Genetic Characaterarizion Of Hemagglutinins(HA)of Measles Virus Circulating In Mainland China During 2013-2014

Background:Measles is a highly contagious human disease manifesting as high fever,rash,respiratory,and conjunctivitis symptoms which is caused by measles virus.Measles is a vaccine preventable disease,by vaccinating with measles containing vaccine(MCV),it can effectively prevent and protect the measles.Objective:The aim of this study is to elucidate the molecular level of measles incidence during 2013～2014,the period when wide-type measles recurred in mainland China after 2012,along with evolutionary characteristics of hemagglutinin MeV strains and to study the dynamic variation law.Methods:In this study,we selected 56 strains of H1 genotype MeV,which were popular in China in 2013～2014,amplified complete coding regions of hemagglutinin(1854nt)and sequenced.H gene complete coding region sequences were downloaded from GenBank,along with Chinese vaccine strains(S-191 and C-47)and 24 WHO reference strains.Phylogenetic analysis and the diversity were done by MEGA(version 5.05).Homology analysis was performed using BioEdit.Then we analyzed the molecular evolution of measles virus in our country by using 76 representative strains of H1 genotype MV,which was popular in mainland China during the year of 1993～2014.Selection pressure analysis of the H gene was performed using Datamonkey.We calculated the dS and dN rates at every codon using the following 3 methods:SLAC,FEL,and IFEL.Results:Results showed that,H1a was circulating in China as the dominant sub-genotype.By making further analysis of the evolutionary tree,Hla could be divided into 3 lineage,and strains from 2013-2014 were mainly in lineage 3b.We found that strains from 2013～2014 all belonged to two distinct lineage in Hla,named as lineage 3b-1 and lineage 3b-2.Strains after 2010 showed the same feature.The homology of nucleotide acid and amino acid among representative strains of measles virus during 2013 to 2014 was 97.8%～99.9%and 97.5%～100.0%,respectively;the homology of nucleotide acid and amino acid between measles virms during 2013 to 2014 and WHO H1 referrence strains was 97.6%～98.1%and 96.9%-97.8%,respectively;the homology of nucleotide acid and amino acid between measles virus during 2013 to 2014 and Chinese vaccine strains was 94.3%～94.9%and 94.4%～95.6%,respectively.Alignment of amino acid sequence of genotype H1 compared to S-191 shows that,an amino acid substitution(Ser240Asn)occurred,which removed a predicted N-linked glycosylation site.All strains conservatively had 4 predicted N-linked glycosylation sites.The amino acid residues of putative binding sites for seven cysteine residues,CD46,SLAM and nectin-4 were relatively conserved.The substitution of Pro397Leu in the hemagglutinin noose epitope(HNE)was identified.The amino acids 236-250 predicting B cell epitopes(BCE)were relatively conserved except site 240 and 243.Conclusion:Functional significant neutralizing antigenic sites of hemagglutinin genes of genotype H1 measles virus were conserved relatively.The measles vaccine has a good protective effect on the wild-type measles virus in China.H genes of wild-type measles virus should be monitored dynamically as part of routine molecular surveillance for measles in China,to clarify the variability of neutralizing antigens in measles virus.Moreover,it can provide a scientific evidence to evaluate the efficiency of the current vaccines.