Biology subjects

Steketee, P. C.

Publications and source records attributed to Steketee, P. C..

6 recordsLinked to original sources

bioRxiv2026

An improved Trypanosoma vivax genome assembly confirms the distinct organisation of its variant antigen repertoire

Trypanosoma vivax is a unicellular parasite spread by biting flies and an important livestock pathogen across sub-Saharan Africa and South America. Alongside its better known relative, T. brucei, it causes animal trypanosomosis. An accurate genome sequence is essential to functional genetics as well as the design of novel diagnostics, drugs and vaccines. However, the existing T. vivax genome sequence is fragmentary, making it difficult to examine genomic features such as the Variant Surface Glycoprotein (VSG) genes that are the basis for antigenic variation, a key phenotype that underpins immune evasion by African trypanosomes. Our aim was to produce a T. vivax genome sequence with improved contiguity to properly characterise the VSG genes. We present a new core genome assembly in 23 scaffolds, forming approximately 10 chromosomes. Many scaffolds are articulated with extensive sub-telomeric domains that, like T. brucei, contain VSG gene arrays but in T. vivax these are near-perfect repeats of intact genes. Using transcriptomic and proteomic analysis of VSG expression during bloodstream infection we show that the active VSG is expressed from a sub-telomeric array while other arrays are silent. We find no evidence for a VSG expression site at the telomeres or elsewhere. Therefore, although monoallelic expression and antigenic switching occur in T. vivax, the familiar regulatory mechanism of T. brucei does not exist in T. vivax. This improved T. vivax genome assembly demonstrates that T. brucei is a poor guide for T. vivax genetics generally and for regulation of antigenic variation specifically.

genomics↗

bioRxiv2026

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

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.

microbiology↗

bioRxiv2025

Development of long-term oyster tissue cultures reveals cellular plasticity, regenerative potential, and sustained physiological activity

Molluscs are ecologically and economically significant, yet progress in understanding their cellular biology has been constrained by the lack of reliable molluscan cell culture systems. Insights into key molluscan biology such as immunity, biomineralization, and host-pathogen interactions, has previously been limited by short term survival of primary culture systems. Here, we establish reproducible long-term in vitro and ex vivo cultures of cells and tissues from the oyster, Ostrea edulis, including whole heart, visceral mass, mantle, and gill explants. Explanted tissues remained viable for over two months, with whole hearts maintaining rhythmic, stimulus-responsive contractions for up to nine months. Cultures maintained structural and functional features while uncovering cellular plasticity, including haemocyte granule turnover, auricular epithelial remodelling with novel ciliation, and the emergence of de novo multicellular microtissues. Previously under-characterized tissue-specific cell types were maintained in culture, including adipocytes from the visceral mass and myocytes from the mantle, thereby expanding the cellular repertoire accessible in vitro. Mineralized structures were observed across tissue cultures, highlighting the potential of this system for studying biomineralization. By sustaining diverse cell types in vitro, these cultures provide a novel tractable platform for studying molluscan diseases, while also laying the foundation for deeper investigation into comparative invertebrate biology and the development of immortalised molluscan cell lines.

cell biology↗

bioRxiv2025

Trypanosoma brucei cattle infections contain cryptic transmission-adapted bloodstream forms at low parasitaemia

Tsetse-transmitted Trypanosoma parasites infect a wide host range and cause Human African Trypanosomiasis and Animal African Trypanosomosis in sub-Saharan Africa. The primary hosts of Trypanosoma brucei in tsetse fly endemic regions are non-human mammals, including agriculturally important cattle. In rodent infection models, T. brucei transitions from proliferative slender to tsetse-transmissible stumpy forms at high parasitaemia in a density-dependent quorum sensing-type process. However, chronic bovine infections are characterised by markedly lower blood parasitaemia levels; in most cases substantially below the density assumed to trigger slender-to-stumpy differentiation. This challenges the current (rodent-based) assumptions and quantitative parameter estimations around the generation of stumpy forms in the mammalian bloodstream by quorum sensing. By combining scRNA-seq and microscopy in the first molecular characterisation of T. brucei forms in cattle blood, we observed mixed populations of parasites with slender and stumpy-like transcriptomes. The appearance of stumpy-like forms coincided with fewer proliferating parasites and parasites exhibited a shortened flagellum indicative of differentiation, despite the absence of an extreme stumpy morphology or developmental marker protein expression. Comparisons with slender and stumpy form transcriptomes from murine infection and in vitro culture demonstrated conserved transcriptomic signatures for both slender and stumpy-like forms in bovines, as well as host specific differences. These similarities and differences are key to understanding parasite development and transmission in its natural host.

