Potentiation of Th1-Type Immune Responses to Mycobacterium tuberculosis Antigens in Mice by Cationic Liposomes Combined with De-O-Acylated Lipooligosaccharide.

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis. Bacillus Calmette-Guérin (BCG) vaccine is the only TB vaccine currently available, but it is not sufficiently effective in preventing active pulmonary TB or adult infection. With the purpose of developing an improved vaccine against TB that can overcome the limitations of the current BCG vaccine, we investigated whether adjuvant formulations containing de-O-acylated lipooligosaccharide (dLOS) are capable of enhancing the immunogenicity and protective efficacy of TB subunit vaccine. The results revealed that dLOS/dimethyl dioctadecyl ammonium bromide (DDA) adjuvant formulation significantly increased both humoral and Th1-type cellular responses to TB subunit vaccine that are composed of three antigens, Ag85A, ESAT-6, and HspX. The adjuvanted TB vaccine also effectively induced Th1-type response in a BCG-primed mouse model, suggesting a potential as a booster vaccine. Finally, dLOS/DDA-adjuvanted TB vaccine showed protective efficacy against M. tuberculosis infection in vitro and in vivo. These data indicate that dLOS/DDA adjuvant enhances the Th1-type immunity and protective efficacy of TB subunit vaccine suggesting that it would be a promising adjuvant candidate for development of a booster vaccine.