Experiences with Mycobacterium leprae soluble antigens in a leprosy endemic population

Rees and Convit antigens prepared from armadillo-derived Mycobacterium leprae were used for skin testing in two leprosy endemic villages to understand their use in the epidemiology of leprosy. In all, 2602 individuals comprising 202 patients with leprosy detected in a prevalence survey, 476 household contacts and 1924 persons residing in non-case households were tested with two antigens. There was a strong and positive correlation (r = 0.85) between reactions to the Rees and Convit antigens. The distribution of reactions was bimodal and considering reactions of 12 mm or more as 'positive', the positivity rate steeply increased with the increase in age. However, the distributions of reactions to these antigens in patients with leprosy, their household contacts and persons living in non-case households were very similar. These results indicate that Rees and Convit antigens are not useful in the identification of M. leprae infection or in the confirmation of leprosy diagnosis in a leprosy endemic population with a high prevalence of nonspecific sensitivity.     

Characterization of circulating immune complexes in leprosy patients and their correlation with specific antibodies against Mycobacterium leprae

Circulating immune complex (CIC) levels and their antibody and antigenic composition were evaluated in patients with leprosy as well as in any individuals living with them; they were precipitated with 3.5% polyethylene glycol (PEG) and, after affinity chromatography isolation and purification, analysed by sodium dodecyl sulphate—polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblot with monoclonal antibodies (Mabs). The presence of CICs was demonstrated throughout the clinical and immunopathological leprosy spectrum at levels related to bacterial load, and in leprosy patients they showed a positive correlation with specific anti-PGL and anti-65 kDa antibodies. The isolation and analysis, however, failed to identity any Mycobacterium leprae antigenic components; although two specific antibodies anti-PGL-1 and anti-65kDa were identified as possible CIC constituents and may be potentially useful in the follow-up of leprosy patients, especially to chirk bacterial load evolution, PG1.-1 being an authentic antigen of this mycobacterium. Also, the involvement of 65 kDa in CICs, being homologous with the human heat shock protein (HSP) 60 kDa family, suggests an autoimmune mechanism in leprosy pathogenesis, Furthermore, those results support the inclusion of CIC anti-body reactivity studies to enhance the sensitivity of serology.     

Fibronectin in leprosy lesions: observations using monoclonal antibodies to human fibronectin

Croystat sections of dermal lesions from 33 untreated patients with leprosy were studied by indirect immunofluorescence using monoclonal antibodies to human fibronectin. Macrophages in borderline (BL) and lepromatous (LL) leprosy showed intense staining with antifibronectin antibodies. In the tuberculoid lesions cells of the mononuclear phagocyte series in an epithelioid cell granuloma stained for fibronectin. The lymphocytes surrounding these granulomas also showed the presence of fibronectin. These results suggest that the granuloma of leprosy consists of macrophages expressing fibronectin and the lymphocytes in the lesion also appear to express this protein. In six borderline cases, the sub epidermal collagen band showed intense staining with antifibronectin antibodies. In addition, the distribution of Ia-like antigens and fibronectin was studied on the plastic adherent cells obtained from peripheral blood of 11 untreated patients with leprosy. Results indicate that higher percentage of adherent cells from lepromatous patients express fibronectin in comparison to adherent cells from tuberculoid patients or controls. However, no difference was observed in the expression of the Ia-like antigens by the adherent cells, from these patients.     

Immunogenicity of Mycobacterium leprae unique antigens in leprosy endemic populations in Asia and Africa

Ongoing transmission of leprosy is evident from the stable disease incidence in high burden areas. Tools for early detection of Mycobacterium leprae (M. leprae) infection, particularly in sub-clinically infected individuals, are urgently required to reduce transmission. Following the sequencing of the M. leprae genome, many M. leprae-unique candidate proteins have been identified, several of which have been tested for induction of M. leprae specific T cell responses in different leprosy endemic areas. In this study, 21 M. leprae-unique proteins and 10 peptide pools covering the complete sequence of five M. leprae-unique proteins (ML0576, ML1989, ML1990, ML2283, and ML2567) were evaluated in 160 individuals in Nepal and Ethiopia. These included: tuberculoid and borderline tuberculoid (TT/BT), borderline borderline and borderline lepromatous (BB/BL) leprosy patients; healthy household contacts (HHC); tuberculosis (TB) patients and endemic controls (EC). Immunogenicity of the proteins was determined by IFN-gamma secretion via stimulation of PBMC in 6 days lymphocyte stimulation tests (LST) or in whole blood assays (WBA). In LST, BB/BL patients (40%) responded to ML0573 and ML1601 whereas ML1604 was most immunogenic in TT/BT (35%) and HHC (36%). Additionally, significant numbers of EC displayed IFN-gamma production in response to ML0573 (54%), ML1601 (50%) and ML1604 (54%). TB patients on the other hand, hardly responded to any of the proteins except for ML1989. Comparison of IFN-gamma responses to ML0121, ML0141 and ML0188 for TT/BT patients showed specific increase in diluted 6 days WBA compared to the undiluted 24 hours WBA, whereas EC showed a reduced response in the diluted WBA, which may indicate detection of disease-specific responses in the 6 days WBA. In summary, identification of multiple M. leprae proteins inducing M. leprae-specific T cell responses in groups at high risk of developing leprosy may contribute to improve early detection for M. leprae infection.     

