Biology subjects

LaFleur, B. J.

Publications and source records attributed to LaFleur, B. J..

5 recordsLinked to original sources

bioRxiv2026

Single-Cell Transcriptomic Mapping of PD-L1/TLR4 Remodeling Informs Topical Immunoprevention Timing in Skin Carcinogenesis

Cutaneous squamous cell carcinoma (cSCC) represents a growing public health burden, with incidence projected to increase 23-29% over the coming decade. Topical immunoprevention strategies targeting the PD-L1/PD-1 and TLR4 axes have demonstrated preclinical efficacy, yet optimal intervention timing in humans remains undefined. To address this gap, single-cell RNA sequencing was performed on matched sun-protected (SP), sun-damaged (SD), and actinic keratosis (AK) biopsies from the same individuals, along with independent cSCC cases. Immune checkpoint and innate inflammatory signals were detectable as early as SD skin, prior to histologically confirmed dysplasia. Monotonically increasing expression of CD274 (PD-L1), CTLA4, PDCD1, CD27, and STAT1, alongside progressive TLR4-MYD88 innate immune signaling, was revealed through pseudobulk data analysis, with earliest upregulation at the SD stage. Fuzzy c-means trajectory clustering identified cell-typespecific programs across dendritic cells, macrophages, T cells, fibroblasts, endothelial cells, and keratinocytes. Dendritic cells shifted from early inflammatory antigen-presenting programs toward late PD-L1/IFN-regulatory states; macrophages showed monotonically increasing TLR4-associated myeloid activation; and T cells defined a "hot but exhausted" microenvironment in established cSCC. These findings identify SD and AK as biologically active stages for topical immunoprevention and provide a cellular roadmap for PD-L1/PD-1 and TLR4 blockade strategies.

cancer biology↗

bioRxiv2022

T-cell cellular stress and reticulocyte signatures, but not loss of naive T lymphocytes, characterize severe COVID-19 in older adults

In children and younger adults up to 39 years of age, SARS-CoV-2 usually elicits mild symptoms that resemble the common cold. Disease severity increases with age starting at 30 and reaches astounding mortality rates that are ~330 fold higher in persons above 85 years of age compared to those 18-39 years old. To understand age-specific immune pathobiology of COVID-19 we have analyzed soluble mediators, cellular phenotypes, and transcriptome from over 80 COVID-19 patients of varying ages and disease severity, carefully controlling for age as a variable. We found that reticulocyte numbers and peripheral blood transcriptional signatures robustly correlated with disease severity. By contrast, decreased numbers and proportion of naive T-cells, reported previously as a COVID-19 severity risk factor, were found to be general features of aging and not of COVID-19 severity, as they readily occurred in older participants experiencing only mild or no disease at all. Single-cell transcriptional signatures across age and severity groups showed that severe but not moderate/mild COVID-19 causes cell stress response in different T-cell populations, and some of that stress was unique to old severe participants, suggesting that in severe disease of older adults, these defenders of the organism may be disabled from performing immune protection. These findings shed new light on interactions between age and disease severity in COVID-19.

immunology↗

bioRxiv2022

An early decline in ETPs reflects reduced pre-thymic progenitors and altered signals from the thymus microenvironment

Age-related thymus involution results in decreased T-cell production, contributing to increased susceptibility to pathogens. Elucidating mechanisms underlying involution will inform strategies to restore thymopoiesis. The thymus is colonized by circulating bone marrow (BM)-derived thymus seeding progenitors (TSPs) that differentiate into early T-cell progenitors (ETPs). We find ETP cellularity declines as early as 3 months (3MO) in mice. This initial ETP reduction could reflect changes in pre-thymic progenitors and/or thymic stromal niches. We demonstrate that the number of functional TSP/ETP niches is not reduced with age. Instead, the number of pre-thymic BM and circulating lymphoid progenitors is substantially reduced by 3MO, although their intrinsic ability to seed and differentiate in the thymus is maintained. Additionally, Notch signaling in BM progenitors and ETPs declines by 3MO, indicating defective niche quality contributes to the reduction in ETPs. Together, these findings indicate that diminished BM lymphopoiesis and thymic stromal support contribute to the initial decline in ETPs, setting the stage for progressive thymus involution. Summary statementThe number of early T-cell progenitors declines by 3 months of age in mice. This decline reflects a sharp drop in circulating thymus seeding progenitors, fewer bone marrow lymphoid progenitors, and reduced Notch signaling in both bone marrow and thymus.

