Wenshu Li

Identification of immunodominant linear B-cell epitopes within the major outer membrane protein of Chlamydia trachomatis

Chlamydia trachomatis is one of the most prevalent sexually transmitted pathogens. Chlamydial major outer membrane protein (MOMP) can induce strong cellular and humoral immune responses in murine models and has been regarded as a potential vaccine candidate. In this report, the amino acid sequence of MOMP was analyzed using computer-assisted techniques to scan B-cell epitopes, and three possible linear B-cell epitopes peptides (VLKTDVNKE, TKDASIDYHE, TRLIDERAAH) with high predicted antigenicity and high conservation were investigated. The DNA coding region for each potential epitope was cloned into pET32a(+) and expressed as Trx-His-tag fusion proteins in Escherichia coli. The fusion proteins were purified by Ni-NTA agarose beads and followed by SDS-PAGE and western blot analysis. We immunized mice with these three fusion proteins. The sera containing anti-epitope antibodies from the immunized mice could recognize C. trachomatis serovars D and E in ELISA. Antisera of these fusion proteins displayed an inhibitory effect on invasion of serovar E by in vitro neutralization assays. In addition, serum samples from convalescent C. trachomatis-infected patients were reactive with the epitope fusion proteins by western blot assay. Our results showed that the epitope sequences selected by bioinformatic analysis are highly conserved C. trachomatis MOMP B-cell epitopes, and could be good candidates for the development of subunit vaccines, which can be used in clinical diagnosis.

Comparative evaluation of immunization with recombinant protein and plasmid DNA vaccines of fusion antigen ROP2 and SAG1 from Toxoplasma gondii in mice: cellular and humoral immune responses

The aim of this work was to evaluate immune responses in BALB/c mice vaccinated subcutaneously by recombinant protein, or intramuscularly by plasmid DNA with fusion antigen of rhoptry protein 2 (ROP2) and major surface protein 1 (SAG1) from Toxoplasma gondii (T. gondii). BALB/c mice were immunized with one of three different antigen formulations respectively, which were rROP2-SAG1, pcROP2-SAG1, and pcROP2-SAG1 boosted with rROP2-SAG1. The production of IgG, IgG subclasses, lymphoproliferation, and level of gamma interferon (IFN-γ) were detected after vaccination. The animals vaccinated with rROP2-SAG1 quickly developed specific anti-TLA (T. gondii lysate antigen) antibodies, which continued to rise after immunization. However, production of IgG against TLA in mice vaccinated with pcROP2-SAG1 was relatively slow and maintained a high level after reaching plateau. There are more vigorous specific lymphoproliferative responses observed in mice of group rROP2-SAG1 than in pcROP2-SAG1. Immune responses in mice of group pcROP2-SAG1 boosted with rROP2-SAG1 were similar to the protein immunization group. Three immunization procedures resulted in a similar level of IFN-γ production. Our results indicate that BALB/c mice vaccinated by three immunization procedures induce similar humoral and cellular immunity against infection of T. gondii. Mice immunized with recombinant protein rROP2-SAG1 produce more humoral immune responses than mice immunized with other antigen formulations.

Hepatitis B virus surface antigen as delivery vector can enhance Chlamydia trachomatis MOMP multi-epitope immune response in mice.

