Comparative pathogenicity of three genetically distinct types of Trypanosoma congolense in cattle: clinical observations and haematological changes

The pathology of African bovine trypanosomosis was compared in Zebu cattle subcutaneously inoculated with three clones of trypanosomes corresponding to the three genetically distinct types of Trypanosoma congolense; savannah-type, west African riverine/forest-type and kilifi-type. All inoculated animals became parasitaemic between 7 and 11 days post-infection (dpi). The savannah-type showed consistently higher levels of parasitaemia and lower packed red cell volume percentages and leukocyte counts than the other two types. The syndrome was also more severe in the savannah-type and led inexorably to death between 29 and 54 dpi while animals with the forest or the kilifi-types recovered from earlier symptoms and haematological alterations after 3 months of infection. By the end of the experiment, the animals self-cured from the forest-type infection and the kilifi-type passed under control. The results of the present study indicated clear difference in pathogenicity between the three types of T. congolense; the savannah-type was virulent while the forest-type was of low pathogenicity and the kilifi-type was non-pathogenic.

The relationships between intestinal damage and circulating endotoxins in experimental Trypanosoma brucei brucei infections

The involvement of intestinal damage in experimental African trypanosomiasis was investigated in rats infected with Trypanosoma brucei brucei by measuring the urinary excretion of the previously administered non-metabolizable sugar probes, D-mannitol and lactulose, and the flux of FITC-dextran across isolated, everted gut segments. There was increased urinary recovery and flux of the sugar probes across the intestine which were significant (P < 0.05) and maximum at day 21 of the infection, but subsequently reduced, in the terminal stages of infection (day 33 p.i.). In the case of the everted sac studies the reductions were to less than 25% control values (P < 0.001). Levels of circulating endotoxin were increased approximately 3-fold at day 21 p.i., 4-fold at day 33 p.i., compared to controls. At day 21 there was a significant correlation (r = 0.63, P < 0.01) between the log endotoxin levels and the increased sugar excretion expressed as the lactulose/mannitol ratios. Histological studies showed damage to the villi, wall thinning and marked cellular infiltrations, which were very prominent in the proximal jejunum and duodenum. These results demonstrate that during trypanosome infections in rats, increased intestinal leakage and increased circulating endotoxins are significant pathological features.

The relationships between endotoxins, nitric oxide and inflammatory cytokines in blood and intestinal tissues in experimental Trypanosoma brucei brucei infections

Increased levels of circulating endotoxins are a feature of both human and experimental African trypanosomiasis. Studies with rats and mice have shown that these may originate from intestinal damage with altered permeability of the gut epithelium. Endotoxins are potent immunomodulatory substances which can initiate the production of a range of cytokines and mediators from different cell types. In rats infected with T.b. brucei we have examined possible associations of the endotoxin increases with increases in levels of TNF-alpha, IL-1beta, IL-6, IFN-gamma and nitric oxide (NO). Significant increases in each substance occurred at days 21 and 33 post-infection (p.i.). The increases in cytokines were highly correlated with the endotoxin levels (e.g. at day 21 p.i. the correlation-regression values were as follows: TNF-alpha, r = 0.9, P < 0.01; IL-1beta, r = 0.83, P < 0.01; IL-6, r = 0.9, P < 0.01; IFN-gamma, r = 0.7, P < 0.01). There were also strong correlations between the increased levels of several individual cytokines. Biopsies of chopped sections of small intestine tissues of rats showed a parallel production of cytokines, again with significant correlations with the circulating endotoxins. The production of NO and cytokines by the intestine may be associated with the increased transepithelial permeability which occurs during the infection.

Distribution of Trypanosoma congolense in infected multimammate rats (Mastomys coucha): light and electron microscopical studies

In an attempt to determine whether Trypanosoma congolense occurs both within and outside the blood vessels in an infected animal host, multimammate rats (Mastomys coucha) were infected with T. congolense and samples from spleen, lymph nodes, bone marrow, liver, kidney, lungs, brain, heart, intestines, ovaries and testes were collected. The tissue samples were fixed and processed for light and electron microscopical examination. In all the tissues examined, trypanosomes were found only within the lumen of large and small blood vessels, capillaries and sinuses. It is concluded that following entry into the blood circulation after intra-peritoneal infection of M. coucha, T. congolense remains restricted to the bloodstream.

