Selection strategy of phage-displayed immunogens based on an in vitro evaluation of the Th1 response of PBMCs and their potential use as a vaccine against Leishmania infantum infection

Abstract

BackgroundThe development of a vaccine for the prevention of visceral leishmaniasis (VL) still represents a significant unmet medical need. A human vaccine can be found if one takes into consideration that many people living in endemic areas of disease are infected but do not develop active VL, including those subjects with subclinical or asymptomatic infection.MethodsIn this study, a phage display was used to select phage-exposed peptides that were specific to immunoglobulin G (IgG) antibodies from asymptomatic and symptomatic VL patients, separating them from non-infected subjects. Phage clones presenting valid peptide sequences were selected and used as stimuli of peripheral blood mononuclear cells (PBMCs) obtained from both patients’ groups and controls. Those with higher interferon-gamma (IFN-γ)/interleukin (IL)-10 ratios were further selected for vaccination tests.ResultsAmong 17 evaluated clones, two were selected, B1 and D11, and used to immunize BALB/c mice in an attempt to further validate their in vivo protective efficacy against Leishmania infantum infection. Both clones induced partial protection against the parasite challenge, which was evidenced by the reduction of parasitism in the evaluated organs, a process mediated by a specific T helper (Th)1 immune response.ConclusionsTo the best of our knowledge, this study is the first to use a rational strategy based on in vitro stimulation of human PBMCs with selected phage-displayed clones to obtain new immunogens against VL.Electronic supplementary materialThe online version of this article (10.1186/s13071-017-2576-8) contains supplementary material, which is available to authorized users.

A candidate vaccine for human visceral leishmaniasis based on a specific T cell epitope-containing chimeric protein protects mice against Leishmania infantum infection

“…ChimeraT induced lymphoproliferation in PBMC cultures from VL patients after treatment and from healthy subjects, in addition to stimulating IFN-γ production. In this context, ChimeraT could be considered as a promising candidate for future translational studies in humans, due to the induction of markers of immunogenicity from cells isolated from non-exposed healthy individuals, as observed in previous studies with other candidate vaccine antigens [58][59][60][61] .…”

Leishmania infantum β-Tubulin Identified by Reverse Engineering Technology through Phage Display Applied as Theranostic Marker for Human Visceral Leishmaniasis

“…None of them suffered from any other infections or had any pre-existing disease. PBMCs were purified by density centrifugation through Ficoll-Hypaque (GE Healthcare Bio-Sciences AB, Uppsala, Sweden), according described [47]. Cells (10 7 ) were cultured in complete RPMI 1640 medium, which was composed by the medium plus 20% inactivated fetal bovine serum (FBS, Sigma-Aldrich, USA), 2 mM l -glutamine, 200 U/mL penicillin, 100 µg/mL streptomycin, 50 μM 2-mercaptoethanol, 1 mM sodium pyruvate, and 1× non-essential amino acid, and they were incubated in medium (background control) or stimulated with B10, C01 or irrelevant (NRP) phage clones (10 10 phages, each), with the B10 or C01 peptides (10 µg/mL each), or with β-tubulin and L. infantum SLA (10 and 25 µg/mL, respectively), for 5 days at 37°C in 5% CO 2 .…”

Synthetic Peptides Elicit Strong Cellular Immunity in Visceral Leishmaniasis Natural Reservoir and Contribute to Long-Lasting Polyfunctional T-Cells in BALB/c Mice

“…These results corroborate to Martins, et al [45] that observed a decrease in parasitic load in the splenic compartment in the group immunized with a synthetic peptide (P2, which was mapped by immunoinformatics) and challenged with L. infantum. In another study using phages expressing L. infantum peptides, it was possible to observe a decrease in parasite load in the spleen [46]. Thus, the phages B1 and D11 promoted a reduction in the spleen parasite load relative to the saline group of 62% and 48%, respectively.…”