Peptide-based Vaccine Candidates Research Articles

Universal peptide-based potential vaccine design against canine distemper virus (CDV) using a vaccinomic approach

Canine distemper virus (CDV) affects many domestic and wild animals. Variations among CDV genome linages could lead to vaccination failure. To date, there are several vaccine alternatives, such as a modified live virus and a recombinant vaccine; however, most of these alternatives are based on the ancestral strain Onderstepoort, which has not been circulating for years. Vaccine failures and the need to update vaccines have been widely discussed, and the development of new vaccine candidates is necessary to reduce circulation and mortality. Current vaccination alternatives cannot be used in wildlife animals due to the lack of safety data for most of the species, in addition to the insufficient immune response against circulating strains worldwide in domestic species. Computational tools, including peptide-based therapies, have become essential for developing new-generation vaccines for diverse models. In this work, a peptide-based vaccine candidate with a peptide library derived from CDV H and F protein consensus sequences was constructed employing computational tools. The molecular docking and dynamics of the selected peptides with canine MHC-I and MHC-II and with TLR-2 and TLR-4 were evaluated. In silico safety was assayed through determination of antigenicity, allergenicity, toxicity potential, and homologous canine peptides. Additionally, in vitro safety was also evaluated through cytotoxicity in cell lines and canine peripheral blood mononuclear cells (cPBMCs) and through a hemolysis potential assay using canine red blood cells. A multiepitope CDV polypeptide was constructed, synthetized, and evaluated in silico and in vitro by employing the most promising peptides for comparison with single CDV immunogenic peptides. Our findings suggest that predicting immunogenic CDV peptides derived from most antigenic CDV proteins could aid in the development of new vaccine candidates, such as multiple single CDV peptides and multiepitope CDV polypeptides, that are safe in vitro and optimized in silico. In vivo studies are being conducted to validate potential vaccines that may be effective in preventing CDV infection in domestic and wild animals.

Exploring structural antigens of yellow fever virus to design multi-epitope subunit vaccine candidate by utilizing an immuno-informatics approach

BackgroundYellow fever is a mosquito-borne viral hemorrhagic disease transmitted by several species of virus-infected mosquitoes endemic to tropical regions of Central and South America and Africa. Earlier in the twentieth century, mass vaccination integrated with mosquito control was implemented to eradicate the yellow fever virus. However, regular outbreaks occur in these regions which pose a threat to travelers and residents of Africa and South America. There is no specific antiviral therapy, but there can be an effective peptide-based vaccine candidate to combat infection caused by the virus. Therefore, the study aims to design a multi-epitope-based subunit vaccine (MESV) construct against the yellow fever virus to reduce the time and cost using reverse vaccinology (RV) approach. MethodsYellow fever virus contains 10,233 nucleotides that encode for 10 proteins (C, prM, E, NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5) including 3 structural and 7 non-structural proteins. Structural proteins—precursor membrane protein (prM) and envelope protein (E)—were taken as a target for B cell and T cell epitope screening. Further, various immunoinformatics approaches were employed to FASTA sequences of structural proteins to retrieve B cell and T cell epitopes. MESV was constructed from these epitopes based on allergenicity, antigenicity and immunogenicity, toxicity, conservancy, and population coverage followed by structure prediction. The efficacy of the MESV construct to bind with human TLR-3, TLR-4, and TLR-8 were evaluated using molecular docking and simulation studies. Finally, in-silico cloning of vaccine construct was performed withpBR322 Escherichia coli expression system using codon optimization. ResultsPredicted epitopes evaluated and selected for MESV construction were found stable, non-allergenic, highly antigenic, and global population coverage of 68.03% according to in-silico analysis. However, this can be further tested in in-vitro and in-vivo investigations. Epitopes were sequentially merged to construct a MESV consisting of 393 amino acids using adjuvant and linkers. Molecular docking and simulation studies revealed stable and high-affinity interactions. Furthermore, in-silico immune response graphs showed effective immune response generation. Finally, higher CAI value ensured high gene expression of vaccine in the host cell. ConclusionThe designed MESV construct in the present in-silico study can be effective in generating an immune response against the yellow fever virus. Therefore, to prevent yellow fever, it can be an effective vaccine candidate. However, further downstream, in-vitro study is required.

