Selection of receptor-binding variants of human influenza A and B viruses in baby hamster kidney cells.

Cultivation of human influenza viruses in the allantoic cavity of embryonat ed chicken eggs leads to a selection of receptor-binding variants with amin o acid substitutions on the globular head of the hemagglutinin (HA) molecul e. Such selection can be avoided by growing the human viruses in Madin Darb y canine kidney (MDCK) cells. In the present study, we tested whether baby hamster kidney (BHK) cells select receptor-binding mutants of human influen za viruses. After isolating H1N1, H3N2, and type B influenza Viruses from c linical samples in MDCK cells, we passaged them in either BHK cells or chic ken eggs. The BHK-grown viruses differed from their MDCK-grown counterparts by virtue of mutations in the HA: 225 D --> G (H1N1 virus), 128T --> A and 2261 --> V (H3N2), and 187N --> D (type B) (H3 numbering). Variants with d ifferent substitutions were selected by passaging of the same MDCK-grown pa rents in eggs: 141L --> H, 208R --> H, and 225D --> G (H1N1), 194L --> l (H 3N2), and 137G --> R (B). Compared with their MDCK-grown counterparts, both BHK- and egg-grown viruses possessed a higher affinity for the cellular me mbranes of BHK cells and of the chorioallantoic cells of chicken embryos an d for a 3'-sialylgalactose-containing synthetic sialylglycopolymer. By cont rast, changes in the affinity of mutants for a 6'-sialyl-(N-acetyllactosami ne)-containing sialylglycopolymer varied from negative to positive. Fluores cence-activated cell-sorting analysis with linkage-specific lectins showed that the density of the 6'-sialy[-(N-acetyllactosamine)-containing receptor s is substantially lower on the surface of BHK cells than on MDCK cells, pr oviding an explanation for the growth restriction of human viruses in the f ormer cells. Our data demonstrate that cultures of BHK cells, like eggs, ca n select receptor-binding variants of human influenza viruses. (C) 1999 Aca demic Press.