Detection of disease related immune complexes in the serum of leprosy patients. A novel single step method

Mycobacterium leprae antigen and antibody complexes could be detected in the serum of leprosy patients using monoclonal antibody ML34 and anti-BCG antibodies by enzyme-linked immunosorbent assay. This simplified system detects disease related complexes without the need for isolating and purifying them from the serum. Immune complexes captured using monoclonal antibody ML34 revealed positivity in seven out of eight neuritic, two out of nine tuberculoid (TT), five out of ten borderline tuberculoid (BT), four out of ten borderline lepromatous (BL) and four out of ten lepromatous (LL), leprosy cases. One of the controls also showed immune complex of an IgM type. Anti-BCG based IgG immune complexes assay revealed positivity in six out of eight neuritic, one out of nine TT, four out of ten BT, two out of ten BL, four out of ten LL leprosy cases, and two out of 24 healthy controls. IgM type of mycobacterial immune complexes were almost negligible. Capture of complexes using monoclonal antibody ML34 which is against lipoarabinomannan of M. leprae seems to work better than polyclonal anti-BCG antibody. The probable role of immune complexes in nerve damage needs to be evaluated, as very high levels of immune complexes are found in neuritic leprosy by both the assays. The above test would be useful in immunodiagnosis of neuritic leprosy and also in cases where antibody response is not detectable because of the formation of immune complexes.