Biology subjects

Govender, D.

Publications and source records attributed to Govender, D..

4 recordsLinked to original sources

bioRxiv2026

Slow-growing human cell lines are a suitable alternative to rabbit Sf1Ep cells for in vitro cultivation of Treponema pallidum

Treponema pallidum subsp. pallidum, the causative agent of syphilis, remains difficult to study owing to long-standing limitations in in vitro cultivation. Although a rabbit epithelial cell co-culture system (Sf1Ep) enabled major advances, the absence of human cell-based models limits clinical relevance and mechanistic understanding of host-pathogen interactions. Here, we established a co-culture system using human epithelial cell lines capable of supporting T. pallidum growth in vitro. Six epithelial or epithelial-like cell lines from diverse tissues were evaluated under microaerophilic conditions using standard cultivation medium. CAL-39 (vulva) and HepG2 (liver) supported T. pallidum survival, replication, characteristic growth behaviors, and long-term passage at levels comparable to Sf1Ep cells. Growth kinetics, attachment dynamics, and motility were quantified over extended culture. Using live-cell imaging, we defined two distinct host-cell interaction behaviors: surface-associated crawling and stable single-polar attachment. Both behaviors were observed across all tested cell lines but persisted only in those permissive for sustained growth. Together, our findings establish clinically relevant human epithelial co-culture models for T. pallidum, provide new insights into host-cell-dependent growth and motility, and create a platform for mechanistic studies of syphilis pathogenesis and vaccine target discovery.

microbiology↗

bioRxiv2022

A novel transcriptional signature identifies T-cell infiltration in high-risk paediatric cancer

Molecular profiling of the tumour immune microenvironment (TIME) has enabled the rational choice of immunotherapies in some adult cancers. In contrast, the TIME of paediatric cancers is relatively unexplored. We speculated that a more refined appreciation of the TIME in childhood cancers, rather than a reliance on commonly used biomarkers such as tumour mutation burden (TMB), neoantigen load and PD-L1 expression, is an essential prerequisite for improved immunotherapies in childhood solid cancers. We combined immunohistochemistry (IHC) and molecular profiling to develop an alternative, expression-based signature associated with CD8+ T-cell infiltration of the TIME in high-risk paediatric tumours. Using this novel 15-gene immune signature, Immune Paediatric Signature Score (IPASS), we estimate up to 31% of high-risk cancers harbour infiltrating T-cells. Our data provides new insights into the variable immune-suppressive mechanisms dampening responses in paediatric solid cancers. Effective immune-based interventions in high-risk paediatric cancer will require individualised analysis of the TIME.

cancer biology↗

bioRxiv2020

Environmental DNA for tracking waterhole visitation in savanna ecosystems

Game parks are the last preserve of many large mammals, and in savanna ecosystems, management of surface waters poses a conservation challenge. In arid and semi-arid regions, water can be a scarce resource during dry seasons and drought. Artificial waterholes are common in parks and reserves across Africa, but can alter mammal community composition by favoring drought intolerant species, with consequences for disease dynamics, and population viability of drought-tolerant species. Analysis of waterborne environmental DNA (eDNA) is increasingly used to inform conservation of rare and invasive species, and conduct large-scale biodiversity assessments. To explore the reliability of eDNA as an indicator of mammal waterhole use in savannas, we compare eDNA metabarcoding and camera traps for documenting artificial waterhole use in the Kruger National Park, South Africa, a global hotspot for mammal diversity. We show that eDNA metabarcoding can recover the majority of mammal species detected by camera traps, including a number of endangered species, but DNA signatures of mammal visitation are temporally limited, with best performance when tracking water-dependent large bodied mammals visiting within two days of sampling. Our results highlight limitation of eDNA based monitoring in these systems, including the lack of long-term eDNA persistence in small and highly utilized waterholes, and variability in detection rates among species. However, we demonstrate that eDNA-based approaches can be used to track mammals of conservation concern, and reflect patterns of recent waterhole use and co-occurrence across water-dependent species, both of which are crucial for making evidence-based decisions regarding water management and provisioning.

ecology↗

bioRxiv2019

A comparative assessment of adult mosquito trapping methods to estimate spatial patterns of abundance and community composition in southern Africa

BackgroundAssessing adult mosquito populations is an important component of disease surveillance programs and ecosystem health assessments. Inference from adult trapping datasets involves comparing populations across space and time, but comparisons based on different trapping methods may be biased if traps have different efficiencies or sample different subsets of the mosquito community.\n\nMethodsWe compared four widely-used trapping methods for adult mosquito data collection in Kruger National Park (KNP), South Africa: Centers for Disease Control miniature light trap (CDC), Biogents Sentinel trap (BG), Biogents gravid Aedes trap (GAT) and a net trap. We quantified how trap choice and sampling effort influence inferences on the regional distribution of mosquito abundance, richness and community composition.\n\nResultsThe CDC and net traps together collected 96% (47% and 49% individually) of the 955 female mosquitoes sampled and 100% (85% and 78% individually) of the 40 species or species complexes identified. The CDC and net trap also identified similar regional patterns of community composition. However, inference on the regional patterns of abundance differed between these traps because mosquito abundance in the net trap was influenced by variation in weather conditions. The BG and GAT traps collected significantly fewer mosquitoes, limiting regional comparisons of abundance and community composition.\n\nConclusionsThis study represents the first systematic assessment of trapping methods in natural savanna ecosystems in southern Africa. We recommend the CDC trap or the net trap for future monitoring and surveillance programs.

ecology↗