Mycobacterium tuberculosis arabinomannan–protein conjugates protect against tuberculosis

Abstract

Lipoarabinomannan (LAM) is a major structural surface component of mycobacteria. Arabinomannan (AM) oligosaccharides derived from LAM of Mycobacterium tuberculosis H37Rv were isolated and covalently conjugated to tetanus toxoid (TT) or to short-term culture filtrate proteins (antigen 85B (Ag85B) or a 75kDa protein) from M. tuberculosis strain Harlingen. The different AM oligosaccharide (AMOs)–protein conjugate vaccine candidates proved to be highly immunogenic, inducing boosterable IgG responses against the AMOs portion of the conjugates in rabbits and guinea-pigs. Proliferation of T-cells from C57BL/6 mice immunized with the conjugates was seen upon in vitro stimulation with PPD. In C57BL/6 mice subcutaneous immunization with the AMOs–antigen 85B conjugate in alum provided significant protection compared to sham (alum only) immunized mice (P<0.021) as estimated by long term survival against intravenous challenge with 105M. tuberculosis H37Rv. Subcutaneous immunization followed by nasal boost with an AMOs–TT conjugate in Eurocine™ L3 adjuvant provided high (P<0.025) protection as determined by long term survival after intranasal challenge with 105 virulent M. tuberculosis strain Harlingen. This level of protection was comparable to that obtained with the conventional live attenuated BCG vaccine. In guinea-pigs, immunization with AMOs–Ag85B in Eurocine™ L3 adjuvant followed by aerogenic challenge with M. tuberculosis H37Rv resulted in increased survival and reduced pathology in lungs and spleens relative to non-immunized animals.