A new candidate epitope-based vaccine against PspA PhtD of Streptococcus pneumoniae: a computational experimental approach.

Pneumococcus is an important respiratory pathogen that is associated with high rates of death in newborn children and the elderly. Given the disadvantages of current polysaccharide-based vaccines, the most promising alternative for developing improved vaccines may be to use protein antigens with different roles in pneumococcus virulence. PspA and PhtD, highly immunogenic surface proteins expressed by almost all pneumococcal strains, are capable of eliciting protective immunity against lethal infections. In this study using immunoinformatics approaches, we constructed one fusion construct (called PAD) by fusing the immunodominant regions of PspA from families 1 & 2 (PA) to the immunodominant regions of PhtD (PD). The objective of this project was to test the immunogenicity of the fusion protein PAD and to compare its protective activity against S. pneumoniae infection with PA or PD alone and a combination of PA and PD. The prediction of physicochemical properties, antigenicity, allergenicity, toxicity, and 3D-structure of the constructs, as well as molecular docking with HLA receptor and immune simulation were performed using computational tools. Finally, mice were immunized and the serum levels of antibodies/cytokines and functionality of antibodies in vitro were evaluated after immunization. The mice survival rates and decrease of bacterial loads in the blood/spleen were examined following the challenge. The computational analyses indicated the proposed constructs could be antigenic, non-allergenic, non-toxic, soluble and able to elicit robust immune responses. The results of actual animal experiments revealed the candidate vaccines could induce the mice to produce high levels of antibodies and cytokines. The complement-mediated bactericidal activity of antibodies was confirmed and the antibodies provided favorable survival in immunized mice after bacterial challenge. In general, the experimental results verified the immunoinformatics studies. For the first time this report presents novel peptide-based vaccine candidates consisting of immunodominant regions of PspA and PhtD antigens. The obtained findings confirmed that the fusion formulation could be relatively more efficient than the individual and combination formulations. The results propose that the fusion protein alone could be used as a serotype-independent pneumococcal vaccine or as an effective partner protein for a conjugate polysaccharide vaccine.

In Vivo Validation of Novel Synthetic tbp1 Peptide-Based Vaccine Candidates against Haemophilus influenzae Strains in BALB/c Mice.

Haemophilus influenzae is a Gram-negative bacterium characterized as a small, nonmotile, facultative anaerobic coccobacillus. It is a common cause of a variety of invasive and non-invasive infections. Among six serotypes (a-f), H. influenzae type b (Hib) is the most familiar and predominant mostly in children and immunocompromised individuals. Following Hib vaccination, infections due to other serotypes have increased in number, and currently, there is no suitable effective vaccine to induce cross-strain protective antibody responses. The current study was aimed to validate the capability of two 20-mer highly conserved synthetic tbp1 (transferrin-binding protein 1) peptide-based vaccine candidates (tbp1-E1 and tbp1-E2) predicted using in silico approaches to induce immune responses against H. influenzae strains. Cytokine induction ability, immune simulations, and molecular dynamics (MD) simulations were performed to confirm the candidacy of epitopic docked complexes. Synthetic peptide vaccine formulations in combination with two different adjuvants, BGs (Bacterial Ghosts) and CFA/IFA (complete/incomplete Freund's adjuvant), were used in BALB/c mouse groups in three booster shots at two-week intervals. An indirect ELISA was performed to determine endpoint antibody titers using the Student's t-distribution method. The results revealed that the synergistic use of both peptides in combination with BG adjuvants produced better results. Significant differences in absorbance values were observed in comparison to the rest of the peptide-adjuvant combinations. The findings of this study indicate that these tbp1 peptide-based vaccine candidates may present a preliminary set of peptides for the development of an effective cross-strain vaccine against H. influenzae in the future due to their highly conserved nature.

