Immunobiology of African trypanosomes: need of alternative interventions

Advancement in the development of DNA vaccines against Trypanosoma brucei and future perspective

Trypanosomes are the extracellular protozoan parasites that cause human African trypanosomiasis disease in humans and nagana disease in animals. Tsetse flies act as a vector for the transmission of the disease in African countries. Animals infected with these parasites become useless or workless, and if not treated, disease can be fatal. There are many side effects associated with old treatments and some of them result in death in 5% of cases. There is a major surface glycoprotein in the parasite known as variant surface glycoprotein. The immune system of the host develops antibodies against this antigen but due to antigenic variation, parasites evade the immune response. Currently, no vaccine is available that provides complete protection. In murine models, only partial protection was observed using certain antigens. In order to develop vaccines against trypanosomes, molecular biology and immunology tools have been used. Immunization is the sole method for the control of disease because the eradication of the vector from endemic areas is an impossible task. Genetic vaccines can carry multiple genes encoding different antigens of the same parasite or different parasites. DNA immunization induces the activation of both cellular immune response and humoral immune response along with the generation of memory. This review highlights the importance of DNA vaccines and advances in the development of DNA vaccines against T. brucei.

Ginkgo biloba attenuated detrimental inflammatory and oxidative events due to Trypanosoma brucei rhodesiense in mice treated with melarsoprol

BACKGROUND

The severe late stage Human African Trypanosomiasis (HAT) caused by Trypanosoma brucei rhodesiense (T.b.r) is characterized by damage to the blood brain barrier, severe brain inflammation, oxidative stress and organ damage. Melarsoprol (MelB) is currently the only treatment available for this disease. MelB use is limited by its lethal neurotoxicity due to post-treatment reactive encephalopathy. This study sought to assess the potential of Ginkgo biloba (GB), a potent anti-inflammatory and antioxidant, to protect the integrity of the blood brain barrier and ameliorate detrimental inflammatory and oxidative events due to T.b.r in mice treated with MelB.

METHODOLOGY

Group one constituted the control; group two was infected with T.b.r; group three was infected with T.b.r and treated with 2.2 mg/kg melarsoprol for 10 days; group four was infected with T.b.r and administered with GB 80 mg/kg for 30 days; group five was given GB 80mg/kg for two weeks before infection with T.b.r, and continued thereafter and group six was infected with T.b.r, administered with GB and treated with MelB.

RESULTS

Co-administration of MelB and GB improved the survival rate of infected mice. When administered separately, MelB and GB protected the integrity of the blood brain barrier and improved neurological function in infected mice. Furthermore, the administration of MelB and GB prevented T.b.r-induced microcytic hypochromic anaemia and thrombocytopenia, as well as T.b.r-driven downregulation of total WBCs. Glutathione analysis showed that co-administration of MelB and GB prevented T.b.r-induced oxidative stress in the brain, spleen, heart and lungs. Notably, GB averted peroxidation and oxidant damage by ameliorating T.b.r and MelB-driven elevation of malondialdehyde (MDA) in the brain, kidney and liver. In fact, the co-administered group for the liver, registered the lowest MDA levels for infected mice. T.b.r-driven elevation of serum TNF-α, IFN-γ, uric acid and urea was abrogated by MelB and GB. Co-administration of MelB and GB was most effective in stabilizing TNFα levels. GB attenuated T.b.r and MelB-driven up-regulation of nitrite.

CONCLUSION

Utilization of GB as an adjuvant therapy may ameliorate detrimental effects caused by T.b.r infection and MelB toxicity during late stage HAT.

Chemokines: A key driver for inflammation in protozoan infection

Chemokines belong to the group of small proteins within the cytokine family having strong chemo-attractant properties. In most cases, the strong immuno-modulatory role of chemokines is crucial for generating the immune response against pathogens in various protozoan diseases. In this review, we have given a brief update on the classification, characterization, homeostasis, transcellular migration, and immuno-modulatory role of chemokines. Here we will evaluate the potential role of chemokines and their regulation in various protozoan diseases. There is a significant direct relationship between parasitic infection and the recruitment of effector cells of the immune response. Chemokines play an indispensable role in mediating several defense mechanisms against infection, such as leukocyte recruitment and the generation of innate and cell-mediated immunity that aids in controlling/eliminating the pathogen. This process is controlled by the chemotactic movement of chemokines induced as a primary host immune response. We have also addressed that chemokine expressions during infection are time-dependent and orchestrated in a systematic pattern that ultimately assists in generating a protective immune response. Taken together, this review provides a systematic understanding of the complexity of chemokines profiles during protozoan disease conditions and the rationale of targeting chemokines for the development of therapeutic strategies.

African Trypanosomiasis: Extracellular Vesicles Shed by Trypanosoma brucei brucei Manipulate Host Mononuclear Cells

African trypanosomiasis or sleeping sickness is a zoonotic disease caused by Trypanosoma brucei, a protozoan parasite transmitted by Glossina spp. (tsetse fly). Parasite introduction into mammal hosts triggers a succession of events, involving both innate and adaptive immunity. Macrophages (MΦ) have a key role in innate defence since they are antigen-presenting cells and have a microbicidal function essential for trypanosome clearance. Adaptive immune defence is carried out by lymphocytes, especially by T cells that promote an integrated immune response. Like mammal cells, T. b. brucei parasites release extracellular vesicles (TbEVs), which carry macromolecules that can be transferred to host cells, transmitting biological information able to manipulate cell immune response. However, the exact role of TbEVs in host immune response remains poorly understood. Thus, the current study examined the effect elicited by TbEVs on MΦ and T lymphocytes. A combined approach of microscopy, nanoparticle tracking analysis, multiparametric flow cytometry, colourimetric assays and detailed statistical analyses were used to evaluate the influence of TbEVs in mouse mononuclear cells. It was shown that TbEVs can establish direct communication with cells of innate and adaptative immunity. TbEVs induce the differentiation of both M1- and M2-MΦ and elicit the expansion of MHCI⁺, MHCII⁺ and MHCI⁺MHCII⁺ MΦ subpopulations. In T lymphocytes, TbEVs drive the overexpression of cell-surface CD3 and the nuclear factor FoxP3, which lead to the differentiation of regulatory CD4⁺ and CD8⁺ T cells. Moreover, this study indicates that T. b. brucei and TbEVs seem to display opposite but complementary effects in the host, establishing a balance between parasite growth and controlled immune response, at least during the early phase of infection.

