In vitro activity and in vivo efficacy of a combination therapy of diminazene and chloroquine against murine visceral leishmaniasis

The present study evaluated the in vitro activity and in vivo efficacy of diminazene combined with chloroquine as a potential drug against Leishmania donovani. Amphotericin B was used as a positive control drug. In vitro activity involved incubation of various drug concentrations with promastigotes or vero cells in culture before determination of parasite growth inhibition or cell death while in vivo evaluations involved infection of various mice groups with virulent L. donovani parasites and treatment with test drug compounds following disease establishment. Weight changes in experimental mice were also evaluated before infection and throughout the experiment. The results indicated that the diminazene-chloroquine combination was at least nine times more efficacious than individual drugs in killing promastigotes in culture. The diminazene-chloroquine combination was safer （Ld50=0.03±0.04） than Amphotericin B （Ld50=0.02±0.01）. Body weight in infected mice increased significantly （P=0.0007） from day 7 to day 37 following infection （P=0.026）. However, body weight remained comparable in all mice groups during treatment （P=0.16）. The diminazene-chloroquine combination significantly reduced splenic parasite numbers as compared to individual drug therapies （P=0.0001） although Amphotericin B was still more efficacious than any other treatment （P=0.0001）. Amongst the test compounds, the diminazene-chloroquine combination showed the lowest level of IgG antibody responses with results indicating significant negative correlation between antileishmanial antibody responses and protection against disease. These findings demonstrate the positive advantage and the potential use of a combined therapy of diminazene-chloroquine over the constituent drugs. Further evaluation is recommended to determine the most efficacious combination ratio of the two compounds.

A review of adjuvants forLeishmania vaccine candidates

Over the last decade, there has been a flurry of research on adjuvants for vaccines, and several novel adjuvants are now licensed products or in late stage clinical development. The success of adjuvants in enhancing the immune response to antigens has led many researchers to re-focus their vaccine development programs. Although several vaccine candidates have been tested against leishmaniasis, there is yet no effective vaccine against this parasitic disease. Recent research has documented that efforts to develop effective Leishmania vaccine have been limited due to lack of an appropriate adjuvant. In view of this, this review paper outlines some of the adjuvants that have been used in Leishmania vaccine candidates and cites a few of the responses obtained from these studies. The aim of the present review is to consolidate these findings to facilitate the application of these adjuvants in general and experimental vaccinology.

Evaluation of the Therapeutic Potential of Warburgia ugandensis,Prunus africana,and Piliostigma thonningii against Leishmania donovani in vitro and in Balb/c Mice

Leishmaniasis is a zoonotic disease caused by protozoan parasites of the genus Leishmania.Conventional chemotherapy remains to be the most preferred measure against leishmaniasis despite being associated with high toxicity and relapse rates.They are also expensive and require hospitalization.Plant-based compounds provide a better treatment alternative because they are effective,cheap,and less associated with toxicity and resistance.This study examined the therapeutic potential of Warburgia ugandensis,Prunus africana,and Piliostigma thonningii against Leishmania donovani infection in BALB/c mice.Anti-promastigote and toxicity studies were evaluated by incubating the test compound with promastigotes and Vero cells,respectively.Serum was obtained from the mice for total immunoglobulin gamma(IgG)quantification.For in vivo studies,the mice were infected with virulent Leishmania donovani then treated with methanolic extracts of Warburgia ugandensis,Prunus africana,and Piliostigma thonningii and control drug,pentostam(sodium stibogluconate).Treatment with the plant extracts and standard drug resulted to significant reduction in parasite burden.Outcomes in the mice treated with plant extracts were comparable to those treated with pentostam(P≥0.05).In the promastigote assay,all the test compounds killed more than half of the promastigotes at the highest concentration(500μg/mL).Warburgia ugandensis,P.thonningii,and P.africana reduced the number of promastigotes from 2.0×10^(6) to 7.7×10^(3),72.0×10^(3),and 5.0×10^(3),respectively.Pentostam had the lowest IC50(210μg/mL),followed by Warburgia ugandensis(IC50 of 270μg/mL).Piliostigma thonningii and P.africana were less toxic with IC50 of 720μg/mL and 500μg/mL,respectively.There was low production of IgG antibodies following treatment with the plant extracts and high levels in the untreated control.