Epidemiología molecular del virus sincicial respiratorio en pacientes pediátricos en un período de seis a?os

摘要

Human respiratory syncytial virus (HRSV) is the leading cause of acute lower respiratory tract infections (ALRI) in children. Despite considerable efforts there is as yet no satisfactory vaccine available. In this work, nasopharyngeal aspirates taken from hospitalized children with ALRI were analyzed over six consecutive epidemic seasons (1999-2004). By RT-PCR, 353 positive samples for HRSV by direct immunofluorescence were subtypified. Among them, 65.7% belonged to subtype A and 34.3% to subtype B. Therefore, a phylogenetic analysis was performed using RFLP and sequence analysis of the G-glycoprotein gene, the main neutralizing antigen. The results for A subtype, showed that there were two main restriction patterns (PA1 and PA2) and two genotypes (GA2 and GA5) cocirculating during the period studied. The phylodinamic analysis showed that there were some genetic clades which along this period of time alternated their circulation between Argentina and other countries and that other clades cocirculated worldwide. The subtype B analysis enabled the description of an unusual genetic event such us a 60 nucleotide duplication. The phylodinamic analysis showed that all of these viruses, designated BA, circulated in our country during the period studied and were associated with strains reported wordlwide, showing a common ancestor which had probably been generated in a single genetic event between 1997 and 1999 in Argentina. This work contributes to a better understandig of this virus evolution, giving a fundamental role to the virology laboratory in the active molecular surveillance.