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In vivo imaging of trypanosome-brain interactions and development of a rapid screening test for drugs against CNS stage trypanosomiasis.

ABSTRACT: HUMAN AFRICAN TRYPANOSOMIASIS (HAT) MANIFESTS IN TWO STAGES OF DISEASE: firstly, haemolymphatic, and secondly, an encephalitic phase involving the central nervous system (CNS). New drugs to treat the second-stage disease are urgently needed, yet testing of novel drug candidates is a slow process because the established animal model relies on detecting parasitemia in the blood as late as 180 days after treatment. To expedite compound screening, we have modified the GVR35 strain of Trypanosoma brucei brucei to express luciferase, and have monitored parasite distribution in infected mice following treatment with trypanocidal compounds using serial, non-invasive, bioluminescence imaging. Parasites were detected in the brains of infected mice following treatment with diminazene, a drug which cures stage 1 but not stage 2 disease. Intravital multi-photon microscopy revealed that trypanosomes enter the brain meninges as early as day 5 post-infection but can be killed by diminazene, whereas those that cross the blood-brain barrier and enter the parenchyma by day 21 survived treatment and later caused bloodstream recrudescence. In contrast, all bioluminescent parasites were permanently eliminated by treatment with melarsoprol and DB829, compounds known to cure stage 2 disease. We show that this use of imaging reduces by two thirds the time taken to assess drug efficacy and provides a dual-modal imaging platform for monitoring trypanosome infection in different areas of the brain.

SUBMITTER: Myburgh E

PROVIDER: S-EPMC3749981 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundHuman African trypanosomiasis, or sleeping sickness, is a severe disease affecting people in the poorest parts of Africa. It is usually fatal without treatment. Conventional treatments require days of intravenous infusion, but a recently developed drug, fexinidazole, can be given orally. Another oral drug candidate, acoziborole, is undergoing clinical development and will be considered in subsequent editions. OBJECTIVES: To evaluate the effectiveness and safety of currently used drugs for treating second-stage Trypanosoma brucei gambiense trypanosomiasis (gambiense human African trypanosomiasis, g-HAT).Search methodsOn 14 May 2021, we searched the Cochrane Infectious Diseases Group Specialized Register, the Cochrane Central Register of Controlled Trials, MEDLINE, Embase, Latin American and Caribbean Health Science Information database, BIOSIS, ClinicalTrials.gov, and the World Health Organization International Clinical Trials Registry Platform. We also searched reference lists of included studies, contacted researchers working in the field, and contacted relevant organizations.Selection criteriaEligible studies were randomized controlled trials that included adults and children with second-stage g-HAT, treated with anti-trypanosomal drugs currently in use.Data collection and analysisTwo review authors extracted data and assessed risk of bias; a third review author acted as an arbitrator if needed. The included trial only reported dichotomous outcomes, which we presented as risk ratio (RR) or risk difference (RD) with 95% confidence intervals (CI). MAIN RESULTS: We included one trial comparing fexinidazole to nifurtimox combined with eflornithine (NECT). This trial was conducted between October 2012 and November 2016 in the Democratic Republic of the Congo and the Central African Republic, and included 394 participants. The study reported on efficacy and safety, with up to 24 months' follow-up. We judged the study to be at low risk of bias in all domains except blinding; as the route of administration and dosing regimens differed between treatment groups, participants and personnel were not blinded, resulting in a high risk of performance bias. Mortality with fexinidazole may be higher at 24 months compared to NECT. There were 9/264 deaths in the fexinidazole group and 2/130 deaths in the NECT group (RR 2.22, 95% CI 0.49 to 10.11; 394 participants; low-certainty evidence). None of the deaths were related to treatment. Fexinidazole likely results in an increase in the number of people relapsing during follow-up, with 14 participants in the fexinidazole group (14/264) and none in the NECT group (0/130) relapsing at 24 months (RD 0.05, 95% CI 0.02 to 0.08; 394 participants; moderate-certainty evidence). We are uncertain whether there is any difference between the drugs regarding the incidence of serious adverse events at 24 months. (31/264 with fexinidazole and 13/130 with NECT group at 24 months). Adverse events were common with both drugs (247/264 with fexinidazole versus 121/130 with NECT), with no difference between groups (RR 1.01, 95% CI 0.95 to 1.06; 394 participants; moderate-certainty evidence). AUTHORS' CONCLUSIONS: Oral treatment with fexinidazole is much easier to administer than conventional treatment, but deaths and relapse appear to be more common. However, the advantages or an oral option are considerable, in terms of convenience, avoiding hospitalisation and multiple intravenous infusions, thus increasing adherence.

Project description:BACKGROUND:Malaria is endemic in all regions where gambiense or rhodesiense human African trypanosomiasis (HAT) is reported, and both diseases have similarities in their symptomatology. A combined test could be useful for both diseases and would facilitate integration of the screening for gambiense HAT (gHAT) and malaria diagnosis. This study aimed to evaluate a combined prototype rapid diagnostic test (RDT) for gHAT and malaria. METHODS:Blood samples were collected in the Democratic Republic of the Congo and in Uganda to evaluate the performance of a prototype HAT/Malaria Combined RDT in comparison to an individual malaria RDT based on Plasmodium falciparum (P.f.) Histidine Rich Protein II (HRP-II or HRP2) antigen (SD BIOLINE Malaria Ag P.f. RDT) for malaria detection and an individual gHAT RDT based on recombinant antigens, the SD BIOLINE HAT 2.0 RDT for HAT screening. Due to the current low prevalence of gHAT in endemic regions, the set of blood samples that were collected was used to evaluate the specificity of the RDTs for gHAT, and additional archived plasma samples were used to complete the evaluation of the HAT/Malaria Combined RDT in comparison to the HAT 2.0 RDT. RESULTS:Frozen whole blood samples from a total of 486 malaria cases and 239 non-malaria controls, as well as archived plasma samples from 246 gHAT positive and 246 gHAT negative individuals were tested. For malaria, the sensitivity and specificity of the malaria band in the HAT/Malaria Combined RDT were 96.9% (95% CI: 95.0-98.3) and 97.1% (95% CI: 94.1-98.8) respectively. The sensitivity and specificity of the SD BIOLINE malaria Ag P.f. RDT were 97.3% (95% CI: 95.5-98.6) and 97.1% (95% CI: 94.1-98.8) respectively. For gHAT, using archived plasma samples, the sensitivity and specificity were respectively 89% (95% CI: 84.4-92.6) and 93.5% (95% CI: 89.7-96.2) with the HAT/Malaria Combined RDT, and 88.2% (95% CI: 83.5-92) and 94.7% (95% CI: 91.1-97.2) with the HAT 2.0 RDT. Using the whole blood samples that were collected during the study, the specificity of the HAT/Malaria Combined RDT for gHAT was 95.8% (95% CI: 94.3-97.0). CONCLUSION:The HAT/Malaria Combined prototype RDT was as accurate as the individual malaria or gHAT RDTs. The HAT/Malaria Combined prototype RDT is therefore suitable for both malaria diagnosis and gHAT screening. However, there is a need to assess its accuracy using fresh samples in prospective clinical trials.

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In vivo imaging of trypanosome-brain interactions and development of a rapid screening test for drugs against CNS stage trypanosomiasis.

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