Influenza virus A/H1N1, which is currently causing a pandemic, contains gene segments with ancestors in the North American and Eurasian swine lineages. To get insights into virus replication dynamics, clinical symptoms and virus transmission in pigs, we infected animals intranasally with influenza virus A/Regensburg/D6/09/H1N1. Virus excretion in the inoculated pigs was detected in nasal swabs from 1 day post-infection (p.i.) onwards and the pigs developed generally mild symptoms, including fever, sneezing, nasal discharge and diarrhoea. Contact pigs became infected, shed virus and developed clinical symptoms similar to those in the inoculated animals. Plasma samples of all animals remained negative for virus RNA. Nucleoprotein- and haemagglutinin H1-specific antibodies could be detected by ELISA 7 days p.i. CD4(+) T cells became activated immediately after infection and both CD4(+) and CD8(+) T-cell populations expanded from 3 to 7 days p.i., coinciding with clinical signs. Contact chickens remained uninfected, as judged by the absence of virus excretion, clinical signs and seroconversion.
Keywords Pubmed:
Animals Antibodies, Viral/blood CD4-Positive T-Lymphocytes/immunology CD4-Positive T-Lymphocytes/virology Disease Models, Animal Humans Influenza A Virus, H1N1 Subtype/genetics Influenza A Virus, H1N1 Subtype/pathogenicity* Influenza A Virus, H1N1 Subtype/physiology Influenza, Human/immunology Influenza, Human/pathology Influenza, Human/transmission* Influenza, Human/virology Molecular Sequence Data Swine