Preclinical evaluation of Vaxfectin^®-adjuvanted Vero cell-derived seasonal split and pandemic whole virus influenza vaccines

Abstract

Increasing the potency and supply of seasonal and pandemic influenza vaccines remains an important unmet medical need which may be effectively accomplished with adjuvanted egg- or cell culture-derived vaccines. Vaxfectin^®, a cationic lipid-based adjuvant with a favorable safety profile in phase 1 plasmid DNA vaccines trials, was tested in combination with seasonal split, trivalent and pandemic whole virus, monovalent influenza vaccines produced in Vero cell cultures. Comparison of hemagglutination inhibition (HI) antibody titers in Vaxfectin^®-adjuvanted to nonadjuvanted vaccinated mice and guinea pigs revealed 3- to 20-fold increases in antibody titers against each of the trivalent influenza virus vaccine strains and 2- to 8-fold increases in antibody titers against the monovalent H5N1 influenza virus vaccine strain. With the vaccine doses tested, comparable antibody responses were induced with formulations that were freshly prepared or refrigerated at conventional 2–8°C storage conditions for up to 6 mo. Comparison of T-cell frequencies measured by interferon-gamma ELISPOT assay between groups revealed increases of between 2- to 10-fold for each of the adjuvanted trivalent strains and up to 22-fold higher with monovalent H5N1 strain. Both trivalent and monovalent vaccines were easy to formulate with Vaxfectin^® by simple mixing. These preclinical data support further testing of Vaxfectin^®-adjuvanted Vero cell culture vaccines toward clinical studies designed to assess safety and immunogenicity of these vaccines in humans.

Keywords: :

• H5N1
• Vaxfectin^®
• Vero cell culture
• adjuvant
• cationic liposomes
• influenza vaccine

Author Disclosure and Conflict of Interest

All authors are employees of either Vical Inc. or Baxter and may own company’s stock or stock options.

Acknowledgments

The authors thank Claudia Stanislaw, Franz Ferdinand Roch and Isabella Strini for technical assistance with the immunogenicity and stability studies and Lynne “Condor 3” Goldacker for editorial assistance with this manuscript.