Chlamydia trachomatis is the leading cause of sexually transmitted infections worldwide. There is currently no commercially available vaccine against C. trachomatis. Major outer membrane protein (MOMP) of C. trachomatis is considered to be an ideal candidate for prophylactic vaccine. We designed a MOMP multi-epitope containing T- and B-cell epitope-rich peptides and developed hepatitis B surface antigen (HBsAg) as antigen delivery vehicle. In order to study the immunogenicity and efficacy of the candidate vaccine in a murine model of chlamydial genital infection, we engineered a recombinant plasmid expressing HBsAg and MOMP multi-epitope genes. Results of reverse transcription polymerase chain reaction and immunofluorescence assay revealed successful expression of the recombinant HBsAg/MOMP multi-epitope gene at both the transcription and translation levels. Intramuscular administration in mice was able to elicit not only antibodies against Chlamydia and HBsAg but also cytotoxic T lymphocyte activity against Chlamydia. In addition, mice inoculated with the rHBsAg were highly resistant to C. trachomatis genital infection. The rHBsAg DNA with MOMP multi-epitope appended at the C terminus of the HBsAg stimulated a stronger immune response and protective response than that appended at the N terminus. Together, our results suggested that use of a recombinant HBsAg encoding the MOMP multi-epitope could be a powerful approach to developing a safe and immunogenic C. trachomatis vaccine.

Induction of Humoral and Cellular Immune Responses in Mice by Multiepitope Vaccines Composing of Both T and B Lymphocyte Epitopes of MAGE-A3 which are Recombined into HBcAg

BACKGROUND Melanoma-associated antigen-A3 (MAGE-A3) is a tumor specific antigen and a potential candidate for cancer immunotherapy. We had screened three immunodominant multiepitopes of MAGE-A3, and identified these multiepitope peptides had significantly higher reactivity to serum samples from gastric cancer patients. However, the immune responses of three multiepitope peptides carried by HBcAg in mice have not been investigated. OBJECTIVES The main objective of this study was to analyze the humoral and cellular immune responses in mice induced by these three multiepitope vaccines of MAGE-A3. METHODS Three multiepitopes of MAGE-A3 (MAGE-A3(EPI-1, or -2, or -3)) were respectively inserted at HBcAg major immunodominant region (HBcAg(MIR)) of the pET21a(+)/HBcAg(MIR) recombinant plasmid. These recombinant chimeras were identified by PCR, and transfected respectively into E. Coli Ressotta strain. The expression products of rHBcAg(MIR)/MAGE-A3(EPI-1, or -2, or -3) were purified respectively by Ni2+ chelated affinity column, and then confirmed by SDS-PAGE and Western-blot analysis.Purified three rHBcAg(MIR)/MAGE-A3 multiepitopes were administrated respectively into BALB/c (H-2Kd) mice by intradermal injection. The production of rHBcAg(MIR)/MAGE-A3(EPI-1, or -2, or -3) specific IgG in serum from immunized mice were measured by ELISA. Spleen cells from all immunized mice were harvested after one week of last immunization for lymphocyte proliferation assay and cytotoxic T-lymphocyte assay. RESULTS PCR and Sequencing analysis showed the presence of the required gene fragment in pET21a(+)/ HBcAg(MIR)/MAGE-A3(EPI-1, or -2, or -3) recombinant plasmid. Purified rHBcAg(MIR)/MAGE-A3(EPI-1, or -2, or -3) could be probed specifically by McAb of 6×his-tag. ELISA analysis indicated that serum from immunized mice with rHBcAg(MIR)/MAGE-A3(EPI-1, -2, or -3) proteins could be discerned specifically by complete MAGE-A3 protein, and high level of antibodies in immune serum were obtained, and all antibody titers could reach above 1:1600. The splenocytes from groups of rHBcAg(MIR)/MAGE-A3(EPI-1,-2, or -3), stimulated respectively with corresponding peptides showed the higher proliferative responses comparing with control groups of HBcAg(MIR) or PBS (p<0.05, respectively). Splenocytes from mice immunized with rHBcAg(MIR)/MAGE-A3 (EPI-1, or -2, or -3) could killed target cells effectively, and there were significant difference of CTL activities compared with control groups of HBcAg(MIR), or PBS (p<0.05, respectively) at any ratio of effector : target. CONCLUSION Our results indicated MIR in HBcAg presenting platform could present MAGE-A3 multiepitopes efficiently and induced significant humoral or cellular immunity. The immune strategy based on multiepitopeimmunization could have potential for preventing or controlling MAGE-A3 associated malignant disease.

