Eliminating mother-to-child transmission of hepatitis B virus: practice and progress in Baoan, a national pilot district of China.

BACKGROUND: While mother-to-child transmission (MTCT) of hepatitis B virus (HBV) remains a significant challenge in China, research investigating the effectiveness of the September 2017 pilot program to eliminate MTCT of HIV, syphilis, and HBV is limited. Baoan district, which has a higher-than-average rate of hepatitis B infection among pregnant women and strong support from the government, was one of six national pilot districts selected for the program. Therefore, this study aims to assess the progress and implementation of the elimination of MTCT of HBV in Baoan district over a period of 5 years. METHODS: Data was collected from the national information system for the prevention of MTCT, registration forms, and follow-up forms of pregnant women and their live births from 2018 to 2022. Joinpoint models were used to analyze changing trends over time, calculating annual percentage change (APC) and the corresponding 95% confidence interval (95%CI). Multivariate logistic regression models were used to analyze risk factors for HBV MTCT. RESULTS: From 2018 to 2022, the coverage of HBV screening during pregnancy increased from 98.29 to 99.55% (APC = 0.30, P = 0.012). The coverage of HBV early screening within 13 gestational weeks increased from 40.76 to 86.42% (APC = 18.88, P = 0.033). The prevalence of maternal HBV infection declined by an APC of - 3.50 (95% CI -6.28 ~ - 0.63). The coverage of antiviral therapy among high-risk pregnant women increased from 63.59 to 90.04% (APC = 11.90, P = 0.031). Coverage for timely administration of hepatitis B immunoglobulin, hepatitis B birth dose vaccine, and three-dose hepatitis B vaccination remained consistently above 97.50%. The coverage of post-vaccination serological testing (PVST) in high-risk infants was 56.15% (1352/2408), and the MTCT rate of HBV was 0.18%. Mothers with high-school education or below (OR = 3.76, 95% CI 1.04 ~ 13.60, P = 0.04) and hepatitis B e antigen (HBeAg) positivity (OR = 18.89, 95% CI 1.98 ~ 18.50, P = 0.01) had increased MTCT risk. CONCLUSIONS: The implementation of comprehensive prevention strategies in Baoan district, including screening, treatment, and immunoprophylaxis, has proven effective in maintaining the MTCT of HBV at an extremely low level. However, it remains crucial to raise public awareness, specifically on the importance of improving the coverage of PVST for infants exposed to HBV.

Characterization of the complete mitochondrial genome of Ixodes granulatus (Ixodidae) and its phylogenetic implications.

Ticks are deemed to be second only to mosquitoes as the most common vector of human infectious diseases worldwide that give rise to human and animal diseases and economic losses to livestock production. Our understanding of the phylogenetic analysis between tick lineages has been restricted by the phylogenetic markers of individual genes. Genomic data research could help advance our understanding of phylogenetic analysis and molecular evolution. Mitochondrial genomic DNA facilitated the phylogenetic analysis of eukaryotes containing ticks. In this study, we sequenced and assembled the circular complete mitogenome information of Ixodes granulatus. The 14,540-bp mitogenome consists of 37 genes, including 13 protein-coding genes (PCGs), two genes for ribosomal RNA (rRNAs), and 22 genes for transfer RNA (tRNAs), and the origin of the L-strand replication region. The directions of the coding strand and component genes in the non-Australasian Ixodes mitochondrial genome were similar to those found in most other Australasian Ixodes, except for the loss of a lengthy control region. The phylogenetic tree based on maximum likelihood (ML) and Bayesian inference (BI) computational algorithms showed that I. granulatus exhibits a close relationship with I. hexagonus and I. ricinus. To our knowledge, this is the first study exploring the complete mitogenome for the species I. granulatus. Our results provide new insights for further research on the evolution, population genetics, systematics, and molecular ecology of ticks.

Characterization of the complete mitochondrial genome of Haemaphysalis (Alloceraea) kolonini (Ixodidae) and its phylogenetic implications.

