-lution (50 Al/well; 20 min, 37°C). The re-action was stopped by adding 2.5 N H,SO 4

(50 pl/well). The optical densities (OD) wereread at 492 nm using an ELISA reader (Ti-tretek Multiskan Plus; Flow Laboratories).

Relative percent bindings were calculated(using 100% as the mean OD value for bind-ing of P-MLO4 alone to the antigen-coatedwells), and plotted against the correspond-ing dilutions of a scrum. The dilution whichwould cause 50% inhibition of P-MLO4binding is referred to as the TIN, titer of thatserum. On the basis of the results obtainedwith nonleprosy controls ( 19 and this study),a serum with an ID,„ titer of 10 (1:10) ormore was regarded as SACT positive.

ELISA for anti-PGDS antibodies. Theassay was performed according to the meth-od of Cho, et al. ( 3) with minor modifica-tions. Briefly, wells of an ELISA plate werecoated with either ND-O-BSA (natural di-saccharide-octyl-BSA conjugate; kindlyprovided by Dr. D. Chatterjee) synthetic an-tigen (1 ng carbohydrate/50 Al/well, at 4°C,overnight) or with a coating buffer. Afterblocking with 1% milk-TBST, a 1:300 di-lution (in milk-TBST) of each serum wasincubated (50 Al/well, 60 min, 37°C) in fourwells (a pair each of antigen coated and buff-er coated). The plates were washed (withTBST), and incubated (50 ptl/well, 60 min,37°C) with 1:2000 (diluted in milk-TBST)peroxidase-conjugated anti-human IgM(Dakopatts). The remaining steps (washing,color development, reading) were the sameas described above for the SACT-ELISA.On the basis of the results obtained withnonleprosy controls (mean + 2 S.D.), a se-rum (at 1:300 dilution) was regarded asPGDS-ELISA positive if it showed an ODof > 0.20 ( 19 and this study).

RESULTSOf the 20 lepromatous patients (Figs. 1

and 2) who had previously been untreated,6 had received treatment for short periodsranging from 1-4 months (patients 1, 6, 7,13, 15 and 16), and two others (patients 8and 20) had been on treatment for unspe-

17,504

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MONTHS0 2 16 18 204 6 8 10 12 14

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*80 2 4 6 8 13 1 14 16 18

MONTHS

34^

International Journal of Leprosy^ 1991

FIG. I. Sequential value for: A SACT-ELISA (11),„); B PGDS-ELISA C bacterial index in leprosypatients following treatment. Figure shows data on lepromatous leprosy patients who were investigated on twooccasions over a maximum period of 19 months. (-- —) in A and B = cut-off values for corresponding antibodyassays; *8 = timings of 131 and serology determinations are not identical; *9 = only initial BI is known.

cified periods. As mentioned earlier, one pa-tient (no. 9) had remained untreated over aperiod of 9 months after inclusion in thestudy. All of the six tuberculoid leprosy pa-tients (Fig. 3) had no previous treatment.

An appreciable clinical recovery in re-sponse to treatment was generally accom-panied by a net reduction in the BI and inthe levels of specific antibodies in a majorityof the patients. The decline in the levels ofspecific antibodies was continuous in someof the cases, while it was interrupted in oth-ers. This was also true for the BI.

Serological assays. Initially, the SACTwas positive in all of the 20 lepromatousand in 4 of the 6 tuberculoid patients;whereas the PGDS-ELISA was positive inonly 15 lepromatous and 3 tuberculoid cases(Figs. 1-3). Nonetheless, an overall positivecorrelation (r = 0.52, p < 0.01) was notedbetween the corresponding values of theSACT-ELISA and the PGDS-ELISA.

Lepromatous patients. The trends in theBI and the serology results among the le-promatous leprosy patients are shown inTable 1. The patients had consistently high

initial BI values (3.78 ± 0.97), but therewere great individual variations in the rateof its decline in response to treatment (0.73± 0.81 BI units per year). These variationswere equally prominent even if the declinewas expressed in relative terms, i.e., percentof corresponding initial BI (21.73 ± 22.38).In contrast to the BI, the initial values forspecific antibodies measured either by theSACT-ELISA or by the PGDS-ELISAshowed wide variations (3829.23 ± 5319.64and 0.97 ± 0.46, respectively), and so didthe corresponding absolute values for theirdecline per year (2283.92 ± 3380.42 and0.33 ± 0.17, respectively). However, ex-pression in relative terms revealed a strikingconsistency in the rates of decline, especiallyby the SACT-ELISA (60.98 ± 16.10% peryear).