Identification of linear B-cell epitopes within Tarp of Chlamydia trachomatis.

Chlamydia trachomatis is one of the most prevalent sexually transmitted pathogens. There is currently no commercially available vaccine against C. trachomatis. Chlamydial translocated actin‐recruiting phosphoprotein (Tarp) can induce cellular and humoral immune responses in murine models and has been regarded as a potential vaccine candidate. In this report, the amino acid sequence of Tarp was analyzed using computer‐assisted techniques to scan B‐cell epitopes, and six possible linear B‐cell epitopes peptides (aa80–95, aa107–123, aa152–170, aa171–186, aa239–253 and aa497–513) with high predicted antigenicity and high conservation were investigated. Sera from mice immunized with these potential immunodominant peptides was analyzed by ELISA, which showed that epitope 152–170 elicited serum immunoglobulin G (IgG) response and epitope 171–186 elicited both serum IgG and mucosal secretory immunoglobulin A response. The response of immune sera of epitope 171–186 to endogenous Tarp antigen obtained from the Hela229 cells infected with C. trachomatis was confirmed by Western blot and indirect fluorescence assay. In addition, binding of the antibodies against epitope 171–186 to endogenous Tarp was further confirmed by competitive ELISA. Our results demonstrated that the putative epitope (aa171–186) was an immunodominant B‐cell epitope of Tarp. If proven protective and safe, this epitope, in combination with other well‐documented epitopes, might be included into a candidate epitope‐based vaccine against C. trachomatis. Copyright

Immunogenicity of a multiepitope plasmid DNA encoding T and B lymphocyte epitopes from latent membrane protein 2 (LMP2) of Epstein-Barr virus as a vaccine in mice.

Epstein-Barr virus (EBV) is a human oncogenic herpesvirus associating with several malignant diseases. Latent membrane protein 2 (LMP2) of EBV is considered to be an ideal candidate for immunotherapy or prophylactic EBV vaccine. We designed a LMP2 multiepitope containing T and B-cell epitope-rich peptides and constructed a recombinant plasmid containing mammalian codonoptimization EBV LMP2 multiepitope (pcDNA3.1+/EBV-LMP2 multiepitope). After pcDNA3.1+/EBV-LMP2 multiepitope was transfected into COS-7 cells, significant expression of the multiepitope in COS-7 cells was confirmed by RT-PCR and immunofluorescence assay. Western blot analysis indicated that serum from immunized mice could be discerned by the EBV-LMP2 protein and the EBV-LMP2 multiepitope specifically. The plasmid DNA of EBV-LMP2 multiepitope induced high levels anti-EBV membrane protein and anti-EBV LMP2 multiepitope IgG in mice. T lymphocytes from spleen of immunized mice showed a strong CTL activity. The present study suggested that plasmid DNA encoding EBV LMP2 multiepitope capable of stimulating enough cellular and humoral immunity could have potential for preventing or controlling EBV infection and EBV associated disease in mice.

Identification and Characterization of Novel B-Cell Epitopes Within EBV Latent Membrane Protein 2 (LMP2)

The purpose of this study was to screen and identify the linear B cell epitopes of Epstein-Barr virus (EBV) latent membrane protein 2 (LMP2). The secondary structure and the surface properties of EBV LMP2A protein were analyzed. Then, the peptides with good hydrophilicity, high accessibility and flexibility and strong antigenicity were chosen and average antigenicity index (AI) of epitope peptide was further investigated. Three peptides were selected as potential linear B cell epitopes. The location and the sequence of amino acid were 199-209 (RIEDPPFNSLL), 318-322 (TLNLT) and 381-391 (KSLSSTEFIPN), respectively. The genes encoding potential B cell epitope were cloned and expressed in E. coli system. The immune sera of above different purified fusion proteins were obtained from BLAB/c mice by subcutaneously immunization for three times. Western blot showed that these epitope recombinant proteins could be recognized by the serum antibodies against the whole LMP2 of EBV obtained from nasopharyngeal carcinoma (NPC). Indirect ELISA measured the reactivity of individual sera from 196 NPC patients, 44 infectious mononucleosis (IM) and 108 healthy individuals to these epitope-fused proteins indicated that NPC patients were significantly higher compared with IM and healthy individuals (P<0.05). In addition, all the immune sera of peptide-fused proteins could response to native LMP2A antigen obtained from the EBV prototype strain, B95-8 cells. IFA confirmed that the recognition of the specific antibodies induced by the immune sera of epitope peptide-fused proteins was intracellular regions of LMP2A. These results demonstrated that these three predictive epitopes not only were immunodominant B-cell epitopes of LMP2A, but also may be potential targets for application in the design of diagnostic tools.

