EFFECTS OF ANTIBODY TO THE INFLUENZA-A VIRUS M2 PROTEIN ON M2 SURFACEEXPRESSION AND VIRUS ASSEMBLY

We have investigated the effect of a monoclonal antibody on influenza virus release and the cell surface expression of M2, comparing virus s trains which were observed previously to be sensitive (A/Udorn) or res istant (A/WSN and A/Udorn variants) to growth inhibition by M2 antibod y 14C2. Incubation of A/Udorn virus-infected cells in the presence of the inhibitory M2 antibody resulted in a significant reduction in the yield of virus, as measured by infectivity assays as well as by the re lease of purified virions. The release of A/Udorn virus was not inhibi ted by the presence of monovalent 14C2 Fab, in contrast to IgG, indica ting that a bivalent structure is essential for 14C2 antibody-mediated viral growth restriction. The level of M2 surface expression in A/Udo rn virus-infected MDCK cells was found to he reduced to similar to 60% of control levels in cells incubated with the 14C2 antibody. In contr ast, M2 surface expression levels in A/WSN virus-infected cells were d ecreased by only similar to 5-15%, and A/WSN virus assembly appeared t o be unaffected by the M2 antibody treatment. M2 antigen associated wi th cell membranes and virus particles was redistributed into clusters after M2 antibody treatment in infected cells. Incubation in the prese nce of the 14C2 antibody also reduced M2 surface expression by similar to 40-50% in cells infected with a recombinant vaccinia virus that ex presses the M2 A/Udorn protein. These results demonstrate that M2 anti body reduces the level of influenza virus particle formation in a sing le cycle of infection and suggest that inhibition of A/Udorn virus rep lication by the 14C2 antibody is related to the reduced cell surface e xpression and redistribution of the M2 protein induced by the antibody treatment. (C) 1995 academic Press, Inc.