Modified M2 proteins produce heterotypic immunity against influenza A virus

Vaccination with the influenza A transmembrane protein M2 provides enhanced viral clearance and recovery from influenza A virus infection in mice. How ever, the high degree of hydrophobicity of the protein limits its purificat ion for vaccine purposes. We have attempted to alter the structure of the M 2 protein to allow high level recombinant expression in Escherichia coli, t o reduce its hydrophobicity and improve protein solubility, thus improving its properties as a vaccine subunit candidate. Constructs investigated incl ude deletion of the transmembrane domain of M2 (residues 26-43) and an exte nded deletion (residues 26-55). A full-length M2 protein was not pursued be cause of poor expression, even in the presence of amantadine. Expressed as glutathione S-transferase fusion proteins and used to vaccinate mice: eithe r deletion construct was found to raise M2-specific serum antibodies and en hance viral clearance in mice challenged with homologous and heterologous i nfluenza A viruses. Enzymatic cleavage from the GST fusion domain produces soluble protein giving similar results. The results demonstrate that large alterations of M2 protein structure can improve its isolation and purificat ion characteristics without detracting from its immunogenic properties. (C) 1999 Elsevier Science Ltd. All rights reserved.