Genetic diversity of Neuraminidase of Influenza A virus, isolated from children hospitalized in São Paulo city, from 1995 to 2006.

O presente estudo teve por objetivos caracterizar os vírus Influenza circulantes na cidade de São Paulo e verificar a variabilidade genética do gene da neuraminidase (NA) dos Influenzavírus A. Um total de 3009 amostras de crianças internadas no Hospital Universitário da USP, no período de 1995 a 2006, foram submetidas à duplex RT-PCR para detecção dos Influenzavírus A e B (IA e IB). As amostras positivas para IA foram submetidas à subtipagem pela multiplex RT-PCR. Cento e trinta e três amostras (4,4%) foram positivas, sendo 88,0% (117/133) IA e 12,0% (16/133) IB. Entre as amostras IA, 94 eram H3N2, 7 H1N1 e 16 não foram subtipadas pela multiplex. Um total de 74 amostras (71 H3N2 e 3 H1N1) tiveram o gene da neuraminidase sequenciado (total ou parcialmente). As sequências obtidas foram submetidas à análise filogenética, sendo verificado o agrupamento das cepas circulantes em clusters por ano de isolamento, demonstrando sua evolução temporal. Quando comparadas com as cepas vacinais utilizadas no período, foi verificada uma boa similaridade.The aim of this study was to characterize Influenza virus circulating in São Paulo city and the neuraminidase (NA) gene sequence of Influenzavirus A in 3009 samples from children hospitalized at USP University Hospital, from 1995 to 2006. Samples underwent duplex RT-PCR for detection and typing of Influenza virus A and B (IA and IB) and also were submitted to multiplex PCR for subtyping of IA. Among 3009 samples, 4.4% were Influenza virus, being 88.0% IA (117/133) and 12.0% IB (16/133). Among samples of IA, 94 were characterized as H3N2, 7 H1N1 and 16 were not subtyped. A total of 74 samples (71 H3N2 and 3 H1N1) had the NA gene sequenced (total or partially). Sequences obtained were compared to sequences of the world and sequences of vaccine strains. Brazilian samples were grouped in clusters with samples isolated in the same year. It was also found a good similarity between circulating strains and vaccine strains