Serological detection and E gene sequence analysis of dengue virus isolated from 484 patients in / 中华临床感染病杂志

ABSTRACT

Objective To detect dengue virus infection by serological method and to determine the sequences of E gene of dengue virus isolated from Guangzhou in 2006.so as to clarify the possible origin of dengue fever.Methods IgM and IgG antibodies to dengue virus were detected by immunochromatographic test(ICT);NSI antigen and IgM antibody were detected by enzyme-linked immunosorbent assay(ELISA).The virus was cultured and isolated from the serum samples within 2 days using C6/36 cell lines and was identified by immuno-fluorescence assay(IFA)and RT-PCR.The E gene of isolated virus DV1-GZ42/06 was sequenced;homological analysis and phylogenetic tree analysis were performed by comparing with the reference strains and epidemic virus strains.Results The positive rates of IgM and IgG of dengue virus in patients were 89.5%(433/484)and 38.0%(184/484)by ICT,respectively.The positive rates of NS1 antigen were 92.7%(38/41)in day 1 to day 2,83.3%(70/84)in day 3 to day 5,and 10.9%(5/46)in day 6 to day 10;and the IgM detection rates were 2.4%(1/41),51.2%(43/84)and 97.8%(45/46)at the same period by ELISA.Twenty-five strains of dengue virus were isolated from 41 serum samples(6 1.O%)and were identified as type 1 dengue virus by IFA and RT-PCR.The sequencing and phylogenetic analysis of the E gene showed that the homology between the isolated Guangzhou/42/06 strain and standard strain Hawaii/45 was 94.6%.and it had a high homology with the Thailand/NI09V104,Vietnam/06.and Vietnam/07 isolates(99.0%,98.6%and 98.6%,respectively)and belonged to the same cladogram,but had low homology with the isolated strain from Guangdong before 2006.Conclusions The detection of NS1 antigen is important in the early diagnosis of dengue fever.The outbreak of dengue fever in Guangzhou in 2006 was possibly caused by the cases from neighboring countries.