Ticks transmit diverse pathogens that cause human and animal diseases, leading to an increasing number of new challenges around the world. Genomic data research could help advance our learning of phylogenetic analysis and molecular evolution. Mitochondrial genome DNA has been helpful in illustrating the phylogenetic analysis of eukaryotes containing ticks. In this research, we sequenced and assembled the circular complete mitogenome information of Haemaphysalis kolonini. The 14,948-bp mitogenome consists of 37 genes which included 13 genes for protein-coding, two genes for ribosomal RNA, 22 genes for transfer RNA, and two control regions (D-loops). Overall, the composition and arrangement of genes were compared with Haemaphysalis ticks previously recorded in Genbank. The phylogenetic tree based on Maximum likelihood (ML) and Bayesian inference (BI) computational algorithms showed that H. kolonini has a close relationship with Haemaphysalis inermis. The complete mitogenome data provide a preferable perception to the phylogenetic relationship than the single-gene data analysis. To our knowledge, this is the first research exploring the complete mitogenome for the species H. kolonini. Our results provide new insights for further research on the evolution, population genetics, systematics, and molecular ecology of ticks.

Fever with thrombocytopenia associated with a novel bunyavirus in China.

BACKGROUND: Heightened surveillance of acute febrile illness in China since 2009 has led to the identification of a severe fever with thrombocytopenia syndrome (SFTS) with an unknown cause. Infection with Anaplasma phagocytophilum has been suggested as a cause, but the pathogen has not been detected in most patients on laboratory testing. METHODS: We obtained blood samples from patients with the case definition of SFTS in six provinces in China. The blood samples were used to isolate the causal pathogen by inoculation of cell culture and for detection of viral RNA on polymerase-chain-reaction assay. The pathogen was characterized on electron microscopy and nucleic acid sequencing. We used enzyme-linked immunosorbent assay, indirect immunofluorescence assay, and neutralization testing to analyze the level of virus-specific antibody in patients' serum samples. RESULTS: We isolated a novel virus, designated SFTS bunyavirus, from patients who presented with fever, thrombocytopenia, leukocytopenia, and multiorgan dysfunction. RNA sequence analysis revealed that the virus was a newly identified member of the genus phlebovirus in the Bunyaviridae family. Electron-microscopical examination revealed virions with the morphologic characteristics of a bunyavirus. The presence of the virus was confirmed in 171 patients with SFTS from six provinces by detection of viral RNA, specific antibodies to the virus in blood, or both. Serologic assays showed a virus-specific immune response in all 35 pairs of serum samples collected from patients during the acute and convalescent phases of the illness. CONCLUSIONS: A novel phlebovirus was identified in patients with a life-threatening illness associated with fever and thrombocytopenia in China. (Funded by the China Mega-Project for Infectious Diseases and others.).

Clinical progress and risk factors for death in severe fever with thrombocytopenia syndrome patients.

BACKGROUND: Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease caused by the SFTS virus (SFTSV) with an average fatality rate of 12%. The clinical factors for death in SFTS patients remain unclear. METHODS: Clinical features and laboratory parameters were dynamically collected for 11 fatal and 48 non-fatal SFTS cases. Univariate logistic regression was used to evaluate the risk factors associated with death. RESULTS: Dynamic tracking of laboratory parameters revealed that during the initial fever stage, the viral load was comparable for the patients who survived as well as the ones that died. Then in the second stage when multi-organ dysfunction occurred, from 7-13 days after disease onset, the viral load decreased in survivors but it remained high in the patients that died. The key risk factors that contributed to patient death were elevated serum aspartate aminotransferase, lactate dehydrogenase, creatine kinase, and creatine kinase fraction, as well as the appearance of CNS (central nervous system) symptoms, hemorrhagic manifestation, disseminated intravascular coagulation, and multi-organ failure. All clinical markers reverted to normal in the convalescent stage for SFTS patients who survived. CONCLUSIONS: We identified a period of 7-13 days after the onset of illness as the critical stage in SFTS progression. A sustained serum viral load may indicate that disease conditions will worsen and lead to death.

Complete mitochondrial genome of Ctenophthalmus quadratus and Stenischia humilis in China provides insights into fleas phylogeny.

Fleas (Order Siphonaptera) are common blood-feeding ectoparasites, which have important economic significance. Limited mitochondrial genome information has impeded the study of flea biology, population genetics and phylogenetics. The Ctenophthalmus quadratus and Stenischia humilis complete mt genomes are described in this study. The samples were collected from Jianchuan, Yunnan plague foci, China. The mt genomes of C. quadratus and S. humilis were 15,938 bp and 15,617 bp, respectively. The gene arrangement of mt genome was consistent with that of other fleas, which include 22 tRNA genes, 13 protein-coding genes, and two rRNA genes, with a total of 37 genes. The relationship between C. quadratus and S. humilis in fleas was inferred by phylogenetic analysis of mt genome sequence datasets. Phylogenetic analyzes showed that the C. quadratus and S. humilis belonged to different species in the same family, and were closely related to Hystrichopsylla weida qinlingensis in the same family; and revealed that the family Hystrichopsyllidae is paraphyletic, supporting the monophyly of the order Siphonaptera. This study decodes the complete mt genomes of the C. quadratus and S. humilis for the first time. The results demonstrate that the C. quadratus and S. humilis are distinct species, and fleas are monophyletic. Analysis of mt genome provides novel molecular data for further studying the phylogeny and evolution of fleas.

