Establishment of Indirect ELISA Diagnosis Technique based on the VP1 Protein of Foot and Mouth Disease Virus Serotype A

The VP1 protein of foot-and-mouth disease virus serotype A was prokaryotically expressed and purified to replace the traditional virus antigen for estab- lishing a fast, safe, effective indirect ELISA method, so as to detecting antibody of foot-and-mouth disease virus serotype A. Western-Blot test showed that the VP1 recombinant protein could be used as detective antigen as it can be specifically recognized by bovine positive serum of FMDV serotype A. By employing matrix titra- tion method, the optimal parameters were obtained as follows： 1 mg/L VP1 protein as coating antigen, Vserum：Vblocking solution = 1：50 dilution for serum and Vsecondary enzyme-linked antibedies：Vblocking solution ---1：2 000 for enzyme combined antibodies. The results showod that the sensitivity and specificity of this method were 94.32% and 99.09% respectively, the coefficients of variations in intra-assay and inter-assay reproducibility tests was lower than 8%. Compared with liquid phase blocking ELISA kits, the agreement of 201 serum samples reached 92.54%. The VP1-ELISA method established here is specific, sensitive, stable and simple, which can be used to monitor the antibody level of FMD serotype A.

Expression,Purification and Activity Detection of Structural Protein VP1 of Foot-and-Mouth Disease Virus Serotype A

The paper was to obtain the VP1 protein of FMDV serotype A with high activity. With recombinant plasmid pMD19A-T-vp1 as the tem- plate, vpl gene fragment amplified by PCR was connected into prokaryotic expression vector pET28a to construct recombinant plasmid pET-A-vpl. The E. coli BL21 （DE3） strain containing recombinant plasmid pET-A-vpl were induced by IPTG. SDS-PAGE showed that VP1 protein was ex- pressed in the form of inclusion body, and its molecular weight was about 29 ku. Based on the optimizing IPTG concentration and expression time, the largest expression of VP1 protein was induced by 0.3 mmol/L IPTG for 6 h at 37 ℃. Western-Blot analysis indicated that the expression of VP1 protein could be specifically recognized by positive serum of FMDV serotype A. ELISA test showed that VP1 inclusion body protein had high activity after purification by washing and renaturation by urea concentration gradient dialysis.

Isolation and characterization of dengue virus serotype 2 from the large dengue outbreak in Guangdong, China in 2014

Dengue has been well recognized as a global public health threat,but only sporadic epidemics and imported cases were reported in recent decades in China.Since July 2014,an unexpected large dengue outbreak has occurred in Guangdong province,China,resulting in more than 40000 patients including six deaths.To clarify and characterize the causative agent of this outbreak,the acute phase serum from a patient diagnosed with severe dengue was subjected to virus isolation and high-throughput sequencing(HTS).Traditional real-time RT-PCR and HTS with Ion Torrent PGM detected the presence of dengue virus serotype 2(DENV-2).A clinical DENV-2 isolate GZ05/2014 was obtained by culturing the patient serum in mosquito C6/36 cells.The complete genome of GZ05/2014 was determined and deposited in Gen Bank under the access number KP012546.Phylogenetic analysis based on the complete envelope gene showed that the newly DENV-2 isolate belonged to Cosmopolitan genotype and clustered closely with other Guangdong strains isolated in the past decade.No amino acid mutations that are obviously known to increase virulence or replication were identified throughout the genome of GZ05/2014.The high homology of Guangdong DENV-2 strains indicated the possibility of establishment of local DENV-2 circulation in Guangdong,China.These results help clarify the origin of this epidemic and predict the future status of dengue in China.

Expression and Identification of the Type-specific Antigen of FMDV of Serotype C

[Objective]The aim was to provide a theoretical basis for preparation of polyclonal antibodies and monoclonal antibody that of type specificity, as well as Foot-and-mouth Disease Virus （FMDV） typing.[Method] The recombinant plasmid pGEM-CP1 that contained VPI gene of FMDV of serotype C was used as template for the VP1 and its C terminus coding fragments of FMDV of serotypes C amplification. The coding fragments of VP1 and its C terminus were respectively cloned into prokaryotic expression vector for prokaryotic expression and the reactionogenicity was detected. The purified fusion protein of FMDV VP1 and its C terminus of serotype C were used to construct the indirect ELISA method to detect positive sera of four serotypes A, O, C and Asia 1 of guinea pig and determine the cross reactivity of FMDV antibody of VP1 and its C terminus of serotype C with other three serotypes. [ Result] The recombinant prokaryotic expression plasmids of PPRO-CVP1 and pPRO-CVPlc were constructed, FMDV VP1 and its C terminus of serotype C were expressed in high level, and the molecular weight of target proteins was 33 kD and 20 kD respectively. Western blot result showed that the fusion protein of VP1 and its C terminus could react with the positive sera of guinea pig of the same serotype. ELISA results revealed that VP1 and its C terminus of serotype C are type-specific and no cross-reactivities were shown between guinea pig positive sera of FMDV of serotype C with the other three serotypes, and the C terminus showed better type-specificity. [ Conclusion] FMDV specific antigen of serotype C was obtained.

In silico prediction of monovalent and chimeric tetravalent vaccines for prevention and treatment of dengue fever

Reverse vaccinology method was used to predict the monovalent peptide vaccine candidate to produce antibodies for therapeutic purpose and to predict tetravalent vaccine candidate to act as a common vaccine to cover all the dengue virus serotypes. Envelope（E）-proteins of DENV-1-4 serotypes were used for vaccine prediction using NCBI,Uniprot/Swissprot, Swiss-prot viewer, VaxiJen V2.0, TMHMM, BCPREDS, Propred-1, Propred and MHC Pred. Eproteins of DENV-1-4 serotypes were identified as antigen from which T cell epitopes, through B cell epitopes, were predicted to act as peptide vaccine candidates. Each selected T cell epitope of E-protein was confirmed to act as vaccine and to induce complementary antibody against particular serotype of dengue virus. Chimeric tetravalent vaccine was formed by the conjugation of four vaccines, each from four dengue serotypes to act as a common vaccine candidate for all the four dengue serotypes. It can be justifiably concluded that the monovalent 9-mer T cell epitope for each DENV serotype can be used to produce specific antibody against dengue virus and a chimeric common tetravalent vaccine candidate to yield a comparative vaccine to cover any of the four dengue virus serotype. This vaccine is expected to be highly immunogenic against dengue fever.

Zika virus： a new threat from mosquitoes

In the winter of 2015,the first dengue vaccine(Dengvaxia)was approved for clinical use.Dengue virus is the most prevalent mosquito-transmitted viral pathogen in humans(Qin and Shi,2014).Even though the approved Dengvaxia has its weaknesses(e.g.,low protection against serotype-2virus),it has been recently licensed to Mexico,Philippines,