High Granulocyte-Macrophage Colony Stimulating Factor to Interleukin 10 Ratio and Marked Antioxidant Enzyme Activities Predominate in Symptomatic Cattle Naturally Infected with Candidatus Mycoplasma haemobos, Theileria orientalis, Theileria sinensis and Trypanosoma evansi

The aim of this study was to measure the serum proinflammatory (IL-12, GM-CSF & IFN-γ) to anti-inflammatory (IL-10, IL-4) cytokine ratio, oxidant (MDA) level and antioxidant enzyme (SOD; GPx) activities after blood parasite infections. The blood and serum samples were obtained from 130 cattle and screened for identity of the infecting blood parasites by conventional PCR. The following blood parasite species were detected: Candidatus Mycoplasma haemobos (70/130); Theileria orientalis (65/130); Theileria sinensis (32/130); Anaplasma marginale (49/130); Anaplasma platys (7/130); and Trypanosoma evansi (4/130). The GM-CSF/IL-10 ratio showed significantly higher values in all the symptomatic blood parasite infected cattle groups except for symptomatic A. platys infected cattle groups. Anti-inflammatory cytokine immune responses were notable findings in symptomatic and asymptomatic cattle infected with C. M. haemobos and T. orientalis characterized by low serum IL-12:IL-10, IFN-γ:IL-10, IL-12:IL-4 and IFN-γ:IL-4 (p < 0.05). Therefore, high serum GM-CSF:IL:10 in the symptomatic blood parasite infected cattle, low serum IL-12:IL-10, IFN-γ:IL-10, IL-12:IL-4 and IFN-γ:IL-4 ratios in asymptomatic cattle, high MDA level, and increased antioxidant enzyme activities could be useful predictive tools for outcome of natural blood parasite infections in cattle.

Differences in growth of Trypanoplasma borreli in carp serum is dependent on transferrin genotype

Kinetoplastid parasites require transferrin (Tf), being the main source of iron, for growth and multiplication. This group of parasites developed a unique receptor-mediated system for acquiring host Tf which bears no structural homology with the host transferrin receptor. Trypanoplasma borreli, a blood parasite of common carp, probably uses a similar mechanism to sequester iron from host transferrin. In this study, we demonstrate a critical role of Tf for parasite growth. For in vitro studies we isolated and purified Tf from carp homozygous for the D or G allele of Tf. We obtained Tf-depleted serum using specific antibodies to carp Tf and studied gene expression in vivo during T. borreli infection with Real Time-quantitative PCR. We demonstrate that T. borreli cannot survive in medium supplemented with Tf-depleted serum while reconstitution with Tf restores normal growth. The critical role of Tf for parasite survival was shown in incomplete medium (medium without serum): addition of purified Tf significantly increased parasite survival. We also demonstrate that Tf polymorphism has a significant impact on T. borreli multiplication. Cultured parasites die more quickly in an environment containing D-typed Tf, as compared to medium with G-typed Tf. Gene expression during T. borreli infection in carp did not show an acute phase response. We could, however, observe an increased transcription of Tf in the head kidney, which may be associated with an immunological function of the Tf protein.

Bioinformatics and expression analysis of the Xeroderma Pigmentosum complementation group C (XPC) of Trypanosoma evansi in Trypanosoma cruzi cells

Nucleotide excision repair (NER) acts repairing damages in DNA, such as lesions caused by cisplatin. Xeroderma Pigmentosum complementation group C (XPC) protein is involved in recognition of global genome DNA damages during NER (GG-NER) and it has been studied in different organisms due to its importance in other cellular processes. In this work, we studied NER proteins in Trypanosoma cruzi and Trypanosoma evansi, parasites of humans and animals respectively. We performed three-dimensional models of XPC proteins from T. cruzi and T. evansi and observed few structural differences between these proteins. In our tests, insertion of XPC gene from T. evansi (TevXPC) in T. cruzi resulted in slower cell growth under normal conditions. After cisplatin treatment, T. cruzi overexpressing its own XPC gene (TcXPC) was able to recover cell division rates faster than T. cruzi expressing TevXPC gene. Based on these tests, it is suggested that TevXPC (being an exogenous protein in T. cruzi) interferes negatively in cellular processes where TcXPC (the endogenous protein) is involved. This probably occurred due interaction of TevXPC with some endogenous molecules or proteins from T.cruzi but incapacity of interaction with others. This reinforces the importance of correctly XPC functioning within the cell.

Epidemiology of Trypanosomiasis in Wildlife-Implications for Humans at the Wildlife Interface in Africa

While both human and animal trypanosomiasis continue to present as major human and animal public health constraints globally, detailed analyses of trypanosome wildlife reservoir hosts remain sparse. African animal trypanosomiasis (AAT) affects both livestock and wildlife carrying a significant risk of spillover and cross-transmission of species and strains between populations. Increased human activity together with pressure on land resources is increasing wildlife–livestock–human infections. Increasing proximity between human settlements and grazing lands to wildlife reserves and game parks only serves to exacerbate zoonotic risk. Communities living and maintaining livestock on the fringes of wildlife-rich ecosystems require to have in place methods of vector control for prevention of AAT transmission and for the treatment of their livestock. Major Trypanosoma spp. include Trypanosoma brucei rhodesiense, Trypanosoma brucei gambiense, and Trypanosoma cruzi, pathogenic for humans, and Trypanosoma vivax, Trypanosoma congolense, Trypanosoma evansi, Trypanosoma brucei brucei, Trypanosoma dionisii, Trypanosoma thomasbancrofti, Trypanosma elephantis, Trypanosoma vegrandis, Trypanosoma copemani, Trypanosoma irwini, Trypanosoma copemani, Trypanosoma gilletti, Trypanosoma theileri, Trypanosoma godfreyi, Trypansoma simiae, and Trypanosoma (Megatrypanum) pestanai. Wildlife hosts for the trypansomatidae include subfamilies of Bovinae, Suidae, Pantherinae, Equidae, Alcephinae, Cercopithecinae, Crocodilinae, Pteropodidae, Peramelidae, Sigmodontidae, and Meliphagidae. Wildlife species are generally considered tolerant to trypanosome infection following centuries of coexistence of vectors and wildlife hosts. Tolerance is influenced by age, sex, species, and physiological condition and parasite challenge. Cyclic transmission through Glossina species occurs for T. congolense, T. simiae, T. vivax, T. brucei, and T. b. rhodesiense, T. b. gambiense, and within Reduviid bugs for T. cruzi. T. evansi is mechanically transmitted, and T. vixax is also commonly transmitted by biting flies including tsetse. Wildlife animal species serve as long-term reservoirs of infection, but the delicate acquired balance between trypanotolerance and trypanosome challenge can be disrupted by an increase in challenge and/or the introduction of new more virulent species into the ecosystem. There is a need to protect wildlife, animal, and human populations from the infectious consequences of encroachment to preserve and protect these populations. In this review, we explore the ecology and epidemiology of Trypanosoma spp. in wildlife.

