Humoral and cellular immune reactivity to recombinant M. leprae antigens in HLA-Typed leprosy patients and healthy controls

In our search for Mycobacterium leprae antigens that might specifically induce immunity or immunopathology, we have tested both humoral and cellular immune reactivity against purified recombinant M. leprae antigens in 29 paucibacillary (PB), 26 multibacillary (MB) leprosy patients, and 47 matched healthy contacts. The following M. leprae antigens were tested: 2L-1 (65L-1, GroEl-1), 2L-2 (65L-2, GroEl-2), 4L (SoDA), 43L, 10L (B) and 25L (Sra). The individuals were also typed for HLAD-RB1 and DQB1 in order to see whether leprosy status and/or immune reactivity to these antigens might be associated with certain HLA types. We also tested sera from another 48 patients before, during and after multidrug therapy (MDT) to study the relationship between antibody reactivity to recombinant M. leprae antigens and MDT. Antibody titers to the four recombinant M. leprae antigens tested and to D-BSA were higher in MB patients compared to PB patients and healthy controls, and declined with treatment. From a diagnostic or monitoring point of view none of the recombinant antigens seemed to be an improvement over D-BSA, mainly due to the lower sensitivity. IgG subclasses were measured in positive sera of untreated patients. These were mainly of the IgG1 and IgG3 subclasses, but subclass diversity was also observed and antigen dependent: all four subclasses could be detected against 10L (B), only IgG1 and IgG3 against 43L and only IgG1 against 25L and 2L-1. Cellular immune reactivity against the purified recombinant M. leprae antigens was measured in a lymphocyte stimulation test (LST). As for M. leprae, there was an inverse correlation between antibody and T-cell reactivity. However, the number of LST responders to recombinant antigens was much lower than to M. leprae. The 43L antigen was recognized most often (19%-24% of individuals tested) and more often than the 10L (B) antigen (10%-12%). No clear correlation was observed with leprosy type or protection and, in general, M. leprae nonresponders were also negative with recombinant antigens. Finally, we confirmed that HLA-DRB1*02 is associated with leprosy in this population, and we observed an association between DQB1*0601 and lepromatous leprosy. The number of positive individuals was too small to allow a meaningful analysis of the relationship between HLA type and immune reactivity. Although these data do not allow a conclusion as to one of these purified recombinant antigens being either protection or disease related, the antigen-dependent IgG subclass diversity warrants further study on antigen-specific qualitative differences in immune reactivity that may be relevant for the outcome of an infection with M. leprae.

Associations between HLA-DRB1 alleles and leprosy in an Indonesian population

To investigate whether the susceptibility to leprosy (type), subclinical infection with Mycobacterium leprae and the antibody response against M. leprae-specific antigens are associated with HLA-DR phenotypes sequence-specific oligonucleotide HLA-DRB1 and DQA1 typing and antibody assays have been performed in 79 leprosy patients (41 TT/BT and 38 LL/BL) and 50 healthy controls from a Javanese population in Yogyakarta, Indonesia. DRB1*02 was associated with LL/BL [odds ratio (OR) 2.54, 95% confidence interval (CI) 0.97-9.78, p = 0.037 and attributable risk (AR) 41.5%] but not with TT/BT leprosy (p > 0.05). HLA-DRB1*12 was negatively associated with leprosy (either LL/BL or TT/BT [OR 0.33-0.35, p < 0.05, prevented fraction (PF) 58.8%-65.3%]. No significant association was found between HLA-DRB1 or DQA1 type, anti-M. leprae antibody level and subclinical infection with M. leprae. These data indicate that in this population susceptibility to lepromatous leprosy is associated with HLA-DRB1*02, while resistance to leprosy is associated with HLA-DRB1*12. These associations are not paralleled with associations of the same HLA types with anti-M. leprae antibody level. Finally, the results of this study also support the notion that infection with M. leprae per se is not associated with HLA-DRB1 or DQA1 alleles.