Intranasal vaccine from whole Leishmania donovani antigens provides protection and induces specific immune response against visceral leishmaniasis

Abstract

Visceral leishmaniasis is a protozoan disease associated with high fatality rate in developing countries. Although the drug pipeline is constantly improving, available treatments are costly and live-threatening side effects are not uncommon. Moreover, an approved vaccine against human leishmaniasis does not exist yet. Using whole antigens from Leishmania donovani promastigotes (LdAg), we investigated the protective potential of a novel adjuvant-free vaccine strategy. Immunization of mice with LdAg via the intradermal or the intranasal route prior to infection decreases the parasitic burden in primary affected internal organs, including the liver, spleen, and bone marrow. Interestingly, the intranasal route is more efficient than the intradermal route, leading to better parasite clearance and remarkable induction of adaptive immune cells, notably the helper and cytotoxic T cells. In vitro restimulation experiments with Leishmania antigens led to significant IFN-γ secretion by splenocytes; therefore, exemplifying specificity of the adaptive immune response. To improve mucosal delivery and the immunogenic aspects of our vaccine strategy, we used polysaccharide-based nanoparticles (NP) that carry the antigens. The NP-LdAg formulation is remarkably taken up by dendritic cells and induces their maturation in vitro, as revealed by the increased expression of CD80, CD86 and MHC II. Intranasal immunization with NP-LdAg does not improve the parasite clearance in our experimental timeline; however, it does increase the percentage of effector and memory T helper cells in the spleen, suggesting a potential induction of long-term memory. Altogether, this study provides a simple and cost-effective vaccine strategy against visceral leishmaniasis based on LdAg administration via the intranasal route, which could be applicable to other parasitic diseases.

Leishmania donovani Impedes Antileishmanial Immunity by Suppressing Dendritic Cells via the TIM-3 Receptor

“…5A . For this purpose, we prepared splenocytes from the above-described treated mice on the 48th day postinfection, restimulated these cells with soluble L. donovani antigens (SLA) for 48 h ( 40 , 41 ), and assessed the frequencies of type 1 (interferon gamma [IFN-γ] and TNF-α) and type 2 (IL-10) cytokine-producing CD4 + or CD8 + T cells via intracellular staining, followed by flow cytometry. We found that the frequencies of CD4 + and CD8 + T cells expressing IFN-γ and TNF-α were increased and those expressing IL-10 were decreased (also noted by another group [ 38 ]) in the spleens of L. donovani -infected mice following adoptive transfer of LPS-treated but not control (PBS)-treated DCs ( Fig.…”

“…On the 48th day postinfection, the spleens and livers were removed from these mice to measure their weights and the parasite load. In addition, splenocytes (1 × 10 6 /well) derived from these mice were subsequently stimulated with SLA (80 μg/mL) for 48 h or left unstimulated ( 40 , 41 ), and the percentages of splenic CD4 + and CD8 + T cells expressing type 1 (IFN-γ and ΤΝFα) or type 2 (IL-10) cytokines were determined via flow cytometry. To detect type 1 and type 2 cytokine expression in CD4 + and CD8 + T cells, splenocytes were surface stained with anti-CD3-APC along with anti-CD4-FITC (or -PerCP/Cy5.5), anti-CD8-PerCP/Cy5.5 (or -FITC), or the respective isotype control antibody.…”

Leishmania Vaccines: the Current Situation with Its Promising Aspect for the Future

“…Unlike most parasitic infections, protective immunity occurs against reinfection in patients who recover from leishmaniasis or following leishmanization (LZ) [ 16 , 17 ]. This result reveals that immunological mechanisms play a major role in shaping the disease, and this globally important disease can potentially be prevented using vaccines [ 8 , 18 , 19 ]. It also provides a roadmap for the development of successful vaccines that can generate protective immunity against infection [ 20 ].…”

“…However, these studies show that they induce a weaker Th1 type immune response than live parasites, and the results are associated with an inconsistent effect. For these reasons, adjuvants have been used in many studies (e.g., Bacillus Calmette–Guérin (BCG)), and the parasites have been administered through alternative routes such as the mucosal route [ 19 , 39 , 49 ].…”

A Recombinant Chimeric Protein-Based Vaccine Containing T-Cell Epitopes from Amastigote Proteins and Combined with Distinct Adjuvants, Induces Immunogenicity and Protection against Leishmania infantum Infection

“…Many distinct VL vaccine candidates have been tested in murine and/or canine models [ 13 , 14 , 15 , 16 ], including plasmid DNA-based [ 17 , 18 ] and recombinant protein-based vaccines [ 19 , 20 ]. However, few have progressed to human trials, and the use of individual Leishmania proteins as recombinant molecules limits the antigenic repertoire of the experimental vaccines.…”