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As a result of human-to-pig transmission, pandemic influenza A (H1N1) 2009 virus was detected in pigs soon after it emerged in humans. In the United States, this transmission was quickly followed by multiple reassortment between the pandemic virus and endemic swine viruses. Nine reassortant viruses representing 7 genotypes were detected in commercial pig farms in the United States. Field observations suggested that the newly described reassortant viruses did not differ substantially from pandemic (H1N1) 2009 or endemic strains in their ability to cause disease. Comparable growth properties of reassortant and endemic viruses in vitro supported these observations; similarly, a representative reassortant virus replicated in ferrets to the same extent as did pandemic (H1N1) 2009 and endemic swine virus. These novel reassortant viruses highlight the increasing complexity of influenza viruses within pig populations and the frequency at which viral diversification occurs in this ecologically important viral reservoir. [ABSTRACT FROM AUTHOR]

The emergence of pandemic (H1N1) 2009 virus highlighted the need for enhanced surveillance of swine influenza viruses. We used real-time reverse-transcription PCR-based genotyping and found that this rapid and simple genotyping method may identify reassortants derived from viruses of Eurasian avian-like, triple reassortant-like, and pandemic (H1N1) 2009 virus lineages. [ABSTRACT FROM AUTHOR]

Plasmid DNA (pDNA) vaccines represent an alternative to conventional inactivated influenza vaccines that are likely to experience supply constraints during a pandemic. Several Vaxfectin-formulated pDNA vaccines were tested in mice and ferrets for efficacy against a lethal challenge with the highly pathogenic A/Vietnam/1203/04 (H5N1) influenza virus strain; the vaccines encoded influenza A virus hemagglutinin (HA), and/or nucleoprotein (NP), and M2 protein. Complete protection from death and disease was achieved in mice and ferrets with 2 doses of a Vaxfectin-formulated vaccine containing H5 HA, NP, and M2 plasmids and in ferrets with only 1 dose. A Vaxfectin-formulated vaccine containing NP and M2 pDNA provided significant protection against death in mice and provided some benefit in ferrets (i.e., 17% survival, delayed time to illness and death, and significant reduction in viral load compared with that in negative control animals). These experiments support the clinical testing of pDNA vaccine candidates that may ultimately increase global vaccine supply options during pandemics. Copyright © 2008 Infectious Diseases Society of America [ABSTRACT FROM AUTHOR]

Background. Multiple cases of transmission of avian H5N1 influenza viruses to humans illustrate the urgent need for an efficacious, cross-protective vaccine. Methods. Ferrets were immunized with inactivated whole-virus vaccine produced by reverse genetics with the hemagglutinin (HA) and neuraminidase genes of A/HK/213/03 virus. Ferrets received a single dose of vaccine (7 or 15 microg of HA) with aluminum hydroxide adjuvant or 2 doses (7 microg of HA each) without adjuvant and were challenged with 10(6) 50% egg infectious doses of A/HK/213/03, A/HK/156/97, or A/Vietnam/1203/04 virus. Results. One or 2 doses of vaccine induced a protective antibody response to the vaccine strain. All immunization regimens completely protected ferrets from challenge with homologous wild-type A/HK/213/03 virus: no clinical signs of infection were observed, virus replication was significantly reduced (P<.05) and was restricted to the upper respiratory tract, and spread of virus to the brain was prevented. Importantly, all vaccinated ferrets were protected against lethal challenge with the highly pathogenic strain A/Vietnam/1203/04. The 2-dose schedule induced higher levels of antibodies that were cross-reactive to antigenically distinct H5N1 viruses. Conclusions. H5N1 vaccines may stimulate an immune response that is more cross-protective than what might be predicted by in vitro assays and, thus, hold potential for being stockpiled as 'initial' pandemic vaccines. Copyright © 2006 Infectious Diseases Society of America [ABSTRACT FROM AUTHOR]

Co-infection with seasonal influenza A (H1N1) and pandemic (H1N1) 2009 could result in reassortant viruses that may acquire new characteristics of transmission, virulence, and oseltamivir susceptibility. Results from oseltamivir-sensitivity testing on viral culture suggested the possibility of co-infections with oseltamivir-resistant (seasonal A [H1N1]) and -susceptible (pandemic [H1N1] 2009) viruses. [ABSTRACT FROM AUTHOR]