Comparative lipidomic profiling of the livestock pathogens Trypanosoma congolense and Trypanosoma brucei

Abstract

African Animal Trypanosomosis (AAT) is a disease affecting domestic animals, in particular cattle, in sub-Saharan Africa, resulting in billion-dollar losses annually. New drugs to combat and control AAT are urgently required, yet few treatment candidates are currently on the horizon. This can be attributed, in part, to the relative challenges associated with culturing the clinically relevant parasite species in a laboratory environment. Particularly, effective culture of bloodstream form Trypanosoma congolense, the trypanosome species responsible for a large proportion of AAT disease in cattle, requires the use of goat serum, whilst T. brucei is typically cultured in FBS-supplemented culture. This constrains in vitro studies on biology, especially comparative analyses between AAT-causing species. The differing serum supplementation requirements of these two trypanosome species point to metabolic distinctions, which may be important considerations in developing experimental systems to enable the identification and design of novel, pan-species therapies. In this study, untargeted LC-MS lipidomics analyses were conducted to determine the relative lipidomic profiles of T. congolense and T. brucei bloodstream form parasites. Employing a new media formulation that permits effective in vitro culture of both species, it was possible to establish that their global lipidomic profiles are distinct. Notably, T. congolense exhibits a relatively low abundance of ether phospholipids compared to T. brucei, whilst also possessing an enrichment of long-chain polyunsaturated fatty acids (PUFAs). These observations indicate that there are significant differences in the ways these parasites synthesise and remodel their lipid complement, highlighting an evolutionary divergence between the species that likely carries implications for host-pathogen interactions as well as trypanosome membrane biology. Furthermore, this study demonstrates that fine-tuning fatty acid supplementation may aid in optimising a universal medium suited for multiple species of AAT parasites. SummaryMultiple species of protozoan parasites can cause African Animal Trypanosomosis (AAT) in livestock and other animals. However, AAT research has largely centred on a single species, Trypanosoma brucei, partially due to the comparative difficulties in sustaining the other economically important parasite species - Trypanosoma congolense and Trypanosoma vivax - in laboratory culture. In this work, we aimed to determine whether distinctions in use of lipids between T. brucei and T. congolense explains their differing in vitro culture requirements. Using a newly designed media formulation, it was possible to culture mammalian-infective forms of both parasite species under identical conditions, enabling direct comparison of their lipidome - a complete inventory of the different fats and lipids the cells contain. We demonstrate that the T. congolense lipidome significantly differs from that of T. brucei, and that T. congolense shows a preference for longer, more unsaturated lipids. These differences are likely to underlie species-specific differences observed during host infections. Furthermore, our work demonstrates that understanding the lipid biology of protozoan parasites aids in optimisation of laboratory culturing conditions, thereby facilitating further research into these understudied pathogens, including the development of new therapies.