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

Abstract

Resistance of Leishmania donovani to sodium antimony gluconate has become a critical issue in the current, prolonged epidemic in India. Hence, there is an urgent need for a vaccine that is protective against both antimony-susceptible and -resistant strains of L. donovani. The multigene LD1 locus located on chromosome 35 of Leishmania is amplified in ∼15% of the isolates examined. The open reading frame F (ORFF), a potential vaccine candidate against visceral leishmaniasis, is part of the multigene LD1 locus. ORFF was expressed as a chimeric conjugate of ubiquitin to elicit an Ag-specific cell-mediated immune response. Analysis of the cellular immune responses of ubiquitin-conjugated ORFF (UBQ-ORFF) DNA-immunized, uninfected BALB/c mice demonstrated that the vaccine induced enhanced IFN-γ-producing CD4+ and CD8+ T cells compared with nonubiquitinated ORFF DNA vaccine. Higher levels of IL-12 and IFN-γ and the low levels of IL-4 and IL-10 further indicated that the immune responses with UBQ-ORFF were mediated toward the Th1 rather than Th2 type. Infection of immunized mice with either the antimony-susceptible (AG83) or -resistant (GE1F8R) L. donovani strain showed that UBQ-ORFF DNA vaccine induced higher protection when compared with ORFF DNA. UBQ-ORFF DNA-immunized and -infected mice showed a significant increase in IL-12 and IFN-γ and significant down-regulation of IL-10. High levels of production of nitrite and superoxide, two macrophage-derived oxidants that are critical in controlling Leishmania infection, were observed in protected mice. The feasibility of using ubiquitinated-conjugated ORFF DNA vaccine as a promising immune enhancer for vaccination against both antimony-susceptible and -resistant strains of L. donovani is reported.

Ub Combination Enhanced Cellular Immune Response Elicited by HSP65 DNA Vaccine against <i>Mycobacterium tuberculosis</i>

“…The modulated immune response indicated that the expressed HSP65 protein had a higher rate of intracellular degradation in a proteasome pathway because of the addition of UbGR. Our result is consistent with the Sharma A's report [28], which showed that immunization with DNA vaccine encoding ORFF fused to Ub induced higher IFN-γ, stronger Th 1 responses than those of unmodified vaccines. However, no effect was seen for another antigen PyCSP using the same targeting strategies.…”

MAPK-directed phosphatases preferentially regulate pro- and anti-inflammatory cytokines in experimental visceral leishmaniasis: involvement of distinct protein kinase C isoforms

“…Promotion of the Th1 response over that of Th2 is associated with control of disease in case of cutaneous leishmaniasis. Although such clear polarization is not the case in visceral leishmaniasis, the Th1 response correlates with resistance to infection [32]. In this light, the modulation of proinflammatory over anti-inflammatory cytokines by PTP inhibitors might favor a better control over infection in vivo.…”

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

“…Carter et al (71) and Sharma and Madhubala (72) vaccinated mice with pVAXγGCS (gamma-glutamyl cysteine synthetase) and UBQ-ORFF, respectively, which resulted in a protective response to increased levels of IL-12 and IFN-γ and the lower levels of IL-4 and IL-10 confirming Th1-type response.…”