Antigen epitopes of animal coronaviruses:a mini-review

Coronaviruses are widespread in nature and can infect mammals and poultry,making them a public health concern.Globally,prevention and control of emerging and re-emerging animal coronaviruses is a great challenge.The mecha-nisms of virus-mediated immune responses have important implications for research on virus prevention and control.The antigenic epitope is a chemical group capable of stimulating the production of antibodies or sensitized lympho-cytes,playing an important role in antiviral immune responses.Thus,it can shed light on the development of diagnos-tic methods and novel vaccines.Here,we have reviewed advances in animal coronavirus antigenic epitope research,aiming to provide a reference for the prevention and control of animal and human coronaviruses.

Bioinformatics analysis of the structure and linear B-cell epitopes of aquaporin-3 from Schistosoma japonicum

Objective:To analyze the structure of aquaporins-3(AQP-3) from Schistosoma japonicum(SJAQP-3) using bioinformalical methods,and to provid of references for vaccine targets research.Methods:Protparam,BepiPred,TMHMM Server,MLRC,Geno3d,DNA star software packages were used to predict the physical and chemical properties,hydrophilicity plot, flexibility regions,antigenic index,surface probability plot,secondary structure,and tertiary structure of amino acid sequence of SJAQP-3.Results:SJAQP-3 had six transmembrane regions and two half-spanning helices that form a central channel.The half-spanning helices fold into the centre of the channel.Either of the half-spanning helix had a conserved motif of NPA common to all aquaporins.Predicted linear B-Cell epitopes were most likely at the N-terminal amino acid residues of Saa-7aa,59aa- 62aa,225aa-230aa,282aa -288aa,294aa -29Saa and 305aa -307aa area.59aa- 62aa,22Saa-230aa located outside the membrane,the others located inside the cell.Conclusions:SJAQP-3 is a integral membrane protein in Schistosoma japonicum tegument.There are six potential epitopes in SJ AQP-3.It might be a potential molecular target for the development of vaccines.

An Indirect ELISA of Classical Swine Fever Virus Based on Quadruple Antigenic Epitope Peptide Expressed in E.coli

In this study,a synthesized quadruple antigenic epitope gene region of the classical swine fever virus (CSFV)E2 glycoprotein was expressed in E.coli to a obtain target protein.This target protein was used as a coating antigen to establish an indirect ELISA for specifically detecting anti-CSFV antibodies in serum samples from pigs.The P/N cut-off value of this assay was 1.92 by receiver operating characteristic curve(ROC)analysis based on 30 negative sera and 80 positive samples.The test gave 97.5%sensitivity and 96.7%specificity compared with the indirect hemagglutination(IHA)test.The inter-assay and intra-assay coefficients of variation (CVs)for 16 sera were both≤6.8%.No cross-reactivity between the coating antigen and anti-bovine viral diarrhoea virus(BVDV)antibodies was observed.

Theoretical Study of Continuous B-Cell Epitopes with Developed BP Neural Network

In order to identify continuous B-cell epitopes effectively and to increase the success rate of experimental identification, the modified Back Propagation artificial neural network (BP neural network) was used to predict the continuous B-cell epitopes, and finally the predictive model for the B-cells epitopes was established. Comparing with the other predictive models, the prediction performance of this model is more excellent (AUC = 0.723). For the purpose of verifying the performance of the model, the prediction to the SWISS PROT NUMBER: P08677 was carried on, and the satisfying results were obtained.

An immunoglobulin Y that specifically binds to an in silico-predicted unique epitope of Zika virus non-structural 1 antigen

Objective:To identify unique immunogenic epitopes of Zika virus non-structural 1(NS1)antigen and produce immunoglobulin Y(IgY)for potential use in he diagnosis of of Zika virus infection.Methods:Immunogenic epitopes were identified using in silico B-cell epitope prediction.A synthetic peptide analog of the predicted epitope was used to induce antipeptide IgY production in hens which was purified using affinity chromatography.Presence of purified IgY and its binding specificity were performed by gel electrophoresis and ELISA,respectively.Results:Out of the nine continuous epitopes identified,the sequence at position 193-208(LKVREDYSLECDPAVI)was selected and used to produce anti-peptide IgY.The produced IgY was found to bind to the synthetic analog of the Zika virus NS1 immunogenic epitope but not to other flaviviruses and random peptides from other pathogens.Conclusions:In this study,we identified an immunogenic epitope unique to Zika virus that can be used to develop a serodiagnostic tool that specifically detect Zika virus infection.

