| Pigs are considered important in interspecies transmission of influenza A viruses as their respiratory tracts contain receptors used by both avian and mammalian-tropic viruses. Residue 627 of the viral polymerase basic protein 2 (PB2) is thought to determine temperature sensitivity in certain mammalian systems, but its role has yet to be investigated in a swine system. Ten influenza viruses from avian, human and swine hosts were evaluated for their ability to grow at 33°C, 37°C and 41°C in an immortalized swine alveolar macrophage cell line. Of TNF-alpha, IL-1, and IFN-alpha, only TNF-alpha was induced following 48 hours of infection, in response to only certain viruses. Temperature-dependent growth of each virus was not consistently correlated to species of isolation, and PB2 residue 627 did not dictate temperature preference. These results suggest that, in a swine system, factors allowing for efficient replication at various temperatures are likely polygenic, possibly of viral and host origin. |
