| ObjectionTo study the infectious situation and molecular epidemiological characteristics of rotavirus(RV)among children less than 5 years old in Suzhou during the years from 2010 to 2016,to explore the molecular evolution characteristics of strains,to provide scientific basis for better prevention and treatment of RV infection.Methods1.Fecal samples were collected from children less than 5 years old with diarrhea at Suzhou Children's Hospital during the period from Jan,2010 to Dec,2016.Viral RNA of all the samples was extracted and then tested for RV by real-time RT-PCR.The patient data including age,sex,and dates of disease onset were also collected.SPSS17.0 was used to analysis the relevant parameters.Nested RT-PCR was used to amplify the VP7 and VP4 genes of the strains which were positive for RV for further G/P genotyping,to analysis the molecular epidemiological characteristics.2.Individual gene fragments of 7 G9P[8]strains were amplified and the PCR products were sequenced.All the 11 gene fragments genotypes were determined by use of RotaC2.0(http://rotac.regatools.be/)and the phylogenetic relationships were inferred by use of MEGA 5.0,to explore the genetic changes and evolutionary trend.Results1.The infectious situation of RV in Suzhou1.1 Epidemiological characterisistics of RV among children less than 5 years old in SuzhouA total of 2658 samples were collected during the period from 2010 to 2016,including 1566 from male and 1092 from female.914 out of 2658(34.39%)were positive for RV,among which 567 cases(62.04%,567/914)were male and 347 cases(37.96%,347/914)were female.RV positive rates of male and female were 36.21%(567/1566)and 31.78%(347/1092),respectively.There was no significant difference in gender(?~2=5.597,P=0.18).Out of the 914 RV positive cases,most cases(95.62%,874/914)were in children<35months group,among which 358 cases(39.17%,358/914)in 12~17months group,followed by cases in 6~8months(15.54%,142/914)and those in 9~11months(14.99%,137/914).RV positive rates of different age groups were 19.25%(41/213)for 0~2months,24.48%(83/339)for 3~5months,29.16%(142/487)for 6~8months,39.14%(137/350)for 9~11months,49.04%(358/730)for 12~17months,32.24%(49/152)for 18~23months,29.63%(64/211)for24~35months,26.60%(25/87)for 36~47months and 15.15%(15/89)for48~59months,there was significant difference in age(?~2=130.467,P=0.0001).RV infections were found whole the year,but showed a distinct seasonal pattern in Suzhou.RV positive rates of different months in the year 2016 were 70.45%(31/44)for January,64.71%(11/17)for February,42.11%(8/19)for March,15.00%(3/20)for April,11.54%(3/26)for May,10.00%(2/20)for June,0.00%(0/28)for July,2.50%(1/40)for August,8.00%(2/25)for September,10.00%(3/30)for October,53.13%(17/32)for November and 58.14%(25/43)for December,with epidemic peaks occurring predominantly in months from November to February next year.The positive rate was highest in January(70.45%,31/44).There was significant difference in month(?~2=181.426,P=0.0001).1.2 G/P genotype distribution of RVG genotype:G9 has become the predominate G-type(61.16%,559/914)since2012,followed by G1(15.10%,138/914),G3(10.39%,95/914),G2(7.44%,68/914),G4(0.4%,4/914).Co-infections(G3+9 and G1+9)were detected in 14 samples.3.94%(36/914)of positive samples was failed to determine its G genotype.P genotype:P[8]was the most common P-type(87.09%,796/914),followed by P[4](7.88%,72/914).Co-infections(P[4+8])were detected in 16samples.3.28%(30/914)of positive samples was unclassified P genotype.G/P genotype:G9P[8]has become the most common strain(58.4%,534/914)prevalent in Suzhou since 2012,followed by G1P[8](13.46%,123/914),G3P[8](10.61%,97/914),G2P[4](4.16%,38/914),G2P[8](3.17%,29/914),G9P[4](1.64%,15/914),G1P[4](1.20%,11/914)and G3P[4](0.55%,5/914).Co-infections of G/P were 22 cases and un-typed 40 cases.2.Whole-genome analysis of G9P[8]All the 7 study G9P[8]strains showed the Wa-like constellation,with the molecular characteristics G9-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1.The VP7 genes clustered into lineage G9-III and G9-VI,with nucleotide identities ranged from90.75%~99.90%.Most of the VP4 sequences belonged to the P[8]-3 lineage and one in P[8]-4 lineage.Nucleotide identities of 84.93%~99.60%were noted for VP4 genes.Amino acid changes were present in the antigenic regions of the VP7 and VP4 genes when compared to the related prototype strains.There were also multiple mutations in antigenic sites I and II of the nonstructural proteins 4(NSP4)genes.ConclusionsThis study indicates that RV is the leading cause of acute viral gastroenteritis among children less than 5 years of age in Suzhou.RV infections display a distinct seasonal pattern,with epidemic peaks occurring predominantly in the autumn and winter months.RV varies across regions and time.G9P[8]is the most common genotype and has been persistently prevalent in Suzhou with slow mutation rate.Hence,continued surveillance is necessary to explore the epidemiology and molecular evolutionary characteristics of RV. |
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