The per annum fall in the BI and serologyvalues in eight patients who showed marked-to-complete clinical recovery over the studyperiod are compiled in Table 2. The rate ofrelative decline in the serological value ofspecific antibodies in these patients (Table1) were also noticeably steeper and more

A C

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59, 1^Chaturvedi, et al.: Serology to Monitor Chemotherapy^35

FIG. 2. Sequential values for SACT-ELISA, PGDS-ELISA, and BI in lepromatous patients investigated onthree to four occasions; * = points of time at which patients 12 and 18 were experiencing ENL (see Fig. Ilegend for details).

consistent (54.15 ± 15.13 for the SACT-ELISA and 38.58 ± 17.17 for the PGDS-ELISA) than that in the BI (22.63 ± 26.31).

Table 3 shows the data on three patientswho had varying degrees of clinical im-provement along with a marked reductionin antibody titers (especially by the SACT-ELISA), but no bacteriological improve-ment. In fact, in one of them (no. 13) anincrease (29.4%) in the BI value was re-corded despite clinical improvement.

Two patients did not show any change inclinical activity even after 18 months oftreatment, although they were not beingconsidered refractory to therapy as yet (Ta-ble 4). One of them showed a net 1233%increase in the SACT-ELISA titers, whilehis PGDS-ELISA and the BI values de-clined. The other patient (no. 18) showed asharp rise in the SACT-ELISA titers (1775%)over the level 3 months previously, the pointat which he was experiencing an episode of

FIG. 3. Sequential value for SACT-ELISA, PGDS-ELISA, and BI in tuberculoid leprosy patients investigatedon two to three occasions (see Fig. 1 legend for details).

36^ International Journal of Leprosy^ 1991

TABLE 1. Trends in the bacterial index (BI) and serology results in lepromatous leprosypatients."

BI SACT-ELISA PGDS-ELISA

Initialvalue

Fall/year Initialvalue(IDs„)

Fall/year Initialvalue

(0D4„,)

Fall/year

Absolute Relative" Absolute Relative Absolute Relative

Median 4.00 0.79 21.23 2150 877 59.79 1.06 0.36^33.33Mean 3.78 0.73 21.73 3829.23 2283.92 60.98 0.97 0.33^37.15S.D. 0.97 0.81 22.38 5319.64 3380.42 16.10 0.46 0.17^17.48C.V. (%)" 25.66 110.96 102.99 138.92 148.01 26.40 47.42 51.52^47.05

Data is based on those 13 patients who were either untreated (N = 8) or treated for < 4 months (N = 5)and had been followed up for > 12 months.

6 Based on % fall per year in corresponding initial values.S.D. = standard deviation.C.V. (%) = coefficient of variation (%) = S.D./mean x 100%.

erythema nodosum leprosum (ENL) (Fig.2). However, this patient was also a case ofirregular treatment.

Patient no. 9 also showed a reduction inantibody levels, particularly with the SACT-ELISA (28% relative decline), despite re-maining untreated over a period of 9 monthsbetween the initial and second examination.

At the end of the study period, 15 lepro-matous patients still had a BI of > 2 (Figs.1 and 2). Two patients (nos. 7 and 20) hadbecome negative by both antibody assays,although one of them was still positive witha BI of 2.5. Four other patients finallyshowed negativity for the PGDS-ELISA butnot for the SACT-ELISA.

Tuberculoid patients. Of the six tuber-culoid leprosy patients, only one was posi-

tive for both the BI and antibodies (patientno. 4, Fig. 3). In this group, the initial an-tibody titers in the four patients who werepositive for the SACT-ELISA (three ofwhom were also positive for the PGDS-ELISA) were significantly lower than thoseof the lepromatous group. A gradual fall intiters was noted in the antibody-positive tu-berculoid patients, along with a progressivedecline in disease activity.

DISCUSSIONIt has been repeatedly recorded that ri-

fampin, the crucial component of MDT, killsAI. leprae with exceptional speed (> 99%kill within a few days); whereas the BI showsa slow and steady decline of about 0.6 to 1log per year (14, 26

). This is thought to be due

TABLE 2. Data on patients showing marked (3+) to complete (4+) clinical recovery.

Patientno.

Leprosytype

Follow-upduration

(mo.)