Interleukin (IL)-6, IL-8 and IL-10 in serum and CSF of Trypanosoma brucei gambiense sleeping sickness patients before and after treatment

Serum and cerebrospinal fluid (CSF) concentrations of interleukin (IL)-6, IL-8, IL-10, tumour necrosis factor-alpha and interferon-gamma were determined in 46 Trypanosoma brucei gambiense sleeping sickness patients in DR Congo, before and after treatment. According to their CSF cell number before treatment, patients were classified as early-stage (0-5 cells/microL), intermediate-stage (6-20 cells/microL) or late-stage patients (> 20 cells/microL). In serum, slightly higher IL-8 concentrations were found in early-stage patients compared to intermediate- or late-stage patients. These high IL-8 levels dropped after treatment. Higher IL-10 concentrations were detected in serum of patients in intermediate or late stage compared to early-stage patients. In both intermediate- and late-stage groups, serum IL-10 decreased after treatment. In CSF, elevated concentrations of IL-6, IL-8 and especially of IL-10 were observed in late-stage T. b. gambiense patients. After treatment, these concentrations dropped to levels similar to those of the other patients. Tumour necrosis factor-alpha was detected only in a few serum and CSF samples, which were scattered over the different patient groups. Interferon-gamma was detected in serum of 5 patients and remained undetectable in CSF.

Congopain from Trypanosoma congolense: drug target and vaccine candidate

Trypanosomes are the etiological agents of human sleeping sickness and livestock trypanosomosis (nagana), which are major diseases in Africa. Their cysteine proteases (CPs), which are members of the papain family, are expressed during the infective stages of the parasites' life cycle. They are suspected to act as pathogenic factors in the mammalian host, where they also trigger prominent immune responses. Trypanosoma congolense, a major pathogenic species in livestock, possesses at least two families of closely related CPs, named CP1 and CP2. Congopain, a CP2-type of enzyme, shares structural and functional resemblances with cruzipain from T. cruzi and with mammalian cathepsin L. Like CPs from other Trypanosomatids, congopain might be an attractive target for trypanocidal drugs. Here we summarise the current knowledge in the two main areas of research on congopain: first, the biochemical properties of congopain were characterised and its substrate specificity was determined, as a first step towards drug design; second, the possibility was being explored that inhibition of congopain by host-specific antibodies may mitigate the pathology associated with trypanosome infection.

Evaluation of the micro-CATT, CATT/Trypanosoma brucei gambiense, and LATEX/T b gambiense methods for serodiagnosis and surveillance of human African trypanosomiasis in West and Central Africa

OBJECTIVE

To evaluate the performance of serological tests using dried blood on filter-papers (micro-card agglutination test for trypanosomiasis (micro-CATT)) performed under field and laboratory conditions and using whole blood ((CATT/T.b. gambiense) (wb-CATT) and latex agglutination (LATEX/T.b. gambiense) (wb-LATEX)) for the serodiagnosis and surveillance of human African trypanosomiasis in West and Central Africa.

METHODS

We evaluated the micro-CATT, wb-CATT and wb-LATEX methods in Côte d'Ivoire and the Central African Republic by screening 940 people. Sensitivity and specificity were calculated for each serological test; only patients with the confirmed presence of trypanosomes in the blood or lymph aspirate were considered true positives. Positive and negative predictive values were also calculated.

FINDINGS

Each of the tests showed a lower sensitivity in the Central African Republic than in Côte d'Ivoire.

CONCLUSION

The results confirmed the efficiency of the classic wb-CATT to detect sleeping sickness patients. The micro-CATT method can be used for human African trypanosomiasis surveillance if the test is performed on the same day as the blood collection, or if samples are stored at 4 degrees C. Otherwise, micro-CATT can be used when absolute sensitivity is not required. wb-LATEX should only be used for high-specificity screening.