Synthesis and evaluation of trypanocidal activity of derivatives of naturally occurring 2,5-diphenyloxazoles

African trypanosomiasis is a zoonotic protozoan disease affecting the nervous system. Various natural products reportedly exhibit trypanocidal activity. Naturally occurring 2,5-diphenyloxazoles present in Oxytropis lanata, and their derivatives, were synthesized. The trypanocidal activities of the synthesized compounds were evaluated against Trypanosoma brucei brucei, T. b. gambiense, T. b. rhodesiense, T. congolense, and T. evansi. Natural product 1 exhibited trypanocidal activity against all the species/subspecies of trypanosomes, exhibiting half-maximal inhibitory concentrations (IC₅₀) of 1.1-13.5 μM. Modification of the oxazole core improved the trypanocidal activity. The 1,3,4-oxadiazole (7) and 2,4-diphenyloxazole (9) analogs exhibited potency superior to that of 1. However, these compounds exhibited cytotoxicity in Madin-Darby bovine kidney cells. The O-methylated analog of 1 (12) was non-cytotoxic and exhibited selective trypanocidal activity against T. congolense (IC₅₀ = 0.78 µM). Structure-activity relationship studies of the 2,5-diphenyloxazole analogs revealed aspects of the molecular structure critical for maintaining selective trypanocidal activity against T. congolense.

Toxicity study and anti-trypanosomal activities of aqueous and methanol whole plant extracts of Brillantaisia owariensis on Trypanosoma brucei-induced infection in BALB/c mice

Background

The problem of drug resistance and toxicity in trypanosomiasis is ever-increasing, thereby creating a need to search for efficacious and safer alternatives that are of plant origin. We designed the present study to assess the oral acute toxicity, and anti-trypanosomal activity of Brillantaisia owariensis in mice.

Methods

Fifty-eight BALB/c mice were used for this study. For toxicity assessment, eighteen mice were divided into two groups of nine mice each, and acute single oral administration of the aqueous and methanol whole plant extracts of B. owariensis was assessed for each group as per Lorke’s method. Mice were observed for signs of toxicity of liver and kidney organs after two weeks of oral administration. For the anti-trypanosomal activity, forty mice were divided into eight groups of five mice. Mouse in each group was inoculated with 0.1 mL containing106T. brucei /mL. Following patency of 3 days, mice were treated at different dosages of methanol and aqueous extracts. Pre-infection, post-infection, and post-treatment data for rectal temperature, body weight, parasiteamia level, packed cell volume, and daily survival were monitored.

Results

The acute oral toxicity studies (LD50) for methanol and aqueous plant extracts in this study were calculated as 3535 mg/kg/body weight, and are non-toxic. No obvious histopathologic observation in the liver and kidney tissues. The mean daily rectal temperature and mean weights of all the treated mice were restored to normal values and significant (P, 0.05) in comparison to the positive control.

Parasitaemia clearance by both extracts was suppressive. The mean PCV values were significantly increased following treatment, and there was prolonged survival especially in mice treated with methanol extracts.

Conclusion

The study concludes that the extracts of B. owariensis are relatively non-toxic with a good safety margin when administered to mice orally. Crude methanol extract exhibited better suppressive and haematinic antitrypanosomal activities than the aqueous extract, and it has a promising effect by its ability to reduce anaemia in mice challenged with T. brucei brucei, and prolonged survival.

To the Skin and Beyond: The Immune Response to African Trypanosomes as They Enter and Exit the Vertebrate Host

African trypanosomes are single-celled extracellular protozoan parasites transmitted by tsetse fly vectors across sub-Saharan Africa, causing serious disease in both humans and animals. Mammalian infections begin when the tsetse fly penetrates the skin in order to take a blood meal, depositing trypanosomes into the dermal layer. Similarly, onward transmission occurs when differentiated and insect pre-adapted forms are ingested by the fly during a blood meal. Between these transmission steps, trypanosomes access the systemic circulation of the vertebrate host via the skin-draining lymph nodes, disseminating into multiple tissues and organs, and establishing chronic, and long-lasting infections. However, most studies of the immunobiology of African trypanosomes have been conducted under experimental conditions that bypass the skin as a route for systemic dissemination (typically via intraperitoneal or intravenous routes). Therefore, the importance of these initial interactions between trypanosomes and the skin at the site of initial infection, and the implications for these processes in infection establishment, have largely been overlooked. Recent studies have also demonstrated active and complex interactions between the mammalian host and trypanosomes in the skin during initial infection and revealed the skin as an overlooked anatomical reservoir for transmission. This highlights the importance of this organ when investigating the biology of trypanosome infections and the associated immune responses at the initial site of infection. Here, we review the mechanisms involved in establishing African trypanosome infections and potential of the skin as a reservoir, the role of innate immune cells in the skin during initial infection, and the subsequent immune interactions as the parasites migrate from the skin. We suggest that a thorough identification of the mechanisms involved in establishing African trypanosome infections in the skin and their progression through the host is essential for the development of novel approaches to interrupt disease transmission and control these important diseases.

Screening for Small Molecule Modulators of Trypanosoma brucei Hsp70 Chaperone Activity Based upon Alcyonarian Coral-Derived Natural Products

The Trypanosoma brucei Hsp70/J-protein machinery plays an essential role in survival, differentiation, and pathogenesis of the protozoan parasite, and is an emerging target against African Trypanosomiasis. This study evaluated a set of small molecules, inspired by the malonganenones and nuttingins, as modulators of the chaperone activity of the cytosolic heat inducible T. brucei Hsp70 and constitutive TbHsp70.4 proteins. The compounds were assessed for cytotoxicity on both the bloodstream form of T. b. brucei parasites and a mammalian cell line. The compounds were then investigated for their modulatory effect on the aggregation suppression and ATPase activities of the TbHsp70 proteins. A structure-activity relationship for the malonganenone-class of alkaloids is proposed based upon these results.

Host Immune Responses and Immune Evasion Strategies in African Trypanosomiasis

Parasites, including African trypanosomes, utilize several immune evasion strategies to ensure their survival and completion of their life cycles within their hosts. The defense factors activated by the host to resolve inflammation and restore homeostasis during active infection could be exploited and/or manipulated by the parasites in an attempt to ensure their survival and propagation. This often results in the parasites evading the host immune responses as well as the host sustaining some self-inflicted collateral tissue damage. During infection with African trypanosomes, both effector and suppressor cells are activated and the balance between these opposing arms of immunity determines susceptibility or resistance of infected host to the parasites. Immune evasion by the parasites could be directly related to parasite factors, (e.g., antigenic variation), or indirectly through the induction of suppressor cells following infection. Several cell types, including suppressive macrophages, myeloid-derived suppressor cells (MDSCs), and regulatory T cells have been shown to contribute to immunosuppression in African trypanosomiasis. In this review, we discuss the key factors that contribute to immunity and immunosuppression during T. congolense infection, and how these factors could aid immune evasion by African trypanosomes. Understanding the regulatory mechanisms that influence resistance and/or susceptibility during African trypanosomiasis could be beneficial in designing effective vaccination and therapeutic strategies against the disease.

