Cross-Reactivity of Antigens from the Cytoplasm and Cell Walls of Some Corynebacteria and Mycobacteria

Abstract

Leprosy-derived corynebacteria (LDC) are non-acid-fast organisms isolated from leprosy lesions in humans. In this study 20 antigens of native LDC cytoplasm were identified by immunoelectrophoresis, and autoclaving yielded the M₁ component, which strongly cross-reacted with antigen 60 of Mycobacterium bovis BCG (bacille Calmette-Guérin) and antigen 7 of Mycobacterium leprae. The polysaccharide moiety of M₁ was immunologically related to the LDC cell wall polysaccharide previously characterized as arabinogalactomannan. The latter polysaccharide competitively inhibited the formation of immune complexes by labeled M₁ and antisera to the LDC cell wall; cytoplasm and wall polysaccharides from other bacteria produced lower-level inhibition. In a radioimmunoassay with ¹²⁵I-Iabeled antigen 7 of M leprae, sera from patients with leprosy and antisera to the LDC cell wall yielded overlapping curves. Sera from patients with tuber-culoid leprosy and those from patients with lepromatous leprosy afforded different levels of inhibition in this radioimmunoassay; this result indicated a difference in antibody specificity in the two forms of leprosy. In conclusion, the cell wall polysaccharide of LDC corresponds to the main thermostable cytoplasmic antigen M₁; which strongly cross-reacts with sera from patients with leprosy and, more specifically, with antigen 7 of M. leprae.