Investigation of the antigenicity and protective efficacy of Leishmania promastigote membrane antigens in search of potential diagnostic and vaccine candidates against visceral leishmaniasis

Abstract

Background Visceral leishmaniasis (VL), is a parasitic disease that causes serious medical consequences if treatment is delayed. Despite a decline in the number of VL cases in the Indian subcontinent, the commencement of the disease in newer areas continues to be a major concern. Although serological diagnosis mainly by immunochromatographic tests has been found to be effective, a test of cure in different phases of treatment is still desired. Even though a good prophylactic response has been obtained in murine models by a number of vaccine candidates, few have been proposed for human use. Methods In this study, nine antigenic components (31, 34, 36, 45, 51, 63, 72, 91 and 97 kDa) of Leishmania promastigote membrane antigens (LAg), were electroeluted and evaluated through ELISA to diagnose and distinguish active VL from one month cured and six months post-treatment patients. Further, to investigate the immunogenicity of electroeluted proteins, human PBMCs of cured VL patients were stimulated with 31, 34, 51, 63, 72 and 91 kDa proteins. Results We found that 34 and 51 kDa proteins show 100% sensitivity and specificity with healthy controls and other diseases. After six months post-treatment, antibodies to 72 and 91 kDa antigens show a significant decline to almost normal levels. This suggests that 34 and 51 kDa proteins are efficient in diagnosis, whereas 72 and 91 kDa proteins may be used to monitor treatment outcome. In another assay, 51 and 63 kDa proteins demonstrated maximum ability to upregulate IFN-γ and IL-12 with minimum induction of IL-10 and TGF-β. The results indicating that 51 and 63 kDa proteins could be strong candidates for human immunization against VL. In contrast, 34 and 91 kDa proteins demonstrated a reverse profile and may not be a good vaccine candidate. Conclusions The preliminary data obtained in this study proposes the potential of some of the antigens in Leishmania diagnosis and for test of cure. Additionally, some antigens demonstrated good immunoprophylactic cytokine production through T cell-mediated immune response, suggesting future vaccine candidates for VL. However, further studies are necessary to explore these antigens in diagnosis and to access the long-term immune response.

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

“…Immuno-proteomic techniques are now extensively used to define immunogenic candidates in both promastigote and amastigote antigens [ 51 – 53 ]. Based on several previous studies highlighting the presence of highly immunogenic antigens in the promastigote form that initiates infection [ 54 – 56 ], we designed our prophylactic vaccine with total antigens from promastigote and identified the optimal mode of administration. Interestingly, no liver and spleen biopsies from IN LdAg vaccinated mice yielded viable parasites in vitro , suggesting significant protection against promastigote infection.…”

The pathogenicity and virulence of Leishmania - interplay of virulence factors with host defenses

“…In one of the studies, L. donovani proteins of different molecular weights such as 31, 34, 36, 45, 51, 63, 72, 91, and 97 kDa were purified and evaluated in a serological ELISA. It was observed that 34 and 51 kDa proteins showed 100% sensitivity and no cross-reactivity with other diseases [ 287 ]. Advancement in molecular biology led to the discovery of more defined recombinant proteins that were easier in purification with no batch-to-batch variation, unlike crude proteins.…”

Development of Immunological Assays Based on Leishmania donovani Antigen for Diagnosis of Canine Visceral Leishmaniasis and Their Multicenter Evaluation in Brazil and Italy

“…Leishmanial membrane antigen (LAg) was isolated from the promastigotes of L. donovani strain AG83 (ATCC ® PRA-413 ™ ) according to the protocol discussed earlier (Ejazi et al, 2020). In an indirect ELISA, Brazilian sera from UFPI were tested for antibodies against LAg.…”