Yaqing Qie

Fusion protein Ag85B-MPT64190-198-Mtb8.4 has higher immunogenicity than Ag85B with capacity to boost BCG-primed immunity against Mycobacterium tuberculosis in mice

Tuberculosis (TB) remains a major infectious disease worldwide despite chemotherapy and BCG vaccine. The efficacy of the current TB vaccine BCG varies from 0 to 80%. New vaccines that have better protection than BCG or have the capability to boost BCG-primed immunity are urgently needed. We have previously constructed a fusion protein Ag85B-MPT64(190-198)-Mtb8.4 (AMM). In this study, we investigated the immunogenicity of the fusion protein AMM in a novel adjuvant of dimethyl-dioctyldecyl ammonium bromide and BCG polysaccharide nucleic acid (DDA-BCG PSN), and its capacity to boost BCG-primed immunity. The anti-Ag85B antibodies IgG1 and IgG2a were determined using ELISA and the number of spleen cells secreting IFN-gamma was determined by ELISPOT. In addition, the ability of the subunit vaccine AMM to boost BCG-primed immunity against Mycobacterium tuberculosis was analyzed. The fusion protein AMM induced more effective humoral and cell-mediated immune responses in mice than Ag85B alone. Mice primed with BCG vaccination followed by boosting with AMM produced a stronger immune response and afforded a better protection against M. tuberculosis infection than mice immunized with BCG alone or BCG priming followed by boosting with Ag85B. These findings suggest that AMM is a promising candidate subunit vaccine to enhance the protective efficiency of BCG.

PPE protein (Rv3425) from DNA segment RD11 of Mycobacterium tuberculosis : a novel immunodominant antigen of Mycobacterium tuberculosis induces humoral and cellular immune responses in mice

Subtractive DNA hybridization of pathogenic M. bovis and BCG, and comparative genome‐wide DNA microarray analysis of M. tuberculosis H37Rv and BCG identified several RD, designated as RD1 to RD16, between M. tuberculosis and M. bovis on the one hand and BCG on the other. These regions cover 108 ORF of M. tuberculosis H37Rv, and are deleted from all 13 BCG sub‐strains currently used as anti‐tuberculosis vaccines in different parts of the world. In this study, we evaluated cellular and humoral immune response in C57BL/6 mice immunized with the PPE protein Rv3425, encoded by an ORF found in RD11 of M. tuberculosis. Rv3425 protein induced an increased Th1/Th2 type immune response in mice, characterized by an elevated concentration of IFN‐γ in antigen stimulated splenocyte culture and a strong IgG1 antibody response. These results provide evidence on the immunogenicity of the PPE protein Rv3425 which, together with its reported immunodominant characteristics, imply that it may be a candidate for development of a vaccine for the control of TB.

More Vaccine Efficacy Studies on the Recombinant Bacille Calmette-Guerin Co-expressing Ag85B, Mpt64190–198 and Mtb8.4

The immunogenicity of the recombinant Bacille Calmette‐Guerin: rBCG‐Ag85B‐Mpt64190–198‐Mtb8.4 (rBCG‐AMM) was evaluated in our previous study. This paper compares the protective efficacy of rBCG‐AMM, rBCG‐A which overexpresses Ag85B and BCG in C57BL/6 mice. There was no significant difference in proliferation characteristics among rBCG‐AMM, rBCG‐A and BCG. The growth characteristics of rBCG‐AMM in host tissue were identical to control BCG, suggesting the improved protective efficacy was directly related to the expression of the Ag85B‐Mpt64190–198‐Mtb8.4 fusion protein. The protective experiment demonstrated that rBCG‐AMM could confer similar or even better protective efficacy against Mycobacterium tuberculosis infection compared with BCG or rBCG‐A as evaluated by bacterial organ loads, lung histopathology and net weight gain or loss. The results suggested that the recombinant BCG: rBCG‐Ag85B‐Mpt64190–198‐Mtb8.4 is a potential vaccine candidate for further study.

Chimaeric protein improved immunogenicity compared with fusion protein of Ag85B and ESAT-6 antigens of Mycobacterium tuberculosis

Antigen 85B (Ag85B) and ESAT‐6 are important immunodominant antigens of Mycobacterium tuberculosis, and both are very promising vaccine candidate molecules. In this study, we relied on the T‐cell epitopes of Ag85B and ESAT‐6 to design a chimaeric protein by inserting ESAT‐6 into Ag85B from the amino acids 167–182. We found the ratio of IgG2b/IgG1 and the secretion of interferon (IFN)‐γ in the mice vaccinated with the new protein with adjuvant MPL and TDM were higher than the mice immunized with fusion protein Ag85B‐ESAT‐6, which have been reported and could induce levels of protective immunity similar to BCG in the mouse model of tuberculosis (TB) infection. These results suggest that the chimaeric protein Ag85BN‐ESAT‐6‐Ag85BC is a strong candidate for further study and the T‐cell epitopes of the antigens should be considered when we design the subunit vaccine.

Evaluation of a new Recombinant BCG which Contains Mycobacterial Antigen ag85B–mpt64190–198–mtb8.4 in C57/BL6 Mice

Tuberculosis (TB) caused by Mycobacterium tuberculosis continues to be one of the major public health problems in the world. The eventual control of this disease will require the development of a safe and effective vaccine. Bacille Calmette‐Guerin (BCG), the only vaccine against TB, is not perfect for its limited ability to protect against the adult form of TB. Some improvements of TB vaccines relied to strengthening the immunogenicity and/or persistence of genetically modified recombinant BCG (rBCG) strain. Antigen 85B (Ag85B) and Mtb8.4 are importantly immunodominant antigens of M. tuberculosis, and both are very promising vaccine candidate molecules. MPT64190–198, is presented to CD8+ T cells during mycobacterial infections. In this study, we combined these above genes into one recombinant gene of ag85B–mpt64190–198–mtb8.4. Then we constructed the new rBCG containing this united gene. This rBCG can induce an increased Th1‐type immune response in mice, characterized by an elevated level of interferon‐γ in antigen‐stimulated splenocyte culture and a strong IgG2a antibody response. Also, it can elicit longer immune responses than BCG. The results show that this rBCG is a promising candidate for further study.

Protective efficacy of a recombinant BCG secreting antigen 85B/Rv3425 fusion protein against Mycobacterium tuberculosis infection in mice.

In this study, the protective efficacy of a novel recombinant BCG strain co-expressing Ag85B and Rv3425 against Mycobacterium tuberculosis H37Rv was evaluated in mice. This rBCG::Ag85B-Rv3425 strain could provide similar or even better protective efficacy against M. tuberculosis challenge compared with BCG, as shown by no weight loss, significantly reduced lung:body weight ratios and lung bacteria load only at early time of infection. The results suggest that rBCG::Ag85B-Rv3425 could be a potential tuberculosis vaccine candidate for further study.