Catalase compromises the development of the insect and mammalian stages of Trypanosoma brucei

Catalase is a widespread heme-containing enzyme, which converts hydrogen peroxide (H₂ O₂ ) to water and molecular oxygen, thereby protecting cells from the toxic effects of H₂ O₂ . Trypanosoma brucei is an aerobic protist, which conspicuously lacks this potent enzyme, present in virtually all organisms exposed to oxidative stress. To uncover the reasons for its absence in T. brucei, we overexpressed different catalases in procyclic and bloodstream stages of the parasite. The heterologous enzymes originated from the related insect-confined trypanosomatid Crithidia fasciculata and the human. While the trypanosomatid enzyme (cCAT) operates at low temperatures, its human homolog (hCAT) is adapted to the warm-blooded environment. Despite the presence of peroxisomal targeting signal in hCAT, both human and C. fasciculata catalases localized to the cytosol of T. brucei. Even though cCAT was efficiently expressed in both life cycle stages, the enzyme was active in the procyclic stage, increasing cell's resistance to the H₂ O₂ stress, yet its activity was suppressed in the cultured bloodstream stage. Surprisingly, following the expression of hCAT, the ability to establish the T. brucei infection in the tsetse fly midgut was compromised. In the mouse model, hCAT attenuated parasitemia and, consequently, increased the host's survival. Hence, we suggest that the activity of catalase in T. brucei is beneficial in vitro, yet it becomes detrimental for parasite's proliferation in both invertebrate and vertebrate hosts, leading to an inability to carry this, otherwise omnipresent, enzyme.

The Trypanosomal Transferrin Receptor of Trypanosoma Brucei-A Review

Iron is an essential element for life. Its uptake and utility requires a careful balancing with its toxic capacity, with mammals evolving a safe and bio-viable means of its transport and storage. This transport and storage is also utilized as part of the iron-sequestration arsenal employed by the mammalian hosts’ ‘nutritional immunity’ against parasites. Interestingly, a key element of iron transport, i.e., serum transferrin (Tf), is an essential growth factor for parasitic haemo-protozoans of the genus Trypanosoma. These are major mammalian parasites causing the diseases human African trypanosomosis (HAT) and animal trypanosomosis (AT). Using components of their well-characterized immune evasion system, bloodstream Trypanosoma brucei parasites adapt and scavenge for the mammalian host serum transferrin within their broad host range. The expression site associated genes (ESAG6 and 7) are utilized to construct a heterodimeric serum Tf binding complex which, within its niche in the flagellar pocket, and coupled to the trypanosomes’ fast endocytic rate, allows receptor-mediated acquisition of essential iron from their environment. This review summarizes current knowledge of the trypanosomal transferrin receptor (TfR), with emphasis on the structure and function of the receptor, both in physiological conditions as well as in conditions where the iron supply to parasites is being limited. Potential applications using current knowledge of the parasite receptor are also briefly discussed, primarily focused on potential therapeutic interventions.

NK Cells Are Critical for Optimal Immunity to Experimental Trypanosoma congolense Infection

NK cells are key innate immune cells that play critical roles in host defense. Although NK cells have been shown to regulate immunity to some infectious diseases, their role in immunity to Trypanosoma congolense has not been investigated. NK cells are vital sources of IFN-γ and TNF-α; two key cytokines that are known to play important roles in resistance to African trypanosomes. In this article, we show that infection with T. congolense leads to increased levels of activated and functional NK cells in multiple tissue compartments. Systemic depletion of NK cells with anti-NK1.1 mAb led to increased parasitemia, which was accompanied by significant reduction in IFN-γ production by immune cells in the spleens and liver of infected mice. Strikingly, infected NFIL3^-/- mice (which genetically lack NK cell development and function) on the normally resistant background were highly susceptible to T. congolense infection. These mice developed fulminating and uncontrolled parasitemia and died significantly earlier (13 ± 1 d) than their wild-type control mice (106 ± 26 d). The enhanced susceptibility of NFIL3^-/- mice to infection was accompanied by significantly impaired cytokine (IFN-γ and TNF-α) response by CD3⁺ T cells in the spleens and liver. Adoptive transfer of NK cells into NFIL3^-/- mice before infection rescued them from acute death in a perforin-dependent manner. Collectively, these studies show that NK cells are critical for optimal resistance to T. congolense, and its deficiency leads to enhanced susceptibility in infected mice.

Trypanosoma brucei Interaction with Host: Mechanism of VSG Release as Target for Drug Discovery for African Trypanosomiasis

The protozoan Trypanosoma brucei, responsible for animal and human trypanosomiasis, has a family of major surface proteases (MSPs) and phospholipase-C (PLC), both involved in some mechanisms of virulence during mammalian infections. During parasitism in the mammalian host, this protozoan is exclusively extracellular and presents a robust mechanism of antigenic variation that allows the persistence of infection. There has been incredible progress in our understanding of how variable surface glycoproteins (VSGs) are organised and expressed, and how expression is switched, particularly through recombination. The objective of this manuscript is to create a reflection about the mechanisms of antigenic variation in T. brucei, more specifically, in the process of variable surface glycoprotein (VSG) release. We firstly explore the mechanism of VSG release as a potential pathway and target for the development of anti-T. brucei drugs.

Metarhizium anisopliae infection reduces Trypanosoma congolense reproduction in Glossina fuscipes fuscipes and its ability to acquire or transmit the parasite

Background

Tsetse fly-borne trypanosomiasis remains a significant problem in Africa despite years of interventions and research. The need for new strategies to control and possibly eliminate trypanosomiasis cannot be over-emphasized. Entomopathogenic fungi (EPF) infect their hosts through the cuticle and proliferate within the body of the host causing death in about 3–14 days depending on the concentration. During the infection process, EPF can reduce blood feeding abilities in hematophagous arthropods such as mosquitoes, tsetse flies and ticks, which may subsequently impact the development and transmission of parasites. Here, we report on the effects of infection of tsetse fly (Glossina fuscipes fuscipes) by the EPF, Metarhizium anisopliae ICIPE 30 wild-type strain (WT) and green fluorescent protein-transformed strain (GZP-1) on the ability of the flies to harbor and transmit the parasite, Trypanosoma congolense.

Results

Teneral flies were fed T. congolense-infected blood for 2 h and then infected using velvet carpet fabric impregnated with conidia covered inside a cylindrical plastic tube for 12 h. Control flies were fed with T. congolense-infected blood but not exposed to the fungal treatment via the carpet fabric inside a cylindrical plastic tube. Insects were dissected at 2, 3, 5 and 7 days post-fungal exposure and the density of parasites quantified. Parasite load decreased from 8.7 × 10⁷ at day 2 to between 8.3 × 10⁴ and 1.3 × 10⁵ T. congolense ml^− 1 at day 3 post-fungal exposure in fungus-treated (WT and GZP-1) fly groups. When T. congolense-infected flies were exposed to either fungal strain, they did not transmit the parasite to mice whereas control treatment flies remained capable of parasite transmission. Furthermore, M. anisopliae-inoculated flies which fed on T. congolense-infected mice were not able to acquire the parasites at 4 days post-fungal exposure while parasite acquisition was observed in the control treatment during the same period.