Molecular Simulation of B-Cell Epitope Mapping from Nipah Virus Attachment Protein to Construct Peptide-Based Vaccine Candidate: A Reverse Vaccinology Approach

Molecular Simulation of B-Cell Epitope Mapping from Nipah Virus Attachment Protein to Construct Peptide-Based Vaccine Candidate: A Reverse Vaccinology Approach

Experimental Validation of MHC Class I and II Peptide-Based Potential Vaccine Candidates for Human Papilloma Virus Using Sprague-Dawly Models.

Human papilloma virus (HPV) causes cervical and many other cancers. Recent trend in vaccine design is shifted toward epitope-based developments that are more specific, safe, and easy to produce. In this study, we predicted eight immunogenic peptides of CD4+ and CD8+ T-lymphocytes (MHC class I and II as M1 and M2) including early proteins (E2 and E6), major (L1) and minor capsid protein (L2). Male and female Sprague Dawly rats in groups were immunized with each synthetic peptide. L1M1, L1M2, L2M1, and L2M2 induced significant immunogenic response compared to E2M1, E2M2, E6M1 and E6M2. We observed optimal titer of IgG antibodies (>1.25 g/L), interferon-γ (>64 ng/L), and granzyme-B (>40 pg/mL) compared to control at second booster dose (240 µg/500 µL). The induction of peptide-specific IgG antibodies in immunized rats indicates the T-cell dependent B-lymphocyte activation. A substantial CD4+ and CD8+ cell count was observed at 240 µg/500 µL. In male and female rats, CD8+ cell count for L1 and L2 peptide is 3000 and 3118, and CD4+ is 3369 and 3484 respectively compared to control. In conclusion, we demonstrated that L1M1, L1M2, L2M1, L2M2 are likely to contain potential epitopes for induction of immune responses supporting the feasibility of peptide-based vaccine development for HPV.

Designing, characterization, and immune stimulation of a novel multi-epitopic peptide-based potential vaccine candidate against monkeypox virus through screening its whole genome encoded proteins: An immunoinformatics approach

BackgroundThe current monkeypox virus (MPXV) spread in the non-epidemic regions raises global concern. Presently, the smallpox vaccine is used against monkeypox with several difficulties. Conversely, no next-generation vaccine is available against MPXV. Here, we proposed a novel multi-epitopic peptide-based in-silico potential vaccine candidate against the monkeypox virus. MethodsThe multi-epitopic potential vaccine construct was developed from antigen screening through whole genome-encoded 176 proteins of MPXV. Afterward, ten common B and T cell epitopes (9-mer) having the highest antigenicity and high population coverage were chosen, and a vaccine construct was developed using peptide linkers. The vaccine was characterized through bioinformatics to understand antigenicity, non-allergenicity, physicochemical properties, and binding affinity to immune receptors (TLR4/MD2-complex). Finally, the immune system simulation of the vaccine was performed through immunoinformatics and machine learning approaches. ResultsThe highest antigenic epitopes were used to design the vaccine. The docked complex of the vaccine and TLR4/MD2 had shown significant free binding energy (−98.37 kcal/mol) with a definite binding affinity. Likewise, the eigenvalue (2.428517e-05) from NMA analysis of this docked complex reflects greater flexibility, adequate molecular motion, and reduced protein deformability, and it can provoke a robust immune response. ConclusionsThe designed vaccine has shown the required effectiveness against MPXV without any side effects, a significant milestone against the neglected disease.

