Abdominal and Pelvic Organ Failure Induced by Intraperitoneal Influenza A Virus Infection in Mice

Comparison of vaccination efficacy using live or ultraviolet-inactivated influenza viruses introduced by different routes in a mouse model

Influenza is a major cause of highly contagious respiratory illness resulting in high mortality and morbidity worldwide. Annual vaccination is an effective way to prevent infection and complication from constantly mutating influenza strains. Vaccination utilizes preemptive inoculation with live virus, live attenuated virus, inactivated virus, or virus segments for optimal immune activation. The route of administration also affects the efficacy of the vaccination. Here, we evaluated the effects of inoculation with ultraviolet (UV)-inactivated or live influenza A virus strains and compared their effectiveness and cross protection when intraperitoneal and intramuscular routes of administration were used in mice. Intramuscular or intraperitoneal inoculation with UV-inactivated Influenza A/WSN/1933 provided some protection against intranasal challenge with a lethal dose of live Influenza A/WSN/1933 but only when a high dose of the virus was used in the inoculation. By contrast, inoculation with a low dose of live virus via either route provided complete protection against the same intranasal challenge. Intraperitoneal inoculation with live or UV-inactivated Influenza A/Philippines/2/1982 and intramuscular inoculation with UV-inactivated Influenza A/Philippines/2/1982 failed to produce cross-reactive antibodies against Influenza A/WSN/1933. Intramuscular inoculation with live Influenza A/Philippines/2/1982 induced small amounts of cross-reactive antibodies but could not suppress the cytokine storm produced upon intranasal challenge with Influenza A/WSN/1993. None of the tested inoculation conditions provided observable cross protection against intranasal challenge with a different influenza strain. Taken together, vaccination efficacy was affected by the state and dose of the vaccine virus and the route of administration. These results provide practical data for the development of effective vaccines against influenza virus.

Deimmunization of flagellin for repeated administration as a vaccine adjuvant

Flagellin, a protein-based Toll-like receptor agonist, is a versatile adjuvant applicable to wide spectrum of vaccines and immunotherapies. Given reiterated treatments of immunogenic biopharmaceuticals should lead to antibody responses precluding repeated administration, the development of flagellin not inducing specific antibodies would greatly expand the chances of clinical applications. Here we computationally identified immunogenic regions in Vibrio vulnificus flagellin B and deimmunized by simply removing a B cell epitope region. The recombinant deimmunized FlaB (dFlaB) maintains stable TLR5-stimulating activity. Multiple immunization of dFlaB does not induce FlaB-specific B cell responses in mice. Intranasally co-administered dFlaB with influenza vaccine enhanced strong Ag-specific immune responses in both systemic and mucosal compartments devoid of FlaB-specific Ab production. Notably, dFlaB showed better protective immune responses against lethal viral challenge compared with wild type FlaB. The deimmunizing B cell epitope deletion did not compromise stability and adjuvanticity, while suppressing unwanted antibody responses that may negatively affected vaccine antigen-directed immune responses in repeated vaccinations. We explain the underlying mechanism of deimmunization by employing molecular dynamics analysis.

CD83 expression regulates antibody production in response to influenza A virus infection

BACKGROUND

CD83 is known to regulate lymphocyte maturation, activation, homeostasis, and antibody response to immunization and infection. While CD83 has a major part in B cell function, its role in influenza A virus infection has not yet been investigated.

METHODS

We investigated the role of CD83 using C57BL/6J wild type mice and CD83 knockout (KO) mice after intraperitoneal administration of the influenza A/WSN/1933 virus. We analyzed cells of the peritoneal cavity, splenocytes, and cells of the bone marrow with FACS to investigate CD83 expression and cell population change in response to the virus infection. ELISA was performed with sera and peritoneal cavity fluids to detect A/WSN/1933 virus-specific IgG and the subclasses of IgG.

RESULTS

FACS analysis data showed a transient but distinct induction of CD83 expression in the peritoneal B cells of wild type mice. CD83 KO mice exhibited a delayed recovery of B cells in the bone marrow after influenza virus infection and overall, a smaller T cell population compared to wild type mice. The peritoneal cavity and serum of the wild type mice contained a high titer of IgG within 14 days after infection, whereas the CD83 KO mice had a very low titer of IgG.

CONCLUSIONS

These results show the importance of CD83 in lymphocytes homeostasis and antibody production during influenza A virus infection.