Conclusions

Infection of the vector G. f. fuscipes by the entomopathogenic fungus M. anisopliae negatively affected the multiplication of the parasite T. congolense in the fly and reduced the vectorial capacity to acquire or transmit the parasite.

Proteome characterization in various biological fluids of Trypanosoma brucei gambiense-infected subjects

Human African trypanosomiasis (HAT) is a neglected tropical disease that is endemic in sub-Saharan Africa. Control of the disease has been recently improved by better screening and treatment strategies, and the disease is on the WHO list of possible elimination. However, some physiopathological aspects of the disease transmission and progression remain unclear. We propose a new proteomic approach to identify new targets and thus possible new biomarkers of the disease. We also focused our attention on fluids classically associated with HAT (serum and cerebrospinal fluid (CSF)) and on the more easily accessible biological fluids urine and saliva. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) established the proteomic profile of patients with early and late stage disease. The serum, CSF, urine and saliva of 3 uninfected controls, 3 early stage patients and 4 late stage patients were analyzed. Among proteins identified, in CSF, urine and saliva, respectively, 37, 8 and 24 proteins were differentially expressed and showed particular interest with regards to their function. The most promising proteins (Neogenin, Neuroserpin, secretogranin 2 in CSF; moesin in urine and intelectin 2 in saliva) were quantified by enzyme-linked immunosorbent assay in a confirmatory cohort of 14 uninfected controls, 23 patients with early stage disease and 43 patients with late stage disease. The potential of two proteins, neuroserpin and moesin, with the latter present in urine, were further characterized. Our results showed the potential of proteomic analysis to discover new biomarkers and provide the basis of the establishment of a new proteomic catalogue applied to HAT-infected subjects and controls. SIGNIFICANCE: Sleeping sickness, also called Human African Trypanosomiasis (HAT), is a parasitic infection caused by a parasitic protozoan, Trypanosoma brucei gambiense or T. b. rhodesiense which are transmitted via an infected tsetse fly: Glossina. For both, the haemolymphatic stage (or first stage) signs and symptoms are intermittent fever, lymphadenopathy, hepatosplenomegaly, headaches, pruritus, and for T. b. rhodesiense infection a chancre is often formed at the bite site. Meningoencephalitic stage (or second stage) occurs when parasites invade the CNS, it is characterised by neurological signs and symptoms such as altered gait, tremors, neuropathy, somnolence which can lead to coma and death if untreated. first stage of the disease is characterizing by fevers, headaches, itchiness, and joint pains and progressive lethargy corresponding to the second stage with confusion, poor coordination, numbness and trouble sleeping. Actually, diagnosing HAT requires specialized expertise and significant resources such as well-equipped health centers and qualified staff. Such resources are lacking in many endemic areas that are often in rural locales, so many individuals with HAT die before the diagnosis is established. In this study, we analysed by mass spectrometry the entire proteome of serum, CSF, urine and saliva samples from infected and non-infected Angolan individuals to define new biomarkers of the disease. This work of proteomics analysis is a preliminary stage to the characterization of the whole proteome, of these 4 biological fluids, of HAT patients. We have identified 69 new biomarkers. Five of them have been thoroughly investigated by ELISA quantification. Neuroserpine and Moesin are respectively promising new biomarkers in CSF and urine's patient for a better diagnosis.

Comparative experimental studies on Trypanosoma isolates in mice and response to diminazene aceturate and isometamidium chloride treatment

The current study was undertaken from December 2015 to May 2016 with the aim of determining and comparing the pathogenicity and response to diminazene aceturate (DA) and isometamidium chloride (ISM) treatment in experimentally infected mice with trypanosome isolates from Jawi and Birsheleko areas of northwest Ethiopia. A total of 42 mice were used for the experiment. These mice were randomly assigned in to 7 groups of 6 mice per group. Three of the groups (Group 1, 4 and 5) were inoculated with trypanosome isolated from Jawi and three other groups (Group-2, 6 and 7) were inoculated with trypanosome isolated from Birsheleko and the remaining one group (Group 3) was negative control. Each experimental mice were received 0.3 ml of positive blood at the 10⁵ parasites/ml from donor animals intraperitoneally while negative control group were received 0.3 ml sterile water. The mice were clinically observed daily during the study period. Parameters including level of parasitaemia, body weight, PCV and hemoglobin value were recorded once per week for ten consecutive weeks post infection. Trypanocidal treatment was given on day 21 post infection when peak parasitaemia was detected in groups (Group 4-DA-Jawi, 5-ISM-Jawi, 6-DA-BRSH and 7-ISM-BRSH). The treatment doses for DA was at 28 mg/kg and for ISM at 4 mg/kg. In all experimental groups during study period when the mice showed severe clinical signs and at the end of the experiment they were euthanized with 70% ethanol for gross and histopathological examinations. The parameters measured during the study period revealed markers leading to pathological changes in all infected groups. Parasitaemia were detected early in the Jawi isolate infected groups compared to the Birsheleko groups. All infected mice showed clear clinical manifestation of depression, weight loss, reduction in feed intake and huddled together in the corner of the cage. Significant (P < 0.05) reduction was observed in the mean PCV and hemoglobin value of s infected mice compared to the negative control. The mean PCV values of Birsheleko isolate infected group was significantly (P < 0.05) lower than Jawi isolate infected group. This study showed that treatment with either DA or ISM were unable to clear parasitaemia indicating the presence of drug resistance problems for both isolates. Relative improvement in clinical and pathological changes was observed as compared with untreated infected groups. Gross and histopathological lesions were observed in infected groups. In conclusion, the current study suggests the presence of strain difference in virulence between isolates and the drugs unable to cure infections indicating the presence of resistance problems necessitate further molecular characterization of the strains and drug resistance detection in the natural host.

Serum biochemical parameters and cytokine profiles associated with natural African trypanosome infections in cattle

Background

Animal African trypanosomiasis (AAT) greatly affects livestock production in sub-Saharan Africa. In Ghana prevalence of AAT is estimated to range between 5 and 50%. Studies have reported serum biochemical aberrations and variability in cytokine profiles in animals during infection. However, information regarding the biochemical parameters and cytokine profiles associated with natural infections are limited. This study was therefore aimed at investigating changes in the levels of serum biochemical parameters and inflammatory cytokines during a natural infection.

