Caracterização molecular de vírus influenza detectados em crianças com doença respiratória aguda, atendidas em Uberlândia, MG, entre 2001 e 2010

Abstract

Influenza remains a major health problem due to the seasonal epidemics that occur every year caused by the emergence of new virus strains. Therefore, this study aimed to identify and to characterize molecularly the influenza viruses from cases of acute respiratory disease in children less than five years of age in Uberlândia, MG. For this purpose, 605 nasopharyngeal aspirates were collected between 2001 and 2010. Influenza virus was detected in 40 (6.6%) samples, 39 were of type A and one of type B, from cases that occurred between February and September. The percentage of children with influenza attended at ambulatory pediatrics was higher than hospitalized, and the cases that required hospitalization had a median of four months old. The type A viruses were further characterized in subtypes by RT-PCR, and the H3N2 subtype was the most prevalent. Deduced amino acid sequence analysis of partial hemagglutinin sequence indicated that, compared to strains sequences used in the vaccines provided in the same periods, the receptor binding sites were preserved, although substitutions with similar amino acids in these sites were observed in few cases. The neuraminidase sequences did not show significant changes, i.e., in the antigenic sites. The influenza B virus was characterized as Victoria lineage, whereas the vaccine strain used in the same year (2002) belonged to the Yamagata lineage. The subtype H3N2 viruses showed substantial changes in antigenic sites and those detected between 2001 and 2003 also presented lower identity in nucleotide sequences compared to the sequence of the vaccine strain. These results suggest that viral variants that circulated in those seasons were not affected by the vaccination. Thus, an early monitoring of variants circulating in the country or in a region may provide important information about the probable efficacy of the vaccine that will be administered in the season.