Evaluation of Leishmania donovani Protein Disulfide Isomerase as a Potential Immunogenic Protein/Vaccine Candidate against Visceral Leishmaniasis

Abstract

In Leishmania species, Protein disulfide isomerase (PDI) - a redox chaperone, is reported to be involved in its virulence and survival. This protein has also been identified, through proteomics, as a Th1 stimulatory protein in the soluble lysate of a clinical isolate of Leishmania donovani (LdPDI). In the present study, the molecular characterization of LdPDI was carried out and the immunogenicity of recombinant LdPDI (rLdPDI) was assessed by lymphocyte proliferation assay (LTT), nitric oxide (NO) production, estimation of Th1 cytokines (IFN-γ and IL-12) as well as IL-10 in PBMCs of cured/endemic/infected Leishmania patients and cured L. donovani infected hamsters. A significantly higher proliferative response against rLdPDI as well as elevated levels of IFN-γ and IL-12 were observed. The level of IL-10 was found to be highly down regulated in response to rLdPDI. A significant increase in the level of NO production in stimulated hamster macrophages as well as IgG2 antibody and a low level of IgG1 in cured patient's serum was observed. Higher level of IgG2 antibody indicated its Th1 stimulatory potential. The efficacy of pcDNA-LdPDI construct was further evaluated for its prophylactic potential. Vaccination with this construct conferred remarkably good prophylactic efficacy (∼90%) and generated a robust cellular immune response with significant increases in the levels of iNOS transcript as well as TNF-α, IFN-γ and IL-12 cytokines. This was further supported by the high level of IgG2 antibody in vaccinated animals. The in vitro as well as in vivo results thus indicate that LdPDI may be exploited as a potential vaccine candidate against visceral Leishmaniasis (VL).

Visceral Leishmaniasis: Advancements in Vaccine Development via Classical and Molecular Approaches

“…Kushawaha et al (48, 50, 51) studied the immunogenicity of LelF-2, TPI, and PDI of L. donovani in PBMCs of cured Leishmania -infected patients and hamsters where they found Thl-type cytokine profile (production of IFN-γ, IL-12, and TNF-α but not IL-4 or IL-10) with a remarkable increase in IgG2 and considerable protection. Gupta et al (49, 53) reported p45, enolase, and aldolase as a potential vaccine candidate with considerable prophylactic efficacy to the tune of 85–90% with an increased mRNA expression of iNOS, IFN-γ, TNF-α, and IL-12 and decrease in TGF-β and IL-4.…”

Identifying vaccine targets for anti-leishmanial vaccine development

“…In agreement with these observations, PDI in the form of DNA vaccine has been shown to down regulate the expressions of IL-10 and IL-4 mRNA levels in hamsters as compared with infected controls [71]. As a potential vaccine antigen, PDI has shown good prophylactic potential along with robust immune responses in vaccinated animal against visceral form of disease [72]. …”

Cloning, expression, purification and characterization of Leishmania tropica PDI-2 protein

“…Recent studies have obviously characterized L. donovani PDIs as important protein for the design of new drug or vaccine against Leishmania parasites. In this species two groups have reported a 15 kDa atypical PDI with only one catalysing site "CGHC" [23] and a 55 kDa PDI [19]. Amit et al 2014 showed that protein of 15 kDa PDI promoted L. donovani infection, rendering macrophages more toxic which up regulates immunosuppressive factors such as IL-10 and causes retardation of anti-Leishmania activity of macrophage.…”

“…Previous results showed that PDI-2 was identified as one of the soluble leishmanial protein that induced a Th1 response in the PBMCs of Leishmania infected cured/endemic patients [18]. Further, rLdPDI-2 has been identified as a Th1 stimulatory and supposed to be the effector molecules for defense mechanism against Leishmania infection [19]. In this report, we described the isolation, cloning, sequencing, expression and characterization of the putative PDI-2 protein of L. tropica.…”