Validation of in vitro-produced and freeze-dried whole cell lysate antigens for ELISA Trypanosoma evansi antibody detection in camels

Trypanosoma evansi is a blood parasite responsible for surra in mammals, with a high impact in camels and horses. The WOAH-recommended reference method for detecting immunoglobulin G directed against T. evansi is ELISA, using whole cell lysate antigens (WCLAs). WCLAs are prepared with T. evansi produced in laboratory rodents, separated from blood cells using DE-cellulose anion exchange chromatography. As parasite lysates are fragile, antigens are preserved frozen pending use. For these reasons and others, T. evansi WCLAs are not commercially available. They are produced in small quantities, in a limited number of specialized laboratories, and they require a reliable and expensive cold chain for their shipment. In this study, we assessed and validated in vitro production of T. evansi and lyophilization of WCLAs in comparison with the reference method using frozen WCLAs prepared with parasites produced in rodents. Using a set of 400 samples monthly collected from 12 naturally infected camels followed-up for 1384 days, and two batches of referenced serum samples (infected, n = 12; non-infected, n = 15), statistical studies on qualitative and semi-quantitative results of the ELISAs did not show any significant difference when comparing the four combinations of parasites produced in vivo or in vitro, and frozen or freeze-dried WCLSAs. A repeatability study (28 repeats in 9 serum samples) was fully satisfying (p-value = 0.055). With the more convenient in vitro-produced freeze-dried WCLAs it was possible to: (i) avoid the ethical concern of in vivo production, (ii) improve the standardization of antigen production, (iii) secure antigen preservation during shipment and (iv) save a considerable amount of money (DE52-cellulose and dry-ice cold chain being avoided). Additional studies with other Trypanosoma spp are required for further extending ELISA to regional laboratories in enzootic areas, especially in view of the current progress in the "Progressive Control Pathway" (PCP) for trypanosomes in Africa.

Diagnosis of animal trypanosomoses: proper use of current tools and future prospects

Reliable diagnostic tools are needed to choose the appropriate treatment and proper control measures for animal trypanosomoses, some of which are pathogenic. Trypanosoma cruzi, for example, is responsible for Chagas disease in Latin America. Similarly, pathogenic animal trypanosomoses of African origin (ATAO), including a variety of Trypanosoma species and subspecies, are currently found in Africa, Latin America and Asia. ATAO limit global livestock productivity and impact food security and the welfare of domestic animals. This review focusses on implementing previously reviewed diagnostic methods, in a complex epizootiological scenario, by critically assessing diagnostic results at the individual or herd level. In most cases, a single diagnostic method applied at a given time does not unequivocally identify the various parasitological and disease statuses of a host. These include “non-infected”, “asymptomatic carrier”, “sick infected”, “cured/not cured” and/or “multi-infected”. The diversity of hosts affected by these animal trypanosomoses and their vectors (or other routes of transmission) is such that integrative, diachronic approaches are needed that combine: (i) parasite detection, (ii) DNA, RNA or antigen detection and (iii) antibody detection, along with epizootiological information. The specificity of antibody detection tests is restricted to the genus or subgenus due to cross-reactivity with other Trypanosoma spp. and Trypanosomatidae, but sensitivity is high. The DNA-based methods implemented over the last three decades have yielded higher specificity and sensitivity for active infection detection in hosts and vectors. However, no single diagnostic method can detect all active infections and/or trypanosome species or subspecies. The proposed integrative approach will improve the prevention, surveillance and monitoring of animal trypanosomoses with the available diagnostic tools. However, further developments are required to address specific gaps in diagnostic methods and the sustainable control or elimination of these diseases.

