Characterization of the virions of mopyridone-sensitive wild strain and mopyridone-resistant mutant of influenza virus A(H3N2).

Some differences were established between mopyridone-sensitive (MCU-s) wild strain and mopyridone-resistant (MCU-r) mutant progenies of influenza virus A/Hong Kong/1/68 (H3N2). The virions of MCU-r mutant had a lower buoyant density in linear sucrose gradient as compared to those of MCU-s strain, and an increased ability of aggregation as well. HA content (HAU/micrograms protein) in the purified virions of MCU-r mutant was twice lower as compared to MCU-s strain. The surface glycoproteins of MCU-r mutant were solubilized by octylglucoside faster than those of MCU-s strain. No differences were found between MCU-r strain and MCU-s mutant-induced red blood cell lysis at acid pH, and mopyridone did not influence this phenomenon. MCU-r mutant showed a lower thermostability as compared with MCU-s strain, but similar UV-inactivation curves for both viruses were observed. The quantity of the purified HA-NA complex and M1 protein incorporated into multilamellar liposomes was greater in the case of MCU-s mutant. Electron microscopy examination of liposomes which contained M1 protein from MCU-r mutant manifested pleomorphism with unusual gigantic forms tending to aggregate, whereas MCU-s M1 protein-containing liposomes were uniform and did not form aggregates. No morphological differences were found between the two viruses in HA-NA complex containing liposomes. These data indicate changes in the protein-lipid interactions in MCU-r mutant virions. Amino acid analysis of M1 protein revealed significantly lower content of asparagine, glutamine and serine, and a higher one oof hisitidine in MCU-r mutant as compared to MCU-s wild strain.