Humoral immunity in leprosy: immunoglobulin G and M antibody responses to Mycobacterium leprae in relation to various disease patterns

B lymphocytes deficiency results in altered immune response and increased susceptibility to Mycobacterium leprae in a murine leprosy model

Leprosy is a chronic and infectious disease that primarily affects the skin and peripheral nervous system, presenting a wide spectrum of clinical forms with different degrees of severity. The distinct host immune response patters developed in the response to the bacillus Mycobacterium leprae, the leprosy etiologic agent, are associated with the spectral clinical forms and outcome of the disease. In this context, B cells are allegedly involved in the disease immunopathogenesis, usually as antibody-producing cells, but also as potential effector or regulatory elements. In order to determine the regulatory B cells role in experimental leprosy, this study evaluated the outcome of M. leprae infection in B cell deficient mice (BKO) and WT C57Bl/6 control, by means of microbiological/bacilloscopic, immunohistochemical and molecular analysis, performed 8 months after M. leprae inoculation. The results demonstrated that infected BKO showed a higher bacilli number when compared with WT animals, demonstrating the importance of these cells in experimental leprosy. The molecular analysis demonstrates that the expression of IL-4, IL-10 and TGF-β was significantly higher in the BKO footpads when compared to WT group. Conversely, there was no difference in IFN-γ, TNF-α and IL-17 expression levels in BKO and WT groups. IL-17 expression was significantly higher in the lymph nodes of WT group. The immunohistochemical analysis revealed that M1 (CD80⁺) cells counts were significantly lower in the BKO group, while no significant difference was observed to M2 (CD206⁺) counts, resulting a skewed M1/M2 balance. These results demonstrated that the absence of B lymphocytes contribute to the persistence and multiplication of M. leprae, probably due to the increased expression of the IL-4, IL-10 and TGF-β cytokines, as well as a decrease in the number of M1 macrophages in the inflammatory site.

Differential Expression of IFN-γ, IL-10, TLR1, and TLR2 and Their Potential Effects on Downgrading Leprosy Reaction and Erythema Nodosum Leprosum

Leprosy reactions are acute immunological events that occur during the evolution of chronic infectious disease causing neural damage and disabilities. A study using blood samples of 17 leprosy reaction patients and 17 reaction-free was carried out by means of associations between antigens, receptors, and expression of cytokines, using path analysis providing new insights into the immunological mechanisms involved in triggering leprosy reactions. Toll-like receptors (TLR) such as TLR1 and TLR2, presented balanced expression in the reaction-free multibacillary (MB) group (TLR1: 1.01 ± 0.23, TLR2: 1.22 ± 0.18; p = 0.267). On the other hand, downgrading type 1 reaction (T1R) (TLR1: 1.24 ± 0.17, TLR2: 2.88 ± 0.37; p = 0.002) and erythema nodosum leprosum (ENL) (TLR1: 1.93 ± 0.17, TLR2: 2.81 ± 0.15; p = 0.004) revealed an unbalance in relation to the expression of these receptors. When the path analysis was approached, it was noted that interleukin 10 (IL-10) expression showed a dependence relation with phenolic glycolipid I (PGL-I) in downgrading T1R (direct effect = 0.503 > residual effect = 0.364), whereas in ENL, such relationship occurred with lipoarabinomannan (LAM) (direct effect = 0.778 > residual effect = 0.280). On the contrary, in the reaction-free leprosy group, interferon-gamma (IFN-γ) levels were dependent on the association between TLR2 and TLR1 (0.8735). The high TLR2 expression associated with IL-10 levels, in the leprosy reaction groups, may be hypothetically related to the formation of TLR2/2 homodimers and/or TLR2/6 heterodimers linked to evasion mechanisms in downgrading reactions and pathophysiology of ENL.

Increased activated memory B-cells in the peripheral blood of patients with erythema nodosum leprosum reactions