A review on the diagnosis of animal trypanosomoses

This review focuses on the most reliable and up-to-date methods for diagnosing trypanosomoses, a group of diseases of wild and domestic mammals, caused by trypanosomes, parasitic zooflagellate protozoans mainly transmitted by insects. In Africa, the Americas and Asia, these diseases, which in some cases affect humans, result in significant illness in animals and cause major economic losses in livestock. A number of pathogens are described in this review, including several Salivarian trypanosomes, such as Trypanosoma brucei sspp. (among which are the agents of sleeping sickness, the human African trypanosomiasis [HAT]), Trypanosoma congolense and Trypanosoma vivax (causing “Nagana” or animal African trypanosomosis [AAT]), Trypanosoma evansi (“Surra”) and Trypanosoma equiperdum (“Dourine”), and Trypanosoma cruzi, a Stercorarian trypanosome, etiological agent of the American trypanosomiasis (Chagas disease). Diagnostic methods for detecting zoonotic trypanosomes causing Chagas disease and HAT in animals, as well as a diagnostic method for detecting animal trypanosomes in humans (the so-called “atypical human infections by animal trypanosomes” [a-HT]), including T. evansi and Trypanosoma lewisi (a rat parasite), are also reviewed. Our goal is to present an integrated view of the various diagnostic methods and techniques, including those for: (i) parasite detection; (ii) DNA detection; and (iii) antibody detection. The discussion covers various other factors that need to be considered, such as the sensitivity and specificity of the various diagnostic methods, critical cross-reactions that may be expected among Trypanosomatidae, additional complementary information, such as clinical observations and epizootiological context, scale of study and logistic and cost constraints. The suitability of examining multiple specimens and samples using several techniques is discussed, as well as risks to technicians, in the context of specific geographical regions and settings. This overview also addresses the challenge of diagnosing mixed infections with different Trypanosoma species and/or kinetoplastid parasites. Improving and strengthening procedures for diagnosing animal trypanosomoses throughout the world will result in a better control of infections and will significantly impact on “One Health,” by advancing and preserving animal, human and environmental health.

The separation of trypanosomes from blood by anion exchange chromatography: From Sheila Lanham's discovery 50 years ago to a gold standard for sleeping sickness diagnosis

Human African trypanosomiasis (HAT), or sleeping sickness, is a neglected tropical disease that is fatal if untreated, caused by Trypanosoma brucei gambiense and T. brucei rhodesiense. In its 2012 roadmap, WHO targeted HAT for elimination as a public health problem in 2020 and for zero transmission in 2030. Diagnosis of HAT is a multistep procedure comprising of clinical suspicion, confirmation, and stage determination. Suspects are identified on clinical signs and/or on screening for specific antibodies. Parasitological confirmation of suspects remains mandatory to avoid unnecessary toxic drug administration. The positive predictive value of the antibody detection tests is low. Simple parasite detection techniques, microscopic examination of lymph node aspirate, or stained thick blood films lack sensitivity, whereas in T. brucei gambiense patients, the number of blood trypanosomes may be very low. Parasite concentration techniques are therefore indispensable. Half a century ago, Sheila Lanham discovered a technique to separate trypanosomes from the blood of infected rodents, based on anion exchange chromatography with diethyl amino ethyl (DEAE) cellulose, a weak anion exchanger. Between pH 6−9, trypanosome surface is less negatively charged than that of blood cells. When blood is poured on top of a DEAE cellulose column, blood cells are retained, whereas parasites pass the column together with the elution buffer. The result is a pure suspension of trypanosomes that retain their morphology and infectivity. Because cell surface charges vary among trypanosome and mammal species, the optimal buffer pH and ionic strength conditions for different combinations of host and trypanosome species were established. Lanham's technique revolutionized the diagnosis of HAT. It is indispensable in the production of the Card Agglutination Test for Trypanosomiasis (CATT), the most used field test for screening in T. brucei gambiense HAT foci and essential to confirm the diagnosis in suspected people. Lumsden and colleagues developed the mini anion exchange centrifugation technique (mAECT). After adaptation for field conditions, its superior diagnostic and analytical sensitivity compared to another concentration technique was demonstrated. It was recommended as the most sensitive test for demonstrating trypanosomes in human blood. At the beginning of the 21st century, the mAECT was redesigned, allowing examination of a larger volume of blood, up to 0.35 ml with whole blood and up to 10 ml with buffy coat. The plastic collector tube in the new kit is also used for detection of trypanosomes in the cerebrospinal fluid. Unfortunately, mAECT also has some disadvantages, including its price, the need to centrifuge the collector tube, and the fact that it is manufactured on a noncommercial basis at only two research institutes. In conclusion, 50 years after Sheila Lanham's discovery, CATT and mAECT have become essential elements in the elimination of HAT.

