Antigenic variations of respiratory syncytial virus (RSV) strains were analyzed using a collection of nine, seven, two, and one monoclonal antibodies (MAbs), respectively, raised against the fusion protein (F), large glycoprotein (G), nucleoprotein (NP), and phosphoprotein (P) components of the Long strain of RSV. Competitive binding assay by these MAbs demonstrated eight, four, and two distinct epitopes o n F, G, and NP components, respectively. Comparison of prototype Long with ten field strains isolated in Sapporo, Japan, during a 9-year period from 1980 to 1988 by radioimmunoprecipitation (RIP), immunofluorescence (IF), and enzyrne-linked immunosorbent assay (ELISA) test revealed four different patterns of reaction to these MAbs. Thus, prototype Long reacted to all 19 MAbs. Six field strains have shown a different reactivity to one of nine anti-F and to one of seven anti-G antibodies (subgroup A). Three of the remaining isolates failed to react with three of nine anti-F and with all of seven anti-G antibodies (subgroup B). One strain (58-104) isolated in 1983 was similar to subgroup A except for a lack of reaction with two anti-G antibodies. All field strains reacted with two anti-NP and one anti-P antibodies. The numbers of altered epitopes in subgroup A were 118 and 114; in subgroup B, 318 and 414; and in 58-104, 118 and 214 on the F and G components, respectively. No other variations have been observed among field isolates tested.
MATERIALS AND METHODS
Virus Strains
The ten virus field strains tested were isolated from infants with acute respiratory tract illness in Sapporo,