The leprosy agents Mycobacterium lepromatosis and Mycobacterium leprae in Mexico

Background Mycobacterium leprae was the only known cause of leprosy until 2008, when a new species, named Mycobacterium lepromatosis, was found to cause diffuse lepromatous leprosy (DLL), a unique form of leprosy endemic in Mexico. Methods We sought to differentiate the leprosy agents among 120 Mexican patients with various clinical forms of leprosy and to compare their relative prevalences and disease features. Archived skin biopsy specimens from these patients were tested for both M. leprae and M. lepromatosis using polymerase chain reaction‐based species‐specific assays. Results Etiologic species were confirmed in 87 (72.5%) patients, of whom 55 were infected with M. lepromatosis, 18 with M. leprae, and 14 with both organisms. The endemic regions of each agent differed but overlapped. Patients with M. lepromatosis were younger and were distributed across more states; their clinical diagnoses included DLL (n = 13), lepromatous leprosy (LL) (n = 34), and eight other forms of leprosy. By contrast, the diagnoses of patients with M. leprae did not include DLL but did include LL (n = 15) and three other forms of leprosy. Thus, M. lepromatosis caused DLL specifically (P = 0.023). Patients with M. lepromatosis also showed more variable skin lesions; the extremities were the most common sites of biopsy in these patients. Finally, patients with dual infections manifested all clinical forms and accounted for 16.1% of all species‐confirmed cases. Conclusions Mycobacterium lepromatosis is another cause of leprosy and is probably more prevalent than M. leprae in Mexico. It mainly causes LL and also specifically DLL. Dual infections caused by both species may occur in endemic areas.     

Postgenomic Mycobacterium leprae antigens for cellular and serological diagnosis of M. leprae exposure, infection and leprosy disease

Due to changes in leprosy control programs and the special expertise required for diagnosis, the need for simple rapid diagnostic tests that could be applied in non-expert settings may now be greater than ever before. Since the sequencing of the M. leprae genome, many research groups have investigated the potential of M. leprae antigens in either serologic or cell mediated assays. Here we provide an overview of the nearly 200 recombinant single proteins that were investigated during the last decade for their potential to be applied in field-friendly tests for the early diagnosis of leprosy.     

Sub-clinical infection with Mycobacterium leprae in household contacts of leprosy

870 household contacts of leprosy patients were examined for sub-clinical infection with M. leprae by smear (skin and nasal), lepromin and FLA-ABS tests. 0.6%, 3.3%, 71.5% and 14.4% of the contacts were found to be positive for skin smear, nasal smear, lepromin and FLA-ABS tests respectively. An analysis of the results revealed that 4% of the lepromin positive contacts and 3.6% of the lepromin negative contacts were positive to both FLA-ABS and skin or nasal smear.     

Mycobacterium leprae DNA in daily using water as a possible source of leprosy infection.

Some environmental factors were suspected to be sources of leprosy infection according to the results of total survey in the highly endemic villages in Indonesia. M. leprae DNA were detected by PCR from 21 out of 44 water sources used daily by villagers. Prevalence of leprosy among the people using PCR-positive water for bathing and washing was significantly higher than that among the people who used PCR-negative water. No significant difference in prevalence was, however, recognized in case of usage of negative or positive water for drinking. Water was regarded as a reservoir and infectious source of M. leprae. Transmission of leprosy through the contaminated water was strongly suggested by epidemiological analysis.     

Effect of multidrug therapy on the levels of antibodies to Mycobacterium leprae glycolipid-1 in the leprosy spectrum

Sera from one hundred and forty five untreated leprosy patients, ten proven cases of active pulmonary tuberculosis and twenty five healthy volunteers not exposed to M. leprae infection were assayed for PGL-1 antibodies. All available follow up samples after multidrug therapy were also assayed. A decline in the level of PGL-1 antibodies were seen in many of the post-treatment samples, giving an indirect assessment of the bacterial load and the prognosis of the disease.