The protective efficacy of a liposomal encapsulated 30 kDa secretory protein of Mycobacterium tuberculosis H37Ra against tuberculosis in mice.

The immunoprotective efficacy of the 30 kDa secretory protein isolated from mid-log phase culture filtrate of Mycobacterium tuberculosis H37Ra was investigated using liposomes as adjuvant. Immunization of animals with the 30 kDa protein entrapped in liposomes prepared by a freeze-thaw method and absorbed on alum induced both cellular (monitored by T cell proliferation assay and cytokine secretion, viz. IL-2, IFN-gamma) and humoral (evaluated by ELISA) responses which were comparable to those induced in the 30 kDa IFA-immunized group. The protection induced by liposome-encapsulated 30 kDa secretory protein was slightly lower than that induced in 30 kDa IFA-immunized animals on the basis of higher survival rates and decreased viable counts of M. tuberculosis H37Rv in various organs (spleen, lung and liver) after 30 days of infection compared to the controls. The results strongly indicate that liposomes are an ideal vaccine delivery system which can effectively replace IFA for the delivery of the immunoprotective 30 kDa secretory protein of M. tuberculosis H37Ra.