Abstract CT258: Interim safety and immunogenicity results of a phase I trial evaluating the multi-peptide COVID-19 vaccine candidate CoVac-1 for induction of SARS-CoV-2 T cell immunity in cancer patients with disease- or treatment-related immunoglobulin deficiency

Abstract Individuals with impaired ability to mount a humoral immune response, either during natural infection or upon prophylactic vaccination, are at high risk for a severe course of COVID-19. Besides humoral immunity mediated by B cells, T cell immunity is key for the control of viral infections. We developed the peptide-based vaccine candidate CoVac-1, which primarily aims for the induction of SARS-CoV-2-specific T cells. CoVac-1 comprises six promiscuous HLA-DR-binding SARS-CoV-2-derived T cell epitopes from various viral proteins proven (i) to be frequently and HLA-independently recognized by T cells in COVID-19 convalescents, (ii) to be of pathophysiological relevance for T cell immunity to combat COVID-19, and (iii) to mediate long-term immunity after infection (Nelde et al. Nat Immunol 2021, Bilich et al. Sci Transl Med 2021). CoVac-1 vaccine peptides are adjuvanted with the novel toll-like receptor 1/2 agonist XS15 emulsified in Montanide࣪ ISA51 VG. In a first-in-human clinical trial in healthy adults (NCT04546841), CoVac-1 showed a favorable safety profile and induced profound and long-lasting T cell immunity after single dose administration in 100% of the study subjects, mediated by multifunctional T-helper 1 CD4+ and CD8+ T cells. CoVac-1-induced T cell responses surpassed those after SARS-CoV-2 infection as well as those after vaccination with approved vaccines and were unaffected by current SARS-CoV-2 variants of concern (Heitmann et al. Nature 2021). Here we present the interim safety and immunogenicity results of our Phase I/II trial evaluating CoVac-1 in patients with congenital or acquired B cell deficiency, mainly comprising leukemia and lymphoma patients (NCT04954469). 64% of study subjects had previously been vaccinated with approved vaccines without developing any humoral immune response. Alike in the healthy adults, CoVac-1 showed a good safety and tolerability profile without relevant systemic adverse events. CoVac-1-specific T cell responses could be documented in 93% of study subjects on day 28 after CoVac-1 application, with earliest responses evidenced at day 14 (71%). Vaccine-induced T cell responses were mediated by multifunctional T-helper 1 CD4+ T cells. Of note, CoVac-1 induced T cell responses in this highly immune compromised study population were similar to those occurring in healthy volunteers after natural infection or induced by approved vaccines. These results identify CoVac-1 as promising vaccine candidate for cancer and other immunocompromised patients with immunoglobulin deficiency. Recruitment of the Phase II part of the trial is ongoing with results expected for March 2022. Citation Format: Claudia Tandler, Jonas S. Heitmann, Maddalena Marconato, Yacine Maringer, Monika Denk, Marion Richter, Annika Nelde, Imma Fischer, Markus W. Löffler, Hans-Georg Rammensee, Helmut R. Salih, Juliane S. Walz. Interim safety and immunogenicity results of a phase I trial evaluating the multi-peptide COVID-19 vaccine candidate CoVac-1 for induction of SARS-CoV-2 T cell immunity in cancer patients with disease- or treatment-related immunoglobulin deficiency [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT258.

Design and Synthesis of Bovine Leukemia Virus-Associated Peptide-Based Qβ Conjugate Eliciting Long-Lasting Neutralizing Antibodies in Mice.

Bovine leukemia virus (BLV) is a C-type retrovirus of cattle that causes huge economic losses with high infection rates in the majority of countries worldwide. To develop an anti-BLV vaccine, we constructed a peptide conjugate using the envelope glycoprotein gp51-peptide epitope, a putative receptor-binding site. This highly antigenic peptide was covalently linked to a mutant bacteriophage carrier (mQβ) using two different linker strategies, isothiocyanate (NCS) and dinitrophenyl adipate. Both constructs elicited higher anti-BLV peptide IgG titers than the corresponding conjugate with keyhole limpet hemocyanin protein carrier (gold standard) in mice with the NCS linker strategy requiring less sample processing. The mQβ-gp51-peptide construct is the first BLV peptide-based vaccine candidate to generate durable immunity (>539 days), which recognized both native gp51 protein and BLV particles and significantly decreased fusion of a susceptible cell line exposed to infectious BLV. These results support the high translational and animal health potential of the vaccine construct.

