Different incubation temperatures affect viral polymerase activity and yields of low-pathogenic avian influenza viruses in embryonated chicken eggs

摘要

Various incubation conditions (35°C–38°C, 2d–7d) have been used in surveillance studies of the prevalence of avian influenza viruses in wild birds. Here, we studied viral polymerase activity and virus growth kinetics of low-pathogenic avian influenza viruses (LPAIVs) isolated from field samples [A/duck/Hong Kong/365/1978 (H4N6) and A/duck/Nanchang/-0480/2000 (H9N2)] during incubation at different temperatures (35°C, 37°C, and 39°C) in the allantoic cavity of 10-day-old embryonated chicken eggs (ECE). The higher incubation temperatures (37°C and 39°C) significantly promoted virus growth which is most likely as a result of greater viral polymerase activity (20%–60%) than that observed at 35°C and as much as 100% greater virus yield (as measured by hemagglutination assay) 2 days after inoculation. Our findings revealed that the optimal activity of viral polymerase complex resulting in highest yield of LPAIV field isolates could be obtained by incubation for 2 days in ECE at 37°C and 39°C.