Quantitative analysis of the 2009 pandemic A (H1N1) influenza virus genome at different time course of infection in virion and in Madin-Darby Canine Kidney (MDCK) cells

The 2009 pandemic A (H1N1) influenza virus was first identified in Mexico in April 2009 and spread world wide over a short period of time. Well validated diagnostic methods that are rapid and sensitive for detection and tracking of this virus are urgently needed. In this study, time course kinetic characterizations of the abundances of all ten genes of the 2009 pandemic A (H1N1) influenza virus in standard virions and infected Madin-Darby Canine Kidney (MDCK) cells were monitored. Results showed that the amounts of each gene in infected cells were significantly higher than those in virions, so that cell lysates were more recommended to be the nucleotide materials detection object than virions. Meanwhile, all genes were present in virions in approximately equimolar amounts, whereas the copy numbers of each gene in cell lysates were distinguishing. The abundances of M1 and NP genes were highest and may be the optimized choice for nucleotide detection in infected cells. Furthermore, the most sensitive time point for viral nucleotide detection in cells was 48 to 56 h post infection. In infected MDCK cells, the total RNAs amounts of NP and NS1 genes began to rise at 3 h post infection, whereas other eight genes escalated from 8 h post infection just as the situation of all genes in standard virions. All these data may be useful for more sensitive diagnosis and surveillance of the novel A (H1N1) virus, and might further limit the transmission of this pandemic disease in the future.