CFP10: mFcγ2 as a novel tuberculosis vaccine candidate increases immune response in mouse.

OBJECTIVES: Despite treatment with antibiotics and vaccination with BCG, tuberculosis (TB) is still considered as one of the most important public health problems in the world. Therefore, designing and producing a more effective vaccine against TB seems urgently. In this study, immunogenicity of a fusion protein which consisting or comprising CFP-10 from Mycobacterium tuberculosis and the Fc-domain of mouse IgG2a was evaluated as a novel subunit vaccine candidate against TB. MATERIALS AND METHODS: The genetic constructs were cloned in pPICZαA expression vector and recombinant vectors (pPICZαA-CFP-10: Fcγ2a and pPICZαA-CFP-10:His) were transformed into Pichia pastoris. To evaluate the expression of recombinant proteins, SDS-PAGE and immunoblotting were used. The immunogenicity of recombinant proteins, with and without BCG were assessed in BALB/c mice and specific cytokines against recombinant proteins (IFN-γ, IL-12, IL-4, IL-17 and TGF-ß) were evaluated. RESULTS: The levels of IFN-γ and IL-12 in mice that received recombinant proteins was higher than the control groups (BCG and PBS). Thus, both recombinant proteins (CFP-10:Fcγ2a and CFP-10:His) could excite good response in Th1-cells. The Fc-tagged protein had a stronger Th1 response with low levels of IL-4, as compared to CFP-10:His. However, the highest level of Th1 response was observed in groups that were vaccinated with BCG (prime) and then received recombinant protein CFP-10: Fcγ2a (booster). CONCLUSION: The results demonstrated that binding mice Fc-domain to CFP-10 protein can increase the immunogenicity of the subunit vaccine. Further studies, might be able to design and produce a new generation of subunit vaccines based on the Fc-fused immunogen.

APC targeting enhances immunogenicity of a novel multistage Fc-fusion tuberculosis vaccine in mice.

Numerous studies have demonstrated that targeting immunogens to FcγR on antigen-presenting cells (APCs) can selectively uptake and increase cellular immunity in vitro and in vivo. Therefore, the present study was conducted to evaluate immunogenicity of a novel multistage tuberculosis vaccine, a combination of an early and a dormant immunogenic protein, ESAT6 and HspX, fused to Fcγ2a fragment of mouse IgG2a to target all forms of tuberculosis. Codon-optimized genes consisting of ESAT6, a linker, and HspX fused either to mouse Fcγ2a (ESAT6:HspX:mFcγ2a) or 6× His-tag (ESAT6:HspX:His) were synthesized. The resulting proteins were then produced in Pichia pastoris. The fusion proteins were separately emulsified in dimethyldioctadecylammonium bromide(DDA)-trehalose-6,6-dibehenate(TDB) adjuvant, and their immunogenicity with and without bacille Calmette-Guérin (BCG) was assessed in C57BL/6 mice. Th1, Th2, Th17, and T-reg cytokine patterns were evaluated using the ELISA method. Both multistage vaccines induced very strong IL-12 and IFN-γ secretion from splenic cells; the Fc-tagged subunit vaccine induced a more effective Th1 immune response (IFN-γ, 910 pg/mL, and IL-12, 854 pg/mL) with a very low increase in IL-17 (∼0.1 pg/mL) and IL-4 (37 pg/mL) and a mild increase in TGF-ß (543 pg/mL) compared to the BCG or ESAT6:HspX:His primed and boosted groups. The production of IFN-γ to ESAT6:HspX:Fcγ2a was very consistent and showed an increasing trend for IL-12 compared to the BCG or ESAT6:HspX:His primed and boosted groups. Fcγ2a used as a delivery vehicle supported the idea of selective uptake, inducing cross-presentation and forming a proper anti-tuberculosis response in context of Th1/Th2 and Th17/T-reg balances, which is important for protection and prevention of damage.