Unusual antigenic and genetic characteristics of human respiratory syncytial viruses isolated in Cuba.

The G protein of 23 strains of human respiratory syncytial virus isolated in Havana, Cuba, between October 1994 and January 1995 was analyzed at the antigenic and genetic level. All viruses reacted with 10 of 11 antibodies specific for the Long strain. Moreover, the G protein gene of the Cuban isolates had only five nucleotide differences from the sequence of the Long gene. The homogeneity of the Cuban isolates and their resemblance to an ancient strain, such as Long, are at odds with previous findings for viruses isolated in countries with a temperate climate and different socioeconomic status. The G proteins of three of four other viruses isolated in Havana 2 years later (1996) were also identical to those of the 1994-to-1995 isolates, and the fourth virus had a single extra nucleotide difference. This, again, is unusual, since no identical viruses had been isolated in different epidemics previously. The singular characteristics of the Cuban isolates reported here are discussed in terms of the epidemiological, climatic, and socioeconomic characteristics of Cuba.