An H1N1 influenza A virus, A/swine/Ohio/24366/07, was isolated from pigs in an Ohio county fair. Twenty-six people who came in contact with the infected pigs developed respiratory disease and two of these people were laboratory confirmed as H1N1 by the Centers for Disease Control and Prevention (CDC). The A/swine/Ohio/24366/07 virus we isolated from swine was shown at the CDC to have 100% identical genome sequence to the human virus associated with the county fair. This prompted us to characterize three swine and two human origin H1N1 influenza A viruses isolated at different time points in the State of Ohio. The three swine viruses were shown to be triple reassortant viruses harboring genes of human (PB1), swine (HA, NA, NP, M, and NS), and avian (PB2 and PA) lineage viruses. Although viruses evaluated in this study were isolated during a short time interval (3 years), genetic drift was observed within the HA and NA genes, including changes at the receptor binding and antigenic sites of HA1 protein. Nevertheless, all viruses exhibited antigenic similarity as evaluated with hemagglutination inhibition and virus neutralizing tests. Internal genes were similar to other reassortant viruses of various subtypes currently circulating in the United States. Interestingly, two of the swine viruses including the 2007 isolate replicated well in human airway epithelial cells, however, another virus isolated in 2006 showed very little replication.
Genomic sequencing and phylogenetic characterization revealed that H1N1 viruses from swine and humans in Ohio were triple reassortants with human, swine, and avian lineage genes and showed genetic drift in HA and NA genes.
The A/swine/Ohio/24366/07 virus we isolated from swine was shown at the CDC to have 100% identical genome sequence to the human virus associated with the county fair. The three swine viruses were shown to be triple reassortant viruses harboring genes of human (PB1), swine (HA, NA, NP, M, and NS), and avian (PB2 and PA) lineage viruses. Although viruses evaluated in this study were isolated during a short time interval (3 years), genetic drift was observed within the HA and NA genes, including changes at the receptor binding and antigenic sites of HA1 protein.
Triple reassortant H1N1 swine influenza viruses exhibited genetic changes at HA receptor binding and antigenic sites and showed enhanced replication in human airway epithelial cells, consistent with molecular adaptation to human hosts.
Genetic drift was observed within the HA and NA genes, including changes at the receptor binding and antigenic sites of HA1 protein. Interestingly, two of the swine viruses including the 2007 isolate replicated well in human airway epithelial cells.
Genetic drift was observed within the HA and NA genes, including changes at the receptor binding and antigenic sites of HA1 protein.
Method
sequence analysis
Receptors
HA1 receptor binding site
Recombination Or Reassortment1 records
Recombination Or ReassortmentExtraction confidence 0.95
Key finding
Triple reassortant H1N1 influenza A viruses containing human, swine, and avian gene segments replicated efficiently in human airway epithelial cells, linking reassortment with cross-species infectivity.
The three swine viruses were shown to be triple reassortant viruses harboring genes of human (PB1), swine (HA, NA, NP, M, and NS), and avian (PB2 and PA) lineage viruses. Interestingly, two of the swine viruses including the 2007 isolate replicated well in human airway epithelial cells.
Event type
reassortment
Genes or segments
PB1; HA; NA; NP; M; NS; PB2; PA
Spillover Event1 records
Spillover EventExtraction confidence 0.95
Key finding
Two humans who had contact with infected pigs at an Ohio county fair were confirmed with H1N1 infection genetically identical to the swine virus, supporting swine-to-human transmission.
An H1N1 influenza A virus, A/swine/Ohio/24366/07, was isolated from pigs in an Ohio county fair. Twenty-six people who came in contact with the infected pigs developed respiratory disease and two of these people were laboratory confirmed as H1N1. The A/swine/Ohio/24366/07 virus we isolated from swine was shown ... to have 100% identical genome sequence to the human virus associated with the county fair.
