| H7N9 virus with some variants have infected humans in 2013through cross-species transmission. Adjuvants can enchance antigen-specific immune responses resulting in higher antibody titer, stronger and longer-lasting protection. Based on the molecular biology and immunogenicity of coccidia, we hypothesize, coccidia can be applied as an effective adjuvant. In this study, we investigated the capacity and mechanism of coccidia adjuvant in the context of H7N9 avian flu virus inactivated vaccine in mice.For establishment of a new mouse model of influenza H7N9, virus was identified and inoculated into SPF BALB/c mice. Clinical manifestation including mortality rate, body weight, and pathological changes of the visceral organs were observed. Virus distribution and replication dynamics, as well as morphological changes of blood cells were detected. The efficacy of coccidia adjuvant in influenza H7N9 vaccine was evaluated in the mouse model. SPF BALB/c mice were immunized with different doses of cocktails of H7N9 flu inactivated vaccine. Three kinds of coceidia adjuvant (Coc104, Coc106, Coc108) were chosen for comparative analysis. Comprehensive examination including clinical manifestation, virus yield, and pathological changes were determined after virus challenge in immunized mice. To reveal the mechanism of immune-enhancing effect of Coc106, which was the optimal adjuvant in this study, cytokines, including G-CSF, KC, IFN-gamma, IL-1, IL-6, MCP-1, MIG, MIP, MIP-1, RANTENS, TNF-alpha, in blood serum and injection site were monitored. Furthermore, the effect of Coc106 on macrophage phagocytosis in vitro was also surveyed.Our data showed that infection resulted in more than 30% weight loss in mice with significant clinical manifestations, and succumbed within 11 days. Viral replication in many organs, including the target tissue (i.e. lung) were detected. At 2 to 5 dpi when the virus yield reached peak, samples were taken. Vaccination experiment revealed 100 μg inactivated H7N9 influenza virus was the optimal vaccine dose. Coccidia adjuvant Coc106 combined inactivated virus vaccine showed prominent in protection of vaccinated mice against virus challenge. Two doses of aforementioned Coc106 combined inactivated virus vaccine completely inhibited replication of virus in lung.Moreover, the coccidia adjuvant Coc106 stimulated the production of chemokines and inflammatory cytokines that aggregated on the injection site and in blood serum which in turn strengthened the function of phagocyte and enhanced the efficacy of the vaccine. Coc106 functioned as an adjuvant-delivery systems.In conclusion, coccidia adjuvant Coc106 significantly enhanced the efficacy of the inactivated H7N9 influenza virus vaccine, functioning as an adjuvant-delivery systems. The results encouraging optimization of Coc 106 as an adjuvant for further study. |
