Study On Molecular Epidemiology Of Norovirus Infection And Its Interaction With Host Receptor In Shenzhen

Objective:To study molecular epidemiology of norovirus infection in Shenzhen.To trace the origins of NoVs,NoVs from waterborne diarrhea outbreaks and shellfish oyster were detected.Study on interaction of norovirus infection with histo-blood group antigen?HBGA?of the host receptor in diarrhea outbreaks,so as to predict the prevalence of norovirus.Method:A total of 9580 samples in diarrhea cases from 2005 to 2016 were collected in Shenzhen.NoVs were screened and typed using Real-time RT-PCR,RT-PCR with specific G? and G? primers.And calicivirus was tested by triplex real-time RT-PCR.The phylogenetic analysis and genotype of NoVs were be done by gene sequencing.To establish a simple membrane adsorption-elution method to concentrate NoVs in water.NoVs in shellfish oyster also be concentrated.The HBGA phenotypes of ABO/H and Lewis antigen of saliva samples from outbreaks of acute gastroenteritis were determined by EIA assays using the corresponding monoclonal antibodies against individual HBGAs.Results:?1?The detectable rate of NoVs infection associated with sporadic cases ranged from 12.24%to 25.37%.The prevalence of NoVs substantially increased every other year,with the peak in July and August.NoVs were detected in all age groups?from 12.58%to 21.32%?.Six months to three years old children and adults over 20 years of age are at high risk.?2?There were 139 gastroenteritis outbreaks in Shenzhen,122 of which were caused by NoVs.The outbreaks of gastroenteritis occurred throughout the year,and the peaked in Winter and Spring.The outbreaks of gastroenteritis occurred mainly in Nanshan district,Shenzhen.Most of locations were kindergartens,schools and communities.?3?The NoVs were detected in the stool samples and water samples associted the four waterborne gastroenteritis outbreaks.Sequencing confirmed that pathogen was NoV G?.4/Den_Haag₂006b in the two waterborne outbreaks of gastroenteritis,the other two outbreaks were cuased by NoV G?.3.The gastroenteritis outbreaks were due to source drinking water,underground reservoir water,villagers' source of drinking water?spring water?and the secondary water polluted by viruses.The NoVs were also detected in the four oysters' samples.?4?Complete genome sequences of 4 NoVs strains shared 86.8-99.1%nucleoside identity and 94.6-99.2%amino acid identity,respectively.The three sense mutation sites were found in the strains SZ2012054.According to the analysis of the Simplot,the recombination of the strain s SZ2012054?SZ2012049 and SZ2010422 occurred in the overlap of ORF1/ORF2.The suqences analysis of 935 NoVs strains indicated that the homology of NoV G?and G? in Shenzhen was 62.1-100.0%and 67.4-100.0%,respectively.43 NoVs G?strains,including seven different genotypes?G?.1-6 and G?.8?,were identified;892 NoVs G? strains,including fifteen different genotypes?G?.4 Sydney₂012,G?.4 Den Hagg₂006b,G?.4 Hunter₂004,G?.4 Asia₂003,G?.4 New Orleans₂009,G?.3,G?.2,G?.5-7,G?.12-14,G?.17,G?.21?,were determined,and some G?.4 strains belonged to unknown type.?5?Two of 122 gastroenteritis outbreaks were caused by G?.3 and G?.6,repectiely,the others were cuased by G?,including G?.1,G?.2,G?.3,G?.6,G?.8,G?.17,G?.21,G?.4 Sydney-2012,G?.4 Den Haag₂006b and G?.4 Asia 2003.And genotypes were uncertain in the ten gastroenteritis outbreaks.The first case of new NoV G?.4/Sydney₂012 strain was detected in July 2012,which successfully forecasted the outbreak epidemic of NoV G?.4/Sydney₂012 strain.The dominant genotypes of NoVs outbreaks were G?.4 Den Haag₂006b,G?.3 and G?.4 Sydney₂012,which was similar in the sporadic cases.?6?The secretor individuals were susceptible to norovirus in the two outbreaks,and can bind to nonsecretor saliva and antigens.Conclusion:Norovirus was the main pathogen of sporadic gastroenteritis and outbreaks in Shenzhen.There was one dominant strain and secondary dominant strain every year in Shenzhen.The new strain will gradually replace the previous dominant strain and become a new prevalence strain.The prevalent genotypes of NoVs from 2005 to 2014 were G?.4 Den Haag₂006b,G?.3 and G?.4 Sydney₂012 in gastroenteritis outbreaks and sporadic cases in Shenzhen.22 different genotypes NoVs were associated with sporadic cases.Ten different genotypes No Vs were involved in gastroenteritis outbreaks.And some strains were untyped.The NoVs were detected in the four waterborne gastroenteritis outbreaks and four batches of oyster samples in Shenzhen.Study on interaction between NoVs infection and the HBGA of the host,it was found that both secretor and nonsecretor were susceptible to NoV G?.4 and G?.3.TheNoV G?.4 may share the same or similar binding profile with Cairo 1.