Avian-adapted influenza virus hemagglutinins bind sialic acid receptors linked via alpha 2-3 glycosidic bonds, while human-adapted hemagglutinins bind alpha 2-6 receptors. Sequence analysis of 1918 isolates showed hemagglutinin genes with alpha 2-6 or mixed alpha 2-6/alpha 2-3 binding. To characterize the role of the sialic acid binding specificity of the 1918 hemagglutinin, we evaluated in mice chimeric selleck compound influenza viruses expressing wild-type and mutant hemagglutinin genes from avian and 1918 strains with differing receptor specificities. Viruses expressing

1918 hemagglutinin possessing either alpha 2-6, alpha 2-3, or alpha 2-3/alpha 2-6 sialic acid specificity were fatal to mice, with similar pathology and cellular tropism. Changing alpha 2-3 to alpha 2-6 binding Acalabrutinib in vitro specificity did not increase the lethality of an avian-adapted hemagglutinin. Thus, the 1918 hemagglutinin contains murine virulence determinants independent of receptor binding specificity.”
“Rift Valley fever virus (RVFV) is a member of the genus Phlebovirus within the family Bunyaviridae. It is a mosquito-borne zoonotic agent that can cause hemorrhagic fever

in humans. The enveloped RVFV virions are known to be covered by capsomers of the glycoproteins G(N) and GC, organized on a T = 12 icosahedral lattice. However, the structural units forming the RVFV capsomers have not been determined. Conflicting biochemical results for another phlebovirus (Uukuniemi virus) have indicated the existence of either GN and GC homodimers or G(N)-G(C) heterodimers in virions. Here, we have studied the structure of RVFV using electron cryo-microscopy combined with three-dimensional reconstruction and single-particle averaging. The reconstruction at 2.2-nm resolution revealed the organization of the glycoprotein shell, the lipid bilayer, AR-13324 datasheet and a layer of ribonucleoprotein (RNP). Five- and six-coordinated capsomers are formed by the same basic structural unit. Molecular-mass measurements suggest a G(N)-G(C) heterodimer as the most likely candidate for this structural unit. Both leaflets

of the lipid bilayer were discernible, and the glycoprotein transmembrane densities were seen to modulate the curvature of the lipid bilayer. RNP densities were situated directly underneath the transmembrane densities, suggesting an interaction between the glycoprotein cytoplasmic tails and the RNPs. The success of the single-particle averaging approach taken in this study suggests that it is applicable in the study of other phleboviruses, as well, enabling higher-resolution description of these medically important pathogens.”
“By using fluorescent in situ hybridization ( FISH), we visualized viral RNA of human rhinovirus type 2 (HRV2) during its entry into HeLa cells. RNA uncoating of HRV2 is entirely dependent on low endosomal pH (<= 5.6).