Occurrence of respiratory syncytial virus subtypes A and B strains in Sweden.

The subtype characteristics of 22 strains of respiratory syncytial (RS) virus isolated in Sweden were determined by the use of monoclonal antibodies. Eleven antibodies specific for distinct epitopes on five different structural proteins were used in immunofluorescence and radioimmune precipitation assays. One group of 12 isolates were derived from a three-month epidemic during 1984, whereas the other ten virus isolates were recovered during a time period of 13 years (1971-1983). All isolates could be allocated to the previously defined groups of subtype A and B strains of RS virus. During the single epidemic season, five subtype A and seven subtype B strains were found. During the 13-year period a randomly alternating appearance of six subtype A and four subtype B strains was observed. Thus RS virus strains of different subtype characteristics may occur alternately or concomitantly. The possible significance of consecutive infections with RS virus subtypes for immunopathological events deserves further studies.