Characterization of recombinant Trypanosoma brucei gambiense Translationally Controlled Tumor Protein (rTbgTCTP) and its interaction with Glossina midgut bacteria

In humans, sleeping sickness (i.e. Human African Trypanosomiasis) is caused by the protozoan parasites Trypanosoma brucei gambiense (Tbg) in West and Central Africa, and T. b. rhodesiense in East Africa. We previously showed in vitro that Tbg is able to excrete/secrete a large number of proteins, including Translationally Controlled Tumor Protein (TCTP). Moreover, the tctp gene was described previously to be expressed in Tbg-infected flies. Aside from its involvement in diverse cellular processes, we have investigated a possible alternative role within the interactions occurring between the trypanosome parasite, its tsetse fly vector, and the associated midgut bacteria. In this context, the Tbg tctp gene was synthesized and cloned into the baculovirus vector pAcGHLT-A, and the corresponding protein was produced using the baculovirus Spodoptera frugicola (strain 9) / insect cell system. The purified recombinant protein rTbgTCTP was incubated together with bacteria isolated from the gut of tsetse flies, and was shown to bind to 24 out of the 39 tested bacteria strains belonging to several genera. Furthermore, it was shown to affect the growth of the majority of these bacteria, especially when cultivated under microaerobiosis and anaerobiosis. Finally, we discuss the potential for TCTP to modulate the fly microbiome composition toward favoring trypanosome survival.

In vitro Activity of a Novel Series of Polyoxosilicotungstates against Human Myxo-, Herpes- and Retroviruses

A series of silicon-containing polyoxotungstates belonging to the ‘Keggin-type’ (‘Keggin’, ‘Keggin sandwich’) were evaluated for their antiviral activity against enveloped viruses (myxo-, herpes- and retroviruses). The compounds exhibited antiviral activity against influenza virus type A, respiratory syncytial virus (RSV), herpes simplex virus type-1 (HSV-1), type-2 (HSV-2), thymidine kinase-deficient (TIC) HSV-1, human cytomegalovirus (HCMV), human immunodeficiency virus type-1 (HIV-1) and type-2 (HIV-2) at concentrations that were well below their cytotoxic threshold. The ‘Keggin’ compound JM2815 (K5[Si-(TiCp)W11O39].12H2O) and the ‘Keggin sandwich’ compound JM1590 (K13[Ce(SiW11O39)2].26H2O) resulted in the highest selectivity indices against HIV-1 and HIV-2, and compound JM2820 ([Me3NH]8.[Si2Nb6W18O77]) was the most potent inhibitor of HSV and HCMV replication. These compounds proved active against HCMV and HSV when present during virus adsorption, and against influenza virus A and RSV when present after virus adsorption. Polyoxosilicotungstates inhibited the binding of radiolabeled HCMV particles to the cells at concentrations that were antivirally active, and the compounds were able to displace HCMV particles that were bound to a heparin-Sepharose matrix. Presumably, the polyoxosilicotungstates interact with positively charged domains on the viral envelope site(s) involved in the attachment of the (HCMV) virions to the cell surface receptor heparan sulphate.

Escaping Deleterious Immune Response in Their Hosts: Lessons from Trypanosomatids

The Trypanosomatidae family includes the genera Trypanosoma and Leishmania, protozoan parasites displaying complex digenetic life cycles requiring a vertebrate host and an insect vector. Trypanosoma brucei gambiense, Trypanosoma cruzi, and Leishmania spp. are important human pathogens causing human African trypanosomiasis (HAT or sleeping sickness), Chagas' disease, and various clinical forms of Leishmaniasis, respectively. They are transmitted to humans by tsetse flies, triatomine bugs, or sandflies, and affect millions of people worldwide. In humans, extracellular African trypanosomes (T. brucei) evade the hosts' immune defenses, allowing their transmission to the next host, via the tsetse vector. By contrast, T. cruzi and Leishmania sp. have developed a complex intracellular lifestyle, also preventing several mechanisms to circumvent the host's immune response. This review seeks to set out the immune evasion strategies developed by the different trypanosomatids resulting from parasite-host interactions and will focus on: clinical and epidemiological importance of diseases; life cycles: parasites-hosts-vectors; innate immunity: key steps for trypanosomatids in invading hosts; deregulation of antigen-presenting cells; disruption of efficient specific immunity; and the immune responses used for parasite proliferation.

