Innate signalling molecules as genetic adjuvants do not alter the efficacy of a DNA-based influenza A vaccine

Abstract

In respect to the heterogeneity among influenza A virus strains and the shortcomings of current vaccination programs, there is a huge interest in the development of alternative vaccines that provide a broader and more long-lasting protection. Gene-based approaches are considered as promising candidates for such flu vaccines. In our study, innate signalling molecules from the RIG-I and the NALP3 pathways were evaluated as genetic adjuvants in intramuscular DNA immunizations. Plasmids encoding a constitutive active form of RIG-I (cRIG-I), IPS-1, IL-1β, or IL-18 were co-administered with plasmids encoding the hemagglutinin and nucleoprotein derived from H1N1/Puerto Rico/8/1934 via electroporation in BALB/ c mice. Immunogenicity was analysed in detail and efficacy was demonstrated in homologous and heterologous influenza challenge experiments. Although the biological activities of the adjuvants have been confirmed by in vitro reporter assays, their single or combined inclusion in the vaccine did not result in superior vaccine efficacy. With the exception of significantly increased levels of antigen-specific IgG1 after the co-administration of IL-1β, there were only minor alterations concerning the immunogenicity. Since DNA electroporation alone induced substantial inflammation at the injection site, as demonstrated in this study using Mx2-Luc reporter mice, it might override the adjuvants´contribution to the inflammatory microenvironment and thereby minimizes the influence on the immunogenicity. Taken together, the DNA immunization was protective against subsequent challenge infections but could not be further improved by the genetic adjuvants analysed in this study.

Interleukin-1 as Innate Mediator of T Cell Immunity

“…In a follow-up study, these authors evaluated whether DNA plasmid-encoded IL-1β could act as a cellular adjuvant to improve the efficiency of a DNA vaccine with plasmids encoding the IAV antigens HA and NP. However, while intramuscular co-delivery of IL-1β slightly improved the formation of cross-reactive anti-HA antibodies, no stimulatory effect on NP- and HA-specific CD8 + T cells could be observed, suggesting that IL-1β might act as a strictly mucosal adjuvant in IAV vaccination strategies ( 265 ).…”

Genetic Co-Administration of Soluble PD-1 Ectodomains Modifies Immune Responses against Influenza A Virus Induced by DNA Vaccination

“…For genetic immunization against influenza A virus, we selected a DNA vaccine consisting of HA and NP expressing plasmids (pHA and pNP) [ 17 ]. First, we monitored the durability of in vivo expression for influenza antigens after DNA electroporation.…”

“…Influenza antigen expression was analyzed as described before [ 17 , 20 ]. Briefly, mice received 20 µg of luciferase-encoding plasmid by intramuscular electroporation.…”

“…Although application methods like gene gun and electroporation have already significantly improved DNA vaccination efficacy, genetic adjuvants might offer an additional way to increase and influence the quality and amplitude of immune responses [ 12 , 13 , 14 , 15 , 16 ]. However, the adjuvant-mediated modulation of influenza DNA vaccine responses still poses a challenging task [ 17 ].…”

Protective mucosal immunity against SARS-CoV-2 after heterologous systemic RNA-mucosal adenoviral vector immunization

“…For intramuscular immunizations, inhalative isoflurane anaesthesia was applied and the vaccines were injected in a volume of 30 µl PBS in the musculus gastrocnemius of each hind leg. In case of DNA immunizations, the injection was followed by electroporation as described previously 84 . Under general anaesthesia (100 mg/kg ketamine and 15 mg/kg xylazine), intranasal immunizations were performed by slowly pipetting a volume of 50 µl into one nostril containing the final vaccine dose.…”