Where is HRSV during the summer?

VIEGAS MARIANA; VELEZ RUEDA ANA JULIA; MISTCHENKO ALICIA SUSANA

SANTA FE

Simposio; 8th ANNUAL RESPIRATORY SYNCYTIAL VIRUS SYMPOSIUM; 2012

RSV 2012 SYMPOSIUM COMMITTEE

Virus transmission chains in humans are posssible to elucidate by phylogeography. From 110 Argentine nucleotide sequences of the G protein gene of HRSV, we performed a phylogeographic analysis for the most common world circulating subtype A-genotypes (GA2 and GA5) between 1997 and 2011. The overall analysis between Argentine strains and those from all over the world showed that those genetic clades that dissapeared in Argentina for some years were found in other countries. Several clades first circulated in other parts of the world and then emerged in our country, while other clades remained cocirculating throughout the world during the studied period. The estimates of the nucleotide substitution rates (expressed as nt.subst/site/year) and the time of the MRCA (year) were 2.38x10-3 and 1990 for GA2; and 2.88x10-3 and 1994 for GA5. The analysis of the demographic history for these genotypes showed a general expansion of the efective viral population for GA2 whereas GA5 showed a deacrease after the year 2000. Interestingly, a higher aa diversity was estimated for GA2 than for GA5 (5.3% vs 3.1%, respectively). Probably, these data are suggesting that GA2 has a higher fitness than GA5 to withstand the immune selection pressure of the host. In order to analyze what happens to HSRV between outbreaks we analyze prolonged infections and reinfections at the intrapatient variation level. We found that reinfections during the same outbreak were only possible if two distinct genotypes infect the patients, but in prolonged infections the patients could be coinfected with two genotypes at the same time. These results suggested that HRSV circulates in the human population following the winter outbreaks or rainy seasons around the world, probably favoured by communications and human circulation and thus does not cut its chain of transmission. In addition it may also be harbored in certain susceptible individuals surviving until the next outbreak in which there are new susceptible hosts with naive immunity. This kind of analysis will be very important for future vaccine development.