A pol I transcriptional body associated with VSG mono-allelic expression in Trypanosoma brucei

In the mammalian host, African trypanosomes generate consecutive waves of parasitaemia by changing their antigenic coat. Because this coat consists of a single type of variant surface glycoprotein (VSG), the question arises of how a trypanosome accomplishes the transcription of only one of a multi-allelic family of VSG expression site loci to display a single VSG type on the surface at any one time. No major differences have been detected between the single active expression site and the cohort of inactive expression sites. Here we identify an extranucleolar body containing RNA polymerase I (pol I) that is transcriptionally active and present only in the bloodstream form of the parasite. Visualization of the active expression site locus by tagging with green fluorescent protein shows that it is specifically located at this unique pol I transcriptional factory. The presence of this transcriptional body in postmitotic nuclei and its stability in the nucleus after DNA digestion provide evidence for a coherent structure. We propose that the recruitment of a single expression site and the concomitant exclusion of inactive loci from a discrete transcriptional body define the mechanism responsible for VSG mono-allelic expression.

Immunisation of cattle with cysteine proteinases of Trypanosoma congolense: targetting the disease rather than the parasite

In order to test the hypothesis that trypanosome cysteine proteinases (CPs) contribute to pathology of trypanosomosis, cattle were immunised with CP1 and/or CP2, the major CPs of Trypanosoma congolense, and subsequently challenged with T. congolense. Immunisation had no effect on the establishment of infection and the development of acute anaemia. However, immunised cattle, unlike control cattle, maintained or gained weight during infection. Their haematocrit and leukocyte counts showed a tendency to recovery after 2-3 months of infection. Cattle immunised with CP2 mounted early and prominent IgG responses to CPs and to the variable surface glycoprotein following challenge. Thus trypanosome CPs may play a role in anaemia and immunosuppression; conversely, anti-CP antibody may modulate the trypanosome-induced pathology.

Nitric oxide and cytokine synthesis in human African trypanosomiasis

Plasma and cerebrospinal fluid (CSF) concentrations of nitrate and the cytokines interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, interleukin (IL)-10, and IL-4 were measured in 91 African trypanosomiasis patients before and after treatment. Nitrate levels overall were not significantly elevated over those for control persons, but a marginal increase in plasma nitrate was detected in patients reporting illness of <40 days' duration. Plasma IFN-gamma and total TNF-alpha concentrations increased during infection, but free TNF-alpha levels were low in all patients. The most dramatic cytokine response was for IL-10, which was significantly elevated in both plasma and CSF during infection but returned to control levels after treatment. The results indicate that human African trypanosomiasis leads to the development of a strong anti-inflammatory cytokine response.

The distribution of bovine trypanosomosis in Zimbabwe and an evaluation of the value of an anti-trypanosomal antibody detection ELISA as a tool for monitoring the effectiveness of tsetse control operations

Tsetse have been cleared from large areas of Zimbabwe during the past 65 years. In most areas, they are prevented from re-invading cleared areas by barriers of odour-baited, insecticide-treated targets. A trypanosomosis survey was conducted to determine the effectiveness of such barriers against re-invasion and to confirm the absence of tsetse in areas where they had previously been eradicated. Parasitological diagnostic methods and an anti-trypanosomal antibody detection enzyme-linked immunosorbent assay (antibody ELISA) were used. The prevalence of trypanosomal infections in the tsetse-cleared areas was generally low. However, the prevalence of anti-trypanosomal antibodies was unexpectedly high in some areas. This high proportion of cattle with antibodies could, in most cases, be explained by recent or historic information on the distribution and density of tsetse. The results from the survey demonstrated the value of anti-trypanosomal antibody detection as an additional sensitive tool for monitoring the effectiveness of tsetse control operations.

Purification, cloning and characterization of a GPI inositol deacylase from Trypanosoma brucei

Inositol acylation is an obligatory step in glycosylphosphatidylinositol (GPI) biosynthesis whereas mature GPI anchors often lack this modification. The GPI anchors of Trypanosoma brucei variant surface glycoproteins (VSGs) undergo rounds of inositol acylation and deacylation during GPI biosynthesis and the deacylation reactions are inhibited by diisopropylfluorophosphate (DFP). Inositol deacylase was affinity labelled with [3H]DFP and purified. Peptide sequencing was used to clone GPIdeAc, which encodes a protein with significant sequence and hydropathy similarity to mammalian acyloxyacyl hydrolase, an enzyme that removes fatty acids from bacterial lipopolysaccharide. Both contain a signal sequence followed by a saposin domain and a GDSL-lipase domain. GPIdeAc(-/-) trypanosomes were viable in vitro and in animals. Affinity-purified HA-tagged GPIdeAc was shown to have inositol deacylase activity. However, total inositol deacylase activity was only reduced in GPIdeAc(-/-) trypanosomes and the VSG GPI anchor was indistinguishable from wild type. These results suggest that there is redundancy in T.brucei inositol deacylase activity and that there is another enzyme whose sequence is not recognizably related to GPIdeAc.

