Differences In The Transmission Of Dengue Fever By Different Serotypes Of Dengue Virus

Background and ObjectiveDengue fever is the most common viral infectious disease transmitted by mosquitoes worldwide.Aedes albopictus and Aedes aegypti are the most important media for dengue virus and can quickly cause the spread of the virus.In the more than 100 subtropical and tropical countries around the world,about 2.5 billion people are at risk of contracting dengue virus,and the range is also expanding year by year.Dengue fever has now become the most concerned virological disease transmitted by arthropods.The dengue epidemics in China are mainly caused by imported cases,mainly in coastal provinces such as Fujian,Jiangsu,Zhejiang,Hainan and Guangdong.However,in recent years,there has been a trend of inland transmission,and the provinces of Shandong and Zhejiang have witnessed the dengue epidemic since the historical record.Due to the convenience of transportation and the increasing living needs of the people,globalization,urbanization,tourism and commercial trade,especially the national strategy of the Belt and Road Initiative implemented in China,have increased the import of dengue pathogens.Climate change and environmental transformation are more suitable for Aedes mosquito breeding.At the same time,virus evolution and mutation may lead to the influence of transmission potential and its toxicity changes.The epidemic of dengue fever is increasing,and the number of cases is increasing.At present,there is no specific treatment plan for dengue fever,and clinical treatment is mainly based on symptomatic treatment.And the development of dengue vaccine is limited by the antigenicity and genetic diversity of the virus,as well as the lack of cross-immunoprotecting between different serotypes.In particular,the antibody-inducing effect of viral infection between different serotypes,is,Antibody-Dependent Enhancement(ADE),has made the research and application of dengue vaccine severely difficult.Therefore,it is necessary to study the differences in the transmission potential and pathogenicity of different serotypes of dengue virus and their interactions.It is currently believed that dengue fever is still a local outbreak due to imported cases,but different input serotypes of dengue virus besides spreading differences.It is currently believed that dengue fever is still a local outbreak caused by imported cases,but different input serotypes of dengue viruses show differences in transmission.This study intends to analyze the epidemiological characteristics of dengue fever in Guangdong Province in recent years,and to explain the epidemiological phenomenon of type ? and type ? dengue fever in the region.To investigate the epidemiological differences and strain differences between different serotypes of type ? and type ? dengue virus,and to provide a theoretical basis for dengue heat transmission blocking mechanism and its disease prevention and control research.Methods1.Collect the epidemic data of dengue fever in Guangdong Province from 2014 to 2018,analyze the molecular epidemiological characteristics of the major subtypes of dengue fever outbreaks in Guangdong Province fr-om 2014 to 2018;2.Collect acute serum samples fr-om patients with dengue fever in Shenzhen from 2014 to 2018,perform nucleic acid monitoring and serological tests,and isolate viral of the positive clinical samples;3.Amplify the full-length sequence of the successfully isolated dengue virus E gene and the full-length sequence of the NS1 gene,perform sequence alignment and homology analysis,and draw a phylogenetic tree;4.The mixture containing NS1 protein,dengue virus and mouse blood was fed to Aedes mosquitoes in an in vitro feeding systel to study the effect of NS1 on the replication of dengue virus in vitro;5.Comparison of different serotypes of dengue virus infection in Vero cells and C6/36 cells,and plaque assay to confirm dengue virus replication differences between different serotypes;6.Enzyme-linked immunosorbent assay and Western blotting were used to compare the difference in secretory NS 1 secretion of dengue virus in different serotypes.Results1.In 2014,95%of the 49,000 cases of dengue fever in Guangdong were caused by type ? dengue virus infection;in 2015,88.5%of 1796 cases of dengue fever in Guangdong were caused by type ? dengue virus infection;in 2018,59%of 2963 cases of dengue fever in Guangdong were caused by type ? dengue virus infection,and 36%were caused by type ? dengue virus infection.Although dengue cases caused by type? and type IV dengue virus infections were imported every year,such imported cases did not cause outbreaks of local cases.2.It is epidemiologically confirmed that the different serological dengue viruses imported have significant differences in the ability to cause second-generation infections in Guangdong Province.The transmission ability of type ? and type ? is significantly higher than that of type ? dengue virus.3.Successfully isolated type ? and IV dengue viruses from the serum of imported dengue cases,5 of them were infected with type ? dengue virus and 3 were infected with IV dengue virus.And successfully isolated 4 copies of type ? dengue virus and 2 types of dengue virus type ?;4.BLAST homology analysis and phylogenetic tree results show that the popular strain with high homology with the Shenzhen type ? dengue virus isolate is the Philippine isolate and the Indonesian isolate.The epidemic strains with higher homology with Shenzhen type IV dengue virus isolates are Italian isolates,Philippine isolates,and Indonesia isolates;5.The amino acid sequence analysis of NS1 gene showed that the amino acid similarity of the four different serotypes of dengue virus was 77.69%,and the dengue virus NS 1 of four different serotypes had a 5-7 amimo acid conserved region;6.The difference in the infection rate of Aedes mosquitoes showed that the recombinant NS 1 protein significantly promoted the mosquito-infected dengue virus.7.The results of in vivo replication kinetics of dengue virus indicate that cells infected with DENV-2 showed lesions such as rounding,fusion,and cell shedding earlier than those infected with DENV-3,and the disease changed nore significantly,DENV-2 replicates intracellularly faster than DENV?3;8.Enzyme-linked immunosorbent assay and Western blotting results showed that Vero cells infected with DEN-V-2 secreted more NS1 protein than DENV-3 infected Vero cells.ConclusionsSince 2014,all subtypes of dengue fever in Guangdong Province have been imported,and second-generation infections caused by imported cases have caused local epidemics.However,the local epidemic was mainly dengue type ? and dengue type ?,and type ? and type IV imported dengue cases did not lead to local outbreaks.Epidemiologically,it was confirmed that the imported type ? and type ? dengue viruses were significantly more likely to cause second-generation infections in Guangdong Province than type ? dengue viruses.Early detection,early diagnosis,and early treatment of imported cases should be made,especially for early diagnosis and treatment of clinical atypical cases.At the same time,it is necessary to strengthen the detection and investigation of the immigration and floating population,do a good job in the patriotic health campaign,and do a good job in mosquito vector monitoring and killing.The dengue virus amino acids of the four different serotypes are highly similar,so the NS1 protein conserved regions of different serotypes can be used as a candidate molecule for diagnostic antigens.Genetic variation is an important detenninant of serotyping and branching and determines different viral,virulence and epidemic potentials.This study demonstrates that type ? dengue virus exhibits greater replication and pathogenicity in cells,and type ? dengue virus has a slightly greater ability to replicate in mosquitoes than type ? dengue virus.Type ? dengue virus secretes higher levels of NS1 protein,and mosquito-borne experiments have confirmed that the same subtype of NS1 protein promotes the virus to more efficiently infect Aedes,which in turn leads to a significant increase in the virus infection rate of mosquitoes.However,the prevalence of dengue virus and the severity of the disease are affected by many factors.The mechanism of the difference in the transmission potential of type ? dengue virus and type ? dengue virus in mosquito media remains to be further studied.