Immunomodulatory activity of Buchholzia coriacea seed methanol extract on Trypanosoma brucei brucei infected mice.

CONTEXT: The seeds of Buchholzia coriacea Engler (Capparaceae) are used in Eastern Nigeria to treat feverish conditions, and to treat malaria and sleeping sickness that cause fever. OBJECTIVE: The current study assesses the immunomodulatory activity of Buchholzia coriacea seed extract on Trypanosoma brucei brucei infected mice. MATERIALS AND METHODS: Delayed hypersensitivity reaction, humoral antibody response and in-vivo leucocyte mobilization tests were assessed in three different experiments to determine the effect of the extract on immune response. Seventy-five (75) mice (25 mice per experiment) were used for the study and were each infected with 1.00 × 106 trypanosomes intra-peritoneally. Groups A, B and C were given 250, 500 and 1000 mg/kg of the extract, respectively, group D received 7.5 mg/kg body weight of levamisole and group E was the control. Sheep RBCs were used as antigen. RESULTS: The acute toxicity tests did not cause clinical signs or death within 24 h post treatment at all the doses tested. The extract inhibited delayed hypersensitivity reaction by 20.9 and 20.8% at 250 and 500 mg/kg, respectively, while at 1000 mg/kg, the paw size increased (-101.9%) when compared with the control. The extract elevated the antibody titre from 1.60 ± 0.40 for control to 8.00 ± 3.58 for 500 mg/kg group. The extract increased in total leucocytes counts. DISCUSSION AND CONCLUSION: The extract has a very wide safety margin and was able to improve immune response. The results of the present study showed that Buchholzia coriacea seed methanol extract possesses immunostimulatory activity on trypanosome-infected mice.

The beneficial effect of dietary zinc supplementation on anaemia and immunosuppression in Trypanosoma brucei infected rats.

Zinc is an essential trace element crucial for normal development and function of cells mediating nonspecific immunity and protects bio-molecules from oxidative damage. This study was designed to assess the effects of dietary zinc supplementation on anaemia and immunity of trypanosome-infected rats. Thirty rats, divided into five groups (A-E) of 6 each, were used for the study. Parameters used to assess the effect of the supplementation are antibody response to Sheep RBC using direct haemagglutination test, parasitaemia using the rapid matching method, WBC count using the improved Neubauer haemocytometer method, haemoglobin concentration using the cynomethaemoglobin technique while PCV was determined using the microhaematocrit method. The pre-infection supplementation did not prolong the pre-patent period significantly (p > 0.05). However, it significantly (p < 0.05) increased the packed cell volume (PCV), haemoglobin (Hb) concentration, leucocyte count, and antibody titre by day 7 on the supplementation (OTS). Following infection on day 7 OTS, the PCV and Hb decreased but remained significantly (p < 0.05) higher than the infected not supplemented (INS) group, while on day 14 OTS, they maintained a significantly (p < 0.05) higher antibody titre as compared to other groups. On day 21 OTS, theweight of 8 ppm and not infected not supplemented (NINS) groups was significantly (p < 0.05) higher but the relative organ weight of their liver and spleen was significantly (p < 0.05) lower than 2 ppm, 4 ppm and INS groups. On day 21 OTS, the parasitaemia levels of INS group was significantly (p < 0.05) higher than the supplemented groups. From the results, dietary zinc supplementation can be useful in the management of anaemia and immunosupression caused by trypanosomes in rats.

New insights in staging and chemotherapy of African trypanosomiasis and possible contribution of medicinal plants.

