Characterization of high-growth reassortant influenza A viruses generated in MDCK cells cultured in serum-free medium

In the present study reassortant influenza A viruses of both the H1N1 and H 3N2 type were generated in Madin Darby Canine Kidney cells grown in the abs ence of fetal bovine serum (MDCK-SF1 cells). To this end, MDCK-SF1 cells we re simultaneously infected with one of the high-growth laboratory strains A /Puerto Rico/8/34 (H1N1) or A/Hong Kong/2/68 (H3N2) and recent H3N2 and H1N 1 vaccine strains, respectively. Reassortant viruses obtained from these mi xed infections were genetically characterized by RT-PCR and restriction enz yme analysis and their growth properties were compared to those of the corr esponding field strains. Reassortant H3N2 viruses inherited the matrix and polymerase pa gene whilst H1N1 reassortant viruses inherited the matrix and polymerase pbl gene of the high-growth parent, Reassortant viruses general ly gave higher viral yields, as measured by a haemagglutination assay, than their wild type counterparts. The procedure followed results in the genera tion of high-growth reassortant viruses in weeks. The use of MDCK-SF1 cells together with these reassortants for generating influenza virus antigens c an significantly speed up the vaccine production procedure. (C) 1999 Elsevi er Science Ltd. All rights reserved.