Genetic variability of attachment (G) and Fusion (F) protein genes of human metapneumovirus strains circulating during 2006-2009 in Kolkata, Eastern India

BACKGROUND: Human metapneumovirus (hMPV) is associated with the acute respiratory tract infection (ARTI) in all the age groups. However, there is limited information on prevalence and genetic diversity of human metapneumovirus (hMPV) strains circulating in India. OBJECTIVE: To study prevalence and genomic diversity of hMPV strains among ARTI patients reporting in outpatient departments of hospitals in Kolkata, Eastern India. METHODS: Nasal and/or throat swabs from 2309 patients during January 2006 to December 2009, were screened for the presence of hMPV by RT-PCR of nucleocapsid (N) gene. The G and F genes of representative hMPV positive samples were sequenced. RESULTS: 118 of 2309 (5.11%) clinical samples were positive for hMPV. The majority (≈80%) of the positive cases were detected during July-November all through the study period. Genetic analysis revealed that 77% strains belong to A2 subgroup whereas rest clustered in B1 subgroup. G sequences showed higher diversity at the nucleotide and amino acid level. In contrast, less than 10% variation was observed in F gene of representative strains of all four years. Sequence analysis also revealed changes in the position of stop codon in G protein, which resulted in variable length (217-231 aa) polypeptides. CONCLUSION: The study suggests that approximately 5% of ARTI in the region were caused by hMPV. This is the first report on the genetic variability of G and F gene of hMPV strains from India which clearly shows that the G protein of hMPV is continuously evolving. Though the study partially fulfills lacunae of information, further studies from other regions are necessary for better understanding of prevalence, epidemiology and virus evolution in Indian subcontinent.