Human African trypanosomiasis (HAT) is a fatal if untreated fly-borne neuroinflammatory disease caused by protozoa of the species Trypanosoma brucei (T.b.). The increasing trend of HAT cases has been reversed, but according to WHO experts, new epidemics of this disease could appear. In addition, HAT is still a considerable burden for life quality and economy in 36 sub-Saharan Africa countries with 15-20 million persons at risk. Following joined initiatives of WHO and private partners, the fight against HAT was re-engaged, resulting in considerable breakthrough. We present here what is known at this day about HAT etiology and pathogenesis and the new insights in the development of accurate tools and tests for disease staging and severity monitoring in the field. Also, we elaborate herein the promising progresses made in the development of less toxic and more efficient trypanocidal drugs including the potential of medicinal plants and related alternative drug therapies.

Different types of tea products attenuate inflammation induced in Trypanosoma brucei infected mice.

An in vivo study was carried out to determine the effect of different types of Kenyan tea extracts on male Swiss albino mice infected with Trypanosoma brucei brucei isolate KETRI 2710. The isolate produced a similar clinical picture after a pre-patent period of 5 days post-infection (DPI). Parasitemia levels in the untreated mice and those given different teas developed exponentially at similar rates reaching similar densities at the peak of parasitemia 8 DPI. Between 9 and 13 DPI parasitemia decreased more rapidly in tea treated compared to the untreated mice which indicated that tea lowered parasitemia level. Anaemia indicated by a fall in erythrocyte packed cell volume (PCV) occurred within 4 DPI and remained below the normal levels until the terminal stages of the disease. A significant difference (P<0.05) was observed 11 DPI between the tea treated and the untreated mice indicating that tea enhanced resistance to erythrocyte destruction. Mice treated with tea exhibited significantly (P<0.01) reduced parasite-induced hypoalbuminemia as compared to the untreated. Since albumin is a negative acute phase protein, it shows a decrease during inflammatory conditions and therefore its elevation in the mice given tea in this study clearly demonstrated that tea ameliorated inflammation induced by T. b. brucei. Although green and white teas were superior in most of these characteristics, black tea, which is the principle tea product from Kenya, displayed remarkable properties some even comparable to those of green tea. Interestingly, tea was more efficacious than dexamethasone an established anti-inflammatory drug, demonstrating its therapeutic potential.

Clone-specific immune colostrum induces increased resistance in goat kids challenged with Trypanosoma congolense.

The course of infection and the humoral immune response to Trypanosoma congolense clone ILNat 3.1 were studied in test goat kids receiving colostrum from dams immunized with the surface coat of ILNat 3.1 and control kids that received colostrum from nonimmunized dams. At 24-48 h after birth, all test kids had detectable serum antibodies to the trypanosome clone. There was no difference in the prepatent period between the test and control kids following challenge with 10(3) T. congolense ILNat 3.1 trypanosomes 8 days after birth. After the first 7 days of the experimental period, significantly lower parasitemia was recorded in test kids than in control kids. The mean packed red cell volume of test kids was not significantly different from that of control kids 7 days after infection. The test kids gained as much weight as noninfected control kids; both groups gained twice as much weight as infected control kids. Following infection, all kids developed antibodies against the infecting trypanosome clone. Fifteen test kids had titers equal to or greater than 1280 compared to only two control kids. The test kids survived longer after infection compared to control kids. The results suggest that colostrum from does immunized with the surface of a T. congolense clone did not prevent infection, but decreased parasitemia and prolonged survival of kids challenged with the same clone.

Depletion of CD8+ T cells suppresses growth of Trypanosoma brucei brucei and interferon-gamma) production in infected rats.

Sprague-Dawley rats infected with Trypanosoma brucei brucei showed a strong and rapid induction of splenocyte IFN-gamma (within 12 h post-infection) as measured by a single cell assay for IFN-gamma secretion. Depletion of CD8+ cells in infected rats abrogated the IFN-gamma production, suppressed parasite growth and increased survival of the animals. Induction of MHC class I antigens in the paraventricular and supra-optic hypothalamic nuclei caused by the trypanosome infection was also inhibited by the CD8+ cell depletion. It is suggested that the CD8+ cells are involved directly or indirectly in growth regulation of the parasite and that IFN-gamma induced by the parasite may be one of the factors that trigger MHC expression and immunosuppression.

