[The effect of different factors on the reproduction of influenza viruses and reassortants in cell cultures].

The influence of the maintenance medium, polyethylene glycol (PEG), DEAE-dextran, and low temperature on reproduction of influenza A, B, and C viruses and their reassortants in diploid and continuous cell cultures was determined. Lowering of pH in the maintenance medium to 6.5 was found to decrease reproduction of influenza A (H1N1) and A (H3N2) viruses and increase that of influenza B viruses. Treatment of cells with PEG solution increased the yield of influenza B and C but not A viruses. However, influenza A virus strains proved to be capable of producing infectious progeny in nonpermissive cell lines treated with PEG. Addition of DEAE-dextran to the medium exerted no effect on the infectivity of influenza A and B reassortants. Moreover, infection of MDCK cells after a "cold shock" led to an increase in hemagglutinin titres in influenza A reassortants.