The Correlation of IFN <i>γ</i> to the Preferential Isolation of Influenza Type B over Type A Viruses in Madin Darby Canine Kidney Cells

The isolation of influenza viruses in Madin Darby Canine Kidney (MDCK)cells has shown preferential isolation of a great percentage of Influenza Bstrains at the first passage than Influenza A strains. During in vitro isolation of Influenza viruses,majority of type A viruses are not confirmed as positive isolates by Hemagglutination(HA) assay despite having higher virulence and pathogenicity versus influenza Bviruses. This study investigated the differences in IFN-γ and IL-10 cytokines secreted by MDCK cells upon exposure to theviruses and thus provided possible answers as to why influenza type B caneasily be isolated from MDCK cells compared to influenza A. Positive influenzaviruses were inoculated onto MDCK cells. IFN-γ andIL-10 cytokines stimulated by the viruses in MDCK cells were measured byindirect ELISA at 1 hour, 12 hours, 48 hours and 72 hourspost inoculation (pi). A total of 46 specimens, with 23 specimens from eachvirus type were analyzed. IFN-γ was significantly higher at 1 hour pi in MDCK cells forinfluenza type A at p value of 0.024 than type B. No statistical significancewas observed in means of cytokine IL-10 between influenza type A and type B.The study may show that IFN-γ is correlated to the preferential isolation of influenza type B overtype A viruses. Anti-inflammatory cytokines may not necessarily be playing arole in the preferential growth of influenza type B, aless virulent type over influenza type A in MDCK cells.