Refractory hypoglycaemia in a dog infected with Trypanosoma congolense

A 20 kg German shepherd dog was presented to a French veterinary teaching hospital for seizures and hyperthermia. The dog had returned 1 month previously from a six-month stay in Senegal and sub-Saharan Africa. Biochemistry and haematology showed severe hypoglycaemia (0.12 g/L), anaemia and thrombocytopenia. Despite administration of large amounts of glucose (30 mL of 30% glucose IV and 10 mL of 70% sucrose by gavage tube hourly), 26 consecutive blood glucose measurements were below 0.25 g/L (except one). Routine cytological examination of blood smears revealed numerous free extracytoplasmic protozoa consistent with Trypanosoma congolense. PCR confirmed a Trypanosoma congolense forest-type infection. Treatment consisted of six injections of pentamidine at 48-hour intervals. Trypanosomes had disappeared from the blood smears four days following the first injection. Clinical improvement was correlated with the normalization of laboratory values. The infection relapsed twice and the dog was treated again; clinical signs and parasites disappeared and the dog was considered cured; however, 6 years after this incident, serological examination by ELISA T. congolense was positive. The status of this dog (infected or non-infected) remains unclear. Hypoglycaemia was the most notable clinical feature in this case. It was spectacular in its severity and in its refractory nature; glucose administration seemed only to feed the trypanosomes, indicating that treatment of hypoglycaemia may in fact have been detrimental.

Secreted proteases of Trypanosoma brucei gambiense: possible targets for sleeping sickness control?

Human African trypanosomiasis (HAT) is caused by trypanosomes of the species Trypanosoma brucei and belongs to the neglected tropical diseases. Presently, WHO has listed 36 countries as being endemic for sleeping sickness. No vaccine is available, and disease treatment is difficult and has life-threatening side effects. Therefore, there is a crucial need to search for new therapeutic targets against the parasite. Trypanosome excreted-secreted proteins could be promising targets, as the total secretome was shown to inhibit, in vitro, host dendritic cell maturation and their ability to induce lymphocytic allogenic responses. The secretome was found surprisingly rich in various proteins and unexpectedly rich in diverse peptidases, covering more than ten peptidase families or subfamilies. Given their abundance, one may speculate that they would play a genuine role not only in classical "housekeeping" tasks but also in pathogenesis. The paper reviews the deleterious role of proteases from trypanosomes, owing to their capacity to degrade host circulating or structural proteins, as well as proteic hormones, causing severe damage and preventing host immune response. In addition, proteases account for a number of drug targets, such drugs being used to treat severe diseases such AIDS. This review underlines the importance of secreted proteins and especially of secreted proteases as potential targets in HAT-fighting strategies. It points out the need to conduct further investigations on the specific role of each of these various proteases in order to identify those playing a central role in sleeping sickness and would be suitable for drug targeting.

[Severe cases of A(H1N1)v2009 infection in Réunion Island in 2009 and 2010]

Dans l’hémisphère sud, La Réunion est la sentinelle des infections survenant préférentiellement au cours de l’hiver austral, susceptibles de gagner quelques mois plus tard l’hémisphère nord, telle l’infection à A(H1N1)v2009. Nous rapportons les caractéristiques des patients admis en 2009 et 2010 dans notre service de réanimation principalement pour détresse respiratoire aiguë, à la suite d’une infection à A(H1N1)v2009. Les données démographiques, cliniques, biologiques, ainsi que les traitements et le devenir des patients admis pour infection virale à A(H1N1)v2009 exclusivement confirmée par RT-PCR ont été recueillis de façon prospective. Au cours des années 2009 et 2010, 25 patients ont répondu aux critères définis d’infection à A(H1N1)v2009. L’âge médian était de 40,4 (±17,4) ans. La plupart d’entre eux (22/25) présentaient des facteurs de comorbidité: pathologies chroniques, surpoids ou obésité, grossesse, trisomie. Les principaux motifs d’admission en réanimation ont été les pneumonies virales avec tableau de syndrome de détresse respiratoire aiguë. Le recours à la ventilation artificielle a été nécessaire chez 22 des 25 patients, avec recours à des méthodes sophistiquées et réservées à quelques centres au niveau national, telles que les techniques d’oxygénation extracorporelle (ECMO) ou ventilation à haute fréquence (HFO). Au cours des deux années, 12 décès (48 %) sont survenus essentiellement dans des tableaux de défaillance multiviscérale. Au cours des hivers et automnes australs 2009 et 2010 et pendant une période de plusieurs semaines, l’infection à A(H1N1) v2009 a entraîné une surcharge d’activité notable dans les services de réanimation de La Réunion. L’échec de la campagne de vaccination, notamment des personnes à risques, a eu pour conséquence la survenue de nouveaux cas graves en 2010, notamment parmi les personnes à risques. Le recueil de ces données peut aider à la planification et à l’anticipation de la prise en charge d’autres épidémies grippales.

