Molecular characteristics of the human pandemic influenza A virus (H1N1).

The outbreak of the human pandemic influenza A (H1N1) has caused a considerable public concern. The aim of this review was to improve our understanding of this novel virus by analyzing the relationships between its molecular characteristics and pathogenic properties. Results of this analysis indicate that the human pandemic influenza A (H1N1) virus is a new re-assorted virus, which combines genetic materials from the avian flu (H1N1) virus, classical swine flu (H1N1) virus, human flu (H3N2) virus, and Eurasian swine flu (H1N1) virus. Analysis of the sequences for receptor-binding and cleavage sites of hemagglutinin (HA), stalk region of neuraminidase (NA), non-structural protein 1 (NS1), polymerase basic protein 2 (PB2), and polymerase basic protein 1 (PB1) suggested that (i) the human pandemic influenza A (H1N1) virus is a low virulent and low pathogenic virus, (ii) its replication is restricted to the cells of upper respiratory tract, so it does not lead to a systemic infection, (iii) it spreads among humans only, (iv) its replication could be inhibited by oseltamivir, zanamivir, interferon (IFN), and tumor necrosis factor alpha (TNF-alpha). A potential application of amantadine might be complicated by the drug-resistant virus strains.