B-cells, in addition to antibody secretion, have emerged increasingly as effector and immunoregulatory cells in several chronic inflammatory diseases. Although Erythema Nodosum Leprosum (ENL) is an inflammatory complication of leprosy, the role of B- cell subsets has never been studied in this patient group. Therefore, it would be interesting to examine the contribution of B-cells in the pathogenesis of ENL. A case-control study design was used to recruit 30 untreated patients with ENL and 30 non-reactional lepromatous leprosy (LL) patient controls at ALERT Hospital, Ethiopia. Peripheral blood samples were obtained before, during and after treatment from each patient. Peripheral blood mononuclear cells (PBMCs) were isolated and used for immunophenotyping of B- cell subsets by flow cytometry. The kinetics of B-cells in patients with ENL before, during and after Prednisolone treatment of ENL was compared with LL patient controls as well as within ENL group. Total B-cells, mature B-cells and resting memory B-cells were not significantly different between patients with ENL reactions and LL controls before treatment. Interestingly, while the percentage of naive B-cells was significantly lower in untreated ENL patients than in LL patient controls, the percentage of activated memory B-cells was significantly higher in these untreated ENL patients than in LL controls. On the other hand, the percentage of tissue-like memory B-cells was considerably low in untreated ENL patients compared to LL controls. It appears that the lower frequency of tissue-like memory B-cells in untreated ENL could promote the B-cell/T-cell interaction in these patients through downregulation of inhibitory molecules unlike in LL patients. Conversely, the increased production of activated memory B-cells in ENL patients could imply the scale up of immune activation through antigen presentation to T-cells. However, the generation and differential function of these memory B-cells need further investigation. The finding of increased percentage of activated memory B-cells in untreated patients with ENL reactions suggests the association of these cells with the ENL pathology. The mechanism by which inflammatory reactions like ENL affecting these memory cells and contributing to the disease pathology is an interesting area to be explored for and could lead to the development of novel and highly efficacious drug for ENL treatment.

Excavating the surface-associated and secretory proteome of Mycobacterium leprae for identifying vaccines and diagnostic markers relevant immunodominant epitopes

For centuries, Mycobacterium leprae, etiological agent of leprosy, has been afflicting mankind regardless of extensive use of live-attenuated vaccines and antibiotics. Surface-associated and secretory proteins (SASPs) are attractive targets against bacteria. We have integrated biological knowledge with computational approaches and present a proteome-wide identification of SASPs. We also performed computational assignment of immunodominant epitopes as coordinates of prospective antigenic candidates in most important class of SASPs, the outer membrane proteins (OMPs). Exploiting the known protein sequence and structural characteristics shared by the SASPs from bacteria, 17 lipoproteins, 11 secretory and 19 novel OMPs (including 4 essential proteins) were identified in M. leprae As OMPs represent the most exposed antigens on the cell surface, their immunoinformatics analysis showed that the identified 19 OMPs harbor T-cell MHC class I epitopes and class II epitopes against HLA-DR alleles (54), while 15 OMPs present potential T-cell class II epitopes against HLA-DQ alleles (6) and 7 OMPs possess T-cell class II epitopes against HLA-DP alleles (5) of humans. Additionally, 11 M. leprae OMPs were found to have B-cell epitopes and these may be considered as prime candidates for the development of new immunotherapeutics against M. leprae.

Early detection of leprosy by examination of household contacts, determination of serum anti-PGL-1 antibodies and consanguinity

A cross-sectional clinical trial in which the serum anti-phenolic glycolipid (anti-PGL-1) antibodies were analysed in household contacts (HHC) of patients with leprosy as an adjunct early leprosy diagnostic marker was conducted. The families of 83 patients underwent clinical examination and serum anti-PGL1 measurement using enzyme-linked immunosorbent assay. Of 320 HHC, 98 were contacts of lepromatous leprosy (LL), 80 were contacts of borderline lepromatous (BL), 28 were contacts of borderline (BB) leprosy, 54 were contacts of borderline tuberculoid (BT), 40 were contacts of tuberculoid (TT) and 20 were contacts of indeterminate (I) leprosy. Consanguinity with the patients was determined for 232 (72.5%) HHC. Of those 232 contacts, 183 had linear consanguinity. Forty-nine HHC had collateral consanguinity. Fifty-eight contacts (18.1%) tested positive for anti-PGL1 antibodies. The number of seropositive contacts based on the clinical forms of the index case was 17 (29.3%) for LL, 15 (25.9%) for BL, one (1.7%) for BB, 14 (24.1%) for BT, three (5.2%) for TT and eight (13.7%) for I. At the one year follow-up, two (3.4%) of these seropositive contacts had developed BT leprosy. The results of the present study indicate that the serum anti-PGL-1 IgM antibody may be useful for evaluating antigen exposure and as a tool for an early leprosy diagnosis in HHC.

