Immune responses induced in HHD mice by multiepitope HIV vaccine based on cryptic epitope modification

In silico prediction of T-cell and B-cell epitopes of human papillomavirus type 16 L1 protein

Human papillomavirus type 16 (HPV-16) is one of the most important cause of developing cervical cancer. Therefore, effective epitope-based vaccine design for HPV-16 would be of major medical benefit. The aim of our study was to identify B- and T-cell epitopes of HPV-16 L1 protein. In this study, the HPV-16 L1 gene was isolated from HPV recovered from five vaginal swab samples using specific primers and finally sequenced. The ExPASy translate tool (http://web.expasy.org/translate/) was used to convert nucleotide sequence into amino acid sequence. Bioinformatic analysis was employed to predict suitable B- and T-cell epitopes and immunogenicity, allergenicity, and toxicity of predicted epitopes were then evaluated. Afterward, the selected T-cell epitopes were docked using Molegro Virtual Docker software. The two epitopes ₂₀₇ AMDFTTLQA₂₁₅ and ₂₀₀ MVDTGFGAM₂₀₈ have showed a very strong binding affinity to HLA-A0201 and HLA-B3501 molecules, respectively. Outcome of B-cell epitope prediction showed that epitope ₄₇₅ KAKPKFTLGKRK ATPTTSSTSTTAKRKK₅₀₂ contained overlapped epitope, which might be the epitope associated with the production of neutralizing antibody response. Based on this finding, the predicted B- and T-cell epitopes are promising targets for epitope-based vaccine development against HPV-16. Further in vivo and in vitro experiments are needed to confirm our findings.

The Peptide Vaccine of the Future

The approach of peptide-based anticancer vaccination has proven the ability to induce cancer-specific immune responses in multiple studies for various cancer entities. However, clinical responses remain so far limited to single patients and broad clinical applicability was not achieved. Therefore, further efforts are required to improve peptide vaccination in order to integrate this low-side-effect therapy into the clinical routine of cancer therapy. To design clinically effective peptide vaccines in the future, different issues have to be addressed and optimized comprising antigen target selection as well as choice of optimal adjuvants and vaccination schedules. Furthermore, the combination of peptide-based vaccines with other immuno- and molecular targeted therapies as well as the development of predictive biomarkers could further improve efficacy. In this review, current approaches in the development of peptide-based vaccines and critical implications for optimal vaccine design are discussed.

Development of HPV16,18,31,45 E5 and E7 peptides-based vaccines predicted by immunoinformatics tools

Objectives

Viral oncoproteins are ideal targets in therapeutic vaccines for functional inhibition of human papillomaviruses (HPVs). Herein, we designed the peptide constructs derived from E5 and E7 oncoproteins of high-risk HPV types 16, 18, 31 and 45 using the bioinformatics tools and investigated their potency in mice.

Results

The framework of the combined in silico/in vivo analysis included (1) to determine physicochemical properties of the designed constructs, (2) to identify potential IFN-γ-inducing epitopes, (3) to assess allergenicity, (4) to recognize linear and discontinuous B cell epitopes using modeling and validation of 3D structure of the designed constructs, and (5) to evaluate immune responses and tumor growth in vivo. Our in silico data determined high potency of the HPV_16,18,31,45 E5 and HPV_16,18,31,45 E7 peptides for trigger B- and T-cell responses, and IFN-γ secretion. In vivo study indicated that the mixture of E5 and E7 immunodominant peptides from four types of high-risk HPV could induce Th1 immune response, and protect completely mice against TC-1 tumor cells.

Conclusion

Generally, the combined in silico/in vivo approaches showed the ability of the designed E5 and E7 peptide constructs from four major high-risk HPV types for development of therapeutic vaccines.

Electronic supplementary material

The online version of this article (10.1007/s10529-020-02792-6) contains supplementary material, which is available to authorized users.

