Influenza virus penetrates cells by fusion of viral and endosomal membranes catalyzed by the viral hemagglutinin (HA). Structures of the initial and final states of the HA trimer define the fusion endpoints, but do not specify intermediates. We have characterized these transitions by analyzing low-pH-induced fusion kinetics of individual virions and validated the analysis by computer simulation...

BACKGROUND In April 2009, a novel swine-derived influenza A virus (H1N1pdm) emerged and rapidly spread around the world, including Japan. It has been suggested that the virus can bind to both 2,3- and 2,6-linked sialic acid receptors in infected mammals, in contrast to contemporary seasonal H1N1 viruses, which have a predilection for 2,6-linked sialic acid. METHODS/RESULTS To elucidate the ex...

3) Heat stability of hemagglutinins is higher with Q virus than P virus. 4) Bovine red cell agglutinins are detectable only with Q virus but not with P virus. In this article, the fact that the activity of receptor destroying enzyme is higher with Q virus than when P virus was added as the fifth marker. In the second place, higher avidity of P virus than Q virus to immune sera was studied furth...

Influenza inflicts significant global mortality and morbidity that can be combated by effective immunization. However, the protective efficacy of current vaccines is limited by both the significant antigenic diversity of the viral hemagglutinin protein and the capacity for rapid antigenic change. This necessitates global influenza surveillance efforts, frequent vaccine reformulation and annual ...

BACKGROUND Surfactant protein D (SP-D) plays an important role in innate defense against influenza A viruses (IAVs) and other pathogens. METHODS We tested antiviral activities of recombinant human SP-D against a panel of IAV strains that vary in glycosylation sites on their hemagglutinin (HA). For these experiments a recombinant version of human SP-D of the Met11, Ala160 genotype was used aft...

Influenza A viruses (IAVs) are the most relevant and continual source of severe infectious respiratory complications in humans and different animal species, especially poultry. Therefore, an efficient vaccination that elicits protective and neutralizing antibodies against the viral hemagglutinin (HA) and neuraminidase (NA) is an important strategy to counter annual epidemics or occasional pande...

Seasonal influenza A viruses (IAV) originate from pandemic IAV and have undergone changes in antigenic structure, including addition of glycans to the viral hemagglutinin (HA). Glycans on the head of HA promote virus survival by shielding antigenic sites, but highly glycosylated seasonal IAV are inactivated by soluble lectins of the innate immune system. In 2009, human strains of pandemic H1N1 ...