Methods

Nested internal transcribed spacer (ITS)-based PCR and sequencing were used to characterise trypanosome infection in cattle at two areas in Ghana (Adidome and Accra) of different endemicities. The cattle were sampled at four to five-week intervals over a period of six months. Levels of serum biochemical parameters, including creatinine, cholesterol, alkaline phosphatase (ALP), alanine aminotransferase (ALT), total bilirubin and total protein and cytokines (interleukin 10, interleukin 4, interleukin 12, interferon gamma and tumor necrosis factor alpha) were measured in serum samples and then compared between infected cattle and uninfected controls.

Results

The predominant trypanosome species detected in Accra (non-endemic) and Adidome (endemic) were Trypanosoma theileri and Trypanosoma vivax, respectively. Serum biochemical parameters were similar between infected and uninfected cattle in Accra. Infected cattle at Adidome however, had significantly higher levels of ALP, creatinine, total protein and total bilirubin (P < 0.05) and significantly lower levels of cholesterol (P < 0.05) at specific time points. At basal levels and during infection, significantly higher pro-inflammatory to anti-inflammatory (Th1/Th2) cytokine ratios were observed in cattle at Adidome compared to Accra (P < 0.05), indicating a shift towards Th1 immune response in Adidome. Levels of IL-10 were, however, significantly elevated in infected cattle in Accra (P < 0.05), suggesting high anti-inflammatory cytokine response in Accra.

Conclusion

These results suggests that cattle in an endemic area repeatedly infected with trypanosomes of different species or different antigenic types demonstrate high pro-inflammatory (Th1) immune response and biochemical alterations whereas cattle in a non-endemic area with predominantly chronic T. theileri infections demonstrate high anti-inflammatory response and no biochemical alterations.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2255-9) contains supplementary material, which is available to authorized users.

Camelid Single-Domain Antibodies As an Alternative to Overcome Challenges Related to the Prevention, Detection, and Control of Neglected Tropical Diseases

Due mainly to properties such as high affinity and antigen specificity, antibodies have become important tools for biomedical research, diagnosis, and treatment of several human diseases. When the objective is to administer them for therapy, strategies are used to reduce the heterologous protein immunogenicity and to improve pharmacokinetic and pharmacodynamic characteristics. Size minimization contributes to ameliorate these characteristics, while preserving the antigen-antibody interaction site. Since the discovery that camelids produce functional antibodies devoid of light chains, studies have proposed the use of single domains for biosensors, monitoring and treatment of tumors, therapies for inflammatory and neurodegenerative diseases, drug delivery, or passive immunotherapy. Despite an expected increase in antibody and related products in the pharmaceutical market over the next years, few research initiatives are related to the development of alternatives for helping to manage neglected tropical diseases (NTDs). In this review, we summarize developments of camelid single-domain antibodies (VHH) in the field of NTDs. Particular attention is given to VHH-derived products, i.e., VHHs fused to nanoparticles, constructed for the development of rapid diagnostic kits; fused to oligomeric matrix proteins for viral neutralization; and conjugated with proteins for the treatment of human parasites. Moreover, paratransgenesis technology using VHHs is an interesting approach to control parasite development in vectors. With enormous biotechnological versatility, facility and low cost for heterologous production, and greater ability to recognize different epitopes, VHHs have appeared as an opportunity to overcome challenges related to the prevention, detection, and control of human diseases, especially NTDs.

Cattle genome-wide analysis reveals genetic signatures in trypanotolerant N'Dama

BACKGROUND

Indigenous cattle in Africa have adapted to various local environments to acquire superior phenotypes that enhance their survival under harsh conditions. While many studies investigated the adaptation of overall African cattle, genetic characteristics of each breed have been poorly studied.

RESULTS

We performed the comparative genome-wide analysis to assess evidence for subspeciation within species at the genetic level in trypanotolerant N'Dama cattle. We analysed genetic variation patterns in N'Dama from the genomes of 101 cattle breeds including 48 samples of five indigenous African cattle breeds and 53 samples of various commercial breeds. Analysis of SNP variances between cattle breeds using wMI, XP-CLR, and XP-EHH detected genes containing N'Dama-specific genetic variants and their potential associations. Functional annotation analysis revealed that these genes are associated with ossification, neurological and immune system. Particularly, the genes involved in bone formation indicate that local adaptation of N'Dama may engage in skeletal growth as well as immune systems.

CONCLUSIONS

Our results imply that N'Dama might have acquired distinct genotypes associated with growth and regulation of regional diseases including trypanosomiasis. Moreover, this study offers significant insights into identifying genetic signatures for natural and artificial selection of diverse African cattle breeds.

The genome landscape of indigenous African cattle

BACKGROUND

The history of African indigenous cattle and their adaptation to environmental and human selection pressure is at the root of their remarkable diversity. Characterization of this diversity is an essential step towards understanding the genomic basis of productivity and adaptation to survival under African farming systems.

RESULTS

We analyze patterns of African cattle genetic variation by sequencing 48 genomes from five indigenous populations and comparing them to the genomes of 53 commercial taurine breeds. We find the highest genetic diversity among African zebu and sanga cattle. Our search for genomic regions under selection reveals signatures of selection for environmental adaptive traits. In particular, we identify signatures of selection including genes and/or pathways controlling anemia and feeding behavior in the trypanotolerant N'Dama, coat color and horn development in Ankole, and heat tolerance and tick resistance across African cattle especially in zebu breeds.

CONCLUSIONS

Our findings unravel at the genome-wide level, the unique adaptive diversity of African cattle while emphasizing the opportunities for sustainable improvement of livestock productivity on the continent.

Combined antiparasitic and anti-inflammatory effects of the natural polyphenol curcumin on turbot scuticociliatosis

The histiophagous scuticociliate Philasterides dicentrarchi is the aetiological agent of scuticociliatosis, a parasitic disease of farmed turbot. Curcumin, a polyphenol from Curcuma longa (turmeric), is known to have antioxidant and anti-inflammatory properties. We investigated the in vitro effects of curcumin on the growth of P. dicentrarchi and on the production of pro-inflammatory cytokines in turbot leucocytes activated by parasite cysteine proteases. At 100 μm, curcumin had a cytotoxic effect and completely inhibited the growth of the parasite. At 50 μm, curcumin inhibited the protease activity of the parasite and expression of genes encoding two virulence-associated proteases: leishmanolysin-like peptidase and cathepsin L-like. At concentrations between 25 and 50 μm, curcumin inhibited the expression of S-adenosyl-L-homocysteine hydrolase, an enzyme involved in the biosynthesis of the amino acids methionine and cysteine. At 100 μm, curcumin inhibited the expression of the cytokines tumour necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) produced in turbot leucocytes activated by parasite proteases. Results show that curcumin has a dual effect on scuticociliatosis: an antiparasitic effect on the catabolism and anabolism of ciliate proteins, and an anti-inflammatory effect that inhibits the production of proinflammatory cytokines in the host. The present findings suggest the potential usefulness of this polyphenol in treating scuticociliatosis.

