The variation of highly pathogenic avian influenza H5N1 virus results in gradually increased virulence in poultry, and human cases continue to accumulate. The neuraminidase (NA) stalk region of influenza virus varies considerably and may associate with its virulence. The NA stalk region of all N1 subtype influenza A viruses can be divided into six different stalk-motifs, H5N1/2004-like (NA-wt), WSN-like, H5N1/97-like, PR/8-like, H7N1/99-like and H5N1/96-like. The NA-wt is a special NA stalk-motif which was first observed in H5N1 influenza virus in 2000, with a 20-amino acid deletion in the 49th to 68th positions of the stalk region. Here we show that there is a gradual increase of the special NA stalk-motif in H5N1 isolates from 2000 to 2007, and notably, the special stalk-motif is observed in all 173 H5N1 human isolates from 2004 to 2007. The recombinant H5N1 virus with the special stalk-motif possesses the highest virulence and pathogenicity in chicken and mice, while the recombinant viruses with the other stalk-motifs display attenuated phenotype. This indicates that the special stalk-motif has contributed to the high virulence and pathogenicity of H5N1 isolates since 2000. The gradually increasing emergence of the special NA stalk-motif in H5N1 isolates, especially in human isolates, deserves attention by all.

During 2004-2006 swine influenza virus surveillance, two strains of H3N8 influenza viruses were isolated from pigs in central China. Sequence and phylogenetic analyses of eight gene segments revealed that the two swine isolates were of equine origin and most closely related to European equine H3N8 influenza viruses from the early 1990s. Comparison of hemagglutinin (HA) amino acid sequences showed several important substitutions. One substitution caused the loss of a potential glycosylation site, and two substitutions, located at the cleavage site and adjacent to the receptor-binding pocket, respectively, had been reported previously in canine H3 HAs. This expansion of host range of equine H3N8 influenza viruses with mutations in the HA protein might raise the possibility of transmission of these viruses to humans.

SUMMARY For successful infection, bacteriophages must overcome multiple barriers to transport the genome and proteins across the bacterial cell envelope. We use cryo-electron tomography to study infection initiation of phage P22 in Salmonella enterica sv. Typhimurium, revealing how a channel forms to allow genome translocation into the cytoplasm. Our results show free phages initially attaching obliquely to the cell through interactions between the O antigen and two of the six tailspikes; the tail needle also abuts the cell surface. The virion then orients to the perpendicular and the needle penetrates the outer membrane. The needle is released and the internal head protein gp7* is ejected and assembles into an extra-cellular channel extending from the gp10 baseplate to the cell surface. A second protein, gp20, is ejected and assembles into a structure that extends the extra-cellular channel across the outer membrane into the periplasm. Insertion of the third ejected protein gp16 into the cytoplasmic membrane likely completes the overall trans-envelope channel into the cytoplasm. Construction of a trans-envelope channel is an essential step during infection by all short-tailed phages of Gram-negative bacteria because such virions cannot directly deliver their genome into the cell cytoplasm.

Bacteriophage SP6 exhibits dual-host adsorption specificity. The SP6 tailspikes are recognized as important in host range determination but the mechanisms underlying dual host specificity are unknown. Cryo-electron tomography and sub-tomogram classification were used to analyze the SP6 virion with a particular focus on the interaction of tailspikes with host membranes. The SP6 tail is surrounded by six V-shaped structures that interconnect in forming a hand-over-hand hexameric garland. Each V-shaped structure consists of two trimeric tailspike proteins: gp46 and gp47, connected through the adaptor protein gp37. SP6 infection of Salmonella enterica serovars Typhimurium and Newport results in distinguishable changes in tailspike orientation, providing the first direct demonstration how tailspikes can confer dual host adsorption specificity. SP6 also infects S. Typhimurium strains lacking O antigen; in these infections tailspikes have no apparent specific role and the phage tail must therefore interact with a distinct receptor to allow infection.

Cyclophilin A (CypA) is a key member of immunophilins that has peptidyl-prolyl cis/trans isomerase (PPIase) activity. Besides acting as a cellular receptor for immunosuppressive drug cyclosporine A (CsA), CypA is involved in various cellular activities. CypA has an important role in viral infection which either facilitates or inhibits their replication. Inhibition of CypA via inhibitors is useful for overcoming several viral infections, indicating that CypA is an attractive target for anti-viral therapy. Collectively, these facts demonstrate the critical roles of CypA in mediating or inhibiting viral infections, suggesting that CypA can be an attractive cellular target for the development of anti-viral therapy.

To study the effect of NS1 eIF4GI binding domain on virulence and pathogenicity of H5N1 influenza A virus, 5 recombinant H5N1 viruses encoding eIF4GI binding domain-truncated NS1 proteins and parental NS1 (NS1‐wt) were generated by an 8‐plasmid-based reverse genetics system. The results indicated that the recombinants with the addition of 5‐amino acid and the deletion position of 85-89 in NS1‐wt were attenuated in replication in vitro and in vivo, compared with the recombinant wild‐type virus rNS1‐wt, whereas the deletion position 85-94 or the entire eIF4GI binding domain in NS1‐wt displayed a significantly attenuated phenotype in chicken and mice. We also showed that the eIF4GI binding domain-truncated mutants were impaired in their ability to inhibit interferon production in vitro, and they did not replicate as efficiently as the parental recombinant strain in embryonated hen eggs, in Madin ‐Darby Canine Kidney cells, or in vivo in chickens and in a mouse model. Therefore, these attenuated NS1‐truncated viruses may have a great potential as live attenuated vaccine candidates against H5N1 influenza A virus.

A certain H5N1 avian influenza virus has gained the ability to cause the classic central nervous system dysfunction in poultry and migratory birds. This study presents the proteomics analysis on the change of proteins to H5N1 avian influenza virus with neurovirulence infection in chicken brain tissue. By using 2-DE, coupled with MALDI-TOF MS/MS, we identified a set of differentially expressed cellular proteins, including 18 up-regulated proteins and 13 down-regulated proteins. The most significant changes were found in cytoskeleton proteins, proteins associated with the ubiquitin-proteasome pathway, and neural signal transduction proteins. Some identified proteins such as CRMP and SEP5 were found to participate in the pathogenesis progress of Parkinson's and Huntington's diseases, which also developed encephalitis accompanied with CNS dysfunction. The obtained data can provide insight into the virus-chicken brain tissue interaction and reveal the potential mechanism of the neuropathogenesis when the host was infected by the neurovirulent avian influenza virus.

The wild‐rice‐derived dominant gene Xa21 conferring multi‐race resistance to bacterial blight and a fused Bt gene cry1Ab/cry1Ac conferring resistance to lepidopteran insects were individually introduced into the same genetic background of an elite indica cytoplasm male sterile (CMS) restorer line ‘Minghui 63′. The line showed the desirable insect‐ and disease‐resistant phenotypes. To maximize the effect, the two genes were also pyramided into the same recipient plant of ‘Minghui 63’ by marker‐assisted selection. After being subjected to natural infestation of leaf‐folders and yellow stem borers and inoculation of Xoo strain mixtures, the pyramiding line and its derived hybrids showed high levels of resistance against both insect damage and disease. Furthermore, data from field trials demonstrated that the hybrids made by crossing this pyramiding line with the CMS lines ‘Zhenshan 97A’ and ‘Maxie A’ retained a similar level of yield under conditions without chemical spray, indicating that the pyramiding genes have a yield‐stabilizing effect on the recipient line and its hybrids.