In silico Design of a New Multi-Epitope Peptide-Based Vaccine Candidate Against Q Fever

Novel types of the vaccines with high immunogenicity and low risks, including epitope-based vaccines, are sought. Among zoonotic disease, Q fever caused by Coxiella burnetii is an important target due to numerous outbreaks and the pandemic potential. Here we present a synthetic multi-epitope vaccine against Coxiella burnetii. This vaccine was developed using immunoinformatics approach. Antigenic proteins were studied, and five T cell epitopes were selected. Antigenicity, allergenicity, and toxicity of the selected epitopes were evaluated using the VaxiJen 2.0, AllerTOP, and ToxinPred servers, respectively. Selected epitopes were joined in a peptide sequence, with the cholera toxin В subunit (CTXB) as an adjuvant. The affinity of the proposed vaccine to MHCI and II molecules was measured in a molecular docking study. Resultant vaccine has high antigenicity, stability, and a half-life compatible with utilization in vaccination programs. In conclusion, the validated epitope sequences may be used as a potential vaccine to ensure protection against Q fever agent.

A COVID-19 peptide vaccine for the induction of SARS-CoV-2 T cell immunity

T cell immunity is central for the control of viral infections. CoVac-1 is a peptide-based vaccine candidate, composed of SARS-CoV-2 T cell epitopes derived from various viral proteins1,2, combined with the Toll-like receptor 1/2 agonist XS15 emulsified in Montanide ISA51 VG, aiming to induce profound SARS-CoV-2 T cell immunity to combat COVID-19. Here we conducted a phase I open-label trial, recruiting 36 participants aged 18–80 years, who received a single subcutaneous CoVac-1 vaccination. The primary end point was safety analysed until day 56. Immunogenicity in terms of CoVac-1-induced T cell response was analysed as the main secondary end point until day 28 and in the follow-up until month 3. No serious adverse events and no grade 4 adverse events were observed. Expected local granuloma formation was observed in all study participants, whereas systemic reactogenicity was absent or mild. SARS-CoV-2-specific T cell responses targeting multiple vaccine peptides were induced in all study participants, mediated by multifunctional T helper 1 CD4+ and CD8+ T cells. CoVac-1-induced IFNγ T cell responses persisted in the follow-up analyses and surpassed those detected after SARS-CoV-2 infection as well as after vaccination with approved vaccines. Furthermore, vaccine-induced T cell responses were unaffected by current SARS-CoV-2 variants of concern. Together, CoVac-1 showed a favourable safety profile and induced broad, potent and variant of concern-independent T cell responses, supporting the presently ongoing evaluation in a phase II trial for patients with B cell or antibody deficiency.

In Silico Design of a New Multi-Epitope Peptide-Based Vaccine Candidate Against Q Fever.

Novel types of the vaccines with high immunogenicity and low risks, including epitope-based vaccines, are sought. Among zoonotic disease, Q fever caused by Coxiella burnetii is an important target due to numerous outbreaks and the pandemic potential. Here we present a synthetic multi-epitope vaccine against Coxiella burnetii. This vaccine was developed using immunoinformatics approach. Antigenic proteins were studied, and five T cell epitopes were selected. Antigenicity, allergenicity, and toxicity of the selected epitopes were evaluated using the VaxiJen 2.0, AllerTOP, and ToxinPred servers, respectively. Selected epitopes were joined in a peptide sequence, with the cholera toxin B subunit (CTXB) as an adjuvant. The affinity of the proposed vaccine to MHC I and II molecules was measured in a molecular docking study. Resultant vaccine has high antigenicity, stability, and a half-life compatible with utilization in vaccination programs. In conclusion, the validated epitope sequences may be used as a potential vaccine to ensure protection against Q fever agent.

Oral Peptide Vaccine against Hookworm Infection: Correlation of Antibody Titers with Protective Efficacy.

