ABSTRACT
Objective To study the evolutionary characteristics and rules of two lineages on influenza B virus.Methods A total of 126 HA1 sequences of strains isolated during 1940 to 2012were downloaded from the GenBank.Time of the most recent common ancestor (TMRCA) and divergence of the two lineages were calculated based on the data from phylogenetic analysis of HA1gene,using Bayesian Markov Chain Monte Carlo (Bayesian-MCMC) and molecular clock method.Results The average amino acid variant ratios were ranged from 5.4％ to 10.2％ within the strains of influenza B virus isolated during 1978 to 2010.Compared with the Victoria-like strains,all Yamagatalike strains showed an amino acid deletion at 163th site,while some of them showing a deletion at position 166.HA1 gene of influenza B virus seemed not have been affected by positive selection except a few sites.The evolutionary average rate on HA1 gene was 2.138 × 10-3 substitutions/site/year (95％HPD:1.833 × 10-3-2.437 × 10-3 substitutions/site/year).The estimated dates for TMRCA of the two lineages of influenza B virus could be dated back to 1971 (95％ HPD:1969-1972),while the divergence times of the two lineages were 1973 (95％ HPD:1971-1974) and 1977 (95％ HPD:1975-1978) respectively.Conclusion Significant differences were found on HA1 gene between earlier and recent identified strains of Victoria and Yamagata lineage.Differences between the two lineages increased and showing the potential of dividing themselves into different subtypes in the future.More attention should be paid to these trends and the related epidemiological significance.
ABSTRACT
Objective To analyze the genetic characteristics of the complete sequence of coxsackievirus A24 variant(CA24v) isolated from acute hemorrhagic conjunctivitis (AHC) outbreaks in Zhejiang province during 2002 to 2010.Methods Complete sequences of CA24v epidemic strains isolated in different years were amplified under the RT-PCR assay,while the sequences of whole genome,VP1,and 3C region of Zhejiang strains were compared with epidemic strains isolated in other areas of China and abroad.Results The whole genome of Zhejiang CA24v strains isolated in 2002 and 2010 was 7456-7458 bp in length,encoding a polyglutamine protein which containing 2214 amino acid residues.There was a insertion with T on site 97 and 119 within 5' non-coding region between epidemic strain Zhejiang/08/10 and strains isolated in 2002.The rates of amino acid homology among Zhejiang/08/10 and other strains isolated since 2002 were between 94.7％ and 100.0％.Compared with the representative strains circulated within the recent 60 years,the largest average amino acid variations had been occurred on region 2A and 3A,with the ratios as 8.4％ and 7.3％ respectively.The smallest variation happened in region 3D,with the ratio only as 1.9％.The rates of stable amino acid variation on the whole genome between strains isolated since 1987 and 2002 were 38 and 20.P-distance within groups appeared that region 3C was more stable than VP1 of strains isolated in 2002-2010,and the 3D of early strain Jamaica/10628/87 might have had a nature of recombination but not observed on those epidemic strains in recent years.Conclusion Within the evolution of CA24v strains,the time course was more significant than the geographical differences.There had been sporadic epidemics of AHC caused by CA24v in Zhejiang province since 2002.
ABSTRACT
Objective To study the genetic variations between measles vaccinc strain S191 and strains that circulated in Zhejiang province causing the epidemics during 1999 to 20 1 1.Methods Complete sequence of the nine Zhejiang measles strains were amplified by RT-PCR assay.Products were sequenced and the obtained sequences were aligned and analyzed with vaccine strains S191 and the major epidemic strains isolated in foreign countries.Results The homology of amino acid among the nine Zhcjiang strains were 98.77％-99.89％.The strains were not affected by positive selection and the variations on each gene were still in random drift.Compared to vaccine strain S191,there were 135 to 159 amino acid changes in Zhejiang measles virus,in which 113 points were common variable positions,resulting in mutations on five glycosylation sites.At the nucleotide level,the biggest differences between the Zhejiang strains and the vaccine strain S191 were found on N gcne,with the average divergent ratio as 5.5％,while the biggest one was P protein,in the amino acid level,with the average mutation rate as 7.7％.In addition,with the complete genome sequences,the genetic distance between Zhcjiang epidemic strains and vaccine strains was greater than the distances between epidenic strains of genotype D4,B3 and vaccine strains (t=-9.76,P＜0.05；t=-12.39,P＜0.05).Conclusion There were significant differcnccs found in the each of the genes between Zhejiang epidemic strains and the vaccine strain S191.The differences between the current vaccine strains and H genotypc epidemic strains were much larger than the differences between the vaccine and the forcign epidemic strains (genotype D4,B3).Therefore,wc should pay close attcntion to this trend,and to develop candidates for the dcvclopnent of vaccines,as early as possible.