Developmentally programmed histone H3 expression regulates cellular plasticity at the parental-to-early embryo transition

During metazoan development, the marked change in developmental potential from the parental germline to the embryo raises an important question regarding how the next life cycle is reset. As the basic unit of chromatin, histones are essential for regulating chromatin structure and function and, accordingly, transcription. However, the genome-wide dynamics of the canonical, replication-coupled (RC) histones during gametogenesis and embryogenesis remain unknown. In this study, we use CRISPR-Cas9-mediated gene editing in Caenorhabditis elegans to investigate the expression pattern and role of individual RC histone H3 genes and compare them to the histone variant, H3.3. We report a tightly regulated epigenome landscape change from the germline to embryos that are regulated through differential expression of distinct histone gene clusters. Together, this study reveals that a change from a H3.3- to H3-enriched epigenome during embryogenesis restricts developmental plasticity and uncovers distinct roles for individual H3 genes in regulating germline chromatin.

Prevalence of human filovirus infections in sub-Saharan Africa: A systematic review and meta-analysis protocol

BACKGROUND

Recent outbreaks of Ebola virus disease (EVD) and Marburg virus disease (MVD) in sub-Saharan Africa illustrate the need to better understand animal reservoirs, burden of disease, and human transmission of filoviruses. This protocol outlines a systematic literature review to assess the prevalence of filoviruses that infect humans in sub-Saharan Africa. A secondary aim is to qualitatively describe and evaluate the assays used to assess prevalence.

METHODS

The data sources for this systematic review include PubMed, Embase, and Web of Science. Titles, abstracts, and full texts will be reviewed for inclusion by a primary reviewer and then by a team of secondary reviewers, and data will be extracted using a pre-specified and piloted data extraction form. The review will include human cross-sectional studies, cohort studies, and randomized controlled trials conducted in sub-Saharan Africa up until March 13, 2024 that have been published in peer-reviewed scientific journals, with no language restrictions. Prevalence will be stratified by pathogen, population, assay, and sampling methodology and presented in forest plots with estimated prevalence and 95% confidence intervals. If there are enough studies within a stratum, I2 statistics will be calculated (using R statistical software), and data will be pooled if heterogeneity is low. In addition, assays used to detect infection will be evaluated. All studies included in the review will be assessed for quality and risk of bias using the JBI Prevalence Critical Appraisal Tool and for certainty using the GRADE certainty ratings.

DISCUSSION

Accurately measuring the rate of exposure to filoviruses infecting humans in sub-Saharan Africa using prevalence provides an essential understanding of natural history, transmission, and the role of subclinical infection. This systematic review will identify research gaps and provide directions for future research seeking to improve our understanding of filovirus infections. Understanding the natural history, transmission, and the role of subclinical infection is critical for predicting the impact of an intervention on disease burden.

SYSTEMATIC REVIEW REGISTRATION

In accordance with the guidelines outlined in the PRISMA-P methodology, this protocol was registered with PROSPERO on April 7, 2023 (ID: CRD42023415358).

DNA Methylation-Derived Immune Cell Proportions and Cancer Risk in Black Participants

SIGNIFICANCE

This study describes associations between immune cell types and cancer risk in a Black population; elevated regulatory T-cell proportions that were associated with increased overall cancer and lung cancer risk, and elevated memory B-cell proportions that were associated with increased prostate and all cancer risk.

DNA Methylation-Derived Immune Cell Proportions and Cancer Risk, Including Lung Cancer, in Black Participants

Prior cohort studies assessing cancer risk based on immune cell subtype profiles have predominantly focused on White populations. This limitation obscures vital insights into how cancer risk varies across race. Immune cell subtype proportions were estimated using deconvolution based on leukocyte DNA methylation markers from blood samples collected at baseline on participants without cancer in the Atherosclerosis Risk in Communities (ARIC) Study. Over a mean of 17.5 years of follow-up, 668 incident cancers were diagnosed in 2,467 Black participants. Cox proportional hazards regression was used to examine immune cell subtype proportions and overall cancer incidence and site-specific incidence (lung, breast, and prostate cancers). Higher T regulatory cell proportions were associated with statistically significantly higher lung cancer risk (hazard ratio = 1.22, 95% confidence interval = 1.06-1.41 per percent increase). Increased memory B cell proportions were associated with significantly higher risk of prostate cancer (1.17, 1.04-1.33) and all cancers (1.13, 1.05-1.22). Increased CD8+ naïve cell proportions were associated with significantly lower risk of all cancers in participants ≥55 years (0.91, 0.83-0.98). Other immune cell subtypes did not display statistically significant associations with cancer risk. These results in Black participants align closely with prior findings in largely White populations. Findings from this study could help identify those at high cancer risk and outline risk stratifying to target patients for cancer screening, prevention, and other interventions. Further studies should assess these relationships in other cancer types, better elucidate the interplay of B cells in cancer risk, and identify biomarkers for personalized risk stratification.

Seroprevalence of Antibodies to Filoviruses with Outbreak Potential in Sub-Saharan Africa: A Systematic Review to Inform Vaccine Development and Deployment

Background/Objectives: Orthoebolaviruses and orthomarburgviruses are filoviruses that can cause viral hemorrhagic fever and significant morbidity and mortality in humans. The evaluation and deployment of vaccines to prevent and control Ebola and Marburg outbreaks must be informed by an understanding of the transmission and natural history of the causative infections, but little is known about the burden of asymptomatic infection or undiagnosed disease. This systematic review of the published literature examined the seroprevalence of antibodies to orthoebolaviruses and orthomarburgviruses in sub-Saharan Africa. Methods: The review protocol was registered on PROSPERO (ID: CRD42023415358) and previously published. Eighty-seven articles describing 85 studies were included, of which seventy-six measured antibodies to orthoebolaviruses and forty-one measured antibodies to orthomarburgviruses. Results: The results highlight three central findings that may have implications for vaccine development and deployment. First, substantial antibody seropositivity to Ebola virus (EBOV) and Sudan virus (SUDV) was observed in populations from outbreak-affected areas (≤33% seroprevalence among general populations; ≤41% seroprevalence among healthcare workers and close contacts of disease cases). Second, antibody seropositivity to EBOV, SUDV, and Marburg virus (MARV) was observed among populations from areas without reported outbreaks, with seroprevalence ranging from <1 to 21%. Third, in Central and East Africa, MARV antibody seroprevalence was substantially lower than EBOV or SUDV antibody seroprevalence, even in outbreak-affected areas and in populations at a moderate or high risk of infection (with MARV seroprevalence mostly ranging from 0 to 3%). Conclusions: Whilst gaps remain in our understanding of the significance of antibody seropositivity in some settings and contexts, these findings may be important in considering target indications for novel filovirus vaccines, in defining study designs and strategies for demonstrating vaccine efficacy or effectiveness, and in planning and evaluating vaccine deployment strategies to prevent and control outbreaks.