Mucosal antibody response induced with a nasal virosome-based influenza vaccine

A vaccination against influenza that elicits both a systemic antibody and a mucosal IgA response would improve on the protective efficacy of currently available vaccines. Previous studies have shown the safety and efficacy of virosomes as delivery systems in vaccination. This study was a controlled, randomised, double-blind, single centre, phase II trial assessing an intranasal virosome vaccine, adjuvanted with heat-labile toxin (HLT) from enterotoxigenic Escherichia coli, versus an intranasal without HLT and comparing it open to an intramuscular vaccine in a total of 88 healthy adults. The development of a new technique enabled for the first time the detection of neutralising IgA antibodies in very dilute nasal wash samples. It was demonstrated that intranasally administered inactivated influenza vaccine, adjuvanted with HLT, not only elicits a spectrum of humoral and cell-mediated responses in healthy adults, critical for the protection and recovery from influenza virus infection, but is also highly effective in eliciting IgA neutralising antibodies at the mucosa. Intranasal virosome-formulated, HLT-adjuvanted, influenza vaccine was effective and well tolerated in this study. Its potential to offer a high level of mucosal protection, not provided by conventional parenteral vaccination, could play a significant role in preventing morbidity and mortality associated with influenza.