Th1-type immune response to aCoccidioides immitisantigen delivered by an attenuated strain of the non-invasive enteropathogenVibrio cholerae

Evaluation of the immunoprotective effects of IF-2 GTPase and SSU05-1022 as a candidate for a Streptococcus suis subunit vaccine

Aim: This study aims to develop a subunit vaccine with high cross-protection for Streptococcus suis. Materials & methods: Four-week-old female BALB/c mice were first immunized with a single and mixed protein. Various indicators, such as antibody titers and various cytokine levels, were further analyzed. Results: The results showed that purified recombinant proteins IF-2 and 1022 had a good protective effect against lethal doses of S. suis serotype 2 and S. suis serotype 9. This study showed immunization with recombinant proteins. Conclusion: IF-2 and 1022 can enhance cross-protection against S. suis serotypes 2 and 9.

Evaluation of immunogenicity and protective efficacy of recombinant outer membrane proteins of Haemophilus parasuis serovar 5 in a murine model

Glässer’s disease is an economically important infectious disease of pigs caused by Haemophilus parasuis. Few vaccines are currently available that could provide effective cross-protection against various serovars of H. parasuis. In this study, five OMPs (OppA, TolC, HxuC, LppC, and HAPS_0926) identified by bioinformatic approaches, were cloned and expressed as recombinant proteins. Antigenicity of the purified proteins was verified through Western blotting, and primary screening for protective potential was evaluated in vivo. Recombinant TolC (rTolC), rLppC, and rHAPS_0926 proteins showing marked protection of mice against H. parasuis infection, and were further evaluated individually or in combination. Mice treated with these three OMPs produced humoral and host cell-mediated responses, with a significant rise in antigen-specific IgG titer and lymphoproliferative response in contrast with the mock-immunized group. Significant increases were noted in CD4⁺, CD8⁺ T cells, and three cytokines (IL-2, IL-4, and IFN-γ) in vaccinated animals. The antisera against candidate antigens could efficiently impede bacterial survival in whole blood bactericidal assay against H. parasuis infection. The multi-protein vaccine induced more pronounced immune responses and offered better protection than individual vaccines. Our findings indicate that these three OMPs are promising antigens for the development of multi-component subunit vaccines against Glässer's disease.

Evaluation of recombinant protein superoxide dismutase of Haemophilus parasuis strain SH0165 as vaccine candidate in a mouse model

Haemophilus parasuis can cause a severe membrane inflammation disorder. It has been documented that superoxide dismutase (SOD) is a potential target to treat systemic inflammatory diseases. Therefore, we constructed an experimental H. parasuis subunit vaccine SOD and determined the protective efficacy of SOD using a lethal dose challenge against H. parasuis serovar 4 strain MD0322 and serovar 5 strain SH0165 in a mouse model. The results demonstrated that SOD could induce a strong humoral immune response in mice and provide significant immunoprotection efficacy against a lethal dose of H. parasuis serovar 4 strain MD0322 or serovar 5 strain SH0165 challenge. IgG subtype analysis indicated SOD protein could trigger a bias toward a Th1-type immune response and induce the proliferation of splenocytes and secretion of IL-2 and IFN-γ of splenocytes. In addition, serum in mice from the SOD-immunized group could inhibit the growth of strain MD0322 and strain SH0165 in the whole-blood killing bacteria assay. This is the first report that immunization of mice with SOD protein could provide protective effect against a lethal dose of H. parasuis serovar 4 and serovar 5 challenge in mice, which may provide a novel approach against heterogeneous serovar infection of H. parasuis in future.

Immunogenicity and protective efficacy of recombinant Haemophilus parasuis SH0165 putative outer membrane proteins

Haemophilus parasuis (H. parasuis), the causative agent of swine polyserositis, polyarthritis, and meningitis, is one of the most important bacterial diseases of pigs worldwide. Little vaccines currently exist that have a significant effect on infections with all pathogenic serovars of H. parasuis. H. parasuis putative outer membrane proteins (OMPs) are potentially essential components of more effective vaccines. Recently, the genomic sequence of H. parasuis serovar 5 strain SH0165 was completed in our laboratory, which allow us to target OMPs for the development of recombinant vaccines. In this study, we focused on 10 putative OMPs and all the putative OMPs were cloned, expressed and purified as HIS fusion proteins. Primary screening for immunoprotective potential was performed in mice challenged with an LD50 challenge. Out of these 10 OMPs three fusion proteins rGAPDH, rOapA, and rHPS-0675 were found to be protective in a mouse model of H. parasuis infection. We further evaluated the immune responses and protective efficacy of rGAPDH, rOapA, and rHPS-0675 in pig models. All three proteins elicited humoral antibody responses and conferred different levels of protection against challenge with a lethal dose of H. parasuis SH0165 in pig models. In addition, the antisera against the three individual proteins and the synergistic protein efficiently inhibited bacterial growth in a whole blood assay. The data demonstrated that the three proteins showed high value individually and the combination of rGAPDH, rOapA, and rHPS-0675 offered the best protection. Our results indicate that rGAPDH, rOapA, and rHPS-0675 induced protection against H. parasuis SH0165 infection, which may facilitate the development of a multi-component vaccine.

Exploiting cholera vaccines as a versatile antigen delivery platform

The development of safe, immunogenic and protective cholera vaccine candidates makes possible their use as a versatile antigen delivery platform. Foreign antigens can be delivered to the immune system with cholera vaccines by expressing heterologous antigens in live attenuated vectors, as fusion proteins with cholera toxin subunits combined with inactivated Vibrio cholerae whole cells or by exposing them on the surface of V. cholerae ghosts. Progress in our understanding of the genes expressed by V. cholerae during infection creates unprecedented opportunities to develop an improved generation of vaccine vectors to induce immune protection against a broad range of pathogenic organisms.