Phylogenetic Comparison of Influenza Virus Isolates from Three Medical Centers in Tehran with the Vaccine Strains during 2008-2009

BACKGROUND Influenza virus is a major infectious pathogen of the respiratory system causing a high degree of morbidity and mortality annually. The worldwide vaccines are decided and produced annually by World Health Organization and licensed companies based on the samples collected from all over the world. The aim of this study was to determine phylogenecity and heterogenecity of the circulating influenza isolates during 2008-2009 outbreaks in Tehran, compare them with the vaccine strains that were recommended by WHO for the same period. METHODS Nasopharyngeal swabs (n=142) were collected from patients with influenza and influenza-like illness. Typing and subtyping of the isolates were performed using multiplex RT-PCR and phylogenetic analysis was carried out for hemagglutinin genes of the isolates. RESULTS Fifty out of 142 samples were positive for influenza A virus, and no influenza B virus was detected. Phylogenetic analyses revealed that the A/H1N1 isolates were related closely to A/Brisbane/59/2007, and the A/H3N2 isolates were close to A/Brisbane/10/2007 vaccine strains. CONCLUSION The findings of the present study demonstrate that the A/H1N1 was the predominant subtype of human influenza virus among the patients studied in Tehran during 2008-2009 winter seasons. In addition, some amino acid variation was found in Tehran/2008/H1N1 isolates from the 2008-2009 vaccine strain, but the H3N2 isolates showed higher genetic resemblance to the vaccine strain.