Molecular identification of the first local dengue fever outbreak in Shenzhen city, China: a potential imported vertical transmission from Southeast Asia?

A suspected dengue fever outbreak occurred in 2010 at a solitary construction site in Shenzhen city, China. To investigate this epidemic, we used serological, molecular biological, and bioinformatics techniques. Of nine serum samples from suspected patients, we detected seven positive for dengue virus (DENV) antibodies, eight for DENV-1 RNA, and three containing live viruses. The isolated virus, SZ1029 strain, was sequenced and confirmed as DENV-1, showing the highest E-gene homology to D1/Malaysia/36000/05 and SG(EHI)DED142808 strains recently reported in Southeast Asia. Further phylogenetic tree analysis confirmed their close relationship. At the epidemic site, we also detected 14 asymptomatic co-workers (out of 291) positive for DENV antibody, and DENV-1-positive mosquitoes. Thus, we concluded that DENV-1 caused the first local dengue fever outbreak in Shenzhen. Because no imported case was identified, the molecular fingerprints of the SZ1029 strain suggest this outbreak may be due to vertical transmission imported from Southeast Asia.

[Comparison of immune responses elicited by recombinant protein and eukaryotic expression plasmid based on histidine rich protein 2 of Plasmodium falciparum].

OBJECTIVE: To identify the immune characteristics of different vaccine prototypes based on HRP2 and to provide experimental evidence for developing P. f. blood stage vaccines. METHODS: BALB/c mice were immunized with recombinant protein TP-HRP2 or eukaryotic expression plasmid pcDNA3.1(-)/HRP2. The kinetics and specificities of antibody responses were analyzed. The proliferation tests of spleen cells were done, and P. f. growth inhibition assays were done with immune sera. RESULTS: The mice immunized with TP-HRP2 in Freund's adjuvant produced high-level and high-specificity antibody response. The antibodies appeared rapidly and lasted for a longer time. Cellular responses were induced simultaneously, and the immune sera could inhibit the development of parasite in IRBCs. The mice immunized with pcDNA3.1(-)/HRP2 produced middle-level antibody response which had some specificity, however, the induction of antibodies required repeated inoculation and a longer duration. Immune cells were well primed and the memorial immune response was obvious but the immune sera had no effect on the growth of P.f. in vitro. CONCLUSION: Both the recombinant protein and plasmid DNA based on HRP2 have different immune characteristics in mice. HRP2 recombinant protein has the potential in practical application.

[Immune response in mice induced by C terminal encoding gene of Plasmodium falciparum histidine rich protein. 2].

OBJECTIVE: To explore the humoral and cellular immune responses in mice to eukaryotic expression recombinant plasmid encoding histidine rich protein 2 (HRP-II) of Plasmodium falciparum. METHODS: The start and stop codes were introduced into HRP-II gene fragment, the reading frame and the position of start and stop codes in HRP-II were identified by sequencing. HRP-II fragment containing the start and stop codes was cloned into pcDNA3.1 (-) to form pcDNA3.1 (-)/HRP-II. The BALB/c mice were immunized i.m. with the plasmids for 3 times in 3 weeks intervals. Two weeks after the last immunization, the sera and splenocytes were collected to investigate anti-HRP-II antibodies by ELISA and the splenocytes proliferation response to HRP-II. RESULTS: Sequence data show that the reading frame and the position of start and stop codes are correct. Restriction enzyme digestion indicated that the HRP-II gene fragment containing start and stop codes was successfully cloned into pcDNA3.1 (-). Mice raised significant anti-HRP-II antibodies after pcDNA3.1 (-)/HRP-II immunization, and the splenocytes proliferated prominently when stimulated with HRP-II protein. CONCLUSION: Eukaryotic expression recombinant plasmid encoding HRP-II gene can induce significantly humoral and cellular immune response in mice. HRP-II gene may be a good candidate for P. falciparum blood-stage multiple DNA vaccine.

[Amplification, cloning and sequence analysis of a SSUrRNA gene fragment of Plasmodium vivax isolates from Yunnan Province].

According to known SSUrDNA sequences of Plasmodium vivax, correlated protozoa and human being, sequences of oligonucleotide primers were defined with computer programming. Specific SSUrDNA fragment of P. vivax, about 640 bp in length, was directly amplified by two temperature point polymerase chain reaction from extracted genomic DNA of two blood samples of vivax malaria patients from Yunnan Province. Using dideoxynucleotide terminator method, the sequences of amplified DNA fragments were determined separately and showed no difference between the two samples. However, comparison of the sequence reported by Waters AP and McCutchan TF (1989) and that of amplified fragment of Yunnan P. vivax isolates revealed the existence of nucleotide substitution and deletion which occurred respectively in the sites 269 and 630, and resulted in the change of restriction map.