Melarsoprol refractory T. b. gambiense from Omugo, north-western Uganda

Culture adapted T. b. gambiense isolated from Northwest Uganda were exposed to 0.001-0.14 microg/ml melarsoprol or 1.56-100 microg/ml DL-alpha-difluoromethylornithine (DFMO). Minimum inhibitory concentrations (MICs) of each drug were scored for each isolate after a period of 10 days drug exposure. The results indicate that T. b. gambiense isolates from Northwest Uganda had elevated MIC values for melarsoprol ranging from 0.009 to 0.072 microg/ml as compared with T. b. gambiense isolates from Cote d'Ivoire with MIC values ranging from 0.001 to 0.018 microg/ml or with T. b. rhodesiense from Southeast Uganda with MIC values from 0.001 to 0.009 microg/ml. All MIC values obtained fell below expected peak melarsoprol concentrations in serum of treated patients. However, it may not be possible to maintain constant drug concentrations in serum of patients as was the case in our in vitro experiments. Importantly, the MIC of 0.072 microg/ml exhibited by one of the isolates from Northwest Uganda was above levels attainable in CSF indicating that this isolate would probably not be eliminated from CSF of treated patients. PCR amplification of the gene encoding the P2-like adenosine transporter followed by restriction digestion with Sfa NI enzyme revealed presence of fragments previously observed in a trypanosome clone with laboratory-induced arsenic resistance. From our findings it appears that reduced drug susceptibility may be one factor for the frequent relapses of sleeping sickness after melarsoprol treatment occurring in Northwest Uganda.

Unravelling the phylogenetic relationships of African trypanosomes of suids

African trypanosomes of the subgenera Nannomonas and Pycnomonas have been recorded from both wild and domestic suids. However, complete descriptions of some of these trypanosomes with regard to host range, pathogenicity, transmission and distribution are still lacking. Neither the recently described Trypanosoma (Nannomonas) godfreyi nor Trypanosoma (Nannomonas) congolense Tsavo have been isolated from mammalian hosts, while Trypanosoma (Pycnomonas) suis remains the rarest of the Salivarian trypanosomes. The only isolate presumed to be of the latter species is maintained at the Kenya Trypanosomiasis Research Institute, Nairobi. We present here the results of characterization of this isolate by morphology, tsetse transmission, the use of species-specific DNA probes and DNA sequence analysis. Morphology in stained blood smears revealed a small trypanosome with a free flagellum. Experimental transmission through Glossina morsitans morsitans showed a developmental cycle typical of subgenus Nannomonas A positive identification was obtained with species-specific PCR primers for T. congolense Tsavo; moreover, the sequence of the SSU rRNA gene was almost identical to that of T. congolense Tsavo on database. In phylogenetic analysis of the SSU rRNA genes of Salivarian trypanosomes, T. congolense Tsavo grouped with T. simiae rather than T. congolense, suggesting that the name T. simiae Tsavo is more appropriate.

Trypanosoma brucei CTP synthetase: a target for the treatment of African sleeping sickness

The drugs in clinical use against African sleeping sickness are toxic, costly, or inefficient. We show that Trypanosoma brucei, which causes this disease, has very low levels of CTP, which are due to a limited capacity for de novo synthesis and the lack of salvage pathways. The CTP synthetase inhibitors 6-diazo-5-oxo-l-norleucine (DON) and alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid (acivicin) reduced the parasite CTP levels even further and inhibited trypanosome proliferation in vitro and in T. brucei-infected mice. In mammalian cells, DON mainly inhibits de novo purine biosynthesis, a pathway lacking in trypanosomes. We could rescue DON-treated human and mouse fibroblasts by the addition of the purine base hypoxanthine to the growth medium. For treatment of sleeping sickness, we propose the use of CTP synthetase inhibitors alone or in combination with appropriate nucleosides or bases.