[Medical paediatric simulation: a European survey]

OBJECTIVE

To present the effective applications of paediatric medical simulation in terms of education, evaluation, density, development, goals and constraints.

STUDY DESIGN

Survey realized within 38 paediatric simulation centres (PSC) in Europe, identified by Web search and through the Society in Europe for Simulation Applied to Medicine (SESAM.

RESULTS

Twenty centers answered the questionnaire (52%). Ninety-four percent of the PSC had beforehand acquired an experience of adult medical simulation, 94.6% of the PSC were created before 2006. Ninety percent of the PSC owned at least one high-fidelity pediatric simulator. The 80% of the PSC indicated multiple funding sources. Eighty percent of the PSC had at least one specific instructor for the paediatric simulation (average=2.7 paediatric instructors per centre). The PCS reported to get onto various topics: neonatology (25% of the PCS), prehospital medicine (36.8%), paediatric anaesthesiology (74%) and paediatric intensive care (89%). Simulation allowed 70% of the centers to lead some research project. Ninety-five percent of the centers agreed about an European collaboration on research projects or about the mutualization of the created scenarios.

CONCLUSION

The material, financial and human means of the interviewed centres are consequential but heterogeneous in Europe. MSP offers numerous and various application fields and generates some research activity.

Identification of total and differentially expressed excreted-secreted proteins from Trypanosoma congolense strains exhibiting different virulence and pathogenicity

Animal trypanosomosis is a major constraint to livestock productivity in the tropics and has a significant impact on the life of millions of people globally (mainly in Africa, South America and south-east Asia). In Africa, the disease in livestock is caused mainly by Trypanosoma congolense, Trypanosoma vivax, Trypanosoma evansi and Trypanosoma brucei brucei. The extracellular position of trypanosomes in the bloodstream of their host requires consideration of both the parasite and its naturally excreted-secreted factors (secretome) in the course of pathophysiological processes. We therefore developed and standardised a method to produce purified proteomes and secretomes of African trypanosomes. In this study, two strains of T. congolense exhibiting opposite properties of both virulence and pathogenicity were further investigated through their secretome expression and its involvement in host-parasite interactions. We used a combined proteomic approach (one-dimensional SDS-PAGE and two-dimensional differential in-gel electrophoresis coupled to mass spectrometry) to characterise the whole and differentially expressed protein contents of secretomes. The molecular identification of differentially expressed trypanosome molecules and their correlation with either the virulence process or pathogenicity are discussed with regard to their potential as new diagnostic or therapeutic tools against animal trypanosomosis.

"Pathogeno-proteomics"

Many scientists working on pathogens (viruses, bacteria, fungi, parasites) are betting heavily on data generated by longitudinal genomic-transcriptomic-proteomic studies to explain biochemical host-vector-pathogen interactions and thus to contribute to disease control. Availability of genome sequences of various organisms, from viruses to complex metazoans, led to the discovery of the functions of the genes themselves. The postgenomic era stimulated the development of proteomic and bioinformatics tools to identify the locations, functions, and interactions of the gene products in tissues and/or cells of living organisms. Because of the diversity of available methods and the level of integration they promote, proteomics tools are potentially able to resolve interesting issues specific not only to host-vector-pathogen interactions in cell immunobiology, but also to ecology and evolution, population biology, and adaptive processes. These new analytical tools, as all new tools, contain pitfalls directly related to experimental design, statistical treatment, and protein identification. Nevertheless, they offer the potency of building large protein-protein interaction networks for in silico analysis of novel biological entities named "interactomes," a way of modeling host-vector-pathogen interactions to define new interference strategies.