Subunit vaccine candidate AMM down-regulated the regulatory T cells and enhanced the protective immunity of BCG on a suitable schedule.

Mycobacterium bovis bacillus Calmette-Guérin (BCG) priming and subunit vaccine boosting strategies are urgently needed to improve the protective efficacy of BCG in adult population. However, the schedule of subunit vaccine boosting is not well investigated, especially the optimal immune responses and vaccine immunization schedules are still not clear. We have constructed a novel subunit vaccine candidate consisting of fusion protein Ag85B-Mpt64 (190-198)-Mtb8.4 (AMM) in a complex adjuvant composed of dimo-thylidioctyl ammonium bromide (DDA) and BCG polysaccharide nucleic acid (BCG-PSN). In this study, we compared the effect of different boosting schedules of the subunit vaccine in the prime-boost strategies. C57BL/6 mice were primed with BCG first and then boosted with the AMM vaccine once at 10th week, twice at 8th, 10th week, or thrice at 6th, 8th, 10th week, respectively. The immune responses were evaluated at the 14th and 20th weeks, respectively. Twelve weeks after the last immunization, the mice were challenged with virulent Mycobacterium tuberculosis strain H37Rv, and the protective effect was evaluated. The results showed that BCG priming and the AMM vaccine boosting twice induced the strongest antigen-specific IFN-γ and IL-2 production, down-regulated CD4+ CD25+ FoxP3+ regulatory T cells (Tregs) and had the best protective effect among all groups, while boosting thrice induced the strongest IL-4 production and did not improve BCG-primed protection significantly. Boosting BCG with the AMM vaccine twice instead of once or thrice induced strong Th1-type immunity and down-regulated Tregs significantly, which correlated with the best protection against M. tuberculosis infection in mice.

Luo Y ，Jiang W ，Da Z ，Wang B ，Hu L ，Zhang Y ，An R ，Yu H ，Sun H ，Tang K ，Tang Z ，Wang Y ，Jing T ，Zhu B ... -  《-》

Immunogenicity and protective efficacy of a fusion protein vaccine consisting of antigen Ag85B and HspX against Mycobacterium tuberculosis infection in mice.

Subunit vaccines have the potential advantage to boost Mycobacterium bovis Bacillus Calmette-Guérin (BCG)-primed immunity in adults. However, most candidates are antigens highly expressed in replicating bacilli but not in dormant or persisting bacilli, which exist during Mycobacterium tuberculosis infection. We constructed M. tuberculosis fusion protein Ag85B-Mpt64(190-198) -HspX (AMH) and Ag85B-Mpt64(190-198) -Mtb8.4 (AMM), which consist of Ag85B, the 190-198 peptide of Mpt64, HspX (Rv2031c) and Mtb8.4 (Rv1174c), respectively. AMH and/or AMM were mixed with adjuvants composed of dimethyl-dioctyldecyl ammonium bromide and BCG polysaccharide nucleic acid (DDA-BCG PSN) to construct subunit vaccines. Mice were immunized thrice with Ag85B, AMH and AMM vaccines and the immunogenicity of the fusion protein vaccines was determined. Then, mice were primed with BCG and boosted twice with Ag85B, AMH, AMM and AMM + AMH vaccines, respectively, followed by challenging with M. tuberculosis virulent strain H37Rv, and the immune responses and protective effects were measured. It was found that mice immunized with AMH vaccine generated high levels of antigen-specific cell-mediated responses. Compared with the group injected only with BCG, the mice boosted with AMM, AMH and AMM + AMH produced higher levels of Ag85B-specific IgG1 and IgG2a and IFN-γ-secreting T cells upon Ag85B and Mycobacterium tuberculosis purified protein derivative (PPD) stimulation. It is interesting that only mice boosted with AMM + AMH had significantly lower bacterial count in the lungs than those receiving BCG, whereas mice boosted with AMH or AMM did not. The results suggest that AMH consisting of HspX, the antigen highly expressed in dormant bacilli, could be combined with antigens from replicating bacilli to enhance BCG primed immunity so as to provide better protection against both growing and non-growing bacteria that occur during the infection process.

Li Q ，Yu H ，Zhang Y ，Wang B ，Jiang W ，Da Z ，Xian Q ，Wang Y ，Liu X ，Zhu B ... -  《-》

Fusion protein Ag85B-MPT64(190-198)-Mtb8.4 has higher immunogenicity than Ag85B with capacity to boost BCG-primed immunity against Mycobacterium tuberculosis in mice.

Luo Y ，Wang B ，Hu L ，Yu H ，Da Z ，Jiang W ，Song N ，Qie Y ，Wang H ，Tang Z ，Xian Q ，Zhang Y ，Zhu B ... -  《-》

[Dimo-thylidioctyl ammonium bromide-BCG polysaccharide nucleic acid adjuvant enhanced the immunogenicity of a Mycobacterium tuberculosis subunit vaccine].

Song NN ，Wang BX ，Shi DZ ，Fu LF ，Luo Y ，Yu HJ ，Han SB ，Jiao L ，Qie YQ ，Wang HH ，Zhang Y ，Zhu BD ... -  《-》

Protection against Mycobacterium tuberculosis challenge in mice by DNA vaccine Ag85A-ESAT-6-IL-21 priming and BCG boosting.

Tuberculosis (TB) is one of most important chronic infectious diseases caused by Mycobacterium tuberculosis and remains a major global health problem. In the study, we developed the DNA vaccine encoding fusion protein of antigen 85 A and 6 kDa early secretory antigen target of M. tuberculosis as well as the cytokine IL-21 to investigate its immune protective efficacy against M. tuberculosis challenge in mice after the DNA vaccine priming and Bacille Calmette-Guérin (BCG) boosting. Compared with the different control groups, the intranasal DNA vaccine priming twice and BCG boosting once markedly increased the cytotoxicities of natural killer cells and splenocytes and enhanced the interferon-γ level in the splenocyte supernatant as well as sIgA level in bronchoalveolar lavage in the vaccinated mice. Importantly, this heterologous prime-boost strategy significantly decreased the bacterial load in the mouse lungs in contrast to that of intranasal or subcutaneous BCG immunization alone. These findings provide further approaches for mucosal-targeted prime-boost vaccination to fight against TB.

Dou J ，Wang Y ，Yu F ，Yang H ，Wang J ，He X ，Xu W ，Chen J ，Hu K ... -  《-》