Identification of Potential MHC Class-II-Restricted Epitopes Derived from Leishmania donovani Antigens by Reverse Vaccinology and Evaluation of Their CD4+ T-Cell Responsiveness against Visceral Leishmaniasis

Abstract

Visceral leishmaniasis (VL) is one of the most neglected tropical diseases for which no vaccine exists. In spite of extensive efforts, no successful vaccine is available against this dreadful infectious disease. To support vaccine development, an immunoinformatics approach was applied to screen potential MHC class-II-restricted epitopes that can activate the immune cells. Initially, 37 epitopes derived from six stage-dependent, overexpressed antigens were predicted, which were presented by at least 26 diverse MHC class-II allele. Based on a population coverage analysis and human leukocyte antigen cross-presentation ability, six of the 37 epitopes were selected for further analysis. Stimulation with synthetic peptide alone or as a cocktail triggered intracellular IFN-γ production. Moreover, specific IgG antibodies were detected in the serum of active VL cases against P1, P4, P5, and P6 in order to evaluate the peptide effect on the humoral immune response. Additionally, most of the peptides, except P2, were found to be non-inducers of CD4+ IL-10 against both active VL as well as treated VL subjects. This finding suggests there is no role of these peptides in the pathogenesis of Leishmania. Peptide immunogenicity was validated in BALB/c mice immunized with a cocktail of synthetic peptide emulsified in complete Freund’s adjuvant/incomplete Freund’s adjuvant. The immunized splenocytes induced strong spleen cell proliferation upon parasite re-stimulation. Furthermore, increased IFN-γ, interleukin-12, IL-17, and IL-22 production augmented with elevated nitric oxide (NO) synthesis is thought to play a crucial role in macrophage activation. In this investigation, we identified six MHC class-II-restricted epitope hotspots of Leishmania antigens that induce CD4+ Th1 and Th17 responses, which could be used to potentiate a human universal T-epitope vaccine against VL.

Retracted: Evaluating the immunomodulatory responses of LdODC‐derived MHC Class‐II restricted peptides against VL

“…The previous report demonstrated that all the T-cell and B-cell epitopes might not evoke the immune cell appropriately. 1,6 Further reports also demonstrated the ability of specific T-cell epitopes to modulate the activation of Th1 and Th2 cells. 35,36 Importantly, in active VL cases, the IL-10 produced by Th2 cells decided the fate of the parasite inside the host.…”

An immunoinformatic approach driven by experimental proteomics: in silico design of a subunit candidate vaccine targeting secretory proteins of Leishmania donovani amastigotes

“…This suggests that the in silico designed vaccines with epitopes derived from appropriate protein targets have the potential to progress toward advanced phases of vaccine development for visceral leishmaniasis. While the in silico studies by Khatoon et al [66] and Singh et al [67] largely utilized available genomic databases of L. donovani to select vaccine targets, Dikhit et al [11,70] performed thorough investigations involving in silico, in vitro and in vivo analysis to screen and validate immunogenic epitopes obtained from proteins that are increasingly expressed at the infective parasite stage. Such highly expressed proteins are likely important for physiological and/or infective process of the parasite and thus can be more effective vaccine targets.…”

“…In addition to in vitro methods of epitope mapping such as phage display library, immunodominance and peptide competition assays, immunoinformatic mapping can be a powerful approach to facilitate screening of desired epitopes in immunogenic proteins [9]. Recent findings of leishmaniasis vaccine research also suggest that in silico predicted MHC class I and class II restricted epitopecontaining peptides derived from Leishmania antigens alone, as a cocktail, as a chimeric peptide or in combination with adjuvant can be substantially immunogenic in vitro and/or in vivo [10][11][12][13]. Thus, the application of immunoinformatics-based pipeline can facilitate largescale screening of peptide epitopes from Leishmania proteome for rational design of potent vaccines.…”

An immunoinformatic approach driven by experimental proteomics: in silico design of a subunit candidate vaccine targeting secretory proteins of Leishmania donovani amastigotes

“…This suggests that the in silico designed vaccines with epitopes derived from appropriate protein targets have the potential to progress toward advanced phases of vaccine development for visceral leishmaniasis. While the in silico studies by Khatoon et al [104] and Singh et al [105] largely utilized available genomic databases of L. donovani to select vaccine targets, Dikhit et al [11,108] performed thorough investigations involving in silico, in vitro and in vivo analysis to screen and validate immunogenic epitopes obtained from proteins that are increasingly expressed at infective stage of parasite. Such highly expressed proteins are likely important for physiological and/or infective process of the parasite and thus can be more effective vaccine targets.…”

“…In addition to in vitro methods of epitope mapping such as phage display library, immunodominance and peptide competition assays, immunoinformatic mapping can be a powerful approach to facilitate screening of desired epitopes in immunogenic proteins [9]. Recent studies on leishmaniasis vaccine research also suggest that in silico predicted MHC class I and class II restricted epitope containing peptides derived from Leishmania antigens alone, as a cocktail, as a chimeric peptide or in combination with adjuvant can be substantially immunogenic in vitro and/or in vivo [10][11][12][13]. Thus, the application of immunoinformatics-based pipeline can facilitate large scale screening of peptide epitopes from Leishmania proteome for rational design of potent vaccines.…”