Change in BI/yrChange in

SACT-ELISA/yr(ID,„)

Change inPGDS-ELISA/yr

(01)4,2)Absolute Relative

Absolute Relative Absolute Relative

1 LL 19 1.58 30.1 9537 54.5 0.17 11.65 BL 14 1.50 40.0 183 67.9 0.59 62.8

10 LL 13 0.92 21.7 877 /6.2 0.36 22.611 BL-LL 18 0.50 11.1 193" 48.3 0.35' 50.713 LL 12 1.25" 29.4 7000 58.3 0.57 45.214 BL 14 1.07 53.5 225 74.9 0.40" 44.015 BL 19 0.79 45.1 65 38.5 0.35 24.517 BB-BL 18 0.33' 8.9 2033` 59.8 0.506 47.2

Mean 0.68 22.63 2514 54.15 0.41 38.58S.D. 0.89 26.31 3672 15.13 0.14 17.17C.V. (%) 131 116.25 146 27.94 33.7 44.49

Net increase. All other BI and serology values denote a net decrease-a result of either continuous orinterrupted ('-g) fall.

Follow-up

duration Absolute(mo.)

Change inSACT-ELISA

Relative ^(1D,„)

Absolute^Relative^Absolute Relative

Patientno. Leprosy type

Change inPGDS-ELISA

(0D,,,,)Change in BI

59, 1^Chaturvedi, et al.: Serology to Monitor Chemotherapy^37

TABLE 3. Data on patients showing clinical and serological but not bacteriologicalimprovement.

Change in Change inFollow- Change in BI SACT-ELISA PGDS-ELISA

Patientno. Leprosy type up

duration(ID,0) (0D„2) Clinical

recoveryAbso- Rela-Abso-^Rela-

lute^tiveAbso-^Rela-lute^tive

(mo.) lute tive

4 LL 6 0.25 7.1" 920^76.7 175 l+12 LL with ENL 14 0.25 6.7" 3850^80.2 0.08^34.8 2+13 LL II 1.25'' 29.4 7000^58.3 0.57^45.2 3+ to 4+

Stable (<10% change) bacteriological status.'' Net increase.Remaining BI and serology values are results of a continuous decline.

to the persistence of dead bacilli in the skinfor long periods awaiting clearance by nor-mal body mechanisms ( 10). The rate of thisclearance may vary from patient to patient,as indicated by the data presented in thisstudy. Against this backdrop, the recom-mended ( 26) "continuation of MDT till at-tainment of bacterial negativity" could leadto unnecessary treatment for long durations(even up to a few years) in some of thepatients ( 10). Serology for Al. /eprae-specificantibodies, especially when performed se-rially, has shown the potential to provide aspeedy and reliable method for monitoringthe load of active infection in the body(1.4.11.12) .

In this study, the expression in relative(to the corresponding initial values) ratherthan absolute terms revealed a greater con-sistency in the rates of decline of antibodylevels following MDT. Similar observationswere made in a recent report based on PG-ELISA ("). The reason for this could be thefact that the fall in titers was rapid in someof the patients who had initially high anti-body levels and slow in some others whohad low initial levels. The rate of relative

decline was higher and less variable for theSACT-ELISA compared to the PGDS-ELISA. The rate of fall in the BI was, how-ever, lowest and inconsistent. This obser-vation, combined with the known efficacyof MDT, suggests that serology could pro-vide sensitive pointers to progression undertreatment. It also implies that the pool ofcorresponding M. /eprae-specific antigens(PGL-I and 35-kDa protein) in the host islargely dependent on the quantum of livebacilli. A sharp decline in a circulating poolof PGL-I (in the absence of any appreciablechange in the BI) is known to occur withina few months of initiation of MDT ( 2). How-ever, the fall in the levels of anti-PGL-I an-tibodies has been reported to be slower, amaximum decline being in the first year un-der therapy ( 4). PGL-I persisting in the skin(23) has been held responsible for the main-tenance of low antibody titers over a con-siderable period of time. It remains to beseen whether the pool of 35-kDa antigen isalso generated and maintained in an iden-tical manner, although its proteinaccous na-ture and rapid decline in corresponding an-tibodies (SACT-ELISA levels) following

TABLE 4. Data on patients showing stable clinical activity.

16^BL^18^2.25^

60^555^1233^0.78^63.918^LL with ENL^18^0.25

^6^4800''^88.9^0.18^15.8

Net increase.'' Net decrease but final value is 1775% above the value 3 months previously.Remaining values represent a net decrease.

38^ International Journal of Leprosy^ 1991

MDT would suggest a faster clearance ofthis antigen than PGL-I.