Expression of HPV6b L1/EBV LMP2 multiepitope and immunogenicity in mice

Human papillomavirus (HPV) major capsid protein L1 is an important vehicle for the delivery of epitopes. To investigate the expression and immunogenicity of hybridized HPV6b L1 containing multiepitope of Epstein-Barr virus (EBV) latency membrane protein 2 (LMP2), a recombinant plasmid pcDNA3.1(+) containing mammalian codon-optimization HPV6b L1 gene and EBV LMP2 multiepitope was constructed. The EBV LMP2 multiepitope containing T- and B-cell epitope-rich peptides was inserted into C-terminal of HPV6b L1-coding sequence. The constructed plasmid after verified by enzyme restriction assay and DNA sequencing was transfected into COS-7 cells. Expression of the chimeric gene in COS-7 cells was confirmed by RT-PCR, western blot analysis and immunofluorescence assay. Results revealed successful expression of the chimeric HPV6b L1/EBV LMP2 multiepitope gene both at the mRNA and protein levels in transfected COS-7 cells. Intramuscular administration in mice was able to elicit not only antibodies against HPV6b L1 virus-like particle and EBV LMP2, but also cytotoxic T lymphocyte activity against the EBV LMP2 epitopes. The present results confirmed that HPV L1 protein is potential to deliver multiepitope of EBV LMP2 as immunogen to the MHC class I and class II pathways, extending the use of HPV L1 as delivery vehicles.

Chimerically fused antigen rich of overlapped epitopes from latent membrane protein 2 (LMP2) of Epstein–Barr virus as a potential vaccine and diagnostic agent

Epstein–Barr virus (EBV) is prevalent throughout the world and is associated with several malignant diseases in humans. Latent membrane protein 2 (LMP2) of EBV plays a crucial role in the pathogenesis of EBV-associated tumors; therefore, LMP2 has been considered to be a potential immunodiagnostic and immunotherapeutic target. A multi-epitope-based antigen is a promising option for therapeutic vaccines and diagnoses of such malignancies. In this study, we systematically screened cytotoxic T lymphocyte (CTL), helper T cell (Th) and B-cell epitopes within EBV-LMP2 using bioinformatics. Based on the screen, two peptides rich in overlapping epitopes of both T cells and B cells were selected to construct a plasmid containing the sequence for a chimeric multi-epitope protein referred to as EBV-LMP2m, which is composed of LMP2aa195∼232 and LMP2aa419∼436. The EBV-LMP2m protein was expressed in E. coli BL21 (DE3) after prokaryotic codon optimization. Inoculation of the purified chimeric antigen in BALB/c mice induced not only high levels of specific IgG in the serum and secretory IgA in the vaginal mucus but also a specific CTL response. By using purified EBV-LMP2m as an antigen, the presence of specific IgG in the serum specimens of 202 nasopharyngeal carcinoma (NPC) patients was effectively detected with 52.84% sensitivity and 95.40% specificity, which represents an improvement over the traditional detection method based on VCA-IgA (60.53% sensitivity and 76.86% specificity). The above results indicate that EBV-LMP2m may be used not only as a potential target antigen for EBV-associated tumors but also a diagnostic agent for NPC patients.