Analysis of macrophage activation in African trypanosomiasis

African trypanosomes cause a fatal disease of man and animals that is characterized by extensive functional, histological, and pathological changes in the lymphoid tissues of infected hosts, including an increase in the numbers and activation state of macrophages. Macrophage activation during infection is the result of exposure of these cells to parasite components and host-derived IFN-gamma, produced in response to parasite antigens. The balance of these different activation signals may determine the outcome of infection. In the experiments described here, we assessed the ability of the variant surface glycoprotein (VSG) of the organism Trypanosoma brucei rhodesiense (T.b. rhodesiense) to activate macrophages directly. Our results demonstrate that macrophages bind and are activated by the VSG molecule. The resulting profile of activation differs from that stimulated by IFN-gamma. These results suggest that the interaction of host macrophages with VSG released during parasite infection may be a key component of trypanosomiasis.

The story of CGP 40 215: studies on its efficacy and pharmacokinetics in African green monkey infected with Trypanosoma brucei rhodesiense

CGP 40 215 is an inhibitor of S-adenosylmethionine decarboxylase, a key enzyme in trypanosomal polyamine biosynthesis. It is highly active against Trypanosoma brucei rhodesiense and T. b. gambiense in vitro and in the corresponding rodent models, and therefore was a promising candidate for further development as a new drug against human African trypanosomiasis. We conducted initial pharmacokinetic and efficacy studies in African green monkeys: based on two dose-finding studies, an infection-treatment and a pharmacokinetic study in eight monkeys infected with T. b. rhodesiense in the 1st stage of infection. PK analysis revealed curative drug levels in the serum but complete absence of the drug in the cerebrospinal fluid. No adverse effects of the drug were observed, although in rats CGP 40 215 had caused hypotension. The following PK parameters were calculated using a two-compartment model: t1/2=1.8 h, VSS/f=0.4 l/kg, CL/f=3.0 ml/min x kg and AUC=21 900 ng x h/ml. Six of the eight monkeys were cured, one animal relapsed on day 222 and one animal died of unknown reasons, but was aparasitaemic. The study confirmed the curative potential of CGP 40 215 for 1st stage T. b. rhodesiense infection. Unfortunately, it was also found that the compound did not pass the blood-brain barrier, a pre-requisite for cure of 2nd stage (CNS) infection. As the majority of sleeping sickness patients seeking treatment are in the 2nd stage of the disease, further development of the compound was stopped.

Trypanosome-derived oligopeptidase B is released into the plasma of infected rodents, where it persists and retains full catalytic activity

A trypsin-like serine peptidase activity, levels of which correlate with blood parasitemia levels, is present in the plasma of rats acutely infected with Trypanosoma brucei brucei. Antibodies to a trypanosome peptidase with a trypsin-like substrate specificity (oligopeptidase B [OP-Tb]) cross-reacted with a protein in the plasma of trypanosome-infected rats on a Western blot. These antibodies also abolished 80% of the activity in the plasma of trypanosome-infected rats, suggesting that the activity may be attributable to a parasite-derived peptidase. We purified the enzyme responsible for the bulk of this activity from parasite-free T. b. brucei-infected rat plasma and confirmed its identity by protein sequencing. We show that live trypanosomes do not release OP-Tb in vitro and propose that disrupted parasites release it into the host circulation, where it is unregulated and retains full catalytic activity and may thus play a role in the pathogenesis of African trypanosomiasis.

Pathobiochemical mechanisms involved in the control of the disease caused by Trypanosoma congolense in African grey duiker (Sylvicapra grimmia)