Complete mitogenomes and phylogenetic relationships of Haemaphysalis nepalensis and Haemaphysalis yeni.

The mitochondrial genome may include crucial data for understanding phylogenetic and molecular evolution. We sequenced the complete mitogenome of Haemaphysalis nepalensis and Haemaphysalis yeni for the first time. H. nepalensis and H. yeni's complete mitogenomes were 14,720 and 14,895 bp in size, respectively, and both contained two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and 13 protein-coding genes (PCG). Haemaphysalis nepalensis have one control region (D-loop). The adenine + thymine concentration of the genomes of H. nepalensis and H. yeni was 77.75 and 78.41%, respectively. The codon use pattern and amino acid content of proteins were both observed to be affected by the AT bias. Genes in the mitogenome were organized and located in a comparable manner to previously known genes from Haemaphysalis ticks. Mitochondrial PCGs were used to perform phylogenetic relationships based on the Minimum Evolution (ME) approach using MEGA 7.0 software, the results reveal that H. nepalensis has tight links with H. tibetensis, H. yeni and H. kolonini share a sister group relationship, and that H. nepalensis and H. yeni belong to Haemaphysalis. The results of this study include the following: (i) discovered and supplied new tick records (H. nepalensis) for China, (ii) provided the first complete mitochondrial genome for H. nepalensis and H. yeni and revealed their phylogenetic relationships, and (iii) the features of the mitochondrial genome of H. nepalensis and H. yeni provided more genetic reference for Phylogeography, systematics, and population genetics of the Haemaphysalis species.

SARS patients-derived human recombinant antibodies to S and M proteins efficiently neutralize SARS-coronavirus infectivity.

OBJECTIVE: To develop a specific SARS virus-targeted antibody preparation for emergent prophylaxis and treatment of SARS virus infection. METHODS: By using phage display technology, we constructed a naive antibody library from convalescent SARS patient lymphocytes. To obtain the neutralizing antibody to SARS virus surface proteins, the library panning procedure was performed on purified SARS virions and the specific Fab antibody clones were enriched by four rounds of repeated panning procedure and screened by highthroughput selection. The selected Fab antibodies expressed in the periplasma of E. coli were soluble and further purified and tested for their binding properties and antiviral function to SARS virus. The functional Fab antibodies were converted to full human IgG antibodies with recombinant baculovirus/insect cell systems and their neutralizing activities were further determined. RESULTS: After four rounds of the panning, a number of SARS-CoV virus-targeted human recombinant Fab antibodies were isolated from the SARS patient antibody library. Most of these were identified to recognize both natural and recombinant SARS spike (S) proteins, two Fab antibodies were specific for the virus membrane (M) protein, only one bound to SARS-CoV nucleocapsid protein. The SARS-CoV S and M protein-targeted Fab or IgG antibodies showed significant neutralizing activities in cytopathic effect (CPE) inhibition neutralization test, these antibodies were able to completely neutralize the SARS virus and protect the Vero cells from CPE after virus infection. However, the N protein-targeted Fab or IgG antibodies failed to neutralize the virus. In addition, the SARS N protein-targeted human Fab antibody reacted with the denatured N proteins, whereas none of the S and M protein specific neutralizing antibodies did. These results suggested that the S and M protein-specific neutralizing antibodies could recognize conformational epitopes which might be involved in the binding of virions to cellular receptors and the fusion activity of the virus. CONCLUSION: The SARS-CoV spike protein and membrane proteins are able to elicite efficient neutralizing antibodies in SARS patients. The neutralizing antibodies we generated in this study may be more promising candidates for prophylaxis and treatment of SARS infection.

[Study on serological cross-reactivity of six pathogenic phleboviruses].