microbiology↗

bioRxiv2024

Cas10 based 7SL-sRNA diagnostic for the detection of active trypanosomiasis

Animal Trypanosomosis (AT) is a significant disease affecting cattle across sub-Saharan Africa, Latin America, and Asia, posing a major threat to economic productivity and animal welfare. The absence of reliable diagnostic tests has led to an over-reliance on widespread pre-emptive drug treatments, which not only compromise animal health but also heighten the risk of drug resistance. The chronic nature of AT, characterized by cyclical low or undetectable parasite levels, and the necessity for field-applicable tests that can distinguish between active infection and prior exposure, present considerable challenges in developing effective diagnostics. In previous work, we identified a parasite-specific small RNA, 7SL-sRNA, which is detectable in the serum of infected cattle, even during the chronic stages of infection. However, existing methods for detecting sRNA require specialized equipment, making them unsuitable for field use. In this study, we have developed a lateral flow diagnostic test utilizing Cas10 technology for the detection of 7SL-sRNA. This assay demonstrates high sensitivity and specificity, effectively identifying active infections in cattle, including during chronic phases (with positive signals observed up to the 63 days post-infection end point). This is the first instance of Cas10 being used for small RNA detection, paving the way for a cost-effective, user-friendly, and field-deployable diagnostic test for AT, while establishing Cas10 technology for the detection of small RNAs in general. Author summaryAnimal Trypanosomosis (AT) is a parasitic disease that affects livestock, causing major economic losses and harm to animal health. Cheap effective diagnostics that can be easily used in the field would have a major impact on the disease burden by enabling better treatment practices. However, parasites causing the disease - trypanosomes - are often undetectable via conventional methods, especially during chronic disease stages. More accurate diagnostics are not suitable for use in the field and are therefore unavailable to farmers. This has led to the overuse of drug treatments that can harm animals and lead to the emergence of drug resistance. We previously discovered a trypanosome-specific small RNA, called 7SL-sRNA, that can be detected in the blood of infected cattle, even during the chronic stages of AT when parasites are not visible via microscopy. However, detecting this RNA has required complex equipment, limiting its use in field settings. Building on this work, we have now developed a field applicable test for trypanosomosis that uses Cas10 technology to detect 7SL-sRNA via a simple lateral flow assay. This test is easy to use and accurately identifies active infections, including during the chronic phase of the disease. This is the first time Cas10 technology has been used to detect small RNAs, offering a promising, cost-effective tool for diagnosing AT and potentially other neglected parasitic diseases.

microbiology↗

bioRxiv2021

Divergent metabolism between Trypanosoma congolense and Trypanosoma brucei results in differential drug sensitivity

Animal African Trypanosomiasis (AAT) is a debilitating livestock disease prevalent across sub-Saharan Africa, a main cause of which is the protozoan parasite Trypanosoma congolense. In comparison to the well-studied T. brucei, there is a major paucity of knowledge regarding the biology of T. congolense. Here, we use a combination of omics technologies and novel genetic tools to characterise core metabolism in T. congolense mammalian-infective bloodstream-form parasites, and test whether metabolic differences compared to T. brucei impact upon drug sensitivity. Like T. brucei, glycolysis plays a major part in T. congolense energy metabolism. However, the rate of glucose uptake is significantly reduced in T. congolense, with cells remaining viable when cultured in concentrations as low as 2 mM. Instead of pyruvate, the primary glycolytic endpoints are succinate, malate and acetate. Comparative transcriptomics analysis showed higher levels of activity associated with the mitochondrial pyruvate dehydrogenase complex, acetate generation and the succinate shunt in T. congolense. However, based on omics analysis and chemical inhibition, there does not appear to be significant levels of oxidative phosphorylation. Stable-isotope labelling of glucose enabled the comparison of carbon usage between T. brucei and T. congolense, highlighting differences in nucleotide and fatty acid metabolism. To validate the metabolic similarities and differences, both species were treated with pharmacological inhibitors, confirming a lack of essential electron transport chain activity in T. congolense, but increased sensitivity to inhibition of mitochondrial pyruvate import. Strikingly, T. congolense exhibited significant resistance to inhibitors of fatty acid synthesis, including a 780-fold greater EC50 against the lipase and fatty acid synthase inhibitor Orlistat, compared to T. brucei. These data highlight that bloodstream form T. congolense diverges from T. brucei in key areas of metabolism, with several features that are intermediate between bloodstream- and insect-stage T. brucei. These results have implications for drug development, mechanisms of drug resistance and host-pathogen interactions.

microbiology↗