Overview of the Diagnostic Methods Used in the Field for Human African Trypanosomiasis: What Could Change in the Next Years?

Sleeping sickness is a parasitic infection caused by two species of trypanosomes (Trypanosoma brucei gambiense and rhodesiense), transmitted by the tsetse fly. The disease eventually affects the central nervous system, resulting in severe neurological symptoms. Without treatment, death is inevitable. During the first stage of the disease, infected patients are mildly symptomatic and early detection of infection allows safer treatment (administered on an outpatient basis) which can avoid death; routine screening of the exposed population is necessary, especially in areas of high endemicity. The current therapeutic treatment of this disease, especially in stage 2, can cause complications and requires a clinical surveillance for several days. A good stage diagnosis of the disease is the cornerstone for delivering the adequate treatment. The task faced by the medical personnel is further complicated by the lack of support from local health infrastructure, which is at best weak, but often nonexistent. Therefore it is crucial to look for new more efficient technics for the diagnosis of stage which are also best suited to use in the field, in areas not possessing high-level health facilities. This review, after an overview of the disease, summarizes the current diagnosis procedures and presents the advances in the field.

CpG-ODN Class C Mediated Immunostimulation in Rabbit Model of Trypanosoma evansi Infection

CpG oligodeoxynucleotides (CpG-ODN) stimulate immune cells from a wide spectrum of mammalian species. Class C CpG-ODN is relatively stable and has the combined immune effects of both A and B classes of CpG-ODN. Trypanosoma evansi produces the state of immuno-suppression in the infected hosts. The current chemotherapeutic agents against this parasite are limited in number and usually associated with severe side effects. The present work aimed to determine the immunostimulatory effects of CpG-ODN class C in T. evansi infected rabbits. Rabbits inoculated with CpG C and challenged with T. evansi resulted in delayed onset of clinical signs with reduced severity in comparison to that of T. evansi infected rabbits. The treatment also enhanced humoral immune responses. Histopathological findings in liver and spleen revealed enhancement of mononuclear cell infiltration and secondary B cell follicles. These results demonstrate that CpG-ODN class C, has immunostimulatory properties in rabbit model of trypanosomosis. The use of booster doses or sustained delivery of CpG-ODN will further elucidate the prolonged CpG-ODN generated immune responses.

Escape mechanisms of African trypanosomes: why trypanosomosis is keeping us awake

African trypanosomes have been around for more than 100 million years, and have adapted to survival in a very wide host range. While various indigenous African mammalian host species display a tolerant phenotype towards this parasitic infection, and hence serve as perpetual reservoirs, many commercially important livestock species are highly disease susceptible. When considering humans, they too display a highly sensitive disease progression phenotype for infections with Trypanosoma brucei rhodesiense or Trypanosoma brucei gambiense, while being intrinsically resistant to infections with other trypanosome species. As extracellular trypanosomes proliferate and live freely in the bloodstream and lymphatics, they are constantly exposed to the immune system. Due to co-evolution, this environment however no longer poses a hostile threat, but has become the niche environment where trypanosomes thrive and obligatory await transmission through the bites of tsetse flies or other haematophagic vectors, ideally without causing severe side infection-associated pathology to their host. Hence, African trypanosomes have acquired various mechanisms to manipulate and control the host immune response, evading effective elimination. Despite the extensive research into trypanosomosis over the past 40 years, many aspects of the anti-parasite immune response remain to be solved and no vaccine is currently available. Here we review the recent work on the different escape mechanisms employed by African Trypanosomes to ensure infection chronicity and transmission potential.

Trypanosomosis, Its Risk Factors, and Anaemia in Cattle Population of Dale Wabera District of Kellem Wollega Zone, Western Ethiopia

Cross-sectional study was conducted in Dale Wabera district of Kellem Wollega zone, Western Ethiopia, to determine the prevalence of bovine trypanosomosis and to evaluate association of bovine trypanosomosis to anaemia. Blood samples collected from 384 randomly selected cattle were subjected to parasitological and haematological analysis. For the parasitological survey, blood samples were examined using a buffy coat technique. The packed cell volume (PCV) value of each animal was also measured using hematocrit reader. The overall prevalence of trypanosomosis was 2.86%. The most common trypanosome species identified were Trypanosoma congolense (63.64%) followed by T. vivax (27.27%) and T. brucei (9%). The prevalence showed no significant difference in susceptibility between sex categories, age groups, and different body conditioned animals. The overall anaemia prevalence in the area was 19.27%. The anaemia prevalence was significantly higher in trypanosome positive cattle (54.54%) than in noninfected animals (18.23%) (P < 0.05). The mean PCV value of the infected animals was lower (22.36% ± 7.39%) compared to noninfected animals (27.86 ± 5.38%). There was statistically significant difference (P < 0.05) in the PCV values of infected and noninfected animals. In conclusion, this study confirmed that trypanosomosis poses a threat to cattle production in the area and also contributed to the occurrence of anaemia.

CpG-ODN class C-mediated immunostimulation and its potential against Trypanosoma evansi in equines

Trypanosoma evansi is the causative agent of surra, which is the most common and widespread trypansomal disease. The infection is mainly restricted to animals, but it has also been documented in human. Trypanosomes possess the thick immunogenic surface coat known as variant surface glycoprotein (VSG). The parasite modifies the VSG constantly resulting in continuous antigenic variations and thus evades the host immune response. Due to antigenic variations, vaccination against trypanosomosis is not useful. Therefore, alternate strategies to augment the immune response are required. CpG-ODN class-C has combined immune effects of both A and B classes of CpG-ODN. In this study, we observed that CpG-ODN class-C stimulated horse peripheral blood mononuclear cells (PBMC) induce the expression of interferon-α (IFN-α), tumor necrosis factor-α (TNF-α), IL-12 and nitric oxide (NO) indicating enhanced innate immune response. We have for the first time demonstrated that co-culture of CpG-ODN with T. evansi antigen induces lymphocyte proliferative responses and result in a synergistic effect in eliciting the immune response.

Insect stage-specific receptor adenylate cyclases are localized to distinct subdomains of the Trypanosoma brucei Flagellar membrane

Increasing evidence indicates that the Trypanosoma brucei flagellum (synonymous with cilium) plays important roles in host-parasite interactions. Several studies have identified virulence factors and signaling proteins in the flagellar membrane of bloodstream-stage T. brucei, but less is known about flagellar membrane proteins in procyclic, insect-stage parasites. Here we report on the identification of several receptor-type flagellar adenylate cyclases (ACs) that are specifically upregulated in procyclic T. brucei parasites. Identification of insect stage-specific ACs is novel, as previously studied ACs were constitutively expressed or confined to bloodstream-stage parasites. We show that procyclic stage-specific ACs are glycosylated, surface-exposed proteins that dimerize and possess catalytic activity. We used gene-specific tags to examine the distribution of individual AC isoforms. All ACs examined localized to the flagellum. Notably, however, while some ACs were distributed along the length of the flagellum, others specifically localized to the flagellum tip. These are the first transmembrane domain proteins to be localized specifically at the flagellum tip in T. brucei, emphasizing that the flagellum membrane is organized into specific subdomains. Deletion analysis reveals that C-terminal sequences are critical for targeting ACs to the flagellum, and sequence comparisons suggest that differential subflagellar localization might be specified by isoform-specific C termini. Our combined results suggest insect stage-specific roles for a subset of flagellar adenylate cyclases and support a microdomain model for flagellar cyclic AMP (cAMP) signaling in T. brucei. In this model, cAMP production is compartmentalized through differential localization of individual ACs, thereby allowing diverse cellular responses to be controlled by a common signaling molecule.