Buruli ulcer

Buruli Ulcer (BU) is a neglected, necrotizing skin disease, caused by M. ulcerans, that can leave patients with prominent scars and lifelong disability. M. ulcerans produces a diffusible lipid toxin, mycolactone, essential for bacterial virulence. Prevention is difficult as little is known about disease transmission and there is no vaccine. There have been several recent advances in the field. These include sequencing of the bacterial genome and of the giant plasmid responsible for mycolactone synthesis, better understanding of the bacterial lifecycle and of the mechanism of action of the toxin. This work has revealed a number of possible vaccine candidates, some of which are shared with other mycobacteria, e.g. M. tuberculosis, while other targets are unique to M. ulcerans. In this review, we discuss several M. ulcerans vaccine targets and vaccination methods, and outline some of the gaps in our understanding of the bacterium and the immune response against it.

Serum Proteome of Leprosy Patients Undergoing Erythema Nodosum Leprosum Reaction: Regulation of Expression of the Isoforms of Haptoglobin

Validated proteome profile allows better understanding of disease progression, subtype classification, susceptibility patterns, and disease prognosis. Leprosy is a spectral disease, with clinically, histologically, immunologically, and bacteriologically distinguishable subtypes. In addition, a significant fraction of patients undergo immune mediated reactions even after multidrug therapy (MDT). Erythema nodosum leprosum (ENL) is an immune complex mediated reactional condition in leprosy, characterized by a systemic inflammatory condition afflicting borderline lepromatous (BL) and lepromatous leprosy patients (LL). In this study, we have analyzed serum proteome of leprosy patients undergoing ENL reactions and compared it with that of healthy noncontact controls. Depletion of albumin and immunoglobulin G (IgG) was optimized using Aurum serum protein mini kit (Bio-Rad), and then two-dimensional gel electrophoresis (2-DE) of these serum samples was performed. Differentially expressed proteins were identified by MALDI-TOF and MALDI-TOF MS/MS mass spectrometry. Significant increase in one of the isoforms of alpha2 chain of haptoglobin was observed in ENL condition. In addition, haptoglobin phenotype was determined for healthy controls and leprosy patients. Hp 0-0 phenotype was detected in 21.4% of the ENL patients undergoing treatment, which on follow up examination showed typable phenotype, thus showing a condition of acquired anhaptoglobinemia. Since ENL still remains a threat to leprosy disease management, the above findings may provide new insights in understanding the development and progression of this inflammatory condition.

Serological responses against the pathogenic dimorphic fungus Mucor amphibiorum in populations of platypus (Ornithorhynchus anatinus) with and without ulcerative mycotic dermatitis

Mucor amphibiorum, a dimorphic fungus, causes ulcerative dermatitis and systemic infections in the platypus Ornithorhynchus anatinus in some river systems in Tasmania but apparently not in other regions of Australia. As yet there are no suitable tests for population surveys, nor for detection of internal lesions in live animals. Consequently, immunoglobulins were purified from the serum of platypuses and anti-immunoglobulin antisera were prepared in rabbits in order to develop an enzyme-linked immunosorbent assay (ELISA) for anti-M. amphibiorum antibodies. Antigens from plate-grown cultures resulted in greater signal-to-noise ratios in indirect ELISA than those from broth-grown cultures. Platypuses with clinical ulcerative dermatitis had elevated anti-Mucor antibody levels compared to apparently unaffected individuals. Seroconversion was observed in one animal coincident with the development of cutaneous ulcers. The results suggested that platypuses in affected rivers were exposed to M. amphibiorum at a higher frequency than the occurrence of clinical disease. Some platypuses from New South Wales had elevated antibody levels but these increased significantly with age suggesting exposure to cross-reactive antigens, although exposure to M. amphibiorum cannot be excluded. Further studies are warranted to determine factors that result in progression from infection to disease, the occurrence of the fungus in areas where disease has not been observed and the specificity of antigen used in ELISA.

Effects of the severity and duration of lesions on the primary and anamnestic humoral responses of sheep to Dichelobacter nodosus and observations of natural resistance to footrot

In a flock of 137 sheep naturally infected with Dichelobacter nodosus the severity of the lesions was the principal factor associated with the humoral response early in the period of spread of D. nodosus, underrun lesions having the greatest effect. However, after five to six weeks, the duration of underrun lesions rather than their severity or number primarily influenced the response. Sheep first affected late in the period of spread had fewer affected feet, milder lesions and a lower humoral response than those affected earlier. An anamnestic humoral response was stimulated by injecting membrane-protein antigen of D nodosus subcutaneously 18 weeks after the sheep had been treated parenterally with antibiotics and antiseptic footbathing. The anamnestic response was related to the antibody level reached during the infection phase, and hence with the duration and severity of the lesions, and with the residual antibody level at the time of the anamnestic challenge, suggesting that the population of memory B cells specific for D nodosus was proportional to the size of the originally activated B cell population. Even after allowing for differences between the duration and severity of the lesions differential responses were detectable among the sheep. Primary and anamnestic responses of a non-specific nature occurred in control sheep.

