Egg-based influenza split virus vaccine with monoglycosylation induces cross-strain protection against influenza virus infections

Significance Glycosylation is important for the proper folding and function of glycoproteins. However, glycosylation on viral surface protein may mask the conserved epitopes and causes poor host immune responses and protection against viral infection. To expose more antigenic sites shielded by glycans, we developed a strategy to remove the glycans on the viral surface by modification of the traditional egg-based influenza vaccine production procedure. By means of immunization with the monoglycosylated split virus vaccine, mice were induced with broader immune responses, and thus better protection against cross-strain H1N1 virus infections. The results showed that the monoglycosylated split virus vaccine is a broadly protective vaccine and can be produced through simple modifications of the current vaccine manufacturing process. Each year influenza virus infections cause hundreds of thousands of deaths worldwide and a significant level of morbidity with major economic burden. At the present time, vaccination with inactivated virus vaccine produced from embryonated chicken eggs is the most prevalent method to prevent the infections. However, current influenza vaccines are only effective against closely matched circulating strains and must be updated and administered yearly. Therefore, generating a vaccine that can provide broad protection is greatly needed for influenza vaccine development. We have previously shown that vaccination of the major surface glycoprotein hemagglutinin (HA) of influenza virus with a single N -acetylglucosamine at each of the N-glycosylation sites [monoglycosylated HA (HA mg )] can elicit better cross-protection compared with the fully glycosylated HA (HA fg ). In the current study, we produced monoglycosylated inactivated split H1N1 virus vaccine from chicken eggs by the N-glycosylation process inhibitor kifunensine and the endoglycosidase Endo H, and intramuscularly immunized mice to examine its efficacy. Compared with vaccination of the traditional influenza vaccine with complex glycosylations from eggs, the monoglycosylated split virus vaccine provided better cross-strain protection against a lethal dose of virus challenge in mice. The enhanced antibody responses induced by the monoglycosylated vaccine immunization include higher neutralization activity, higher hemagglutination inhibition, and more HA stem selectivity, as well as, interestingly, higher antibody-dependent cellular cytotoxicity. This study provides a simple and practical procedure to enhance the cross-strain protection of influenza vaccine by removing the outer part of glycans from the virus surface through modifications of the current egg-based process.