In silico/In vivo analysis of high-risk papillomavirus L1 and L2 conserved sequences for development of cross-subtype prophylactic vaccine

Human papillomavirus (HPV) is the most common sexually transmitted infection in the world and the main cause of cervical cancer. Nowadays, the virus-like particles (VLPs) based on L1 proteins have been considered as the best candidate for vaccine development against HPV infections. Two commercial HPV (Gardasil and Cervarix) are available. These HPV VLP vaccines induce genotype-limited protection. The major impediments such as economic barriers especially gaps in financing obstructed the optimal delivery of vaccines in developing countries. Thus, many efforts are underway to develop the next generation of vaccines against other types of high-risk HPV. In this study, we developed DNA constructs (based on L1 and L2 genes) that were potentially immunogenic and highly conserved among the high-risk HPV types. The framework of analysis include (1) B-cell epitope mapping, (2) T-cell epitope mapping (i.e., CD4⁺ and CD8⁺ T cells), (3) allergenicity assessment, (4) tap transport and proteasomal cleavage, (5) population coverage, (6) global and template-based docking, and (7) data collection, analysis, and design of the L1 and L2 DNA constructs. Our data indicated the 8-epitope candidates for helper T-cell and CTL in L1 and L2 sequences. For the L1 and L2 constructs, combination of these peptides in a single universal vaccine could involve all world population by the rate of 95.55% and 96.33%, respectively. In vitro studies showed high expression rates of multiepitope L1 (~57.86%) and L2 (~68.42%) DNA constructs in HEK-293T cells. Moreover, in vivo studies indicated that the combination of L1 and L2 DNA constructs without any adjuvant or delivery system induced effective immune responses, and protected mice against C3 tumor cells (the percentage of tumor-free mice: ~66.67%). Thus, the designed L1 and L2 DNA constructs would represent promising applications for HPV vaccine development.

A modified HLA-A*0201-restricted CTL epitope from human oncoprotein (hPEBP4) induces more efficient antitumor responses

We previously identified human phosphatidylethanolamine-binding protein 4 (hPEBP4) as an antiapoptotic protein with increased expression levels in breast, ovarian and prostate cancer cells, but low expression levels in normal tissues, which makes hPEBP4 an attractive target for immunotherapy. Here, we developed hPEBP4-derived immunogenic peptides for inducing antigen-specific cytotoxic T lymphocytes (CTLs) targeting breast cancer. A panel of hPEBP4-derived peptides predicted by peptide-MHC-binding algorithms was evaluated to characterize their HLA-A2.1 affinity and immunogenicity. We identified a novel immunogenic peptide, P40-48 (TLFCQGLEV), that was capable of eliciting specific CTL responses in HLA-A2.1/K^b transgenic mice, as well as in peripheral blood lymphocytes from breast cancer patients. Furthermore, amino-acid substitutions in the P40-48 sequence improved its immunogenicity against hPEBP4, a self-antigen, thus circumventing tolerance. We designed peptide analogs by preferred auxiliary HLA-A*0201 anchor residue replacement, which induced CTLs that were crossreactive to the native peptide. Several analogs were able to stably bind to HLA-A*0201 and elicit specific CTL responses better than the native sequence. Importantly, adoptive transfer of CTLs induced by vaccination with two analogs more effectively inhibited tumor growth than the native peptide. These data indicate that peptide analogs with high immunogenicity represent promising candidates for peptide-mediated therapeutic cancer vaccines.

Analysis of the immune response of a new malaria vaccine based on the modification of cryptic epitopes

Malaria is a severe, life-threatening infectious disease that endangers human health. However, there are no vaccines or immune strategy of vaccines succeeding in both erythrocytic and pre-erythrocytic stage. During the liver stage of the Plasmodium life cycle, sporozoites invade the host liver cells. The sporozoites, then, induce a cellular immune response via the major histocompatibility complex (MHC) molecules on their surfaces. The cytotoxic T lymphocytes (CTLs) then recognize the corresponding antigen-MHC complex on the surfaces of these infected liver cells and kill them. However, dominant epitopes with high MHC affinity are prone to mutation due to immune selection pressure. CTLs evoked by the original dominant epitopes cannot recognize the mutated epitopes, leading to immune evasion. In this study, we have modified the cryptic epitopes of different antigens in the sporozoite and liver stages of Plasmodium falciparum to increase their immunogenicity without changing T cell antigen receptor (TCR)-peptide binding specificity. In addition, we have also added an important erythrocytic phase protective antigen, named apical membrane antigen 1 (AMA-1), to this process with the goal of constructing a complex multi-stage, multi-epitope recombinant DNA vaccine against P. falciparum. The vaccine was tested in HHD-2 mice. The method involved multiple stages of the P. falciparum life cycle as well as elucidation both humoral and cellular immunity. The conclusion drawn from the study was that the vaccine might provide an important theoretical and practical basis for generating effective preventative or therapeutic vaccine against P. falciparum.

