Due to constant antigenic drift and shift, current
influenza-A
vaccines need to be redesigned and administered annually. A
universal flu vaccine (UFV) that provides long-lasting protection against both seasonal and emerging pandemic
influenza strains is thus urgently needed. The
hemagglutinin (HA) stem
antigen is a promising target for such a
vaccine as it contains neutralizing
epitopes, known to induce cross-protective
IgG responses against a wide variety of
influenza subtypes. In this study, we describe the development of a UFV candidate consisting of a HAstem trimer displayed on the surface of rigid capsid-like particles (CLP). Compared to soluble unconjugated HAstem trimer, the CLP-HAstem particles induced a more potent, long-lasting immune response and were able to protect mice against both homologous and heterologous H1N1
influenza challenge, even after a single dose.