Identification of the epitopes on HCV core protein recognized by HLA-A2 restricted cytotoxic T lymphocytes

AIM: To identify hepatitis C virus(HCV) core protein epitopes recognized by HLA-A2 restricted cytotoxic T lymphocyte (CTL). METHODS: Utilizing the method of computer prediction followed by a 4h(51)Cr release assay confirmation. RESULTS: The results showed that peripheral blood mononuclear cells (PBMC) obtained from two HLA-A2 positive donors who were infected with HCV could lyse autologous target cells labeled with peptide "ALAHGVRAL (core 150-158)". The rates of specific lysis of the cells from the two donors were 37.5% and 15.8%, respectively. Blocking of the CTL response with anti-CD4 mAb caused no significant decrease of the specific lysis. But blocking of CTL response with anti-CD8 mAb could abolish the lysis. CONCLUSION: The peptide (core 150-158) is the candidate epitope recognized by HLAA2 restricted CTL.

Helicobacter pylori specific immune response induced by conservative flagellin linear B-cell epitope

AIM:To testify the immunogenicity of a conservative B-cell linear epitope of Helicobacter pylori ( H pylori) flagellin A. METHODS: Different programs were used to analyze the secondary structure, molecular hydropathy, and surface accessibility of Hpyloriflagellin A. Linear B-cell epitopes were estimated based on the structural and physiochemical information. Analysis of residue divergence was proposed to screen a conservative linear epitope. The 29-peptide (Pep29mer) synthesized by chemical method, including the predicted conservative B-cell epitope and a known K^2d compatible T-cell epitope, was used to immunize mice, and then H pylori-specific antibodies were detected by ELISA. RESULTS: Based on the analyses of divergent amino acid residues, structural and physiochemical characteristics, it was strongly suggested that the short fragment NDSDGR was the core of a conservative linear epitope in flagellin A. Animals immunized by Pep29mer acquired efficient immune response. In detail, serum Hpylori-specific IgA and IgGl increased significantly in immunized group, while IgG2a only had an insignificant change. Hpylori-specific IgA in gastrointestinal flushing fluid also increased significantly. CONCLUSION: The conservative short fragment NDSDGR is the core of a linear B-cell epitope of flagellin A.

Prokaryotic Expression and Immunogenicity of Major Antigen Epitope of Rabbit Haemorrhagic Disease Virus VP60

[ Objective] To investigate the immunogenicity of main antigen epitope of RHDV （ Rabbit haemorrhagic disease virus） VP60 expressed in a prokaryotic system. [ Method] The major antigen epitope gene of RHDV VP60 was amplified by RT-PCR. It was cloned into pET-28b （ ＋ ） and expressed in E. coli Rosetta strain. The recombinant protein was detected by Western blot. The pudfied recombinant protein was used to immunize rabbits in order to observe its immunogenicity. [ Result] Western blot analysis revealed a clear band at approximately 24.0 kDa. The purified recom- binant protein reacted with the purified RHDV in ELISA. [ Conclusion] The prokaryotically expressed main antigen epitope of RHDV VP60 shows good immunogenicity.

Isolation of Mannooligosaccharides Corresponding to Antigenic Determinants of Pathogenic Yeast <i>Candida catenulata</i>Cell Wall Mannan

To investigate the chemical structure of cell wall mannan of pathogenic yeast, Candida catenulata IFO 0745 strain, which possess the epitopes of antigenic factors 1, 9, and 34 to genus Candida, we previously performed the two-dimensional nuclear magnetic resonance (NMR) analysis of this mannan, Fr. C, without the need for harsh procedures. In this study, three oligosaccharides, biose, triose, and tetraose, and mannose were isolated from Fr. C by acetolysis. The results of NMR analysis indicate that the chemical structures of these oligosaccharides were identified to Manα1-2Man, Manα1-2Manα1-2Man, and Manα1-3Manα1-2Manα1-2Man. The most of resultant mannose seems to be originated from the α-1,6-linked mannan backbone which is recognized by antiserum to factor 9. The inhibition assay of slide agglutination reaction between Fr. C and antigenic antibodies using three oligosaccharides indicate that the Manα1-2Manα1-2Man and Manα1-3Manα1-2Manα1-2Man possess domains corresponding to immunodominants of antigenic factors 1 and 34, respectively.

