2011 Annual Report
Work was initiated to express SIV proteins using a baculovirus expression vector. This system was adopted primarily to make virus-like particles (VLPs), which are comprised of only three viral proteins (HA, NA, M1). VLPs representing different SIV and pandemic H1N1 strains of interest will be tested as non-replicating vaccine antigens. Due to their well-defined and simple composition these constructs will be valuable in ongoing efforts to define protective and non-protective epitopes in the event of heterologous infection.
Matrix protein of the novel 2009 A/H1N1 virus was evaluated as a potential diagnostic target for differentiating pigs exposed to the pandemic virus versus contemporary swine influenza isolates. Such a diagnostic test is against one of the most highly conserved proteins of influenza virus, the matrix (M1) protein. Although the M1 protein is not a structural protein, antibodies to M1 are produced during an influenza infection. We identified antigenic sites unique in the novel 2009 A/H1N1 virus matrix (M1) protein based on virus sequences. Three putative antigenic sites with maximum amino acid dissimilarity to non-pandemic swine H1N1 strains were selected for analysis in an immunoassay designed to differentiate exposure to the pandemic H1N1 strains from previously circulating swine influenza strains. Cross-reactivity at varying levels was found with antisera against several contemporary swine influenza strains containing the traditional North American matrix gene found in nearly all strains of swine influenza widely circulating in North American prior to the emergence of the 2009 A/H1N1 pandemic virus. These data indicate such a diagnostic approach is not possible and will be fraught with varying degrees of cross-reactivity and loss of specificity as the virus of interest undergoes antigenic drift.
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