Approximately 0.4 billion individuals worldwide are infected with hookworm. An effective vaccine is needed to not only improve the health of those affected and at high risk, but also to improve economic growth in disease-endemic areas. An ideal anti-hookworm therapeutic strategy for mass administration is a stable and orally administered vaccine. Oral vaccines are advantageous as they negate the need for trained medical staff for administration and do not require strict sterility conditions. Vaccination, therefore, can be carried out at a significantly reduced cost. One of the most promising current antigenic targets for hookworm vaccine development is the aspartic protease digestive enzyme (APR-1). Antibody-mediated neutralization of APR-1 deprives the worm of nourishment, leading to reduced worm burdens in vaccinated hosts. Previously, we demonstrated that, when incorporated into vaccine delivery systems, the APR-1-derived p3 epitope (TSLIAGPKAQVEAIQKYIGAEL) was able to greatly reduce worm burdens (≥90%) in BALB/c mice; however, multiple, large doses of the vaccine were required. Here, we investigated a variety of p3-antigen conjugates to optimize antigen delivery and establish immune response/protective efficacy relationships. We synthesized, purified, and characterized four p3 peptide-based vaccine candidates with: (a) lipidic (lipid core peptide (LCP)); (b) classical polymeric (polymethylacrylate (PMA)); and (c) novel polymeric (polyleucine in a branched or linear arrangement, BL10 or LL10, respectively) groups as self-adjuvanting moieties. BL10 and LL10 induced the highest serum anti-p3 and anti-APR-1 IgG titers. Upon challenge with rodent hookworms, the highest significant reduction in worm burden was observed in mice immunized with LL10. APR-1-specific serum IgG titers correlated with worm burden reduction. Thus, we provide the first vaccine-triggered immune response-protection relationship for hookworm infection.

Recombinant DBL2β-PfEMP1 of the Indonesian Plasmodium falciparum induces immune responses in Wistar rats

ObjectivesThe Duffy binding-like (DBL) domain of the Plasmodium falciparum Erythrocyte Membrane Protein 1 (PfEMP1) is reportedly responsible for the pathophysiology of cerebral malaria. People living in endemic malaria areas possess specific antibodies against PfEMP1 and elicit immune responses to control the severity of malaria infection. Therefore, PfEMP1 may be a potential protein-based vaccine candidate. This study aimed to explore the humoral and cellular immune responses induced by the recombinant DBL2β-PfEMP1 obtained from the Indonesian P. falciparum isolate. MethodsThe recombinant protein was expressed in Escherichia coli BL21(DE3) as soluble and insoluble fractions, and this protein was purified using affinity chromatography before administration as a subcutaneous injection in Wistar rats on days 1, 21, and 42. Sera were harvested 14 days after the second and third injections to determine the titre of IgG and the concentration of CD4+ cells using the enzyme linked immunosorbent assay (ELISA). ResultsThe IgG titre and the CD4+ cell concentration were found to be increased after the second and third injections. The Mann–Whitney test results showed a significant difference between the control and treatment groups for both the IgG and CD4+ cells (p = 0.001 and p = 0.000, respectively). Western blotting results indicated the presence of a specific antibody against the recombinant DBL2β-PfEMP1. ConclusionsThe recombinant DBL2β-PfEMP1 of the Indonesian P. falciparum isolate could induce humoral and cellular immune responses. Further studies on IgG exerting inhibitory effects and the role of CD4+ cells and their association with other effector cells are essential to determine the efficacy of DBL2β-PfEMP1 and its potential application as a peptide-based malaria vaccine candidate.

A peptide-based subunit candidate vaccine against SARS-CoV-2 delivered by biodegradable mesoporous silica nanoparticles induced high humoral and cellular immunity in mice.