Prediction of promiscuous T-cell epitopes in the Zika virus polyprotein:An in silico approach

Objective:To predict immunogenic promiscuous T-cell epitopes from the polyprotein of the Zika virus using a range of bioinformatics tools.To date,no epitope data are available for the Zika virus in the IEDB database.Methods:We retrieved nearly 54 full length polyprotein sequences of the Zika virus from the NCBI database belonging to different outbreaks.A consensus sequence was then used to predict the promiscuous T cell epitopes that bind MHC 1 and MHC II alleles using Propred1 and Propred immunoinformatic algorithms respectively.The antigencity predicted score was also calculated for each predicted epitope using the Vaxi Jen 2.0 tool.Results:By using Pro Pred1,23 antigenic epitopes for HLA class I and 48 antigenic epitopes for HLA class II were predicted from the consensus polyprotein sequence of Zika virus.The greatest number of MHC class I binding epitopes were projected within the NS5(21%),followed by Envelope(17%).For MHC class II,greatest number of predicted epitopes were in NS5(19%) followed by the Envelope,NS1 and NS2(17% each).A variety of epitopes with good binding affinity,promiscuity and antigenicity were predicted for both the HLA classes.Conclusion:The predicted conserved promiscuous T-cell epitopes examined in this study were reported for the first time and will contribute to the imminent design of Zika virus vaccine candidates,which will be able to induce a broad range of immune responses in a heterogeneous HLA population.However,our results can be verified and employed in future efficacious vaccine formulations only after successful experimental studies.

Antigenicity of the HCV HVR1 Peptide Analyzed by Computer Modeling

To find out the protective polypeptide epitopes of HCV HVR1, the antigenicity of the synthetic peptide was predicted by computer modeling and verified by ELISA and lymphocyte transformation test. It was found that the outcome of the computer modeling was in accord with the experimental results. The method by using computer modeling would be a economic approach by which the protective peptides could be identified quickly.

Chidamide and sintilimab combination in diffuse large B-cell lymphoma progressing after chimeric antigen receptor T therapy

BACKGROUND Diffuse large B-cell lymphoma(DLBCL)is curable with first-line chemoimmunotherapy but patients with relapsed/refractory(R/R)DLBCL still face a poor prognosis.For patients with R/R DLBCL,the complete response rate to traditional next-line therapy is only 7%and the median overall survival is 6.3 mo.Recently,CD19-targeting chimeric antigen receptor T cells(CAR-T)have shown promise in clinical trials.However,approximately 50%of patients treated with CAR-T cells ultimately progress and few salvage therapies are effective.CASE SUMMARY Here,we report on 7 patients with R/R DLBCL whose disease progressed after CAR-T infusion.They received a PD-1 inhibitor(sintilimab)and a histone deacetylase inhibitor(chidamide).Five of the 7 patients tolerated the treatment without any serious adverse events.Two patients discontinued the treatment due to lung infection and rash.At the 20-mo follow-up,the median overall survival of these 7 patients was 6 mo.Of note,there were 2 complete response rates(CRs)and 2 partial response rates(PRs)during this novel therapy,with an overall response rate(ORR)of 57.1%,and one patient had a durable CR that lasted at least 20 mo.CONCLUSION In conclusion,chidamide combined with sintilimab may be a choice for DLBCL patients progressing after CD19-targeting CAR-T therapy.

Hepatitis B surface antigen-negative but hepatitis B envelope antigen-positive false occult hepatitis B virus infection:A case report

BACKGROUND Occult hepatitis B infection(OBI)is characterized by the detection of hepatitis B virus(HBV)DNA in serum(usually HBV DNA<200 IU/mL)or the liver but negativity for hepatitis B surface antigen(HBsAg).The diagnosis of OBI relies on the sensitivity of assays used in the detection of HBV DNA and HBsAg.HBsAg assays with inadequate sensitivity or inability to detect HBV S variants may lead to misdiagnosis of OBI in people with overt HBV infection.CASE SUMMARY We report a HBsAg-negative but hepatitis B envelope antigen-positive patient who had a significant HBV DNA level.The patient was initially diagnosed as having OBI.However,sequence analysis revealed a unique insertion of amino acid residues at positions 120-124 in the S protein,which affects the formation of a disulfide bond that is associated with the formation of a loop.It is well known that there is an overlap between the S protein and Pol protein.We found that this new insertion site occurred in polymerase/reverse transcriptase domain,indi-cating that this insertion might be involved in HBV pathogenicity.The patient was finally diagnosed with a false OBI.CONCLUSION An insertion of amino acid residues at positions 120-124 of the S protein affects the formation of immunodominant epitopes and results in negative HBsAg levels.

