PPD in HBsAg vaccine formulation suppressed IFN-γ and IL-۴ cytokine responses and induced long-lived humoral immune responses: Results from ۲۲۰-day monitoring of specific IgG responses

Objective(s): HBsAg vaccine is unable to induce Th۱ immune responses. Here, immune responses and long-lived IgG responses of HBsAg-Alum, HBsAg-MF۵۹, as well as HBsAg-MF۵۹ were compared when formulated with PPD. Materials and Methods: BALB/c mice were injected with the vaccines subcutaneously three times with a two-week interval. Then, specific IgG, long-lived IgG responses up to ۲۲۰ days, and also IgG۱ and IgG۲a isotypes were assessed using ELISA. Furthermore, IFN-γ and IL-۴ were assessed on spleen cell culture supernatant by ELISA. Results: IFN-γ cytokine response between MF۵۹- and Alum-adjuvanted vaccines did not show a significant difference. HBsAg-Alum vaccine revealed an increase in IL-۴ cytokine, as compared with those immunized with HBsAg-MF۵۹ at borderline (P=۰.۰۵۵۳). In addition, HBsAg-MF۵۹+PPD ۱۰ µg showed a significant decrease in IL-۴ and IFN-γ cytokines, as compared with HBsAg-MF۵۹. Furthermore, the HBsAg-MF۵۹+PPD۱۰ µg group showed a significant increase in the IL-۲/IL-۴ ratio, as compared with HBsAg-MF۵۹ (P=۰.۰۳۳۹). Specific IgG antibody showed a significant increase in HBsAg-MF۵۹, as compared with HBsAg-Alum. Furthermore, HBsAg-MF۵۹ plus PPD showed a significant increase in IgG responses, as compared with HBsAg-MF۵۹ and HBsAg-Alum groups. Long-lived IgG responses up to ۲۲۰ days after the final shot showed a significant increase in HBsAgMF۵۹ versus HBsAg-Alum group and PPD in the HBsAg-MF۵۹ vaccine formulation, resulting in a significant increase in IgG responses versus HBsAg-MF۵۹ group. In addition, PPD in the HBsAg-MF۵۹ vaccine formulation suppressed IgG۱ response versus HBsAg-Alum. However, HBsAg-MF۵۹ showed a significant increase in IgG۲α versus the HBsAg-Alum group (P=۰.۰۱۹۰). Immunization with HBsAg-MF۵۹+PPD (۱۰ µg) showed a significant increase versus the HBsAg-MF۵۹ group (P=۰.۰۰۴۰). Results from the IgG۲a/IgG۱ ratio in HBsAg-MF۵۹+PPD۱µg and HBsAg-MF۵۹+PPD۱۰ µg groups showed a significant increase as compared with HBsAg-MF۵۹ groups (P<۰.۰۳۴۵). Conclusion: PPD in the HBsAg vaccine formulation suppressed IL-۴ and IFN-γ responses, but increased the IL-۲/IL-۴ ratio, IgG۲a, and IgG۲a/IgG۱ responses, which may show Th۱ polarization. Furthermore, PPD leads to more potent long-lived IgG responses in the HBsAg vaccine, highlighting its potential as a component of a complex adjuvant.

Keywords:

Adjuvant , HBs antigen , Long-lived IgG response , MF۵۹ , PPD