Evaluation of Crude Leishmania Donovani Antigen CO Administered with the Adjuvants as a Potential Vaccine for Leishmaniasis in Vervet Monkey Model
Mutiso, J. M.
MetadataShow full item record
Visceral leishmaniasis (VL) or kala-azar is the most dreaded and devastating formof leishmaniasis, causing high mortality rate, mainly in children. A vaccine againstdifferentforms ofleishmaniasis should be feasible considering the wealth of information on geneticsof the parasite, clinical and experimental immunology of leishmaniasis, andandbIO.lobgiylityof vaccines that can protect expenm. entaI' arumaIsagainst challenge With the avallad here i ffectiL. hmaniaspecies. However, to ate, t ere ISno e ectivevaccine against anydifferenftleiesthsmaniasisfor general human use. Efforts to develop an effective vaccine soform 0e been limited due to lack of an appropriate adjuvant. A mixture of safe Leishmaniafar .ha:sandan adjuvant that preferentially stimulates cellular immune response presentsanug.e I option for a vacci.n' e against Ie' ishmam.asi.s, A vaccm. e for man needs to be testeda. rasnuoitnaableprimate models such as the vervet monkey due to their close phylogenetic~lation to humans. This study used the vervet monkey model of visceral leishmaniasis to:valuatethe safety, immunogenicity and efficacy of Leishmaniadonovanisonicateantigen(Ag) delivered alone or in conjunction with alum-BCG (AIBCG), monophosphoryl lipidA (MPL) or montanideISA 720 (MISA) as adjuvants. Following vaccinations of groupsofvervet monkeys at days0, 28 and 42, safety was assessed by observation of indurations and erythema at sites ofvaccination. Antibody responses and cytokines were quantified by enzyme linked immunosorbentassay (ELISA). Antigen recall Iymphoproliferation was measured byblast assay while interferon gamma (IFN-y)-producing CD4+ and CD8+ T cell responseswere measured by intracellular cytokine staining and quantification using flow cytometer.Animals were challenged with L. donovaniparasites and efficacy evaluated by parasitequantification in splenic impression smears. Data were analyzed using CellQuest, oneway analysis of variance (ANOVA), Tukey-Kramer test, Spearman rank correlationanalysis or Wilcoxon matched-paired sign-rank test. A P value <0.05 was consideredsignificant. Results indicated that vaccinations with MPL+Ag or MISA+Ag were safewhile animals vaccinated with AIBCG+Ag developed erythematous ulcerative indurationsat sites of vaccination. Delayedtype hypersensitivity (DTH~ responses were significantlyhigher in the MISA+Ag group than in other vaccinated groups (P <0.001) while boththe AIBCG+Ag and MISA+Ag groups induced the highest total IgG and IgG2 subclassantibody responses as compared to vaccinations with MPL+Ag. Interleukin-4 and IL-IOcytokine responses were relatively higher in the MPL+Ag group than in other groups whilevacinations with AIBCG+Ag and MISA+Ag induced comparable lFN-y or TNF-a levels whichwere significantly higher than levels induced by MPL+Ag vaccination (P <0.001).Interestingly, significantly higher lFN-y producing CD4+ or CD8+ T cells were induced inAIBCG+Agand MISA+Ag vaccinated animal groups as compared to other experimentalgroups (P <0.001). There was a positive and significant correlation between lFN-yproducing CD4+ and CD8+ T cell populations in both experimental and control groups (r= 1.000; P = 0.0167). Positive significant correlations were also observed between eitherCD4+ or CD8+ T cells with lFN-y, TNF-a cytokines or DTH responses (r = 1.000; P. <0.0167). Significant reductions in parasitic loads were associated with vaccinations with AIBCG+AgorvMISA+Agas compared to other studygroups (P <0.001). All Thl immune response parameters including DTH, lFN-y, TNF-a,and lFN-y-producing CD4+ or CD8+ T cells correlated negatively and significantly withparasitic loads. The findings from this study conclude that, MISA 720 is an appropriateadjuvant in terms of safety and immunogenicity and can be effectively used in theformulation of Leishmaniavaccines for clinical applications. The study reconunends theuse of MISA 720 in the development of a Leishmaniavaccine for clinical trials in humans.Data generated in this study is useful in Leishmaniavaccine development