Sequence analysis of the F genes from human metapneumovirus recently isolated from children in Beijing
Objective A novel paramyxovirus,human metapneumovirus(hMPV) was recently isolated from nasopharyngeal aspirates collected from infants and young children with acute respiratory infections in Beijing.To understand the characteristic of these newly discovered hMPV in Beijing,the F genes from two hMPV which were in two different gene clusters from previous investigation were analyzed.Methods Full length of F genes from hMPV was amplified from two specimens,BJ1816 and BJ1887 collected from children hospitalized for acute respiratory infections in November 2002 by reverse-transcription and polymerase chain reaction(RT-PCR).The two PCR amplicons were sequenced after cloning into pBS-T vector and the sequences were compared with the F genes from other hMPV in GenBank.Results The F genes amplified from BJ1816 and BJ1887 were 1620 bp in length.The deduced F proteins were 539 amino acids in length.The identities of nucleotide and amino acid between BJ1816 and BJ1887 were 83.8% and 94.4%,respectively.These two hMPV shared high homology with those within the same cluster(98.3%-99.6%).It was revealed that F proteins of these two hMPV shared typical fusion protein characteristics with those described for the F proteins of other hMPV and other paramyxoviridae members.The inactive precursors(F0) of the F proteins were cleaved by host cell proteases to generate N-terminus F2 subunites and Large C-terminus F1 subunits.F proteins of these two hMPVs shared the similar cleavage sites with other hMPVs,containing the residues RQSR.The sequence similarity of F2 subunits between BJ1816 and BJ1887 displayed a higher degree than F1 subunits(96.9% vs 93.8%).Except the membrane anchor domain and the region of intra-cellular at the C-terminus F1 subunits,the rest of F1 subunits of the two hMPVs showed high sequence identity(95.4%).The potential N-linked glycosylation sites in the F proteins of BJ1816 and BJ1887 were shared with other hMPVs,including two shared with APV and one unique.Phylogenetic analysis showed that BJ1816 and BJ1887 fell into two distinct genetic clusters.Conclusion The sequence analysis of the complete F genes from two samples confirmed that like the results of the gene sequence analysis from other genes,BJ1816 and BJ1887 belong to two different clusters.F protein of hMPV may play a very important role in the infection and immunity by hMPV.