Abstract
In visceral leishmaniasis, the recovery from the disease is always associated with the generation of Th1-type of cellular responses. Based on this, we have previously identified several Th1-stimulatory proteins of Leishmania donovani -triose phosphate isomerase (TPI), protein disulfide isomerase (PDI) and elongation factor-2 (EL-2) etc. including heat shock protein 70 (HSP70) which induced Th1-type of cellular responses in both cured Leishmania patients/hamsters. Since, HSPs, being the logical targets for vaccines aimed at augmenting cellular immunity and can be early targets in the immune response against intracellular pathogens; they could be exploited as vaccine/adjuvant to induce long-term immunity more effectively. Therefore, in this study, we checked whether HSP70 can further enhance the immunogenicity and protective responses of the above said Th1-stimulatory proteins. Since, in most of the studies, immunogenicity of HSP70 of L. donovani was assessed in native condition, herein we generated recombinant HSP70 and tested its potential to stimulate immune responses in lymphocytes of cured Leishmania infected hamsters as well as in the peripheral blood mononuclear cells (PBMCs) of cured patients of VL either individually or in combination with above mentioned recombinant proteins. rLdHSP70 alone elicited strong cellular responses along with remarkable up-regulation of IFN-γ and IL-12 cytokines and extremely lower level of IL-4 and IL-10. Among the various combinations, rLdHSP70 + rLdPDI emerged as superior one augmenting improved cellular responses followed by rLdHSP70 + rLdEL-2. These combinations were further evaluated for its protective potential wherein rLdHSP70 + rLdPDI again conferred utmost protection (∼80%) followed by rLdHSP70 + rLdEL-2 (∼75%) and generated a strong cellular immune response with significant increase in the levels of iNOS transcript as well as IFN-γ and IL-12 cytokines which was further supported by the high level of IgG2 antibody in vaccinated animals. These observations indicated that vaccine(s) based on combination of HSP70 with Th1-stimulatory protein(s) may be a viable proposition against intracellular pathogens.
Highlights
Visceral leishmaniasis (VL) or Kala-azar, one of the most neglected tropical diseases, is caused by three leishmanial species, L. donovani, L. infantum and L. chagasi depending on the geographical area
The LdHSP70 (1548 bp) gene of L. donovani was successfully cloned in T/A vector and sequenced
LdHSP70 was further sub-cloned in bacterial expression vector pET28a+ (Fig. 1A), purified by affinity chromatography using Ni2+ NTA agarose beads containing columns and eluted at 250 mM imidazole concentration
Summary
Visceral leishmaniasis (VL) or Kala-azar, one of the most neglected tropical diseases, is caused by three leishmanial species, L. donovani, L. infantum and L. chagasi depending on the geographical area. In a survey in Bihar, there were a record alarming 100,000 cases of VL, of which 10,000 are unresponsive to SbV [6] This situation demands for an alternative control strategy posing an urgent need of a safe and effective vaccine, the development of an effective Leishmania therapeutic/prophylactic vaccine has been a challenge. Till date besides killed or live-attenuated parasites, several Leishmania antigens from different species either as DNA or as protein vaccines were tested against VL with different level of success. These observations provide sufficient evidences that a vaccine against VL is feasible
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