Enhanced anti-colon cancer immune responses with modified eEF2-derived peptides

Eukaryotic elongation factor-2 (eEF2) is overexpressed in many human cancers and is an attractive target for cancer immunotherapy. The eEF2 derived polypeptides have been shown to be able to induce cytotoxic T lymphocytes from healthy donor. Here, we demonstrate the evidence indicating that modification of a segment of peptides from wild type eEF2-derived immunogenic peptides is able to further enhance its capacity of inducing antigen-specific cytotoxic T lymphocytes (CTLs) against colon cancer cells. Using peptide-MHC binding algorithms, potential HLA-A2.1-restricted epitopes capable of inducing specific CD8(+) CTLs were identified. By analyzing HLA-A2.1 affinity and immunogenicity, we further identified one novel immunogenic peptide, P739-747 (RLMEPIYLV), that elicited specific CTL responses in HLA-A2.1/K(b) transgenic mice and culture with peripheral blood lymphocytes from colon cancer patients. Furthermore, replacing certain amino acids (at positions 1, 3, 7) within the P739-747 sequence improved the immunogenicity against eEF2. Several analogs containing the auxiliary HLA-A*0201 anchor residues were able to stably bind to HLA-A*0201 and enhance CTL responses compared with the native sequence; two of them showed increased anti-tumor effects during the adoptive immunotherapy in vivo. Thus, these results support that modified immunogenic analogs are promising candidates for peptide-based cancer vaccination and immunotherapy.

Design and production of a multiepitope construct derived from hepatitis E virus capsid protein

The aim of this study was to design a high density multiepitope protein, which can be a promising multiepitope vaccine candidate against Hepatitis E virus (HEV). Initially, conserved and antigenic helper T‐lymphocyte (HTL) epitopes in the HEV capsid protein were predicted by in silico analysis. Subsequently, a multiepitope comprising four HTL epitopes with high‐affinity binding to the HLA molecules was designed, and repeated four times as high density multiepitope construct. This construct was synthesized and cloned into pET‐30a (+) vector. Then, it was transformed and expressed in Escherichia coli BL21 cells. The high density multiepitope protein was purified by Ni‐NTA agarose and concentrated using Amicon filters. Finally, the immunological properties of this high density multiepitope protein were evaluated in vitro. The results showed that the high density multiepitope construct was successfully expressed and purified. SDS‐PAGE and Western blot analyses showed the presence of a high density multiepitope protein band of approximately 33 kDa. Approximately 1 mg of the purified protein was obtained from each liter of the culture media. Moreover, the purified multiepitope protein was capable of induction of proliferation responses, IFN‐γ ELISPOT responses and IFN‐γ and IL‐12 cytokines production in a significant level in peripheral blood mononuclear cells (PBMCs) isolated from HEV‐recovered individuals compared to the control group. In conclusion, the newly produced multiepitope protein can induce significant T helper type 1 responses in vitro, and can be considered as a novel strategy for the development of HEV vaccines in the future. J. Med. Virol. 87:1225–1234, 2015. © 2015 Wiley Periodicals, Inc.

An overview of bioinformatics tools for epitope prediction: implications on vaccine development

Exploitation of recombinant DNA and sequencing technologies has led to a new concept in vaccination in which isolated epitopes, capable of stimulating a specific immune response, have been identified and used to achieve advanced vaccine formulations; replacing those constituted by whole pathogen-formulations. In this context, bioinformatics approaches play a critical role on analyzing multiple genomes to select the protective epitopes in silico. It is conceived that cocktails of defined epitopes or chimeric protein arrangements, including the target epitopes, may provide a rationale design capable to elicit convenient humoral or cellular immune responses. This review presents a comprehensive compilation of the most advantageous online immunological software and searchable, in order to facilitate the design and development of vaccines. An outlook on how these tools are supporting vaccine development is presented. HIV and influenza have been taken as examples of promising developments on vaccination against hypervariable viruses. Perspectives in this field are also envisioned.