This article aimed to study the antigenicity of nucleocapsid proteins (NPs) in six pathogenic phleboviruses and to provide theoretical evidence for the development of serological diagnostic reagents. NPs of six pathogenic phleboviruses were expressed and purified using a prokaryotic expression system and rabbits were immunized with individual recombinant NPs. Cross-reactions among NPs and rabbit sera were determined by both indirect ELISA and Western blotting analyses, and the sera titer was determined by indirect ELISA. Furthermore, sera from SFTS patients were also detected by each recombinant NP as a coating antigen using indirect ELISA. The cross-reactions and the sera titer were subsequently determined. Both the concentration and purity of recombinant NPs of six pathogenic phleboviruses met the standards for immunization and detection. The results of indirect ELISA and Western blotting showed that each anti-phlebovirus NP rabbit immune serum had potential serological cross-reactivity with the other five virus NP antigens. Furthermore, the sera from SFTS patients also had cross-reactivity with the other five NP antigens to a certain extent. Our preliminary study evaluated the antigenicity and immune reactivity of six pathogenic phleboviruses NPs and laid the foundation for the development of diagnostic reagents.

[Study on adjuvant effect of oral recombinant subunit vaccine formulated with chitosan against human enterovirus 71].

To evaluate the adjuvant effect of recombinant enterovirus 71 (EV71) subunit vaccine formulated with chitosan, rabbits were orally immunized with recombinant VP1 (rVP1) or rVP1 mixed with chitosan adjuvant. Levels of virus-specific IgG and IgA antibodies in sera, mucosal wash buffer (intestine, nasal cavity, and lung), and feces were determined by indirect enzyme-linked immunosorbent assay (ELISA). The titers of neutralizing antibodies against EV71 were determined using cytopathic effect-based neutralizing assay, and levels of cytokines (IFN-gamma and IL-4) secreted from in vitro-cultured rabbit splenic lymphocytes under antigen stimulation were also determined by ELISA. Results showed that immunization with rVP1 alone could only induce low levels of serum IgG and mucosal IgA, while rVP1 combined with chitosan adjuvant were able to induce significantly higher levels of antibodies, rVP1 can only induce neutralizing antibodies when used in combination with chitosan. Levels of IFN-gamma and IL-4 in the group immunized with rVP1 plus chitosan were significantly higher than those in the group immunized with rVP1 only or those in the control groups. Our study lays the foundation for development of oral VP1 vaccine against EV71 infection.

[Severe fever with thrombocytopenia syndrome virus nucleoprotein specifically binds to 60kD SSA/Ro protein in host cells].

This study aims to investigate whether the nucleoprotein (NP) of severe fever with thrombocytopenia syndrome virus (SFTSV) can impact the cellular immunity of host cells. Gene segments that encode the NP and non-structural protein (NSs) of SFTSV were inserted into eukaryotic expression vector VR1012. Host proteins that interact with NP and affect immunity were identified with co-immunoprecipitation (IP), SDS-PAGE, mass spectrometry (MS), and Western blot. Co-localization of NP and the identified host proteins was confirmed by confocal microscopy. A 60kD SSA/Ro, a protein related to immunity, interacted with NP, as found by IP and MS. Confocal microscopy showed that NP and SSA/Ro were co-localized in cytoplasm. These results indicated that SFTSV NP may specifically bind to 60kD SSA/Ro and cause a series of immune responses and clinical symptoms.

[[Virus-like particle-based immunoglobulin M capture enzyme-linked immunosorbent assay for the detection of IgM antibodies against Chikungunya virus].

To establish a MacELISA method for the detection of IgM antibodies against Chikungunya virus (CHIKV), we prepared virus like particle (VLP) antigens of CHIKV using the whole structural protein C-E3-E2-6K-E1 encoding gene with a baculovirus expression system in Sf9 insect cells. The VLPs were purified and used to immunize Kunming mice. Then, polyclonal antibodies were purified from the samples of ascites with a protein G HiTrap SP column and labeled with horseradish peroxidase. A MacELISA method for the detection of IgM antibodies against CHIKV was assembled with goat anti-human IgM antibody, VLP antigens and an enzyme-labeled polyclonal antibody. The results were evaluated with a serum panel containing serum samples from laboratory-confirmed CHIK, HFRS patients, healthy donors, and commercially available CHIKV IgM as a quality control. It was shown that the MacELISA had a specificity of 99% (99/100), the coefficients of variation (CoV) within a plate were <10%, and the CoV of different ELISA plates in terms of the plate variation coefficient was <15%. A comparative analysis was performed to compare the current method against a commercial CHIKV IgM antibody detection kit for IIFA-IgM. The detection limit of MacELISA was significantly lower than that of the IIFA-IgM commercial kit (P< 0.0001). Here, we demonstrate that the VLP-based MacELISA is a promising tool for the early diagnosis and epidemiological investigation of CHIKV infection, with a high level of sensitivity and specificity for the detection of IgM antibodies against CHIKV.