A role for natural antibody in the pathogenesis of leprosy: antibody in nonimmune serum mediates C3 fixation to the Mycobacterium leprae surface and hence phagocytosis by human mononuclear phagocytes

We have previously determined that complement receptors on human mononuclear phagocytes and complement component C3 in nonimmune serum mediate phagocytosis of the intracellular bacterial pathogen Mycobacterium leprae, the agent of leprosy. We have also determined that C3 fixes selectively to the major surface glycolipid of M. leprae, phenolic glycolipid 1 (PGL-1). In this study, we have explored the role of natural antibody in nonimmune serum in C3 fixation and C1q binding to M. leprae and PGL-1. At serum concentrations within the range at which phagocytosis of M. leprae is maximal, C3 fixation was mediated by both the classical and the alternative complement pathways. At the low end of this serum concentration range (2.5%), C3 fixation was mediated predominantly by the classical pathway. Consistent with a role for both pathways, C3 fixation to M. leprae was enhanced by the addition of either pure C1q to C1q-depleted serum or pure factor B to factor B-depleted serum. C3 fixation to M. leprae was strictly antibody dependent regardless of the serum concentration used. C3 fixation to M. leprae occurred in nonimmune serum but not in agammaglobulinemic serum unless heat-inactivated nonimmune serum or small amounts of pure immunoglobulin G (IgG) or IgM were added. C3 fixation by both the alternative and the classical complement pathways was mediated by antibody, and the antigen-binding portion of the antibody molecule was required. C3, IgG, IgM, and C1q were readily detected on the surface of M. leprae. Consistent with the previously demonstrated exclusive role of the classical complement pathway in C3 fixation to PGL-1, C1q bound to PGL-1 in a dose-dependent fashion; C1q binding was evident in > 1.25% nonimmune serum. C1q binding to PGL-1 was strictly antibody dependent. When PGL-1 was incubated with pure C1q, little or no C1q bound to PGL-1 unless heat-inactivated nonimmune serum or pure IgG or IgM was added. When PGL-1 was incubated in nonimmune serum, C3 bound directly to PGL-1 and not to anti-PGL-1 antibody, since the amount of C3 bound to PGL-1 was not reduced by acid elution of the antibody. However, the amount of C3 bound to PGL-1 was markedly reduced by hydroxylamine treatment, providing evidence for C3 fixation via a covalent ester bond. Nonimmune serum contained antibody to all four major M. leprae surface carbohydrates. Relative to PGL-1, nonimmune serum contained more antibody to the other surface carbohydrates.(ABSTRACT TRUNCATED AT 400 WORDS)

Specificity of IgG subclass antibodies in different clinical manifestations of leprosy

We analysed specific IgG subclasses levels to Mycobacterium leprae sonicate extract (MSE), lipoarabinomannan B (LAM) and phenolic glycolipid I (PGL-I) in the sera of leprosy patients with different clinical manifestations. IgG2 was found to be the predominant antibody to MSE regardless of clinical manifestations, and IgG1 response was mostly seen in lepromatous patients. IgG3 reacted only rarely but IgG4 reacted relatively more in certain clinical groups such as borderline lepromatous and lepromatous with erythema nodosum leprosum (ENL) reaction. Most of the IgG subclass responses to MSE could be accounted for reactivity with LAM, suggesting that LAM is the major immunogen involved in the pathogenesis of leprosy. In contrast to LAM, PGL-I antigen showed considerably lower reactivities for IgG subclasses. An association between IgG subclass responses and clinical manifestations of leprosy was also seen. Whereas borderline lepromatous patients were found to have significantly higher levels of IgG2 and IgG4 to MSE, lepromatous patients had elevated levels of IgG1 and lower levels of IgG2. An interesting observation, however, was the significantly higher levels of IgG2 to LAM in the pure neuritic leprosy patients.