The value of clinical activity scores (")in monitoring response to treatment is ap-parent from studies in which a concurrentand steep progressive fall in the morpho-logical index ( 24), viability of Al. leprae asassessed by the mouse foot pad technique("), and clinical scores were noted (in theabsence of any appreciable change in the BIvalues) within a few weeks of beginning ri-fampin therapy in lepromatous leprosy pa-tients (6 ' 7 ' ' 4 ). However, the assessment ofclinical activity by itself cannot serve as atool for monitoring treatment, since themethod is even less standardized, needsgreater expertise, and can be more subjec-tive than BI determinations. The presentstudy indicates that M. leprae-specific se-rology, as an adjunct to periodical clinicalassessment, may impart a degree of objec-tivity and reliability to the latter. The pa-tients showing a variable degree of clinicalrecovery also showed a steep and consistentrate of relative decline in specific antibodytiters, particularly by the SACT-ELISA.

In two patients who did not show a per-ceptible change in their clinical scores overthe studied duration of treatment, the SACT-ELISA titers increased sharply. Although itis tempting to take it as yet another indi-cation for a role of serology in detectingunresponsiveness to treatment (4) there arecertain constraints. Firstly, this group is verysmall. Secondly, one of the patients was un-dergoing an episode of ENL which is thoughtto cause fluctuations in antibody levels.However, such fluctuations, if any ("), arenot likely to be as great as seen in this case.In fact, another ENL patient in our studywho was clinically responding to treatmentdid not show such results (Fig. 2, Table 3).

The fact that, despite a steep decline, manypatients still had high antibody levels at theend of the study period needs to be consid-ered specifically. It has been documentedthat patients continue to manifest clinico-bacteriological improvement even after afixed duration (coinciding with maximumfollow-up duration in this study) of MDT( 10). Quite likely, a longer follow-up of ourpatients would have seen further reductionin their antibody levels up to negativity ornear-negativity. Whether such progressive-

ly declining trends leading to "substantial-ly" lower antibody titers at the end of atreatment schedule are indicative of successof a treatment or not, can be ascertained bysimilar studies on an extended scale.

The SACT-ELISA has shown greater sen-sitivity compared to the PGDS-ELISA inthe present and previous (I") studies. It alsoshowed the highest and least variable rateof relative decline in patients showing amarked clinical improvement followingtreatment. Nonetheless, these observationsmay partly be attributed to the differencesin commonly practiced methodology of thetwo assays. The SACT involves titration ofantibody in the serum which may reflectantibody concentrations in a better way thanthe PGDS-ELISA which is performed at afixed dilution in which the relationship be-tween concentration and OD is unlikely tobe linear in the higher range.

In conclusion, since there are consider-able individual variations in the severity ofinfection and response to treatment evenwithin a class of leprosy patients (more so,when classified simply as multibacillary orpaucibacillary), M. leprae-specific serologywith the SACT-ELISA may serve as ahelpful adjunct to routine clinico-bacterio-logical methods for deciding treatmentschedules for a given case. It is likely to beparticularly useful when marked clinical re-gression is not accompanied by a similarimprovement in the BI. In post-treatmentsurveillance, serology may be helpful in de-tecting reactivation of residual or hiddenfoci of infection. However, serology maynot be particularly helpful or necessary inthe management of tuberculoid (or pauci-bacillary) leprosy patients.

SUMMARYThe Mycobacterium leprae-specific anti-

body assays—a serum antibody competi-tion test (SACT-ELISA) for the epitope onthe 35-kDa protein, and an enzyme im-munoassay for the disaccharide epitope ofphenolic glycolipid-I (PGDS-ELISA)— wereevaluated as tools for the serological mon-itoring of chemotherapy in 20 lepromatousand 6 tuberculoid leprosy patients. In ad-dition to estimates for Al. leprae-specific an-tibodies, assessments of the bacterial index(BI) and clinical activity of the disease were

59, 1^Chaturvedi, et al.: Serology to Monitor Chemotherapy^39

also carried out prospectively in these pa-tients on two to four occasions over a periodof 19 months. In most cases, a decline inthe BI, clinical scores, and antibody levelswas observed during the course of treat-ment. The relative rate of decline was steep-est and least variable with the SACT-ELISA,followed by the PGDS-ELISA and the BI.In some patients who showed a static oreven an increased BI, despite marked clin-ical improvement, the antibody levels de-creased. These data indicate that, unlike theBI, there is a greater dependence of specificantibody levels on the viability ofM. leprae.This, combined with the fact that antibodytiters would reflect the antigen load in thewhole body, makes M. leprae-specific se-rology a promising tool for monitoring che-motherapy in leprosy patients.