[Subcellular localization of severe fever with thrombocytopenia syndrome virus in macrophages].

OBJECTIVE: To study the subcellular localization of severe fever with thrombocytopenia syndrome virus (SFTSV) in macrophages and understand the replication and assembly mechanism of SFTSV in host cells. METHODS: Using two types of human macrophage cell lines THP-1 and U937, the study analyzed the intracellular colocalization of SFTSV with Golgi apparatus and endoplasmic reticulum by immunefluorescence staining and confocal microscopy. RESULTS: SFTSV infected macrophage cell lines THP-1 and U937. Immunofluorescence staining showed that the SFTSV nuclear protein colocalized with Golgi apparatus and closely surrounded by endoplasmic reticulum in the perinuclear region. CONCLUSION: The results suggested that Golgi complex and endoplasmic reticulum are probably the sites for formation and maturation of SFTSV viral particles.

[A double antibody sandwich ELISA based assay for titration of severe fever with thrombocytopenia syndrome virus].

OBJECTIVE: To develop an assay for titration of severe fever with thrombocytopenia syndrome virus (SFTSV) based on double antibody sandwich ELISA. METHODS: A double antibody sandwich ELISA was developed for detection of SFTSV based on SFTSV nucleocapsid (N) protein specific poly- and monoclonal antibodies, procedures were optimized and evaluated. This ELISA based titration assay was compared with fluorescence assasy and plaque assay based titration method. RESULTS: The results suggested that the titers obtained by ELISA based method are consistent with those obtained by IFA based method (R = 0.999) and the plaque assay titration method (R = 0.949). CONCLUSION: The novel ELISA based titration method with high sensitivity and specificity is easy to manage and perform, and can overcome the subjectivity associated with result determination of the fluorescence assay and plaque assay based methods. The novel ELISA based titration method can also be applied to high throughput detection.

[Establishment of minireplicon system for severe fever with thrombocytopenia syndrome bunyavirus].

Severe fever with thrombocytopenia syndrome bunyavirus is a newly emerging virus in China, enveloped with a tripartite, single-stranded RNA genome of negative polarity. The regulatory elements for viral transcription and replication, as well as encapsidation and packaging signals, are thought to be located within these noncoding regions (NCRs). The terminal nucleotides are genus specific and highly conserved. The function of the remaining nucleotides of the NCRs is still not well understood. In this study, we developed the plasmid-driven RNA polymerase I minireplicon system for SFTSV firstly, using reporter genes GFP and luciferase. The function of the noncoding regions of the three Bunyaviridae RNA segments (L, M, S) in transcription was analyzed. Reporter genes are successfully expressed in SFTSV minireplicon system. Our results suggest that the NCRs of SFTSV from all three segments contain the necessary signals to initiate transcription. Quantitative detection of the luciferase expression level shows that promoter activity in the three segments is different.

[Isolation, identification and characterization of SFTS bunyavirus from ticks collected on the surface of domestic animals].

To understand the maintenance and transmission of SFTS virus, the potential vector ticks were collected from sheep, cattle and dogs in the endemic areas of SFTSV in Shandong Province. Among the collected ticks, the dominant species was H. longicornis ticks. Real-time PCR for RNA detection, virus isolation and characterization, genomic sequencing, phylogenetic and antigenic analysis were performed in this investigation. The results showed that the SFTS viral RNA was detected in 2.14% H. longicornis, and a SFTS virus was isolated from one of viral RNA positive ticks collected from sheep. Whole genome analysis of the SFTSV isolates with 11 human-origin SFTS virus revealed a highly pairwise similarity, and the growth curve analysis showed nearly identical in virus yield and the dynamic of virus reproduction compared to human derived viral isolates. Immunofluorescence and neutralization test showed identical serological reaction character of the two different origin viral strains. In this study, the characters of a SFTSV isolate was firstly described, which suggested that the tick species H. longicornis acting important vector role in the transmission of SFTS virus.

[Generation of recombinant human antibodies for EV71 virus].

