Molecular epidemiology of human respiratory syncytial virus subgroups A and B identified in adults with hematological malignancy attending an Irish hospital between 2004 and 2009

Human respiratory syncytial virus (HRSV) is an important cause of respiratory infection in patients with hematological malignancy, particularly hematopoietic stem cell transplant recipients. This study investigated the genetic variability of the attachment (G) protein gene among HRSV isolates collected from adult patients with hematological malignancy. Between December 2004 and March 2009, 60 samples collected from 58 adults attending an Irish hospital were positive for HRSV by direct immunofluorescence. Nucleotide sequence analysis of the G gene showed a slightly higher frequency of HRSV subgroup A (52%) than HRSV subgroup B (48%). Genetic variability was higher among subgroup A viruses (up to 13% at nucleotide level) than among subgroup B viruses (up to 4%). Phylogenetic analysis revealed two genotypes of HRSV subgroup A, GA2 and GA5, which cocirculated between 2004/2005 and 2007/2008, although GA2 alone was identified in season 2008/2009. Genotype BA was the only genotype of HRSV subgroup B identified. Genotype-specific amino acid substitutions were identified, with two and seven changes for GA2 and GA5, respectively. Furthermore, one to four potential N-glycosylation sites were found among HRSV subgroup A isolates while two to three were identified in HRSV B isolates. Predicted O-glycosylation sites included 25-34 and 40-43 in HRSV subgroups A and B, respectively. The average synonymous mutation-to-non-synonymous mutation ratios (dS/dN) implied neutral selection pressure on both HRSV subgroup isolates. This study provides data for the first time on the molecular epidemiology of HRSV isolates over five successive epidemic seasons among patients attending an Irish hospital.