Design of multi-epitope peptides containing HLA class-I and class-II-restricted epitopes derived from immunogenic Leishmania proteins, and evaluation of CD4+ and CD8+ T cell responses induced in cured cutaneous leishmaniasis subjects

Abstract

Human leishmaniasis is a public health problem worldwide for which the development of a vaccine remains a challenge. T cell-mediated immune responses are crucial for protection. Peptide vaccines based on the identification of immunodominant T cell epitopes able to induce T cell specific immune responses constitute a promising strategy. Here, we report the identification of human leukocyte antigen class-I (HLA-I) and-II (HLA-II)-restricted multiepitope peptides from Leishmania proteins that we have previously described as vaccine candidates. Promastigote Surface Antigen (PSA), LmlRAB (L. major large RAB GTPase) and Histone (H2B) were screened, in silico, for T cell epitopes. 6 HLA-I and 5 HLA-IIrestricted multi-epitope peptides, able to bind to the most frequent HLA molecules, were designed and used as pools to stimulate PBMCs from individuals with healed cutaneous leishmaniasis. IFN-γ, IL-10, TNF-α and granzyme B (GrB) production was evaluated by ELISA/CBA. The frequency of IFN-γ-producing T cells was quantified by ELISpot. T cells secreting cytokines and memory T cells were analyzed by flow cytometry. 16 of 25 peptide pools containing HLA-I, HLA-II or HLA-I and-II peptides were able to induce specific and significant IFN-γ levels. No IL-10 was detected. 6 peptide pools were selected among those inducing the highest IFN-γ levels for further characterization. 3/6 pools were able to induce a significant increase of the percentages of CD4+IFN-γ+, CD8+IFN-γ+ and CD4+GrB+ T cells. The same pools also induced a significant increase of the percentages of bifunctional IFN-γ+/TNF-α+CD4+ and/or central memory T cells. We identified highly promiscuous HLA-I and-II restricted epitope combinations from H2B, PSA and LmlRAB proteins that stimulate both CD4+ and CD8+ T cell responses in recovered individuals. These multi-epitope peptides could be used as potential components of a polytope vaccine for human leishmaniasis.

Deciphering the Structural Enigma of HLA Class-II Binding Peptides for Enhanced Immunoinformatics-based Prediction of Vaccine Epitopes

“…Thus a separate study employing a hybrid approach involving the structure-based prediction and wet bench validation may provide the requisite standardized data set for feeding into algorithms to be implemented in the in silico vaccine prediction techniques. Studies on similar lines have been performed for cancer epitopes and infective diseases; − however, the data set with the peptide HLA-II binding stoichiometry remains missing.…”

Leishmaniac Quest for Developing a Novel Vaccine Platform. Is a Roadmap for Its Advances Provided by the Mad Dash to Produce Vaccines for COVID-19?

“…This is suggested by the fact that most patients of leishmaniasis develop life-long immunity after a spontaneous or chemotherapeutic cure. Indeed, memory T cells were reported to persist in subjects long after a full recovery from cutaneous and visceral leishmaniasis, as they are functionally activatable in vitro with Leishmania-specific antigens [76,77]. Clinically, the best example is the simple cutaneous leishmaniasis (CL) endemic to central Asia and the Middle East.…”

Revisiting the Principles of Designing a Vaccine

“…Recently, 11 immunogenic epitopes were selected from promastigote-surface antigen (PSA), L. major large RAB GTPase (LmlRAB), and H2B (histone subunit) in a study. 3/25 peptide pools were able to induce IFNγ production from PBMC of recovered individuals and able to induce multifunctional Th1-specific effector and central memory T cells [162].…”