Immunization with various cell-wall fractions of M. tuberculosis H37Ra, progressively depleted of lipids (cell-wall-insoluble fraction; CWIF), soluble proteins (cell-wall core; CWC), mycolic acids and arabinogalactans (cell-wall-protein-peptidoglycan complex; CW-PPC) elicited significant levels of both humoral and cell-mediated immune response. Mice immunized with these fractions, when challenged with an LD50 dose of M. tuberculosis H37Rv, exhibited significant protection as revealed by high survival rates and decreased bacterial load in lungs, liver and spleen, as compared to nonimmunized animals.

We wanted to determine the immunoprotective behaviour of cell wall protein peptidoglycan complex (CW-PPC) of Mycobacterium tuberculosis H37Ra, using liposomes as adjuvant, in an experimental animal model. Immunization of mice with CW-PPC entrapped in liposomes induced both humoral response, as measured by enzyme-linked immunosorbent assay (ELISA), and cell-mediated immune responses, as seen by delayed type hypersensitivity (DTH) and leucocyte migration inhibition (LMI) techniques. Ten days after complete immunization, the animals were challenged with median lethal dose (LD50) of M. tuberculosis H37Rv. The animals exhibited significant protection, as evident by 72% survival after 30 days of infection, compared to 38% survival in control animals. Protective effect of immunization with liposome entrapped CW-PPC was further substantiated by significant decrease in the number of viable bacilli in lungs, liver and spleen of immunized animals, as compared to control animals. These results indicate that immunization with liposome-entrapped mycobacterial cell wall protein peptidoglycan complex induces protection against experimental tuberculosis.

No abstract

The cell-wall protein-peptidoglycan complex (CW-PPC) of Mycobacterium tuberculosis, an immunologically potent component, was used to study the correlation between immune response and in vivo bacterial multiplication in the course of experimental tuberculosis infection in mice. Antibodies to CW-PPC were detected only after seven weeks of infection with M. tuberculosis H37Rv and afterwards no significant change was seen throughout the experiment. Delayed type hypersensitivity (DTH) to CW-PPC showed a gradual increase from the fifth week onward with a maximum during the 12th week after infection (p.in.) which did not change significantly afterward. The increased immune response in the course of infection correlated well with the multiplication rate of bacilli in the lungs. These results indicate a role of CW-PPC in antituberculous immunity.