immunology↗

bioRxiv2021

Early age-related atrophy of cutaneous lymph nodes precipitates an early functional decline in skin immunity in mice with aging

Secondary lymphoid organs (SLO; including the spleen and lymph nodes) are critical both for the maintenance of naive T (TN) lymphocytes and for the initiation and coordination of immune responses. How they age, including the exact timing, extent, physiological relevance, and the nature of age-related changes, remains incompletely understood. We used time-stamping to indelibly mark cohorts of newly generated naive T cells (a.k.a. recent thymic emigrants - RTE) in mice, and followed their presence, phenotype and retention in SLO. We found that SLO involute asynchronously. Skin-draining lymph nodes (LN) atrophied early (6-9 months) in life and deeper tissue-draining LN and the spleen late (18-20 months), as measured by the loss of both TN numbers and the fibroblastic reticular cell (FRC) network. Time-stamped RTE cohorts of all ages entered SLO and successfully completed post-thymic differentiation. However, in older mice, these cells were poorly retained, and those found in SLO exhibited an emigration phenotype (CCR7loS1P1hi). Transfers of adult RTE into recipients of different ages formally demonstrated that the defect segregates with the age of the SLO microenvironment and not with the age of T cells. Finally, upon intradermal immunization, RTE generated in mice as early as 6-7 months of age barely participated in de novo immune responses and failed to produce well-armed effector cells. These results highlight changes in structure and function of superficial secondary lymphoid organs in laboratory mice that are earlier than expected and are consistent with the long-appreciated and pronounced reduction of cutaneous immunity with aging.

immunology↗

bioRxiv2021

Competent immune responses to SARS-CoV-2 variants in older adults following mRNA vaccination

Aging is associated with a reduced magnitude of primary immune responses to vaccination and constriction of immune receptor repertoire diversity. Clinical trials demonstrated high efficacy of mRNA based SARS-CoV-2 vaccines in older adults but concerns about virus variant escape have not been well addressed. We have conducted an in-depth analysis of humoral and cellular immunity against an early-pandemic viral isolate and compared that to the P.1. (Gamma) and B.1.617.2 (Delta) variants in <50 and >55 age cohorts of mRNA vaccine recipients. We have further measured neutralizing antibody titers for B.1.617.1 (Kappa) and B.1.595; a SARS-CoV-2 isolate bearing Spike mutation E484Q. As reported, robust immunity required the second dose of vaccine. Older vaccinees manifested robust cellular immunity against early-pandemic SARS-CoV-2 and more recent variants, which remained statistically comparable to the adult group. The older cohort had lower neutralizing capacity at the first time point following the second dose, but at later time points immunity was indistinguishable between them. While the duration of these immune responses remains to be determined over longer periods of time, these results provide reasons for optimism regarding vaccine protection of older adults against SARS-CoV-2 variants and inform thinking about boost vaccination with variant vaccines. eTOC summaryVaccine responses are often diminished with aging, but we found strong responses to SARS-CoV-2 in older adults following mRNA vaccination. T cell responses were not diminished when confronted by SARS-CoV-2 variants. Neutralizing Ab were reduced but not more than those in adults. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=73 SRC="FIGDIR/small/453287v2_ufig1.gif" ALT="Figure 1"> View larger version (16K): org.highwire.dtl.DTLVardef@1091655org.highwire.dtl.DTLVardef@1996173org.highwire.dtl.DTLVardef@ccf2f9org.highwire.dtl.DTLVardef@163ed22_HPS_FORMAT_FIGEXP M_FIG C_FIG Created with BioRender.com

immunology↗