The course of Trypanosoma congolense infections in African grey duiker (Sylvicapra grimmia) and sheep and goats were studied. Several parameters suggested that the grey duiker was much more resistant to trypanosomosis than sheep and goats. They showed increases in weight during infection, had a much longer pre-patent period, and their peak parasitaemia levels were about 100-fold lower than those of sheep and goats. Parasites were no longer detected in grey duiker blood 35 days after infection. Anaemia, measured as drops in packed cell volume (PCV), haemoglobin (Hb) concentration and erythrocyte (RBC) counts were not observed in the grey duiker. In contrast, sheep and goats suffered severe weight losses and had continuously high parasitaemia levels. Sheep and goats developed progressively severe normocytic normochromic anaemia and leucopenia from day 14 post-infection onwards. Serum levels of total protein, globulin and albumin of grey duiker did not change significantly throughout the course of infection, while the levels of total serum protein, globulin and gamma-globulin exhibited significant increases from day 21 post-infection onwards in sheep and goats, with peak values recorded on 28 and 35 days post-infection in sheep and goats, respectively. There were inconsistent variations in albumin levels in sheep and goats throughout the course of infection. There were no significant changes in erythrocyte activities of AST and ALT, while there were transient but significant elevations of ALP level on day 35, and GGT levels between 14 and 35 days post-infection in grey duiker. Conversely, the levels of all the enzymes were progressively depressed, especially from 14 to 49 days post-infection. In vitro erythrocyte peroxidation remained relatively unchanged throughout the period of the experiment in the grey duiker, except for slight but significant increase on day 42 post-infection. However, in vitro erythrocyte peroxidation increased significantly by between 100 and 300% of pre-infection levels from 14th to 42nd day p.i. both in sheep and goats, before returning to pre-infection levels after 14 days of treatment. Haematological values, serum and erythrocyte indices studied returned to near pre-infection levels 14 days after treatment with Berenil((R)). It is concluded that the grey duiker is inherently trypanotolerant. This is shown by its ability to control parasitaemia, suffer less severe anaemia, and to a relative degree resist pathobiochemical derangements of some serum and erythrocyte metabolites and enzymes, as well as reduction of infection-induced erythrocyte lipid peroxidase damage than sheep and goats.

Alternative versus classical macrophage activation during experimental African trypanosomosis

The type I/type II cytokine balance may influence the development of different subsets of suppressive macrophages, i.e., classically activated macrophages (caMphi, type I) versus alternatively activated macrophages (aaMphi, type II). Recently, we showed that although mice infected with phospholipase C-deficient (PLC-/-) Trypanosoma brucei brucei exhibit a clear shift from type I to the type II cytokine production, wild type (WT)-infected mice remain locked in a type I cytokine response. In the present study, phenotype and accessory cell function of macrophages elicited during WT and PLC-/- T. b. brucei infection were compared. Results indicate that caMphi develop in a type I cytokine environment in the early phase of WT and PLC-/- trypanosome infection, correlating with inhibition of T cell activation triggered by a mitogen, a superantigen, or an antigen. In the late stage of infection, only PLC(-/-)-infected mice resisting the infection develop type II cytokine-associated aaMphi correlating with impaired antigen- but not mitogen- or superantigen-induced T cell activation.

The relationship between the parasitological prevalence of trypanosomal infections in cattle and herd average packed cell volume

The relationship between prevalence of trypanosomal infections (Trypanosoma congolense) and average packed cell volume (PCV) in herds of communally managed adult Angoni breed cattle was investigated in four districts of eastern Zambia. In all areas, regression analyses showed that the herd average PCV decreased with increasing prevalence of trypanosomal infections. The slope of the equation between average PCV and trypanosome prevalence decreased with increasing prevalence of trypanosomal infections. For the same increase in prevalence of trypanosomal infection, the decrease in herd PCV was higher in the areas with low to medium prevalence. Season of sampling also determined the slope of the regression equation. For the same increase in prevalence of trypanosomal infection, the decrease in herd PCV was higher during the dry compared to the rainy season suggesting that trypanosomosis is less well tolerated during the dry season. Results from the study suggest that the relationship between the prevalence of trypanosomal infections and herd average PCV could be a useful tool in the management of trypanosomosis and planning of its control. Reasons for the spatial and temporal variations in the relationship are discussed.

Effects of dietary polyamine deficiency on Trypanosoma gambiense infection in rats

Nishimura, K., Araki, N., Ohnishi, Y., and Kozaki, S. 2001. Effects of dietary polyamine deficiency on Trypanosoma gambiense infection in rats. Experimental Parasitology 97, 95-101. A diet deficient in polyamines decreases the availability of dietary polyamines. We used rats infected with the Wellcome strain of Trypanosoma gambiense to examine the effects of polyamine-deficient chow (PDC) on trypanosome proliferation and symptoms of infection. Rats fed PDC showed limited increase of trypanosome and symptoms of infection and limited loss of body weight and anemia. Survival in these rats was prolonged. Before infection, the heparinized plasma concentration of spermidine in the PDC-fed rats was lower than that in control rats fed with standard chow. After infection, the content of spermidine in red blood cells increased in the control rats, but was only slightly increased in PDC-fed rats. The content of spermidine in the trypanosomes after infection was low in the PDC-fed rats. Decreases in the polyamine content of trypanosomes limited their increase. These observations suggest that a reduction in dietary polyamines may help in the regulation of trypanosome infection.

