Comparative genomics to uncover the secrets of tsetse and livestock-infective trypanosomes

Resistance to trypanocidal drugs in cattle populations of Zambezia Province, Mozambique

African animal trypanosomosis is a debilitating tsetse-transmitted parasitic disease of sub-Saharan Africa. Therapeutic and prophylactic drugs were introduced more than 50 years ago, and drug resistance is increasingly reported. In a cross-sectional study, 467 cattle were microscopically screened for trypanosomes. Samples were collected in May-July 2014 from five villages (Botao, Mungama, Zalala-Electrosul, Zalala-Madal, and Namitangurine) in Nicoadala district, Zambezia province. To evaluate treatment efficacy, trypanosome-positive animals in each village were randomly assigned to two groups, one treated with 0.5 mg/kg b.w. isometamidium (Inomidium®), the second with 3.5 mg/kg b.w. diminazene (Inomazene®). Cattle were microscopically monitored at days 0, 14, and 28 post-treatment. At day 28, trypanocides were swapped to investigate single or multiple resistance. Microscopically negative samples from the monitoring days were tested using 18S-PCR-RFLP. 22.9% (107/467) was found positive on day 0. On day 14, nine animals in Botao and seven in Mungama were positive. On day 28, in Botao, four animals from the diminazene group and four from the isometamidium group were positive. In Mungama, four animals from the diminazene group were positive on day 28. On day 42, six animals (9%) in Botao and two (9.5%) in Mungama remained positive after drug swap. No relapses occurred in Namitangurine. The 18S-PCR-RFLP consistently detected more positive than microscopy: indeed, positives reached 12, 13, and 8 in Botao and 9, 7, and 4 in Mungama, at days 14, 28, and 42, respectively. Single- and multi-drug resistance in Nicoadala district, Zambezia province, is thus here confirmed. This should be considered when choosing control options.

Proteomic Identification of Immunodiagnostic Antigens for Trypanosoma vivax Infections in Cattle and Generation of a Proof-of-Concept Lateral Flow Test Diagnostic Device

Trypanosoma vivax is one of the causative agents of Animal African Trypanosomosis in cattle, which is endemic in sub-Saharan Africa and transmitted primarily by the bite of the tsetse fly vector. The parasite can also be mechanically transmitted, and this has allowed its spread to South America. Diagnostics are limited for this parasite and in farm settings diagnosis is mainly symptom-based. We set out to identify, using a proteomic approach, candidate diagnostic antigens to develop into an easy to use pen-side lateral flow test device. Two related members the invariant surface glycoprotein family, TvY486_0045500 and TvY486_0019690, were selected. Segments of these antigens, lacking N-terminal signal peptides and C-terminal transmembrane domains, were expressed in E. coli. Both were developed into ELISA tests and one of them, TvY486_0045500, was developed into a lateral flow test prototype. The tests were all evaluated blind with 113 randomised serum samples, taken from 37 calves before and after infection with T. vivax or T. congolense. The TvY486_0045500 and TvY486_0019690 ELISA tests gave identical sensitivity and specificity values for T. vivax infection of 94.5% (95% CI, 86.5% to 98.5%) and 88.0% (95% CI, 75.7% to 95.5%), respectively, and the TvY486_0045500 lateral flow test prototype a sensitivity and specificity of 92.0% (95% CI, 83.4% to 97.0%) and 89.8% (95% CI, 77.8% to 96.6%), respectively. These data suggest that recombinant TvY486_0045500 shows promise for the development of a pen-side lateral flow test for the diagnosis of T. vivax animal African trypanosomosis.