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.

Anti-trypanosomal effect of Peristrophe bicalyculata extract on Trypanosoma brucei brucei-infected rats

OBJECTIVE

To investigate the in vitro and in vivo effect of whole plant extracts of Peristrophe bicalyculata on Trypanosoma brucei brucei-infected rats.

METHODS

THE EXPERIMENT WAS DIVIDED INTO TWO PHASES: In the first phase, the anti-trypanosomal activity of the hot water, cold water, methanol and butanol extracts of the whole plant were determined by incubating with Trypanosoma brucei brucei. The cold water extract was partially-purified and the anti-trypanosomal activity of the fractions determined. In the second phase, Trypanosoma brucei brucei-infected rats were treated with fraction 2c for nine days. Packed cell volume (PCV), high density lipoprotein (HDL), low density lipoprotein (LDL), total cholesterol (TC), triacylglycerol (TAG), aspartate aminotransferase, alanine aminotransferases (ALT), alkaline phosphatase (ALP), total and direct bilirubin levels were determined at the end of the experiment.

RESULTS

Cold water extract immobilized 90% of the parasites after 60 min of incubation, and fraction 2c completely immobilized the parasites after 35 min. It significantly increased PCV in Trypanosoma brucei brucei-infected rats. Decreased TC, TAG, HDL and LDL levels of infected rats increased significantly when rats were treated with the fraction, while elevated levels of total bilirubin and ALT also decreased. The difference in urea, direct bilirubin and ALP was not significant when infected rats were compared to rats in other groups.

CONCLUSIONS

The ability of the plant to ameliorate the infection-induced biochemical changes calls for detailed investigation of the potentials of the plant for antitrypanosomiasis drug delivery.

Stage progression and neurological symptoms in Trypanosoma brucei rhodesiense sleeping sickness: role of the CNS inflammatory response

BACKGROUND

Human African trypanosomiasis progresses from an early (hemolymphatic) stage, through CNS invasion to the late (meningoencephalitic) stage. In experimental infections disease progression is associated with neuroinflammatory responses and neurological symptoms, but this concept requires evaluation in African trypanosomiasis patients, where correct diagnosis of the disease stage is of critical therapeutic importance.

METHODOLOGY/PRINCIPAL FINDINGS

This was a retrospective study on a cohort of 115 T.b.rhodesiense HAT patients recruited in Eastern Uganda. Paired plasma and CSF samples allowed the measurement of peripheral and CNS immunoglobulin and of CSF cytokine synthesis. Cytokine and immunoglobulin expression were evaluated in relation to disease duration, stage progression and neurological symptoms. Neurological symptoms were not related to stage progression (with the exception of moderate coma). Increases in CNS immunoglobulin, IL-10 and TNF-α synthesis were associated with stage progression and were mirrored by a reduction in TGF-β levels in the CSF. There were no significant associations between CNS immunoglobulin and cytokine production and neurological signs of disease with the exception of moderate coma cases. Within the study group we identified diagnostically early stage cases with no CSF pleocytosis but intrathecal immunoglobulin synthesis and diagnostically late stage cases with marginal CSF pleocytosis and no detectable trypanosomes in the CSF.

CONCLUSIONS

Our results demonstrate that there is not a direct linkage between stage progression, neurological signs of infection and neuroinflammatory responses in rhodesiense HAT. Neurological signs are observed in both early and late stages, and while intrathecal immunoglobulin synthesis is associated with neurological signs, these are also observed in cases lacking a CNS inflammatory response. While there is an increase in inflammatory cytokine production with stage progression, this is paralleled by increases in CSF IL-10. As stage diagnostics, the CSF immunoglobulins and cytokines studied do not have sufficient sensitivity to be of clinical value.

Tsetse fly saliva: Could it be useful in fly infection when feeding in chronically aparasitemic mammalian hosts

Sleeping sickness and nagana are two important diseases cuased by African trypanosomes in humans and animals respectively, in tropical african countries. A number of trypanosome species are implicated in these diseases, but it is the Trypanosoma brucei group that is responsible for the chronic form of sleeping sickness. During the course of this chronic infection the parasite shows a clear tropism for organs and tissues and only sporadically appears in the blood stream. Notwithstanding this feature, tsetse flies normally get infected from chronically infected apparasitemic hosts. For some pathogens like the microfilaria, it has already shown that the saliva of the vector, black fly saliva contribute to orient the pathogen to the site of the vector bite. Chemotaxis of tsetse saliva may perhaps stimulate movement of Trypanosoma brucei parasites from tissues to the bloodstream and via the vascular to the tsetse feeding site, and could explain the relatively high infection rate of tsetse flies feeding on chronically infected animals. This review paper looks into the possible role of trypanosome-vector saliva in ensuring parasite acquisition and its application in the tsetse - trypanosome interaction at the host skin interphase.

Three mitochondrial DNA polymerases are essential for kinetoplast DNA replication and survival of bloodstream form Trypanosoma brucei

Trypanosoma brucei, the causative agent of human African trypanosomiasis, has a complex life cycle that includes multiple life cycle stages and metabolic changes as the parasite switches between insect vector and mammalian host. The parasite's single mitochondrion contains a unique catenated mitochondrial DNA network called kinetoplast DNA (kDNA) that is composed of minicircles and maxicircles. Long-standing uncertainty about the requirement of kDNA in bloodstream form (BF) T. brucei has recently eroded, with reports of posttranscriptional editing and subsequent translation of kDNA-encoded transcripts as essential processes for BF parasites. These studies suggest that kDNA and its faithful replication are indispensable for this life cycle stage. Here we demonstrate that three kDNA replication proteins (mitochondrial DNA polymerases IB, IC, and ID) are required for BF parasite viability. Silencing of each polymerase was lethal, resulting in kDNA loss, persistence of prereplication DNA monomers, and collapse of the mitochondrial membrane potential. These data demonstrate that kDNA replication is indeed crucial for BF T. brucei. The contributions of mitochondrial DNA polymerases IB, IC, and ID to BF parasite viability suggest that these and other kDNA replication proteins warrant further investigation as a new class of targets for the development of antitrypanosomal drugs.