RP-Department of Zoological Sciences
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Browsing RP-Department of Zoological Sciences by Author "Anjili, C. O."
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Item The African Green Monkey Model for Cutaneous and Visceral Leishmaniasis.(PubMed, 2001-12) Gicheru, M. M.; Olobo, J. O.; Anjili, C. O.Non-human primates are valuable models for biomedical research because of their similarities to human anatomy, immunology and physiology. Leishmaniasis, a disease caused by protozoan parasites, has a worldwide distribution and results in high morbidity and mortality. Availability of a non-human primate model of leishmaniasis would facilitate the study of different aspects of this disease and would accelerate the development of vaccines and new drugs. In this article, some interesting features of the vervet monkey (African Green monkey) model of human cutaneous and visceral leishmaniasis are discussed.Item Heterologous Protection by Leishmania Donovani for Leishmania Major Infections in the Vervet Monkey Model of the Disease.(PubMed, 1997-02) Gicheru, M. M.; Olobo, J. O.; Anjili, C. O.The study was aimed at analyzing immunological cross-reactivity between Leishmania major and Leishmania donovani and possible cross-protection between the two parasite species in the vervet monkey model of the disease. Nine vervet monkeys (Cercopithecus aethiops) from the institute animal colony were sued in the study. Five of the animals had been previously infected with L. donovani but had remained asymptomatic while the other four animals were naive and comprised the control group. Immunological responses to both L. major and L. donovani antigens in the five animals with prior exposure to L. donovani were examined before challenge. High antibody titers to the two antigens were demonstrated in an enzyme-linked immunosorbent assay, but the antibody titers to L. donovani were significantly higher than those to L. major (P < 0.005). Positive in vitro peripheral blood leucocyte (PBL) proliferation to L. major and L. donovani antigens was also demonstrated, but there was no significant difference in the response to the two antigens (P > 0.1). High and varying levels of interferon gamma (IFN-gamma) were secreted in PBL from the five vervet monkeys when stimulated with L. major antigen, but vervet monkey 1296 secreted marginal levels of IFN-gamma. When the animals were challenged intradermally with 1 x 10(5) virulent L. major promastigotes mixed with sandfly vector salivary gland lysate all four vervet monkeys in the control group developed nodules of varying sizes at the inoculation sites that eventually ulcerated. However, nodule formation and ulceration occurred at different times among these animals. The other five animals (animals with prior exposure to L. donovani) did not pick up the infection at all, but one animal from this group, vervet monkey 1296, developed a transient lesion that healed within 9 weeks, the same animal that had been shown to secrete low levels of IFN-gamma. The results demonstrate high cross-reactivity between L. donovani and L. major and that L. donovani protects against L. major infections. This finding is important for vaccine development studies against leishmaniasis.Item Vaccination of Vervet Monkeys against Cutaneous Leishmaniosis Using Recombinant Leishmania 'Major Surface Glycoprotein' (Gp63).(PubMed, 1995) Gicheru, M. M.; Olobo, J. O.; Anjili, C. O.; Mbati, P. A.; Kariuki, T. M.; Githure, J. I.; Koech, D. K.; McMaster, W. R.Vervet monkeys (Cercopithicus aethiops) were shown to give a positive delayed-type hypersensitivity (DTH) reaction to gp63, a major surface glycoprotein of Leishmania parasites, and also produce antibodies to the molecule following a triple vaccination with a total dose of 150 micrograms of recombinant gp63 mixed with Bacille Calmette Guerin (BCG). However, peripheral blood leucocytes (PBL) from these animals neither proliferated nor produced any interferon-gamma (IFN-gamma) following in vitro stimulation with the antigen. Analysis of lymphocyte subsets following vaccination did not reveal any striking phenotypic alteration of cellular sub-populations in PBL. When vaccinated animals were rechallenged, via the needle, with virulent Leishmania major promastigotes containing salivary gland extracts from vector sandflies, only partial protection was achieved. We concluded from these studies that rgp63 produced in Escherichia coli is a safe vaccine molecule which gives only partial protection following vaccination in the vervet monkey host. The molecule requires further improvement for vaccine and/or immunodiagnosis application.Item Vaccinations with Live-attenuated Leishmania Major Promastigotes and Challenge Infection with L. Major in BALB/c Mice.(East African medical journal, 2005-04) Onyalo, Janet Achieng'; Mwala, D. M.; Anjili, C. O.; Orago, A. S.; Tonui, W. K.BACKGROUND: Currently there is no vaccine available in use against any form of leishmaniases worldwide. OBJECTIVE: To assess potential of a live-attenuated Leishmania major promastigates, for protection against a challenge infection with L. major in BALB/c mice. DESIGN: A laboratory based study. SETTING: Study was carried out at Centre for Biotechnology Research and Development, Kenya Medical Research Institute, Nairobi. RESULTS: The greatest protection against challenge with L. major was seen in mice immunised with live parasites (P < 0.001) compared to vaccinations with heat killed or soluble antigens. In general, immunised mice produced high level of antileishmanial antibodies and T cell stimulation to their respective antigens. CONCLUSIONS: Our live-attenuated parasites produced by serial sub-culture of L. major parasites 118 times showed the capacity to induce appropriate cell-mediated immune responses and protection against L. major infection in BALB/c mice. Data also suggests that these parasites do not revert to virulence when injected subcutaneously in mice.