甲壳类水产品致敏原及特异性免疫制品的研究进展

甲壳类水产品是我国常见的致敏食物之一,除了规避致敏食物的摄入,目前仍无有效的根治方法。因此,致敏原的性质分析及防控技术方法的研究至关重要。本文针对甲壳类水产品致敏原,介绍了致敏原的免疫学特性与分子结构,归纳了致敏原的抗原表位,探讨了应用于致敏原特异性治疗的免疫制品,比较了不同免疫制品的作用机理及优缺点,可为研发水产品过敏的防控技术方法提供参考。

禽白血病病毒p27蛋白单克隆抗体制备及抗原表位的鉴定

为制备禽白血病病毒(ALV)p27蛋白特异性单克隆抗体,利用原核表达系统表达并纯化ALV p27蛋白,将其作为免疫原免疫注射Balb/c小鼠,用杂交瘤细胞融合和ELISA等筛选出阳性单克隆抗体细胞,对制备的单克隆抗体的抗体亚型、效价及特异性进行鉴定,将目的蛋白截短成4段,初步鉴定单克隆抗体识别的抗原表位区域。结果表明,共筛选出4株单克隆细胞,其抗体亚类皆为IgG1型,其中3A1抗体效价为1∶64000,3B2为1∶256000,5F1为1∶128000,5G2为1∶8000;4株单克隆抗体识别的抗原表位在1-60 aa之间。研究结果为进一步建立ALV相关免疫学检测方法提供了重要的材料。

Hepatocellular carcinoma-specific immunotherapy with synthesized α1,3-galactosyl epitope-ulsed dendritic cells and cytokine-induced killer cells

AIM： To evaluate the safety and clinical efficacy of a new immunotherapy using both α-Gal epitope-pulsed dendritic cells （DCs） and cytokine-induced killer cells. METHODS： Freshly collected hepatocellular carcinoma （HCC） tumor tissues were incubated with a mixture of neuraminidase and recombinant αl,3-galactosyltrans- ferase （αI,3GT） to synthesize α-Gal epitopes on car- bohydrate chains of the glycoproteins of tumor mem- branes. The subsequent incubation of the processed membranes in the presence of human natural anti-Gal IgG resulted in the effective phagocytosis to the tumor membrane by DCs. Eighteen patients aged 38-78 years with stage 111 primary HCC were randomly chosen for the study; 9 patients served as controls, and 9 patients were enrolled in the study group.RESULTS： The evaluation demonstrated that the pro- cedure was safe; no serious side effects or autoimmune diseases were observed. The therapy significantly pro- longed the survival of treated patients as compared with the controls （17.1 ± 2.01 mo vs 10.1 ±4.5 mo, P = 0.00121）. After treatment, all patients in the study group had positive delayed hypersensitivity and robust systemic cytotoxicity in response to tumor lysate as measured by interferon-y-expression in peripheral blood mononuclear cells using enzyme-linked immunosorbent spot assay. They also displayed increased numbers of CD8-, CD45RO- and CD56-positive cells in the peripheral blood and decreased α-fetoprotein level in the se- rum. CONCLUSION： This new tumor-specific immunotherapy is safe, effective and has a great potential for the treat- ment of tumors.

Computational analysis of antigenic epitopes of avian influenza A (H7N9) viruses

Influenza virus can rapidly change its antigenicity, via mutation in the hemagglutinin(HA) protein, to evade host immunity. The emergence of the novel human-infecting avian H7N9 virus in China has caused widespread concern. However, evolution of the antigenicity of this virus is not well understood. Here, we inferred the antigenic epitopes of the HA protein from all H7 viruses, based on the five well-characterized HA epitopes of the human H3N2 virus. By comparing the two major H7 phylogenetic lineages, i.e., the Eurasian lineage and the North American lineage, we found that epitopes A and B are more frequently mutated in the Eurasian lineage, while epitopes B and C are more frequently mutated in the North American lineage. Furthermore, we found that the novel H7N9 virus(derived from the Eurasian lineage) isolated in China in the year 2013, contains six frequently mutated sites on epitopes that include site 135, which is located in the receptor binding domain. This indicates that the novel H7N9 virus that infects human may already have been subjected to gradual immune pressure and receptor-binding variation. Our results not only provide insights into the antigenic evolution of the H7 virus but may also help in the selection of suitable vaccine strains.

