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The current global outbreak of monkeypox (MPX) disease, caused by Monkeypox virus (MPXV), has resulted in 16 thousand infection cases, five deaths, and has been declared a global health emergency of international concern by the World Health Organization. Given current challenges in the safety of existing vaccines, a vaccine to prevent MPX infection and/or onset of symptoms would significantly advance disease management. In this context, a multi-epitope-based vaccine could be a well-suited approach. Herein, we searched a publicly accessible database (Virus Pathogen Database and Analysis Resource) for MPXV immune epitopes from various antigens. We prioritized a group of epitopes (10 CD8+ T cells and four B-cell epitopes) using a computer-aided technique based on desirable immunological and physicochemical properties, sequence conservation criteria, and non-human homology. Three multi-epitope vaccines were constructed (MPXV-1-3) by fusing finalized epitopes with the aid of appropriate linkers and adjuvant (beta-defensin 3, 50S ribosomal protein L7/L12, and Heparin-binding hemagglutinin). Codon optimization and in silico cloning in the pET28a (+) expression vector ensure the optimal expression of each construct in the Escherichia Coli system. Two and three-dimensional structures of the constructed vaccines were predicted and refined. The optimal binding mode of the construct with immune receptors [Toll-like receptors (TLR2, TLR3, and TLR4)] was explored by molecular docking, which revealed high docking energies of MPXV-1-TLR3 (-99.09 kcal/mol), MPXV-2-TLR3 (-98.68 kcal/mol), and MPXV-3-TLR2 (-85.22 kcal/mol). Conformational stability and energetically favourable binding of the vaccine-TLR2/3 complexes were assessed by performing molecular dynamics simulations and free energy calculations (Molecular Mechanics/Generalized Born Surface Area method). In silico immune simulation suggested that innate, adaptive, and humoral responses will be elicited upon administration of such potent multi-epitope vaccine constructs. The vaccine constructs are antigenic, non-allergen, non-toxic, soluble, topographically exposed, and possess favourable physicochemical characteristics. These results may help experimental vaccinologists design a potent MPX vaccine., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Aziz, Almajhdi, Waqas, Ullah, Salim, Khan and Ali.)

CD8+ cytotoxic T lymphocytes (CTLs), are essential for clearance of porcine reproductive and respiratory syndrome virus (PRRSV) infection and regulation of host immune responses. Identification of SLA I-restricted CD8+ CTL epitopes would facilitate PRRSV vaccine development. Here, cells isolated from peripheral blood mononuclear cells (PBMCs) of PRRSV-immunized Large White pigs (JXA1-R strain) were screened for immunodominant PRRSV-2 M protein T cell epitopes via ELISPOT assay. Of nine immunodominant epitopes detected, eight elicited significant IFN-γ secretion responses that varied among individual pigs and according to epitope. To predict which epitopes harbored potential CTL epitopes, swine leukocyte antigen (SLA) class I genes of Large White pigs were cloned and sequenced, yielding fourteen distinct SLA class I gene sequences. Based on ELISPOT and SLA genotyping results, SLA-restricted binding of the fourteen predicted class I proteins to peptides derived from the eight immunodominant epitopes were predicted in-silico. After evaluation of 42 pET-peptide-SLA-I-β2m complexes containing predicted restricted peptides, extracellular SLA class I domains and β2m, ELISA testing of 33 peptide-SLA-I-β2m complexes detected four complexed peptides. These four peptides were evaluated using in vitro complex refolding assays that confirmed that M 2-5 and M 6-1 peptides each formed complexes with SLA-2*0502 and sβ2m, while M 9-1 formed a complex with SLA-2*1201 and sβ2m. ELISPOT results confirmed these three 9-mer potential CTL epitopes efficiently stimulated IFN-γ secretion when presented by SLA class I molecules specified here. This study describes effective CTL epitope identification methods for use in future investigations of swine cellular immunity toward T cell-based vaccine development., (Copyright © 2021. Published by Elsevier B.V.)

An immunoinformatics-based approach was used to identify potential multivalent subunit CTL vaccine candidates for SARS-CoV-2. Criteria for computational screening included antigen processing, antigenicity, allergenicity, and toxicity. A total of 2604 epitopes were found to be strong binders to MHC class I molecules when analyzed using IEDB tools. Further testing for antigen processing yielded 826 peptides of which 451 were 9-mers that were analyzed for potential antigenicity. Antigenic properties were predicted for 102 of the 451 peptides. Further assessment for potential allergenicity and toxicity narrowed the number of candidate CTL epitopes to 50 peptide sequences, 45 of which were present in all strains of SARS-CoV-2 that were tested. The predicted CTL epitopes were then tested to eliminate those with MHC class II binding potential, a property that could induce hyperinflammatory responses mediated by T H 2 cells in immunized hosts. Eighteen of the 50 epitopes did not show class II binding potential. To our knowledge this is the first comprehensive analysis on the proteome of SARS-CoV-2 for prediction of CTL epitopes lacking binding properties that could stimulate unwanted T H 2 responses. Future studies will be needed to assess these epitopes as multivalent subunit vaccine candidates which stimulate protective CTL responses against SARS-COV-2., (Copyright © 2021 Elsevier B.V. All rights reserved.)

