Development of improved control methods of animal trypanosomiasis: A review

Combatting African Animal Trypanosomiasis (AAT) in livestock: The potential role of trypanotolerance

African Animal Trypanosomiasis (AAT) is endemic in at least 37 of the 54 countries in Africa. It is estimated to cause direct and indirect losses to the livestock production industry in excess of US$ 4.5 billion per annum. A century of intervention has yielded limited success, owing largely to the extraordinary complexity of the host-parasite interaction. Trypanotolerance, which refers to the inherent ability of some African livestock breeds, notably Djallonke sheep, N'Dama cattle and West African Dwarf goats, to withstand a trypanosomiasis challenge and still remain productive without any form of therapy, is an economically sustainable option for combatting this disease. Yet trypanotolerance has not been adequately exploited in the fight against AAT. In this review, we describe new insights into the genetic basis of trypanotolerance and discuss the potential of exploring this phenomenon as an integral part of the solution for AAT, particularly, in the context of African animal production systems.

Generation of monoclonal antibodies to the anti-trypanosomal drug isometamidium

Mice were immunized with either an isometamidium-human serum albumin (HSA) conjugate or an isometamidium-porcine thyroglobulin conjugate (PTG). Thereafter, monoclonal antibodies (MAbs) IL-A 1001, IL-A 1002, IL-A 1003, 5F7.B7, and 5F7.C9 were generated and selected on the basis that they recognized conjugated and unconjugated isometamidium, but lacked cross-reactivity with the carrier molecules. All five MAbs were of the IgG1 isotype. Each of the five MAbs was assessed in a competitive ELISA for isometamidium; in each case, the minimum level of detection was approximately 10 ng/ml. Each MAb exhibited approximately 0.1% cross-reactivity with the anti-trypanosomal compound diminazene. However, based on their cross-reactivity with the anti-trypanosomal compound homidium, the MAbs could be divided into two groups; IL-A 1001, IL-A 1002, and IL-A 1003, produced using an isometamidium-HSA conjugate as an immunogen, exhibited low levels of cross-reactivity (approximately 0.1%). In contrast, 5F7.B7 and 5F7.C9, produced using an isometamidium-PTG conjugate as an immunogen, exhibited high levels of cross-reactivity.

Sequence differences between histones of procyclic Trypanosoma brucei brucei and higher eukaryotes

Four histones, a, b, c, d from procyclic Trypanosoma brucei brucei, which show similarities with the amino acid composition of the core histones H3, H2A, H2B and H4, were isolated and cleaved with Endoproteinase Glu-C. The fragments were separated by FPLC reversed phase chromatography and a subset of the fragments (a5, a9, b6, c8, d3, d9, d11) was subjected to sequence analysis. A 54-71% identity was found in the sequences of the fragment c8 and the C-terminal half of H2B and of three fragments of protein d covering the N-terminal half as well as the C-terminal region of H4. The amino acid sequence of the fragment a9 showed a 57 and 54% identity with H3 sequences of Saccharomyces cerevisiae and Xenopus laevis. Neither the a5 nor the b6 sequence could be aligned with histone sequences of other eukaryotes. The significant differences of 21-48% between the T.b. brucei histone sequences and those of calf thymus histones, which are more pronounced than the differences of Tetrahymena pyriformis and the higher eukaryote, resulted partially from replacements of amino acids with different properties and indicate specific patterns of histone-histone and/or histone-DNA contact sites in the nucleosome of T.b. brucei. These differences, together with the lack of a functional histone H1, may be sufficient to explain the lack of a salt-dependent formation of the nucleosome filament into the 30 nm fibre, which reflects alternative methods of organizing and processing the genetic information in the nucleus of the protozoan parasite and which may be of chemotherapeutic significance.