OBJECTIVE: To obtain recombinant human anti-EV71 antibodies from a EV71-associated hand-foot-and-mouth disease patient-derived antibody phage library. METHODS: A combinatorial human scFv library to enterovirus 71 (EV71) virus was constructed using antibody genes harvested from the blood of EV71 virus patients. The library was panned and selected by using purified VP1 protein of EV71 virus with phage display. After that the specific antibody was converted to full human IgG antibody with recombinant baculovirus/insect cell system. RESULTS: One unique human scFv antibody specific for EV71 virus VP1 protein was obtained by ELISA, IFA and analysis of the antibody DNA sequence. The specific anti-VP1 human scFv antibody was converted to full human IgG antibody with recombinant baculovirus/insect cell system. The full human IgG antibody was tested in vitro for EV71 virus neutralization, resulting in no neutralizing activity with EV71 A type and EV71 C4 subtype. CONCLUSION: The obtained human anti-EV71 antibodies without neutralizing activity laid the foundation for diagnosis of human EV71-associated hand-foot-and-mouth disease.

[Expression of structural and non-structural proteins of severe fever with thrombocytopenia syndrome bunyavirus].

Severe fever with thrombocytopenia syndrome bunyavirus (SFTSV) is a novel phlebovirus, causing a life-threatening illness associated with the symptoms of severe fever and thrombocytopenia syndrome. The sequence and structure of the genome have already been illustrated in previous study. However, the characteristics and function of the structure and non-structure proteins is still unclear. In this study, we identified the density of the purified SFTSV virions as 1.135 g/mL in sucrose solution. Using RT-PCR method, we amplified the full coding sequence of RNA dependent RNA polymerase(RdRp), glycoprotein precursor (M), glycoprotein n (Gn), glycoprotein c (Gc), nuclear protein (NP) and non structural protein (NSs) of SFTSV (strain HB29). Respectively inserted the target genes into eukaryotic expression vector pcDNA5/FRT or VR1012, the target protein in 293T cell were successfully expressed. By analyzing the SFTSV virions in SDS-PAGE and using recombinant viral proteins with SFTS patients sera in Western blotting and Immunofluorescent assay, the molecule weight of structure and non-structure proteins of SFTSV were defined. The study provides the first step to understand the molecular characteristics of SFTSV.

[Secreted expression of dengue virus type 2 envelope glycoprotein in eukaryotic cells].

OBJECTIVE: To secreted express envelope glycoprotein (E) of dengue virus type 2 extracellularly. METHODS: The entire prM/E gene was amplified by RT-PCR. An optimized signal sequence gene from Japanese encephalits virus (JEV, SA14-14-2 strain) was introduced using fusion PCR. The impact of E protein transmembrane and cytoplasmatic domains was compared by amplifying prM and E with full length of E gene, with 20% truncation of the E gene at 3' terminus and one chimeric gene, which was generated by replacing the 3' terminal 20% region of E gene with the corresponding sequence of JEV (SA14-14-2 strain). The PCR segments were inserted into the NheI and NotI sites of pcDNA5/FRT vector or into the NheI and XhoI sites of pAcUW51-M. Then they were transfected into 293T cells or Sf9 cells respectively. The expression and secretion of E protein were detected by immunofluorescence assay (IFA) and Western Blot. RESULTS: After transected into 293T cells or Sf9 cells, all constructs expressed E protein intracellularly indentified by IFA while only two plasmids could secret detectable E protein into tissue culture using Western Blot analysis. CONCLUSION: Signal peptide as well as the transmembrane and cytoplasmatic domains is crucial for the secretion of dengue E protein.

[Expression and function analysis of dengue virus type 1 to 4 envelope domain III recombinant fusion protein].

OBJECTIVE: To observe the ability of dengue virus type 1-4 envelope domain III fusion protein to inhibit virus infection and analyze the neutralizing ability of polyclonal antibodies against rE III. METHODS: After being connected by linker peptide, E III protein of Dengue virus serotypes 1-4 were expressed in E coli BL21 (DE3) then purified. Fusion proteins were verified by Western Blot and ELISA. Rabbits were immunized with fusion proteins to produce anti-rE III serum. The activity of anti-rE III serum were detected through indirect immunofluorescence assay test. Inhibition of dengue virus type 1 to 4 infection in BHK-21 cells by rE III fusion protein were tested. Neutralizing activity of anti-rE III serum was analyzed. RESULTS: Dengue virus type 1 to 4 envelope domain III recombinant fusion protein was expressed in E coli BL21 and purified successfully. Then rE III fusion protein and anti-rE III serum were analyzed respectively and rE III fusion protein can effectively inhibit dengue virus type 1 to 4 from infecting BHK cells. The anti-rE III serums can neutralize dengue virus type 1 to 4 but with different neutralizing titer. CONCLUSION: Dengue virus type 1-4 envelope domain III fusion protein can directly inhibit DV infection. Antibodies induced by rE III fusion proteins can neutralize dengue virus type 1-4.