Development of a rapidly scalable vaccine is still an urgent task to halt the spread of COVID-19. We have demonstrated biodegradable mesoporous silica nanoparticles (BMSNs) as a good drug delivery carrier for tumor therapy. In this study, seven linear B cell epitopes and three CD8+ T cell epitopes were screened from the spike (S) glycoprotein of SARS-CoV-2 by computer-based immunoinformatic approaches for vaccine design. A nanoparticle-based candidate vaccine (B/T@BMSNs) against SARS-CoV-2 was rapidly prepared by encapsulating these ten epitope peptides within BMSNs, respectively. BMSNs with potential biodegradability, proved to possess excellent safety in vitro and in vivo, could efficiently deliver epitope peptides into the cytoplasm of RAW264.7 cells. Strong Th1-biased humoral and cellular immunity were induced by B/T@BMSNs in mice and all the 10 selected epitopes were identified as effective antigen epitopes, which could induce robust peptide-specific immune response. The elicited functional antibody could bind to the recombinant S protein and block the binding of the S protein to the ACE-2 receptor. These results demonstrate the potential of a nanoparticles vaccine platform based on BMSNs to rapidly develop peptide-based subunit vaccine candidates against SARS-CoV-2.

An Immunoinformatics Study to Predict Epitopes in the Envelope Protein of SARS-CoV-2.

COVID-19 is a new viral emergent disease caused by a novel strain of coronavirus. This virus has caused a huge problem in the world as millions of people are affected by this disease. We aimed at designing a peptide vaccine for COVID-19 particularly for the envelope protein using computational methods to predict epitopes inducing the immune system. The envelope protein sequence of SARS-CoV-2 has been retrieved from the NCBI database. The bioinformatics analysis was carried out by using the Immune Epitope Database (IEDB) to predict B- and T-cell epitopes. The predicted HTL and CTL epitopes were docked with HLA alleles and binding energies were evaluated. The allergenicity of predicted epitopes was analyzed, the conservancy analysis was performed, and the population coverage was determined throughout the world. Some overlapped CTL, HTL, and B-cell epitopes were suggested to become a universal candidate for peptide-based vaccine against COVID-19. This vaccine peptide could simultaneously elicit humoral and cell-mediated immune responses. We hope to confirm our findings by adding complementary steps of both in vitro and in vivo studies to support this new universal predicted candidate.

Epitopes prediction of PfEMP1-DBL2? recombinant protein from Indonesian Plasmodium falciparum Isolate for malaria vaccine development

The development of an effective vaccine against malaria is essential. Domain Duffy-binding-like (DBL)2?in Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) protein is one of the vaccinecandidate proteins because of its binding capacity to ICAM-1 receptor. However, the high polymorphismneeds epitope identification before formulating a peptide-based vaccine. This study aimed to identify theconserved epitopes in PfEMP1-DBL2? by an immunoinformatic approach. The protein sequences wereanalyzed to predict the hydrophobicity attributes, T-cell and B-cell epitopes. T-cell epitopes were identifiedusing the NetCTL and Propred server and analyzed for population coverage rate using the IEDB analysistool. Moreover, the Bepipred 2.0 and Kolaskar Tangaonkar method combined with the K-means clusteringwere used to predict the B-cell epitopes. This study found that the hydrophobicity value of PfEMP1-DBL2?recombinant protein is 32.62, indicating that this protein is soluble and potentially fit into HLA alleles activesite. Two conserved antigenic CTL epitopes with near 90% population coverage rate in the malaria targetpopulation were identified. For Th cell epitopes, the NN-align algorithm showed no overlapping strongbinding epitope positions for three chosen Indonesian and African alleles. Three B-cell conserved epitopeswere identified at the position of 77-89, 236-254 and 360-377 amino acids with one cluster overlapping withICAM-1 determinant binding area. The predicted conserved epitopes within the protein in this study arevaluable in constructing a subunit peptide-based malaria vaccine candidate. A further experimental study isneeded to validate this approach as the next step in vaccine development.