Serology and leprosy: immunoassays comparing immunoglobulin G antibody responses to 28- and 30-kilodalton proteins purified from Mycobacterium bovis BCG

Two major proteins from Mycobacterium bovis BCG culture filtrates with molecular masses of 28 kDa (P28) and 30 kDa (P30), identified as components of the BCG 85 complex, were purified and used in enzyme-linked immunosorbent assays (ELISAs) for the determination of specific immunoglobulin G (IgG) levels in patients with leprosy or tuberculosis or with exposure to these diseases. High reactivity to both antigens was observed with sera from lepromatous leprosy patients, whereas antibody levels in sera from paucibacillary leprosy patients were not significantly different from those in sera from healthy individuals from an area in which leprosy is endemic. High IgG responses were also found in some contacts of lepromatous leprosy patients. A comparison of the levels of anti-P28 and anti-P30 within the multibacillary leprosy patient group showed much higher IgG reactivity to P28 than to P30, suggesting that the antibody response of lepromatous patients is directed predominantly against the 28-kDa protein. A high degree of correlation in values of ELISAs based on P28 and on the phenolic glycolipid of Mycobacterium leprae was observed in all groups analyzed. The potential use of an assay based on the 28-kDa protein to selectively distinguish individuals destined to develop multibacillary leprosy is discussed, as also is the likelihood that the 28-kDa-30-kDa complex, part of the fibronectin-binding family, is an important component of M. leprae.

Characterization of the immune response to an epitope on Mycobacterium leprae antigen 7 defined by a monoclonal antibody

A mouse monoclonal antibody (038D-C6) was shown by crossed immunoelectrophoresis and radioimmunoassay to react with an epitope on the Mycobacterium leprae antigen 7. This epitope was highly crossreactive with BCG/M. tuberculosis and of a non-arabinogalactan-arabinomannan nature. A solid-phase radioimmunoassay (SPRIA) was applied, based on competitive inhibition by human sera of antigen binding by this anti-M. leprae monoclonal antibody. Inhibitory activity determined by this assay decreased markedly upon treatment in both lepromatous and tuberculoid leprosy patients. A correlation was found between the bacterial load of the patient and the inhibitory activity measured in the SPRIA assay. Serum-inhibitory activity could therefore perhaps be used as a follow-up test for patients on treatment or as a screening method to detect infective cases. A dot enzyme-linked immunosorbent assay based, like the SPRIA assay, on competitive inhibition by human sera, was explored as an inexpensive and technically simple alternative also applicable under field conditions.

Human monoclonal antibodies against Mycobacterium leprae

Human hybridomas were constructed which produce antibodies against three different extracts of Mycobacterium leprae. A thioguanine-resistant (Thgr), ouabain-resistant (Ouar), human lymphoblastoid cell line, KR-4, was hybridized with Epstein-Barr virus-transformed cell lines from lepromatous leprosy patients with fusion frequencies of greater than 10(-5). Non-Epstein-Barr virus-transformed donor cells fused at much lower rates (less than 2 X 10(-7]. Hybrids were selected in medium containing hypoxanthine aminopterin thymidine and 10(-5) M ouabain. An enzyme-linked immunosorbent assay was used to screen for antibodies against three crude extracts of armadillo-derived M. leprae, including (i) a soluble sonic extract preparation, (ii) sodium dodecyl sulfate extract of insoluble sonicated M. leprae, and (iii) a purified phenolic glycolipid antigen. Of a total of 2,200 final clones screened, 359 were found to secrete antibody which bound to soluble sonic extracts and the sodium dodecyl sulfate extract (6.7 and 9.6%, respectively), whereas 12.5% (21 out of 168) showed positivity to the glycolipid antigen. Four selected hybridomas also reacted with the deacylated derivative of M. leprae phenolic-glycolipid antigen. The specificity of these monoclonal antibodies was partially determined by screening on a panel of crude extracts from four other mycobacteria. Nine clones of 122 showed reactivity to M. leprae only. The predominant immunoglobulin was immunoglobulin M, and quantities up to 10 micrograms/ml were produced. Antibody production by hybrid clones was stable in more than 75% of the clones grown in continuous culture. By comparison, 10,000 Epstein-Barr virus-transformed lymphocyte clones from lepromatous leprosy patients were screened for anti-M. leprae antibody production, and all of the 42 clones that were initially positive in the enzyme-linked immunosorbent assay lost their antibody-producing capabilities within 6 weeks in culture. These results suggest that a combination of Epstein-Barr virus transformation and hybridization may be an optimal method in producing human monoclonal antibodies from leprosy patients.