Molecular genomic approaches to infectious diseases in resource-limited settings

Josefina Coloma and Eva Harris discuss advances in genomics in resource-limited settings and argue that access to training and capacity building in bioinformatics and data mining will be crucial for the future

Proline racemases are conserved mitogens: characterization of a Trypanosoma vivax proline racemase

Trypanosoma cruzi proline racemases (TcPRAC) are the only eukaryotic proline racemases described so far. Except their role in the interconversion of free L- and D-proline enantiomers, parasite TcPRACs are involved in major T. cruzi biological pathways. These essential enzymes are implicated in the process of parasite differentiation and the acquisition of virulence during metacyclogenesis and are currently considered as key targets for drug development against Chagas' disease. In this study, we searched for the presence of TcPRAC gene homologues among other trypanosomatid genomes. Despite the high degree of gene synteny observed in Kinetoplastidae genomes, PRAC genes are missing in Trypanosoma brucei, Trypanosoma congolense and Leishmania spp. genomes. Interestingly, we identified a hypothetical PRAC gene in Trypanosoma vivax that is the major hemoparasite responsible for livestock trypanosomiasis, a serious economical impact for most of African and South American countries. We report here that the product of this T. vivax gene is bona fide a proline racemase with an activity comparable to the one we described previously for TcPRAC. Inhibition studies using the pyrrole-2-carboxylic acid confirmed that this compound is a competitive inhibitor for both TcPRAC and TvPRAC enzymes. Similarly to TcPRAC and all members of the racemase family studied so far in other pathogenic and nosocomial bacteria, our results show that TvPRAC is a T-cell-independent B-cell mitogen. Therefore the product of the novel TvPRAC gene identified in T. vivax and reported herein has the potential to be used as a drug target for this parasite-based trypanosomiasis.

Expression of a gene encoding Trypanosoma congolense putative Abc1 family protein is developmentally regulated

During the attempt to seek T. congolense species-specific diagnostic antigens, we discovered one cDNA clone (P74) encoding 74 kDa putative abc1 protein (p74) from T. congolense PCF cDNA library. It has been suggested that members of the abc1 family are novel chaperonins and essential for both the mitochondrial electron transfer in the bc 1 complex and the coenzyme Q biosynthesis. Although abc1 protein in yeast has a nuclear or mitochondrial subcellular location, neither nuclear localization signal nor mitochondrial targeting signal was found within p74. Northern blot analysis revealed that the transcription level of P74 mRNA in bloodstream form (BSF) cells were 4 times higher than that in procyclic form cells. Western blot analysis also indicated that p74 was only expressed in T. congolense BSF cells, and revealed that molecular mass of native p74 was not 74 kDa but 56 kDa. This indicates extensive post-translational modification in p74. Although further characterization of p74 will be required, our findings provide implications for CoQ biosynthesis pathway in T. congolense.

Tropical diseases, pathogens, and vectors biodiversity in developing countries: need for development of genomics and bioinformatics approaches

The world's biodiversity, including many infectious, parasitic disease agents and their vectors whose impact on both human and animal health is significant, is largely retained in the developing countries of the tropics. Owing to the number of species involved and the relatively low-level exploration of pathogens and vectors biodiversity, several organisms are still waiting to be discovered and consequently explored in terms of genomics. Although some parasitic species of humans and animals have been studied through genomics and bioinformatics approaches, a significant number of relevant species are still to be addressed. Through the use of modern technologies, such as genomics and bioinformatics, for assessment of biodiversity and targeting tropical diseases, other relevant advantages of these initiatives for developing countries would be technology transfer and capacity building. Consequently, these initiatives could be critical to the development of the respective countries. Moreover, intra- and interhemispheric scientific collaboration should be encouraged and supported to increase the chances for success. In Brazil, the Ministry of Science and Technology has stepped forward to further such initiatives, co-supporting collaborative genomics and bioinformatics projects. The need for the establishment of working groups on genomics and bioinformatics in developing countries as well as the improvement and strengthening of collaborative research projects between developed and developing countries is discussed from our point of view. As these discussions remain open to debate, we encourage colleagues to promote further discussion on the subject.

Towards a framework for the evolutionary genomics of Kinetoplastids: what kind of data and how much?

The current status of kinetoplastids phylogeny and evolution is discussed in view of the recent progresses on genomics. Some ideas on a potential framework for the evolutionary genomics of kinetoplastids are presented.