Combination chemotherapy with a substance P receptor antagonist (aprepitant) and melarsoprol in a mouse model of human African trypanosomiasis

Bioluminescence Imaging to Detect Late Stage Infection of African Trypanosomiasis

Human African trypanosomiasis (HAT) is a multi-stage disease that manifests in two stages; an early blood stage and a late stage when the parasite invades the central nervous system (CNS). In vivo study of the late stage has been limited as traditional methodologies require the removal of the brain to determine the presence of the parasites. Bioluminescence imaging is a non-invasive, highly sensitive form of optical imaging that enables the visualization of a luciferase-transfected pathogen in real-time. By using a transfected trypanosome strain that has the ability to produce late stage disease in mice we are able to study the kinetics of a CNS infection in a single animal throughout the course of infection, as well as observe the movement and dissemination of a systemic infection. Here we describe a robust protocol to study CNS infections using a bioluminescence model of African trypanosomiasis, providing real time non-invasive observations which can be further analyzed with optional downstream approaches.

A current analysis of chemotherapy strategies for the treatment of human African trypanosomiasis

Despite the recent advances in drug research, finding a safe, effective, and easy to use chemotherapy for human African trypanosomiasis (HAT) remains a challenging task. The four current anti-trypanosomiasis drugs have major disadvantages that limit more widespread use of these drugs in the endemic regions of sub-Saharan Africa. Pentamidine and suramin are limited by their effectiveness against the only first stage of Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense, respectively. In addition, melarsoprol and eflornithine (two second stage drugs) each have disadvantages of their own. The former is toxic and has increasing treatment failures while the latter is expensive, laborious to administer, and lacks efficacy against T. b. rhodesiense. Furthermore, melarsoprol's toxicity and decreasing efficacy are glaring problems and phasing out the drug as a frontline treatment against T. b. gambiense is now possible with the emergence of competent, safe combination chemotherapies such as nifurtimox-eflornithine combination treatment (NECT). The future of eflornithine, on the other hand, is more promising. The drug is useful in the context of combination chemotherapy and potential orally administered analogues. Due to the limits of monotherapies, greater emphasis should be placed on the research and development of combination chemotherapies, based on the successful clinical tests with NECT and its current use as a frontline anti-trypanosomiasis treatment. This review discussed the current and future chemotherapy strategies for the treatment of HAT.

Chemotherapy against human African trypanosomiasis: Is there a road to success?

For over fifty years, human African trypanosomiasis (HAT, sleeping sickness) has been treated with suramin, pentamidine and the very toxic organo-arsenical melarsoprol that was the only drug available for effective treatment of the second stage of the disease. Recently there have been significant efforts using molecular and biochemical approaches to drug design, including high-throughput screening, but the number of lead compounds with promising activity againstT. bruceispp. and an acceptable toxicity index has remained astonishingly small. Clinical research continues to be difficult due to the economic constraints and the complexity of trials on a low prevalence disease in remote and impoverished African regions. Despite those limitations the situation for the patients is improving thanks to the combination of a number of critical factors. By the late 1990s the disease had reached epidemic levels that triggered political support. WHO would sign a donation agreement with the manufacturers for all drugs to treat HAT. A result of this agreement was that eflornithine which is much safer than melarsoprol became available and widely used by non-governmental organizations. TheImpamelI and II programmes demonstrated that against all odds the conduct of clinical trials on HAT was feasible. This allowed the initiation of trials on combination therapies which eventually resulted in the nifurtimox-eflornithine combination treatment (NECT). This combination is currently being introduced as first line treatment, and there is even the prospect of having a new compound, fexinidazole, in the development pipeline. This review summarizes the key information about the existing drugs and gives a comprehensive summary about the recent and currently ongoing efforts towards new drugs.

Trypanosomiasis and the brain

Neurological involvement following trypanosome infection has been recognised for over a century. However, there are still many unanswered questions concerning the mechanisms used by the parasite to gain entry to the CNS and the pathogenesis of the resulting neuroinflammatory reaction. There is a paucity of material from human cases of the disease therefore the majority of current research relies on the use of animal models of trypanosome infection. This review reports contemporary knowledge, from both animal models and human samples, regarding parasite invasion of the CNS and the neuropathological changes that accompany trypanosome infection and disease progression. The effects of trypanosomes on the blood-brain barrier are discussed and possible key molecules in parasite penetration of the barrier highlighted. Changes in the balance of CNS cytokines and chemokines are also described. The article closes by summarising the effects of trypanosome infection on the circadian sleep-wake cycle, and sleep structure, in relation to neuroinflammation and parasite location within the CNS. Although a great deal of progress has been made in recent years, the advent and application of sophisticated analysis techniques, to decipher the complexities of HAT pathogenesis, herald an exciting and rewarding period for advances in trypanosome research.