Virucidal activity and viral protein modification by myeloperoxidase: a candidate for defense factor of human polymorphonuclear leukocytes against influenza virus infection.

Influenza virus (IFV) was inactivated by treatment with degranulated fluid (DF) or myeloperoxidase (MPO) from human polymorphonuclear leukocytes in the presence of H2O2. Hemagglutinin and neuraminidase activities of the virus were also reduced by DF treatment. In addition, treatment with DF or MPO in the presence of H2O2 resulted in delayed migration of viral proteins in SDS-PAGE, indicating extensively modified viral proteins. Parallel with this aberrant migration, the radioactivity of each protein band on SDS-PAGE using [35S]methionine-labeled IFV was greatly reduced. Moreover, some of the modified viral protein did not migrate. A small amount of acid-soluble degraded viral peptide was also generated. The modification of the proteins was exhibited in all major viral proteins, including the inner proteins in the envelope. These results suggest that inactivation of IFV and protein modification by DF is due to MPO present in DF.