Identification of BALB/c Immune Markers Correlated with a Partial Protection to Leishmania infantum after Vaccination with a Rationally Designed Multi-epitope Cysteine Protease A Peptide-Based Nanovaccine

Abstract

BackgroundThrough their increased potential to be engaged and processed by dendritic cells (DCs), nanovaccines consisting of Poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) loaded with both antigenic moieties and adjuvants are attractive candidates for triggering specific defense mechanisms against intracellular pathogens. The aim of the present study was to evaluate the immunogenicity and prophylactic potential of a rationally designed multi-epitope peptide of Leishmania Cysteine Protease A (CPA160-189) co-encapsulated with Monophosphoryl lipid A (MPLA) in PLGA NPs against L. infantum in BALB/c mice and identify immune markers correlated with protective responses.Methodology/Principal FindingsThe DCs phenotypic and functional features exposed to soluble (CPA160-189, CPA160-189+MPLA) or encapsulated in PLGA NPs forms of peptide and adjuvant (PLGA-MPLA, PLGA-CPA160-189, PLGA-CPA160-189+MPLA) was firstly determined using BALB/c bone marrow-derived DCs. The most potent signatures of DCs maturation were obtained with the PLGA-CPA160-189+MPLA NPs. Subcutaneous administration of PLGA-CPA160-189+MPLA NPs in BALB/c mice induced specific anti-CPA160-189 cellular and humoral immune responses characterized by T cells producing high amounts of IL-2, IFN-γ and TNFα and IgG1/IgG2a antibodies. When these mice were challenged with 2x107 stationary phase L. infantum promastigotes, they displayed significant reduced hepatic (48%) and splenic (90%) parasite load at 1 month post-challenge. This protective phenotype was accompanied by a strong spleen lymphoproliferative response and high levels of IL-2, IFN-γ and TNFα versus low IL-4 and IL-10 secretion. Although, at 4 months post-challenge, the reduced parasite load was preserved in the liver (61%), an increase was detected in the spleen (30%), indicating a partial vaccine-induced protection.Conclusions/SignificanceThis study provide a basis for the development of peptide-based nanovaccines against leishmaniasis, since it reveals that vaccination with well-defined Leishmania MHC-restricted epitopes extracted from various immunogenic proteins co-encapsulated with the proper adjuvant or/and phlebotomine fly saliva multi-epitope peptides into clinically compatible PLGA NPs could be a promising approach for the induction of a strong and sustainable protective immunity.

Vaccination with poly(D,L-lactide-co-glycolide) nanoparticles loaded with soluble <em>Leishmania</em> antigens and modified with a TNF&alpha;-mimicking peptide or monophosphoryl lipid A confers protection against experimental visceral leishmaniasis

“…Notably, 4 months post-infection, the level of protection in the liver ranged from 64% to 92%, speeding up the phenomenon of selfhealing observed in this organ, while vaccination with PLGA nanoformulations resulted in significant parasite reduction, also, in the spleen, ranging from 44% to 99% (Figure 1). Encapsulation of MPLA in PLGA-sLiAg NPs resulted in significant reduction of parasitic load in accordance with previous studies demonstrating the necessity for an adjuvant for experimental vaccines against leishmaniasis [36][37][38][39][40] but also against other intracellular pathogens. 41,42 The conjugation of the p8 peptide to PLGA-sLiAg NPs resulted in protection levels similar to those induced by PLGA-sLiAg-MPLA vaccination.…”

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

“…Based on the immunological findings in the spleen of Cockt-1 immunized mice, we assessed the parasite load in the endpoint to evaluate the efficacy of the peptide cocktails vaccine strategy. Regarding peptide vaccines for leishmaniasis, few studies are reported, and they are in immunogenicity phase with no outcome for parasite load [3][4][5]34,43,44]. Our results demonstrate that Cockt-1 can promote a significant reduction of parasite load in the spleen, which was not observed for Cockt-2.…”

Vaccines for Human Leishmaniasis: Where Do We Stand and What Is Still Missing?

“…From the application of such approaches and selection criteria, promising new candidates were proposed. Among them, peptide vaccines, chosen from immunogenic portions of known vaccine candidates such as KMP-11, were tested pre-clinically, often associated with DC-based vaccination strategies or nanosized vaccine-delivery systems [72,94,95]. Interestingly, a recently published work proposes a peptide vaccine candidate (from Leishmania phosphoenolpyruvate carboxykinase-PEPCK) that may be effective for both VL and CL should the results obtained in the pre-clinical context translate into the clinical one [90].…”