Analysis of the major antigenic determinants of the characteristic phenolic glycolipid from Mycobacterium leprae

Antibodies to the major phenolic glycolipid purified from Mycobacterium leprae have been demonstrated previously in sera of leprosy but not tuberculosis patients using an ELISA. The major antigenic determinants on this molecule were investigated using antisera raised in rabbits to the purified glycolipid and with a pool of sera from human lepromatous leprosy patients. A small, but significant cross-reaction was observed with the glycolipids from M. bovis and M. kansasii, which contain the phenolphthiocerol dimycocerosate part of the molecule but have different sugars, and also with a semi-synthetic 'attenuation indicator lipid' which shares the phenolphthiocerol but has no sugars. There was however no cross-reaction with phthiocerol dimycocerosate. The disaccharide, corresponding to the two terminal sugars of the M. leprae glycolipid has been chemically synthesized and shown to inhibit the reaction between glycolipid and antibody in the ELISA. The cross-reactivity observed with the M. bovis and M. kansasii glycolipids was not inhibited by the synthetic disaccharide. These findings suggest that the cross-reactivity is associated with the phenol ring and implies the disaccharide may be a unique antigenic determinant of M. leprae.

A serological test for leprosy with a glycolipid specific for Mycobacterium leprae

A phenolic glycolipid from Mycobacterium leprae was purified and used as antigen in an enzyme-linked immunosorbent assay. Antibodies directed against the lipid were seen in serums from leprosy patients but not in serums from uninfected controls or patients infected with other mycobacteria, including Mycobacterium tuberculosis. The antibody response distinguished between the Mycobacterium leprae lipid and the structurally related phenolic glycolipid from Mycobacterium kansasii. This assay has considerable potential as a specific serodiagnostic test for leprosy infection.

Serological specificity of phenolic glycolipid I from Mycobacterium leprae and use in serodiagnosis of leprosy

The serological activities of the specific phenolic glycolipid I from Mycobacterium leprae, its dissected parts, and related glycolipids from other mycobacteria were examined by enzyme-linked immunosorbent assay against hyperimmune anti-M. leprae rabbit antiserum and sera from patients with leprosy and other mycobacterial diseases. High anti-phenolic glycolipid I immunoglobulin M antibodies were found in 23 of 24 (96%) of lepromatous leprosy patients on short term chemotherapy and in 8 of 13 tuberculoid leprosy patients (62%). Sera from patients with tuberculosis or atypical mycobacterial infections were devoid of anti-phenolic glycolipid I activity. The structurally related phenolic glycolipids from Mycobacterium kansasii and Mycobacterium bovis and the aglycone segments of the M. leprae product showed no significant activity. Thus, the trisaccharide determinant of phenolic glycolipid I is specific in its structure, serological activity, and, to a lesser extent, the antibody class it evokes.

Serological activity of a characteristic phenolic glycolipid from Mycobacterium leprae in sera from patients with leprosy and tuberculosis

Serological activity against a purified phenolic glycolipid from Mycobacterium leprae, which may be obtained in large amounts from M. leprae infected armadillo liver, was investigated using immunodiffusion and an enzyme linked immunosorbent assay (ELISA). Generally a good correlation was obtained between these techniques, but the ELISA was more sensitive and convenient. Relatively high IgG and IgM anti-glycolipid antibody levels were found in lepromatous leprosy patients. The antibody titres to the glycolipid were, however, low when compared with antibody titres to crude sonicates. Since the glycolipid is present in large quantities, this suggests that it is not very immunogenic. Antibody against the glycolipid especially of the IgM class, was demonstrable in some tuberculoid leprosy patients, although at much lower titres than in the lepromatous leprosy sera. In lepromatous leprosy patients that were skin smear negative after more than 5 years of treatment the IgG anti-M. leprae derived glycolipid activity had decreased markedly. The anti-IgG and IgM glycolipid antibody levels in tuberculosis patients did not differ significantly from the levels in appropriate normal healthy subjects. The glycolipid antibody levels in patients infected with M. kansasii, M. avium or M. intracellulare also fell within the range of normal healthy individuals.

A serological test for leprosy based on competitive inhibition of monoclonal antibody binding to the MY2a determinant of Mycobacterium leprae

A novel serological assay for leprosy has been devised on the basis of serum inhibition of binding of 125I-labelled ML04 monoclonal antibody to Mycobacterium leprae sonicate-coated microtitre plates. Antibodies were detected in 93% of lepromatous leprosy patients, whereas controls from the endemic area, including leprosy contacts and patients with tuberculosis, were serologically negative. The specificity and efficacy of the test may offer an advantage over previously used techniques.