Antitrypanosomal properties of cis-platinum-pentamidine bromide, thiocyanate and seleniocyanate on Trypanosoma brucei brucei mouse and sheep models

Three organometallic complexes derived from pentamidine were evaluated for their trypanocidal effect on in vivo Trypanosoma brucei brucei models in comparison to pentamidine isethionate as reference compound. On the T. b.brucei mouse model, the most active compound was cis-platinum-pentamidine bromide. This compound was active when subcutaneously administered at the single dose of 1.5 micromol/kg and its chemotherapeutic index was 200 whereas pentamidine isethionate was active at 6 micromol/kg with a chemotherapeutic index of 13, when administered in the same conditions. Cis-platinum-pentamidine bromide was active at 1 mg/kg (1.44 mmoles/kg), in a single dose by subcutaneous route against the early stage of the T. b.brucei Antat 1-9 sheep model. Platinum kinetics in serum showed a Cmax of 0.2 mg/l reached 80 h after the treatment at this dose. Cis-platinum-pentamidine bromide, cis-platinum-pentamidine seleniocyanate, and cis-platinum-pentamidine thiocyanate were distributed in the deep compartment according to a monocompartmental model. In all cases, platinum was eliminated from the serum 700 hours post-treatment. All data obtained from these models show activity on the early stage of the disease and justify further investigations on the late stage of the disease.

Follow-up of Card Agglutination Trypanosomiasis Test (CATT) positive but apparently aparasitaemic individuals in Côte d'Ivoire: evidence for a complex and heterogeneous population

The aetiological diagnosis of human African trypanosomiasis (HAT) is based on the detection of the parasite, but currently available parasitological tests have low sensitivity and are hampered by fluctuating parasitaemia. The identification of seropositive individuals on whom to focus parasitological examination is based on antibody detection by means of the Card Agglutination Trypanosomiasis Test (CATT/T.b.gambiense). A complicating phenomenon is the occurrence of serologically positive but parasitologically unconfirmed results (isolated CATT positivity). This work presents a two-year longitudinal serological, parasitological and molecular follow-up of CATT-positive individuals including repeated examinations of each individual, to study the evolution over time of seropositivity at both the population and the individual levels. At the population level, the rate of seropositivity decreased during the first months of the survey, and afterwards showed remarkable stability. At the individual level, the results reveal the extreme heterogeneity of this population, with subjects showing fluctuating results, others with a short transient CATT positivity, and subjects that maintain their seropositivity over time. The stability of seropositivity and the pattern of results obtained with both immunological and parasitological examinations support the view that individual factors, such as immune response to infection, might be involved in the isolated CATT positivity phenomenon.

Preliminary evaluation of LATEX/T. b. gambiense and alternative versions of CATT/T. b. gambiense for the serodiagnosis of human african trypanosomiasis of a population at risk in Côte d'Ivoire: considerations for mass-screening

A study was conducted to compare classical card agglutination test for trypanosomiasis (CATT)/T. b. gambiense with CATT-EDTA and LATEX/T. b. gambiense as alternative field tests for serodiagnosis of Human African Trypanosomiasis. The tests were performed on freshly collected blood in an endemic and a low prevalence area in Côte d'Ivoire. Diagnostic performance of each test was assessed using Quantitative Buffy Coat as the parasitological reference and immune trypanolysis as the serological reference test. According to the parasitological data, CATT-EDTA on 10 microl and LATEX/T. b. gambiense on blood diluted 1:4, detecting all confirmed cases with good specificity (respectively 94.6% and 98.1%) yielded better results than the classical CATT did (one false negative and 92.5% specific). However, when immune trypanolysis data and feasibility are taken into account, the classical CATT remains the test of choice for mass screening under the given field conditions.