Immunization with Leishmania vaccine-alum-BCG and montanide ISA 720 adjuvants induces low-grade type 2 cytokines and high levels of IgG2 subclass antibodies in the vervet monkey (Chlorocebus aethiops) model.

The availability of hundreds of adjuvants has prompted a need for identifying rational standards for the selection of adjuvant formulation based on sound immunological principles for human vaccines. As cytokines elaborated by activated T cells are required for the regulation of isotype switch during B-cell development, a study of Th2 cytokines and subclass distribution of the antibodies may shed new light on the processes involved in the polarization of the immune responses during vaccination studies. The aim of this study was to identify an appropriate Leishmania vaccine adjuvant based on low Th2 cytokine and high value IgG2 antibody responses. Groups of vervet monkeys were immunized with Leishmania donovani sonicate antigen (Ag) alone or in conjunction with alum-BCG (AlBCG), monophosphoryl lipid A (MPL) or montanide ISA 720 (MISA) as adjuvants. Following three time point intradermal injections on days 0, 28 and 42, IL-4, IL-10 and IgG antibody subclasses were quantified by enzyme-linked immunosorbent assay (ELISA) and data analysed by one-way analysis of variance, Tukey-Kramer test and Spearman's rank correlation analysis. Results indicated relatively higher IL-4 and IL-10 cytokine responses following MPL + Ag as compared to AlBCG + Ag or MISA + Ag immunization. There was a positive significant correlation between IL-4 and IL-10 levels (r = 1.000; P = 0.0167). Significantly higher IgG2 antibody responses were associated with either AlBCG + Ag or MISA + Ag as compared to MPL + Ag immunization (P < 0.05). The study concludes that both AlBCG and MISA may be used in Leishmania vaccine studies that favour low Th2 cytokine and strong IgG2 antibody responses.

Prevalence of antibodies and cell mediated immune response against Leishmania major in feral nonhuman primates from Kenya.

In Kenya, Leishmania major is responsible for human cutaneous leishmaniasis (CL). Natural infection with L. major of a vervet monkey and experimental susceptibility of some nonhuman primates (NHPs) from Kenya has been established. However, there has been no comprehensive study of the prevalence of zoonotic CL in Kenya. And also, no investigation has been done to assess whether NHPs could be potential reservoir hosts of L. major even when the involvement of reservoir animals is obligatory in transmission of this parasite. To achieve this, wild caught Chlorocebus aethiops (Vervet monkeys n=213), Papio cynocephalus anubis (olive baboons n=101) and Cercopithecus mitis (Syke's monkeys n=64) from five geographical locations in Kenya were screened for antibodies against L. major using enzyme linked immunosorbent assay (ELISA) and Western blot (WB) analysis. From the population of C. aethiops (n=213) captured, 57 were used in lymphocyte proliferation assay. ELISA revealed a high prevalence of leishmaniasis sero conversion in olive baboons 78/101 (77.2%), vervet monkeys 129/213 (60.6%) and Sykes' monkeys 43/64 (67.2%). WB detected anti-L. major antibodies in 48.5% (49/101) of the baboons, 48% (102/213) of vervet monkeys and 37.5% (24/64) of Sykes' monkey sera. Specific proliferation of peripheral blood mononuclear cells to L. major antigen was demonstrated in 17 of the 57 (29.8%) vervet monkeys. In conclusion, the results of serological assays provide strong circumstantial evidence that CL is prevalent in five Provinces of Kenya and that Kenyan NHPs could be could be a potential reservoir hosts of L. major.

Efficacy of Trypan: a diminazene based drug as antileishmanial agent.

Trypan, a diamidine based drug, was tested as an antileishmanial agent. Duplicate cultures of both Leishmania major and Leishmania donovani promastigotes in M199 medium and Trypan at various concentrations were tested. The cultures were incubated at 25 degrees C and parasites counted at 48 h interval, and the data generated was used to establish growth inhibition curves. Drug-free cultures were included to serve as control. In the in vivo study, a total of 40 BALB/c mice were divided into five groups of 8 mice each. They were infected with 2 x 10(6) promastogotes on the left footpad. Two groups were treated with 70 microg/ml of Trypan, a total of 500 microl used immediately after infection, one group by topical application and the other administered intraperitoneally. The treatments were repeated for the two other groups 10 weeks post infection, one by topical application and the other administered intraperitoneally. One group was not treated and thus served as control. Footpad sizes were measured using Vernier calliper every 2 weeks for 21 weeks. In the in vitro studies, Trypan inhibited growth of either L. major or L. donovani promastigotes in all the concentrations tested with more dramatic inhibition in high concentrations. Based on the in vivo studies, it was evident that Trypan had effect on L. major infected lesions when applied topically immediately after infection. However, there was no effect when treatment commenced after the lesions were established. The data is discussed.