Differential reactivity of mouse monoclonal anti-HBs antibodies with recombinant mutant HBs antigens

AIM: To investigate the reactivity of a panel of 8 mouse anti-hepatitis B surface antigen (HBsAg) monoclonal antibodies (mAbs) using a collection of 9 recombinant HBsAg mutants with a variety of amino acid substitutions mostly located within the “a” region.METHODS: The entire HBs genes previously cloned into a mammalian expression vector were transiently transfected into COS7 cells. Two standard unmutated sequences of the ayw and adw subtypes served as controls. Secreted mutant proteins were collected and measured by three commercial diagnostic immunoassays to assess transfection efficiency. Reactivity of anti-HBs mAbs with mutated HBsAgs was determined by sandwich enzyme-linked immunosorbent assay (ELISA).RESULTS: Reactivity of anti-HBs mAbs with mutated HBsAgs revealed different patterns. While three mutants reacted strongly with all mAbs, two mutants reacted weakly with only two mAbs and the remaining proteins displayed variable degrees of reactivity towards different mAbs. Accordingly, four groups of mAbs with different but overlapping reactivity patterns could be envisaged. One group consisting of two mAbs (37C5-S7 and 35C6-S11) was found to recognize stable linear epitopes conserved in all mutants. Mutations outside the “a” determinant at positions 120 (P→S), 123(T→N) and 161(M→T) were found to affect reactivity of these mAbs.CONCLUSION: Our findings could have important implications for biophysical studies, vaccination strategies and immunotherapy of hepatitis B virus (HBV) mutants.

Construction of prokaryotic expression system of TGF-β1 epitope gene and identification of recombinant fusion protein immunity

AIM： To insert the constructed TGF-β1 epitope gene into the el loop of C-terminus of truncated hepatitis B core antigen to increase TGF-β1 antigenicity in its prokaryotic expression system and to identify immunity of the expressed recombinant protein in order to exploit the possibility for obtaining anti- TGF-β1 vaccine. METHODS： The TGF-β1 encoding epitope gene （the mature TGF-β1 from 78-109 amino acid residues, TGF-β1^32） was amplified by polymerase chain reaction from the recombinant pGEM-7z/ TGF-β1 ^32 vector. The HBcAg gene fragments （encoding HBcAg from 1-71 and 89-144 amino acid residues） were amplified from PYTAI- HBcAg vector. The recombinant vector pGEMEX-1 was used to insert HBcAg1-71, TGF-β1^32 and HBcAg89-144 into restrictive endonuclease enzyme and ligated with T4 Ugase. The fusion gene fragments HBc.Ag1-71-TGF-β1^32 HBcAg89-144 were recloned to pET28a（＋） and the DNA sequence was confirmed by the dideoxy chain termination method. The recombinant vector pET28a （＋）/ CTC was transformed and expressed in E. coli BL21 （DE3） under induction of IPTG. After purification with Ni^＋2 NTA agarose resins, the antigenicity of purified protein was detected by ELISA and Western blot and visualized under electron microscope. RESULTS： Enzyme digestion analysis and sequencing showed that TGF-β1 epitope gene was inserted into the el loop of C-terminus of truncated hepatitis B core antigen. SDS-PAGE analysis showed that relative molecular mass （Mr） of the expressed product by pET28a （＋）/CTC was Mr 24 600.The output of the target recombinant protein was approximately 34.8% of the total bacterial protein,mainly presented in the form of inclusion body. Western blotting and ELISA demonstrated that the fusion protein could combine with anti-TGF-β1 polyclonal IgG but not with anti-HBcAg. The purity of protein was about 90 % and the protein was in the form of self-assembling particles visualized under electron microscope. This fusion protein had good anti-TGF-β1 antigenicity and could be used as anti-TGF-β1 vaccine. CONCLUSION： A recombinant prokaryotic expression system with high expression efficiency of the target TGF-β1 epitope gene was successfully established. The fusion protein is in the form of self-assembling particles and HBcAg can increase the antigenicity of TGF-β1. The expressed TGF-β1 epitope gene shows good immunogenicity and antigenicity.

乙型肝炎病毒前S2抗原决定簇（HBVPreS2epitope）与乙型肝炎病毒核心抗原（HBcAg）的基因融合与表达

乙肝前Ｓ２（ＨＢＶＰｒｅＳ２）肽段由５５个氨基酸组成，其Ｎ端肽段含Ｔｈ和Ｂ细胞抗原决定簇。我们将化学合成的ＰｒｅＳ２ｅｐｉｔｏｐｅ（１２０－１４５）基因与ＨＢｃＡｇ基因不同位点进行融合，融合基因在大肠杆菌中获得表达，并对融合蛋白进行了纯化。经ＥＬＩＳＡ和Ｗｅｓｔｅｒｎ－ｂｌｏｔ实验表明，融合蛋白具有ＰｒｅＳ２和ＨＢｃＡｇ两者的抗原性。此外，研究还表明，强启动子能使表达水平有一定提高。