Mutations in influenza virus replication and transcription: detection of amino acid substitutions in hemagglutinin of an avian influenza virus (H1N1).

Influenza A viruses are RNA viruses that contain negative-sense, single-stranded, and segmented RNA genome, which depends on virally encoded RNA-dependent RNA polymerase and cellular DNA-dependent RNA polymerase for replication of viral genome and transcription of viral mRNA, respectively. Hemagglutinin (HA), one of the major surface proteins of the influenza virus, is responsible for virus attachment to the receptor of host cells to initiate an infection. Amino acid (AA) substitutions in HA may cause changes in virus antigenicity and even receptor specificity. To detect the AA substitutions within HA at protein level, nanoelectrospray-MS/MS was used to analyze tryptic digestion of HA antigen directly purified from virus particles of an avian influenza virus, A/WDK/JX/12416/2005 (H1N1), of which the HA gene was sequenced as a reference. The comparison of the sequences obtained from analysis of viral genome and peptide found seven variations between HA gene and protein, namely E103K, R130K, T169I, I338V, N...