Protective effects of Haemophilus parasuis serotype 4, 13 and 14 TbpA on cross-immunity in guinea pigs

Abstract:

[Background] Haemophilus parasuis (HPS) is the pathogen of Gl?sser?s disease. Currently in the prevention and control of the disease, due to antibiotic resistance and the lack of cross-immunity protection of inactivated vaccines, new methods are urgently needed to solve this problem. [Objective] The aim of this study was to explore the cross-immunoprotective properties of different serotype HPS transferrin-binding protein A (TbpA) in guinea pigs for further research in piglets. [Methods] Recombinant TbpA of HPS serotypes 4, 13 and 14 were immunized at 0.1 mg with 20-day interval and then detected the serum antibody (IgG) and cytokines (IL-2, IL-5, IL-8, IFN-γ, MCP-1 and TNF-α) by ELISA. HPS-BZ, HPS-LJ3 and HPS-SZ strains were dosed at 5 LD50 by intraperitoneal injection. Then, the pathological changes and immune protection rate were examined. [Results] Recombinant TbpA of HPS serotypes 4, 13 and 14 could induce high levels of antibody (IgG) and cytokines, and provide cross-immunity protection to guinea pigs. Among them, the HPS serotype 13 TbpA immunization group had the highest cross-immunity protection rate, both serotype 4 and 14 HPS were 50.0%, and the highest immune protection rate against the same serotype HPS was 83.3%. The pathological examination showed that compared with HPS serotype 4 and 14 TbpA immunization group, the difference between the pathological changes of HPS serotype 13 TbpA immunization group and the challenge control group was more significant. [Conclusion] Recombinant TbpA of HPS serotypes 4, 13 and 14 can induce the humoral and cellular immune responses in guinea pigs, among which HPS serotype 13 TbpA has the strongest cross-immunity protection and can be used as a new vaccine candidate antigen.

Key words:Haemophilus parasuis, Serotype, Transferring-binding protein A, Guinea pigs, Cross-immunity protection