Biology subjects

Armistead, B.

Publications and source records attributed to Armistead, B..

5 recordsLinked to original sources

bioRxiv2026

A sensitive and specific microchimerism detection method using custom designed genotyping and companion qPCR assays

Since first reports of the presence of a small number of cells from one individual persisting in another, researchers have developed a number of methods to detect microchimerism. Molecular based detection platforms range from gel electrophoresis to quantitative PCR to Next-Gen Sequencing. Central to all approaches is the need for informative polymorphic loci to effectively distinguish microchimeric cells from the host. However, we observed in our studies of maternal microchimerism that currently published approaches can limit the number of samples available for assessment due to the inability to identify an informative marker of the donor in the recipient. This was most striking in our studies of populations of African descent in which the use of HLA-based markers, a common approach, prevented the testing of 30-50% of participants. Other potential options were cost prohibitive or lacked sufficient sensitivity. To address this challenge, we developed a novel, simple, and low-cost approach that leverages global population frequency databases for polymorphism selection, reduces cost by amplifying multiple targets in one multiplex assay to complete genotyping, and has high sensitivity and specificity using rigorously designed qPCR assays to quantify microchimerism. Herein, we outline our design process, detailed assay protocol, and assessment of maternal microchimerism using this approach in two different populations of infants from the United States and South Africa.

molecular biology↗

bioRxiv2026

Prenatal immune priming to Plasmodium falciparum is characterized by multi-lineage T-cell responses that are influenced by maternal microchimerism and predict malaria outcomes

In malaria endemic settings, the fetus may be exposed to Plasmodium falciparum (Pf) antigens leading to prenatal immune primming (PIP). The fetus also acquires a graft of maternal cells in utero, a phenomenon known as maternal microchimerism (MMc). We have previously identified that MMc at birth predicts altered malaria susceptibility in early childhood, and we hypothesized that this association may be mediated via two potential mechanisms. First, the fetus may acquire Pf-specific MMc T-cells that directly respond to postnatal parasitemia. Alternatively, MMc may indirectly influence the quantity or quality of PIP. To investigate this hypothesis, infant cord bloods from 97 Malian primigravidae were screened for MMc using qPCR. A subset of ten cord blood mononuclear cells with variable MMc levels were stimulated with purified Pf merozoite extract and activated T-cells were sorted by flow cytometry for scRNAseq analysis. Transcriptional profile was used to differentiate Pf-responsive versus bystander activated T-cells, and MMc cells were identified using the Cellector algorithm. Among Pf-responsive cells, we identified four key populations: activated CD4 T-cells, ZBTB16+ CD4 T-cells, activated V{delta}1+ {gamma}{delta} T-cells, and cytotoxic V{gamma}9V{delta}2+ {gamma}{delta} T-cells. The minority of sorted cells were of MMc origin; however, there was a strong association between the presence of MMc and the quantity and quality of PIP. MMc+ infants had significantly fewer Pf-responsive T-cells, as well as a shifted distribution of these cells with fewer ZBTB16+ CD4 and cytotoxic V{gamma}9V{delta}2+ {gamma}{delta} T-cells. Clinically, MMc was protective from incident parasitemia and febrile malaria, whereas the frequencies of ZBTB16+ CD4 and activated CD4 T-cells were associated with increased risk. Together, these data demonstrate that MMc influences malaria outcomes through regulation of offspring inflammatory responses to Pf.

immunology↗

bioRxiv2024

Exposure to HIV alters the composition of maternal microchimeric T cells in infants

Infants exposed to HIV but uninfected (iHEU) display altered cellular immunity and are at increased risk of infection through poorly understood mechanisms. We previously reported that iHEU have lower levels of maternal microchimerism (MMc), maternal cells transferred to the offspring in utero/during breastfeeding. We evaluated MMc levels in T cell subsets in iHEU and HIV unexposed infants (iHU) to determine whether a selective deficiency in MMc may contribute to altered cellular immunity. Across all infants, MMc levels were highest in CD8+ T cells; however, the level of MMc in the CD8 T cell subset was significantly lower in iHEU compared to iHU.

immunology↗

bioRxiv2023

A novel non-invasive method to sample immune cells in the lower female genital tract

T cells in the human female genital tract (FGT)2 are key mediators of susceptibility to and protection from infection, including HIV and other sexually transmitted infections. There is a critical need for increased understanding of the distribution and activation of T cell populations in the FGT, but current sampling methods require a healthcare provider and are expensive, limiting the ability to study these populations longitudinally. To address these challenges, we have developed a method to sample immune cells from the FGT utilizing disposable menstrual discs which are non-invasive, self-applied, and low-cost. To demonstrate reproducibility, we sampled the cervicovaginal fluid (CVF)3 of healthy, reproductive-aged individuals using menstrual discs over three sequential days. CVF was processed for cervicovaginal cells, and high parameter flow cytometry was used to characterize immune populations. We identified large numbers of live, CD45+ leukocytes, as well as distinct populations of T cells and B cells. Within the T cell compartment, activation and suppression status of T cell subsets were consistent with previous studies of the FGT utilizing current approaches, including identification of both tissue resident and migratory populations. In addition, the T cell population structure was highly conserved across days within individuals but divergent across individuals. Our approach to sample immune cells in the FGT with menstrual discs will decrease barriers to participation and empower longitudinal sampling in future research studies.

immunology↗

bioRxiv2022

ARID1A maintains transcriptionally repressive H3.3 associated with CHD4-ZMYND8 chromatin interactions

ARID1A is a signature subunit of the mammalian SWI/SNF (BAF) chromatin remodeling complex and is mutated at a high rate in malignancies and benign diseases originating from the uterine endometrium. Through genome-wide analysis of human endometriotic epithelial cells, we show that more than half of ARID1A binding sites are marked by the variant histone H3.3, including active regulatory elements. ARID1A loss leads to H3.3 depletion at ARID1A bound active regulatory elements and a concomitant redistribution of H3.3 towards genic elements. ARID1A interactions with the repressive chromatin remodeler CHD4 (NuRD) are associated with H3.3-containing chromatin regulation. ZMYND8, the CHD4-interacting acetyl-histone H4 reader, specifies ARID1A-CHD4-H3.3 target regulatory activity towards histone H4 lysine 16 acetylation (H4K16ac) to repress super-enhancers. ARID1A, H3.3, CHD4, and ZMYND8 co-repress the expression of genes governing extracellular matrix, motility, adhesion, and epithelial-to-mesenchymal transition. Moreover, these gene expression alterations are observed in human endometriomas. Altogether, these studies demonstrate that cooperation among a histone reader and different types of chromatin remodelers safeguards the endometrium through transcriptionally repressive H3.3.

genetics↗