Abstract: Objective To study the effct of gradient dilution of Japanese encephalitis virus (JEV) E protein antibody on the replication ability of dengue virus type Ⅱ(DENV-Ⅱ) in THP-1 cells.Methods Human THP-1 cells were co-infected with JEV-E antibodies of different dilution and DENV-Ⅱisolated from the serum of critically ill patients in Xishuangbanna,Yunnan Province.The standard curve of fluorescent quantitative PCR detection of DENV-Ⅱvirus was constructed.We used different dilution of JEV-E antibodies and DENV-Ⅱat different MOI (Multiplicity of infection) to infect THP-1 cells,then DENV-Ⅱvirus copy number was detected by real-time fluorescent quantitative PCR.Results We found 1/4 dilution degrees of JEV-E antibody concentration could promote DENV-Ⅱreplication in THP-1 cells,while high and low concentration of JEV-E antibody had no significant effect on DENV-Ⅱvirus replication in THP-1.Conclusion Flaviviruses JEV E protein antibody can induce antibody dependent enhanced infection of DENV-Ⅱin human THP-1 cells,which lays a theoretical foundation for the further study of antibody dependent enhanced infection among flaviviruses.

Key words: Dengue virus, Japanese Encephalitis virus, Antibody-dependent enhanced infection, THP-1