Designing peptide-based vaccine candidates for Plasmodium falciparum erythrocyte binding antigen 175

Plasmodium falciparum leads to a virulent form of malaria. Progress has been achieved in understanding the mechanisms involved in the malarial infection, still there is no effective vaccine to prevent severe infection. An effective vaccine against malaria should be one which can induce immune responses against multiple epitopes in the context of predominantly occurring HLA alleles. In this study, an integrated approach was employed to identify promiscuous peptides of a well-defined sequence of erythrocyte binding antigen-175 and promiscuous peptides for HLA alleles were designed using bioinformatics tools. A peptide with 15 amino acids (ILAIAIYESRILKRK) was selected based on its high binding affinity score and synthesized. This promiscuous peptide was used as stimulating antigen in lymphoproliferative responses to evaluate the cellular immune response. It was observed this peptide evokes lymphoproliferative and cytokine responses in individuals naturally exposed to the malaria parasite. The intensity of PBMCs proliferation was observed to be higher in sera obtained from P. falciparum exposed as compared to unexposed healthy individuals, suggesting earlier recognition of peptide of this region by T cells. Furthermore, the binding mode of HLA–peptide complex and their interaction may lead to a rational and selective peptide-based vaccine candidate design approach which can be used as a malaria prophylaxis.

Designing Functionally Versatile, Highly Immunogenic Peptide-Based Multiepitopic Vaccines against Foot-and-Mouth Disease Virus.

A broadly protective and biosafe vaccine against foot-and-mouth disease virus (FMDV) remains an unmet need in the animal health sector. We have previously reported solid protection against serotype O FMDV afforded by dendrimeric peptide structures harboring virus-specific B- and T-cell epitopes, and also shown such type of multivalent presentations to be advantageous over simple B-T-epitope linear juxtaposition. Chemically, our vaccine platforms are modular constructions readily made from specified B- and T-cell epitope precursor peptides that are conjugated in solution. With the aim of developing an improved version of our formulations to be used for on-demand vaccine applications, we evaluate in this study a novel design for epitope presentation to the immune system based on a multiple antigen peptide (MAP) containing six immunologically relevant motifs arranged in dendrimeric fashion (named B2T-TB2). Interestingly, two B2T units fused tail-to-tail into a single homodimer platform elicited higher B- and T-cell specific responses than former candidates, with immunization scores remaining stable even after 4 months. Moreover, this macromolecular assembly shows consistent immune response in swine, the natural FMDV host, at reduced dose. Thus, our versatile, immunogenic prototype can find application in the development of peptide-based vaccine candidates for various therapeutic uses using safer and more efficacious vaccination regimens.

Structure-based group A streptococcal vaccine design: Helical wheel homology predicts antibody cross-reactivity among streptococcal M protein–derived peptides

Group A streptococcus (Strep A) surface M protein, an α-helical coiled-coil dimer, is a vaccine target and a major determinant of streptococcal virulence. The sequence-variable N-terminal region of the M protein defines the M type and also contains epitopes that promote opsonophagocytic killing of streptococci. Recent reports have reported considerable cross-reactivity among different M types, suggesting the prospect of identifying cross-protective epitopes that would constitute a broadly protective multivalent vaccine against Strep A isolates. Here, we have used a combination of immunological assays, structural biology, and cheminformatics to construct a recombinant M protein-based vaccine that included six Strep A M peptides that were predicted to elicit antisera that would cross-react with an additional 15 nonvaccine M types of Strep A. Rabbit antisera against this recombinant vaccine cross-reacted with 10 of the 15 nonvaccine M peptides. Two of the five nonvaccine M peptides that did not cross-react shared high sequence identity (≥50%) with the vaccine peptides, implying that high sequence identity alone was insufficient for cross-reactivity among the M peptides. Additional structural analyses revealed that the sequence identity at corresponding polar helical-wheel heptad sites between vaccine and nonvaccine peptides accurately distinguishes cross-reactive from non-cross-reactive peptides. On the basis of these observations, we developed a scoring algorithm based on the sequence identity at polar heptad sites. When applied to all epidemiologically important M types, this algorithm should enable the selection of a minimal number of M peptide-based vaccine candidates that elicit broadly protective immunity against Strep A.