RESUMENSe evaluaron, comparativamente, dos ensayos para

determiner anticucrpos especificos contra Mycobacte-rium leprae: una prucba de competencia de anticucrospor el epitope de la proteina de 35 kDa (SACT-ELISA),y un ensayo enzimatico para el disacarido del glicoli-pido fenOlico I (PGDS-ELISA). Los ensayos se usaronpara visualizar el efecto de la quimioterapia en 20 pa-cientes lepromatosos y en 6 pacientes tuberculoides.Adicionalmente se establecieron el indict bacteriano(IB) y la actividad clinica de la enfermedad de cadapacicntc en 2 a 4 ocasiones dentro de un periodo dc19 meses. Duratc el curso del tratamiento, en la ma-yoria de los pacientes se observO una declinaciOn enel IB, en los parametros clinicos y en los niveles deanticucrpos. El grado relativo de declinaciOn fue masprogresivo y menos variable cuando se analize) porSACT-ELISA que por PGDS-ELISA o por el IB. Enalgunos pacientes que mostraron un IB estatico o in-cluso incrementado, a pcsar de una marcada mejoriaclinica, los niveles de anticuerpos disminuyeron. Estosdatos indican que los niveles de anticuerpos especificosdependen mas de la viabilidad del Al. leprae, que del113. Esto, combinado con el hecho de que los titulos deanticuerpo reflejarian mejor la carga antigênica en todoel cuerpo, hacen a la serologia especifica para A1. leprae,una herramienta promisoria para visualizar la cficaciade la quimioterapia en los pacientes con lepra.

RESUME

Les tests pour les anticorps spêcifiques vis-a-vis duMycobacteriunz leprae—un test de competition pourles anticorps seriques (SACT-ELISA) vis-a-vis detope de la proteine de 35 kDa et un test immuno-enzymatique pour l'epitope disaccharidiquc du gly-colipidc phenolique-I (PGDS-ELISA)—ont etc evaluêsen tant qu'instruments pour la surveillance serologique

de la chimiotherapie chez 20 malades lepromateux et6 tuberculoIdes. En plus de la recherche des anticorpsspecifiques vis-a-vis de M. leprae, des evaluations del'indice bacterien (IB) et de l'activite clinique de lamaladie ont etc realisees de maniere prospective chezces patients de dcux a quatre reprises au cours d'uneperiode de 19 mois. Dans la plupart des cas, une dim-inution de l'indice bacterien, des scores cliniques et destaux d'anticorps ont etc observes au cours du traite-ment. Le taux rclatif du &din Otait le plus fort et lemoins variable avec lc SACT-ELISA, suivi par lePGDS-ELISA et l'indice bacterien. Chez certains pa-tients qui ont montrô un IB stable ou meme en aug-mentation, malgre une amelioration clinique marquee,les taux d'anticorps ont diminué. Ces donnees indi-quent que, au contraire de l'indice bacterien, it y a uneplus grande dependance des taux d'anticorps speci-fiques vis-a-vis de la viabilite de Al. leprae. Ceci,combine au fait que les titres d'anticorps reflêteraientla charge antigênique dans Pensemble de l'organisme,fait de la serologic specifique vis-à-vis de Al. leprae uninstrument prometteur pour la surveillance de lachimiotherapie chez les malades de la lepre.

Acknowledgments. We are grateful to Dr. R. J. W.Rees, National Institute for Medical Research, Lon-don, for the supply of M. leprae antigen from the WHO-IMMLEP Bank; to Dr. J. Ivanyi, MRC Tuberculosisand Related Infections Unit, London, for the supplyof monoclonal antibodies against M. leprae; and to Dr.Delphi Chatterjee, Colorado State University, FortCollins, Colorado, U.S.A., for providing ND-O-BSA.Skillful technical assistance was provided by Mr. H.0. Agarwal and secretarial help was rendered by Mr.A. K. Chopra. We are also grateful to Dr. H. Srinivasanfor helpful suggestions during the preparation of themanuscript. In addition, certain materials used in thisstudy were generous gifts of LEPRA, U.K.

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HOFFENBACH, A. and COTTENOT, F. Antibodiesto phenolic glycolipid-I and to whole M. leprae inleprosy patients: evolution during therapy. Int. J.Lepr. 54 (1986) 256-267.

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