Connors, C. T. | bioRxiv Science

bioRxiv2026

Determination of diagnostic cycle threshold (Ct) cut-offs for qPCR-based prevalence surveys of soil-transmitted helminth infections

WHO guidelines for control of soil-transmitted helminths (STH) rely on coproscopic methods to assess population prevalence. In low-prevalence and light-intensity STH settings, quantitative PCR (qPCR) has higher sensitivity and specificity for detection. For qPCR to accurately identify transmissible infections of public health significance, it is essential to interpret the qPCR cycle threshold (Ct) results. As part of the DeWorm3 community-based cluster randomized trial on interrupting STH transmission, we conducted population-based surveys using high-throughput qPCR and aimed to establish appropriate Ct cut-offs to detect transmissible infections. Experimental approaches including egg and genome-equivalent spiking experiments were hindered by inefficient fecal DNA extraction despite optimization efforts. The Ct results for 29,980 samples (pre-intervention, cross-sectional surveys) revealed a bimodal distribution for two of the four species tested, N. americanus and A. lumbricoides. The first peak was assumed to represent transmissible infections, and the second peak to represent indeterminate or non-transmissible infections. Using a finite mixture model, we defined true qPCR positivity as any Ct result with a [≥]5% chance of belonging to the first peak. This approach yielded Ct cut-offs of 34.4398 for N. americanus and 28.57587 for A. lumbricoides. For hookworms, sensitivity of qPCR was 96.7%, compared to 73.2% for Kato-Katz and moderate- to heavy-intensity infections (median Ct: 19.1, interquartile range [IQR]: 17.9-19.8) were differentiated from light-intensity infections and Kato-Katz negative samples (25.3, IQR: 22.5-27.9). Our findings demonstrate the feasibility and utility of evidence-based Ct cut-offs to identify transmissible STH infections in large scale surveys, and to categorize infection intensity as programmatically relevant. Author SummaryQuantitative PCR (qPCR) has been used for the detection of soil-transmitted helminths but with limited emphasis on determining cycle threshold (Ct) cut-offs to accurately identify transmissible infections which are of public health significance. When qPCR is used to assess interventions, or, in the future, to potentially make programmatic decisions, it will be crucial to validate positivity criteria to avoid underestimation (false negatives) or overestimation (false positives) of results. As part of the DeWorm3 trial, a community-based cluster randomized trial on interrupting transmission of STH, we developed and applied a validated STH qPCR to test 29,980 samples collected pre-intervention and explored experimental approaches to establish assay-specific Ct cut-offs. The Ct values from these samples showed a bimodal distribution for N. americanus and A. lumbricoides, suggesting the presence of two distinct groups. For this reason, a statistical approach with a finite mixture model was employed to determine Ct cut-offs that differentiated epidemiologically relevant, transmissible, egg-positive STH infections from those that are likely to represent detection of non-transmissible DNA or indeterminate results. While our data were applied in three different country settings, India, Benin and Malawi, it is important to note that no single Ct cut-off may be applicable across all epidemiological scenarios. Our findings demonstrate the feasibility of developing evidence-based Ct cut-offs with high sensitivity to accurately detect transmissible STH infections in large scale surveys.

microbiology↗

bioRxiv2023

Deoxyhypusine synthase is required for the translational regulation of pancreatic beta cell maturation

As professional secretory cells, beta cells require adaptable mRNA translation to facilitate a rapid synthesis of proteins, including insulin, in response to changing metabolic cues. Specialized mRNA translation programs are essential drivers of cellular development and differentiation. However, in the pancreatic beta cell, the majority of factors identified to promote growth and development function primarily at the level of transcription. Therefore, despite its importance, the regulatory role of mRNA translation in the formation and maintenance of functional beta cells is not well defined. In this study, we have identified a translational regulatory mechanism in the beta cell driven by the specialized mRNA translation factor, eukaryotic initiation factor 5A (eIF5A), which facilitates beta cell maturation. The mRNA translation function of eIF5A is only active when it is post-translationally modified ("hypusinated") by the enzyme deoxyhypusine synthase (DHPS). We have discovered that the absence of beta cell DHPS in mice reduces the synthesis of proteins critical to beta cell identity and function at the stage of beta cell maturation, leading to a rapid and reproducible onset of diabetes. Therefore, our work has revealed a gatekeeper of specialized mRNA translation that permits the beta cell, a metabolically responsive secretory cell, to maintain the integrity of protein synthesis necessary during times of induced or increased demand. ARTICLE HIGHLIGHTSO_LIPancreatic beta cells are professional secretory cells that require adaptable mRNA translation for the rapid, inducible synthesis of proteins, including insulin, in response to changing metabolic cues. Our previous work in the exocrine pancreas showed that development and function of the acinar cells, which are also professional secretory cells, is regulated at the level of mRNA translation by a specialized mRNA translation factor, eIF5AHYP. We hypothesized that this translational regulation, which can be a response to stress such as changes in growth or metabolism, may also occur in beta cells. C_LIO_LIGiven that the mRNA translation function of eIF5A is only active when the factor is post-translationally modified ("hypusinated") by the enzyme deoxyhypusine synthase (DHPS), we asked the question: does DHPS/eIF5AHYP regulate the formation and maintenance of functional beta cells? C_LIO_LIWe discovered that in the absence of beta cell DHPS in mice, eIF5A is not hypusinated (activated), which leads to a reduction in the synthesis of critical beta cell proteins that interrupts pathways critical for identity and function. This translational regulation occurs at weaning age, which is a stage of cellular stress and maturation for the beta cell. Therefore without DHPS/eIF5AHYP, beta cells do not mature and mice progress to hyperglycemia and diabetes. C_LIO_LIOur findings suggest that secretory cells have a mechanism to regulate mRNA translation during times of cellular stress. Our work also implies that driving an increase in mRNA translation in the beta cell might overcome or possibly reverse the beta cell defects that contribute to early dysfunction and the progression to diabetes. C_LI

developmental biology↗