Maternally derived immunity in young mice to infection with Trypanosoma brucei and its potentiation by Berenil chemotherapy.

Young mice which were allowed to suckle, from birth, a mother infected with Trypanosoma brucei, or a mother whose infection had been cured before parturition with Berenil chemotherapy, were themselves immune to homologous trypanosome challenge. This immunity extended until approximately 25 days of age, and was transmitted in the colostrum/milk of the mother. Mice born of infected mothers, but transferred at birth to normal foster mothers, were susceptible to trypanosome infection. Drug prophylaxis in normal newborn mice was also effective for approximately 25 days, but in mice which, in addition, received colostral antibody from the mother, combined immunochemoprophylaxis protected the offspring for 40-50 days. Since the combination of protective strategies continued to resist challenge beyond the stage when, on its own, each component's efficacy had decayed, it may be of practical value as an approach to improved disease control under certain field conditions where trypanosomiasis prevails.

Immunological clearance of 75Se-labelled Trypanosoma brucei in mice. III. Studies in animals with acute infections.

Using trypanosomes labelled with [75Se]-methionine a series of experiments was conducted to investigate antibody production in mice with acute fulminating T. brucei infections. As measured by the hepatic uptake of radiolabelled parasites, we were unable to demonstrate any evidence of antibody-mediated uptake by the liver in such mice. It was concluded that this was not due to impaired macrophage function but was caused by the inability of antibody production to cope with the massive parasitaemias produced by rapidly-replicating infections so that effective opsonization of the parasites did not occur. In contrast, a train of trypanosome which causes a more chronic infection, although initially having a similar replication, although initially having a similar replication rate, subsequently switched t a slower one and thereby allowed antibody to reach levels which permitted effective opsonization. There was no evidence that the parasite caused any significant suppression of antibody responses in these acute infections since inoculation with trypanosomes of one stock at the same time as vaccination with irradiated organisms of a second stock did not prevent the development of antibody to the latter, as measured by the hepatic uptake of radiolabelled parasites.

Immunological clearance of 75Se-labelled Trypanosoma brucei in mice. II. Mechanisms in immune animals.

Using trypanosomes labelled with [75Se]-methionine a series of experiments was conducted to investigate the respective roles of antibody, macrophage activtion and complement in the removal of trypanosomes from the circulation of immune mice. It was found that clearance in such animals is largely accomplished by antibody-mediated hepatic phagocytosis, which, at least in passively immunized animals, is dependent on opsonization involving C3. No evidence was found to suggest that intravascular lysis or activated macrophages are involved in immune clearance.

Immunological clearance of 75Se-labelled Trypanosoma brucei in mice. I. Aspects of the radiolabelling technique.

A reliable and simple technique for the in vivo labelling of Trypanosoma brucei with [75Se]-methionine was developed. Between 97 and 99% of the radioactivity was protein bound in the trypanosomes and spontaneous elution in vitro was less than 10% over 4 h. The fate of the labelled trypanosomes after i.v. injection into normal and immune mice was studied. Whilst the vast majority of parasites remained in the circulation of normal animals they rapidly disappeared from the blood of immune animals. In the latter the liver was found to be the principal site of phagocytosis removing over 50% of the radiolabelled parasites within 15 min of injection.

Relevance of polyclonal antibody formation to the development of autoimmunity : the model of African trypanosomiasis.

There is an induction of anti-DNA antibodies in mice following the administration of bacterial lipopolysaccharides, Dextran sulfate and PPD, which is closely associated with the property of these substances to trigger a polyclonal B cell activation. In the experiments model of African trypanosomiasis there is also an intense polyclonal antibody synthesis paralleled by the formation of several autoantibodies: anti-DNA, anti-bromelain treated mouse red blood cells and antithymocyte antibodies.