Kinetoplastid Membrane Protein-11 DNA Vaccination Induces Complete Protection against Both Pentavalent Antimonial-Sensitive and -Resistant Strains of Leishmania donovani That Correlates with Inducible Nitric Oxide Synthase Activity and IL-4 Generation: Evidence for Mixed Th1- and Th2-Like Responses in Visceral Leishmaniasis

Abstract

The emergence of an increasing number of Leishmania donovani strains resistant to pentavalent antimonials (SbV), the first line of treatment for visceral leishmaniasis worldwide, accounts for decreasing efficacy of chemotherapeutic interventions. A kinetoplastid membrane protein-11 (KMP-11)-encoding construct protected extremely susceptible golden hamsters from both pentavalent antimony responsive (AG83) and antimony resistant (GE1F8R) virulent L. donovani challenge. All the KMP-11 DNA vaccinated hamsters continued to survive beyond 8 mo postinfection, with the majority showing sterile protection. Vaccinated hamsters showed reversal of T cell anergy with functional IL-2 generation along with vigorous specific anti-KMP-11 CTL-like response. Cytokines known to influence Th1- and Th2-like immune responses hinted toward a complex immune modulation in the presence of a mixed Th1/Th2 response in conferring protection against visceral leishmaniasis. KMP-11 DNA vaccinated hamsters were protected by a surge in IFN-γ, TNF-α, and IL-12 levels along with extreme down-regulation of IL-10. Surprisingly the prototype candidature of IL-4, known as a disease exacerbating cytokine, was found to have a positive correlation to protection. Contrary to some previous reports, inducible NO synthase was actively synthesized by macrophages of the protected hamsters with concomitant high levels of NO production. This is the first report of a vaccine conferring protection to both antimony responsive and resistant Leishmania strains reflecting several aspects of clinical visceral leishmaniasis.

Ubiquitin Conjugation of Open Reading Frame F DNA Vaccine Leads to Enhanced Cell-Mediated Immune Response and Induces Protection against Both Antimony-Susceptible and -Resistant Strains ofLeishmania donovani

“…However, there was no difference in the modulation of immune response and protective efficacy of the pUMVC3-UB-ORFF vaccine in antimony-susceptible AG83 and -resistant GE1F8R-infected mice. A similar observation has been reported earlier with KMP-11 DNA vaccination in antimony-sensitive and -resistant infected hamsters (6). This apparent homogeneity in the mechanism and protection was reported to be the due to the possibility of the limited extent of MHC polymorphism (71).…”

“…However, current chemotherapeutic agents are unsuitable, in part because of their high toxicity and the emergence of drug resistance (4,5). Thus, identification of novel immunological targets that can be effective against both antimony-susceptible and -resistant strains of Leishmania is of tremendous economic and medical importance (6). Leishmaniasis is considered one of the few parasitic diseases likely to be controlled by vaccination, especially because of an uncomplicated leishmanial life cycle and the fact that recovery from infection renders the host resistant to subsequent infection.…”

“…The isolates were provided by Dr. M. Chatterjee (Institute of Postgraduate Medical Education & Research, Kolkata, India) (6,24,41). GE1F8R is approximately eight times more resistant to antimony compared with antimony-sensitive clone AG83 (42).…”

“…In the murine model, IgG1 and IgG2a class switching is governed by the presence of IL-4 and IFN-␥, respectively (6). Eight weeks after the infection, sera from pUMVC3-UB-ORFF DNA-and blank vector-immunized mice challenged with either AG83 or GE1F8R and corresponding infected controls were analyzed for ORFF-specific anti-IgG1 and IgG2a Ab titers by ELISA as described in Materials and Methods.…”

Immunity to a salivary protein of a sand fly vector protects against the fatal outcome of visceral leishmaniasis in a hamster model

“…To date, progressive disease in hamsters, the model of choice for the study of VL, has been mostly achieved by the injection of a large number of parasites via the i.v., intracardial, or i.p. route (21)(22)(23)(24). However, these routes of infection do not mimic natural transmission by sand fly bite where the parasites are delivered into the skin of a mammalian host in the presence of saliva.…”