Dorcas Yole

Parameters of the attenuated schistosome vaccine evaluated in the olive baboon.

ABSTRACT Five exposures of baboons to the attenuated schistosome vaccine gave greater protection than three exposures, but this attenuation was not sustained when challenge was delayed. Within the scope of the data collected, fecal egg counts and circulating antigen levels did not accurately predict the observed worm burdens. Levels of immunoglobulin G at challenge correlated best with protection, but there was little evidence of a recall response.

Previous or ongoing schistosome infections do not compromise the efficacy of the attenuated cercaria vaccine.

ABSTRACT A current or previous schistosome infection might compromise the efficacy of a schistosome vaccine administered to humans. We have therefore investigated the influence of infection on vaccination, using the baboon as the model host and irradiated Schistosoma mansoni cercariae as the vaccine. Protection, determined from worm burdens in test and controls, was not diminished when vaccination was superimposed on a chronic infection, nor was it diminished when it followed a primary infection terminated by chemotherapy. Protection was also assessed indirectly based on fecal egg output and circulating antigen levels, as would be the case in human vaccine trials. In almost all instances, these methods overestimated protection, sometimes with discrepancies of >20%. The overwhelming immune response to egg deposition in infected animals made it difficult to discern a contribution from vaccination. Nevertheless, the well-documented immunomodulation of immune responses that follows egg deposition did not appear to impede the protective mechanisms elicited by vaccination with attenuated cercariae.

Enzootic simian piroplasm (Entopolypoides macaci ) in wild-caught Kenyan non-human primates.

Background  Three species of non‐human primates comprising African green monkeys (AGMs), (Cercopithecus aethiops, n = 89), Syke’s monkeys (Cercopithecus mitis, n = 60) and olive baboons (Papio cynocephalus anubis, n = 30), were screened for Entopolypoides macaci.

The effect of vaccinating S. mansoni –infected BALB/c mice either before or after treatment

In Schistosoma mansoni endemic areas, there are people with ongoing S. mansoni infection, others have been infected and treated while others have never been infected. What would happen if these different groups of people were vaccinated against S. mansoni? BALB / c mice were divided into five groups: Infected-Treated-Vaccinated; Infected-Vaccinated-Treated; Vaccinated-Treated Control; Challenge Control and Untreated Challenge Control. Vaccination (500 20krad irradiated S. mansoni cercariae), Treatment (praziquantel), Infection and Challenge (150 S. mansoni cercariae) were carried out at specified times. Proliferation assay, Enzyme linked immunosorbent assay, gross pathology, histopathology and perfusion were performed. High protection levels were obtained in mice treated after vaccination: Vaccinated-Treated control, 96.5 %; Infected-Vaccinated-Treated, 68.9 %; and Infected-Treated-Vaccinated, 41 %. A good correlation was obtained between proliferative responses and protective levels, implying cellular involvement in protection. Although all protected animals had high IgG levels, there was no strong correlation between the two. Specificity rather than amounts of IgG, seem more important in protection. Praziquantel seemed to boost protective immunity when administered after vaccination. Granuloma development and modulation in the two test groups was similar. It seems better to vaccinate infected patients before treatment, the ideal situation being vaccinating people who have not encountered S. mansoni.

Anti-Schistosomal activity of five plant extracts on Swiss white mice infected with Schistosoma mansoni

Schistosomiasis in humans is a major public health problem worldwide. Schistosomiasis occurs in 76 tropical countries and it is estimated that 85% of the infections are in Africa. In Kenya, it is estimated that 3 million people are infected. The Conventional drugs are effective in the treatment of the disease but very little progress has been achieved on treatment of Schistosomiasis in Kenya. Any effort towards developing alternative drugs for the disease is worthwhile. Praziquantel is the most effective drug against all adult stages of human Schistosomiasis, being the drug of choice for morbidity control of Schistosomiasis. However it is not a satisfying situation to have one drug used for the treatment. Ideally other drugs should be availed in order to avoid development of drug resistance. The use of plant extracts in treatment of diseases is universal. The results obtained showed that Ocimum americanum and Bridelia micrantha plant extracts had antischistosomal activity as indicated by high worm reduction and reduced gross pathology. Histopathology showed no or few granuloma in the liver tissue. Further work should be done on the efficacious extracts, towards drug development.

Immunological Responses of Mice After Treatment with Ocimum Americanum Hexane and Bridelia Micrantha Water Plant Extracts

Background-The T helper 1 (TH1) and TH2 dichotomy was first shown in murine CD4+ lymphocytes clones and these cells could be differentiated in terms of the cytokines they secrete. The TH1 subsets produce interleukin 2 (IL-2,) interferon gamma (IFN-γ) and lymphotoxin, TH2 subsets produce IL-4, IL-5, IL-6 IL-10 and IL-13. An important function of the TH2 response during infection is to produce cytokines that can prevent or dampen the production or effector functions of potentially dangerous inflammatory mediators. Results The results obtained showed that Ocimum americanum hexane (OAH) and Bridelia micrantha (BMW) water extract had antischistosomal activity. This was indicated by low worm recovery, high worm reduction, and reduced gross pathology with histopathology showing no or few granulomas in the liver tissue, which was similar to Praziquantel (PZQ). The two extracts had both cellular and humoral responses as demonstrated by IFN-γ, IL-5 and IgG responses. OAH and BMW were significantly similar to PZQ; however BMW had higher IgG responses. BMW had higher IFN-γ responses for both spleen and lymph node cells. Conclusion this implied that treatment groups were able to produce the TH-1 response which is important for cell mediated immunity. Although both extracts induced production of IL-5 for both lymph node and spleen cells, OAH generated more IL-5.

A simple method of preparing clean intact granulomas and granuloma cells from livers of definitive hosts infected with either Schistosoma mansoni or Schistosoma japonicum

The drawback of existing techniques for obtaining intact granulomas and granuloma cells have been, (1) lack of clean intact granulomas without adhering liver tissues, (2) isolating inadequate numbers of clean intact granulomas, and (3) obtaining low numbers of viable granuloma cells from the granulomas. This work aims at developing a method which eliminates these problems. C57B1/6 mice and baboons have been utilized as definitive hosts. Major emphasis has been on Schistosoma mansoni liver egg granuloma, though some work was carried out using S. japonicum. The work demonstrates that it is possible to obtain enough clean liver granulomas and large numbers of granuloma cells from animals with schistosome infection by using two stages of digestion with collagenase. However, one needs to adjust the concentration of collagenase and also the periods of incubation, depending on the parasite and the host species.