We proposed a new HIV-1 therapeutic vaccine based on conserved cytotoxic T lymphocyte (CTL) epitopes of archived HIV-1 DNA according to their affinity to the dominant HLA-A and -B alleles of the population investigated. Our proposal (Hla Fitted VAC, HFVAC) was composed of 15 peptides originating from the RT, gag and nef parts of proviral DNA. Our aim was to investigate baseline immune reactivity to the vaccine in HIV-1 chronically infected patients at success of antiretroviral therapy (ART) who would be eligible for a therapeutic vaccine. Forty-one patients were tested. Most of them had been infected with HIV-1 subtype B and all had been receiving successful ART for 2 to 20 years. The predominant HLA-A and -B alleles were those of a Caucasian population. ELISPOT was carried out using the HFVAC peptides. In 22 patients, the PD-1 marker was investigated on CD4+ and CD8+ T cells by flow cytometry in order to evaluate global T cell exhaustion. ELISPOT positivity was 65% overall and 69% in patients exhibiting at least one HLA allele fitting with HFVAC. The percentages of CD4+ and CD8+ T cells expressing PD-1 were high (median values 23.70 and 32.60, respectively), but did not seem to be associated with an impairment of the immune response investigated in vitro. In conclusion, reactivity to HFVAC was high in this ART-treated population with dominant HLA alleles, despite potential cellular exhaustion associated with the PD-1 marker.

There is an urgent need for a more effective vaccine against tuberculosis (TB). Cytotoxic T lymphocytes (CTLs) play a critical role in combating Mycobacterium tuberculosis (M.tb). The identification of novel CTL epitopes is essential for the design of peptide-based vaccines. In this study, we predicted CTL epitope peptides of M.tb antigen Rv2629 restricted by HLA-A2, using bioinformatics methods. The affinity and stability of binding of these peptides with HLA-A2 molecules were detected by flow cytometry. Their ability to induce CTLs generation was determined in peripheral blood mononuclear cells (PBMCs) from healthy uninfected subjects, Latent tuberculosis infection (LTBI) subjects, and TB patients ex vivo. The cytotoxic activity induced by the epitope peptides was tested by lactate dehydrogenase (LDH) release assay. Finally, we found four novel CTL epitope peptides, Rv2629-p190-2L, Rv2629-p190-1Y2L, Rv2629-p274, and Rv2629-p315, which had high-affinity and stability of binding with T2 cells. Their ability of inducing CTLs was highest in PBMCs from TB patients (P < 0.05). In addition, these peptides could induce the CTLs to generate specific cytotoxic activity. They showed higher immunogenicity in TB patients and had the potential to become candidate vaccines for TB therapy., (Copyright © 2018. Published by Elsevier B.V.)

The scientific and medical community is seeking to cure HIV. Several pathways have been or are being explored including therapeutic vaccination. Viroimmunological studies on primary infection as well as on elite controllers have demonstrated the importance of the cytotoxic CD8 response and have mainly oriented research on vaccine constructs toward this type of response. The results of these trials are clearly not commensurate with the hope placed in them. Might there be one or more uncontrolled variables? The genetics of patients need to be taken into consideration, especially their human lymphocyte antigen (HLA) alleles. There is a need to find a balance between the conservation of cytotoxic T lymphocyte (CTL) epitopes and presentation by HLA alleles. The pathway is a narrow one between adaptation of the virus to HLA I restriction and the definition of conserved proviral CTL epitopes presentable by HLA I alleles. It is likely that the genetics of patients will need to be considered for HIV-1 vaccine studies and that multidisciplinary collaboration will be essential in this field of infectious diseases.

Both the recognition of HIV-infected cells and the immunogenicity of candidate CTL vaccines depend on the presentation of a peptide epitope at the cell surface, which in turn depends on intracellular antigen processing. Differential antigen processing maybe responsible for the differences in both the quality and the quantity of epitopes produced, influencing the immunodominance hierarchy of viral epitopes. Previously, we showed that the magnitude of the HIV-2 gag-specific T-cell response is inversely correlated with plasma viral load, particularly when responses are directed against an epitope, 165 DRFYKSLRA173 , within the highly conserved Major Homology Region of gag-p26. We also showed that the presence of three proline residues, at positions 119, 159 and 178 of gag-p26, was significantly correlated with low viral load. Since this proline motif was also associated with stronger gag-specific CTL responses, we investigated the impact of these prolines on proteasomal processing of the protective 165 DRFYKSLRA173 epitope. Our data demonstrate that the 165 DRFYKSLRA173 epitope is most efficiently processed from precursors that contain two flanking proline residues, found naturally in low viral-load patients. Superior antigen processing and enhanced presentation may account for the link between infection with HIV-2 encoding the "PPP-gag" sequence and both strong gag-specific CTL responses as well as lower viral load., (© 2015 The Authors. European Journal of Immunology published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)