Biology subjects

Coplen, C. P.

Publications and source records attributed to Coplen, C. P..

6 recordsLinked to original sources

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↗

bioRxiv2021

LIFELONG CYTOMEGALOVIRUS AND EARLY-LIFE IRRADIATION SYNERGISTICALLY POTENTIATE AGE-RELATED DEFECTS IN RESPONSE TO VACCINATION AND INFECTION

A popular "DNA-damage theory" of aging posits that unrepaired DNA damage leads to cellular (and organismal) senescence. Indeed, some hallmarks of immune aging are more prevalent in individuals exposed to Whole-Body Irradiation (WBI). To test this hypothesis in a model relevant to human immune aging, we examined separate and joint effects of lifelong latent Murine Cytomegalovirus (MCMV) and early-life WBI (i) over the course of the lifespan; (ii) in response to a West Nile virus (WNV) live attenuated vaccine; and (iii) following lethal WNV challenge subsequent to vaccination. We recently published that a single dose of non-lethal WBI in youth, on its own, was not sufficient to accelerate aging of the murine immune system despite causing widespread DNA damage and repopulation stress in hematopoietic cells. However, 4Gy sub-lethal WBI caused manifest reactivation of MCMV. Following vaccination and challenge with WNV in the old age, MCMV-infected animals experiencing 4Gy, but not lower, dose of sub-lethal WBI in youth had reduced survival. By contrast, old irradiated mice lacking MCMV and MCMV-infected, but not irradiated, mice were both protected to the same high level as the old non-irradiated, uninfected controls. Analysis of the quality and quantity of anti-WNV immunity showed that higher mortality in MCMV-positive WBI mice correlated with increased levels of MCMV-specific immune activation during WNV challenge. Moreover, we demonstrate that infection, including that by WNV, led to MCMV reactivation. Our data suggest that MCMV reactivation may be an important determinant of increased late-life mortality following early-life irradiation and late-life acute infection.

immunology↗

bioRxiv2021

The impact of murine cytomegalovirus (mCMV) route and age at infection upon virus spread, immune responses and the establishment of latency

Cytomegalovirus (CMV) is a ubiquitous human virus, which establishes a characteristic lifetime infection in its host. Murine CMV (mCMV) is a widely-used infection model that has been employed to investigate the nature and extent of CMVs contribution to inflammatory, immunological, and health disturbances in humans. In an effort to assess the role of route and age in modeling hCMV infection in mice, we have performed a comparative analysis of two common experimental modes of infection (intraperitoneal and intranasal) at two different clinically relevant ages (4 weeks, or prepubescent childhood equivalent, and 12 weeks, or young postpubescent adult). We found that while both routes of infection led to similar early viral loads, differential activation of several parameters of innate immune function were observed. In particular, younger, prepubescent mice exhibited the strongest NK activation in the blood in response to i.p. infection, with this trend holding true in NK cells expressing the mCMV-specific receptor Ly49H. Moreover, i.p. infected animals accumulated a larger amount of anti-mCMV IgG and experienced a greater expansion of both acute and latent phase CD8+ T cells. This was especially true for young postpubescent mice, further illustrating a distinction in the bloodborne immune response across not only infection routes, but also ages. These results may be important in the understanding of how a more physiologically applicable model of CMV influences immunity, inflammation, and health over the lifespan.

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

Quantitative Restoration of Immune Defense in Old Animals Determined by Naive Antigen-Specific CD8 T cell Numbers

Older humans and animals often exhibit reduced immune responses to infection and vaccination, and this often directly correlates to the numbers and frequency of naive T (Tn) cells. We found such a correlation between reduced numbers of blood CD8+ Tn cells and severe clinical outcomes of West Nile virus (WNV) in both humans naturally exposed to, and mice experimentally infected with, WNV. To examine possible causality, we sought to increase the number of CD8 Tn cells by treating C57BL/6 mice with IL-7 complexes (IL-7C, anti-IL-7 mAb bound to IL-7), shown previously to efficiently increase peripheral T cell numbers by homeostatic proliferation. T cells underwent robust expansion following IL-7C administration to old mice increasing the number of total T cells (>four-fold) and NS4b:H-2Db-restricted antigen-specific CD8 T cells (two-fold). This improved the numbers of NS4b-specific CD8 T cells detected at the peak of the response against WNV, but not survival of WNV challenge. IL-7C treated old animals also showed no improvement in WNV-specific effector immunity (neutralizing antibody and in vivo T cell cytotoxicity). To test quantitative limits to which CD8 Tn cell restoration could improve protective immunity, we transferred graded doses of Ag-specific precursors into old mice and showed that injection of 5,400 (but not of 1,800 or 600) adult naive WNV-specific CD8 T cells significantly increased survival after WNV. These results set quantitative limits to the level of Tn reconstitution necessary to improve immune defense in older organisms and are discussed in light of targets of immune reconstitution.

immunology↗

bioRxiv2020

New complexities of SOS-induced untargeted mutagenesis in Escherichia coli as revealed by mutation accumulation and whole-genome sequencing

When its DNA is damaged, Escherichia coli induces the SOS response, which consists of about 40 genes that encode activities to repair or tolerate the damage. Certain alleles of the major SOS-control genes, recA and lexA, cause constitutive expression of the response, resulting in an increase in spontaneous mutations. These mutations, historically called "untargeted", have been the subject of many previous studies. Here we re-examine SOS-induced mutagenesis using mutation accumulation followed by whole-genome sequencing (MA/WGS), which allows a detailed picture of the types of mutations induced as well as their sequence-specificity. Our results confirm previous findings that SOS expression specifically induces transversion base-pair substitutions, with rates averaging about 60-fold above wild-type levels. Surprisingly, the rates of G:C to C:G transversions, normally an extremely rare mutation, were induced an average of 160-fold above wild-type levels. The SOS-induced transversion showed strong sequence specificity, the most extreme of which was the G:C to C:G transversions, 60% of which occurred at the middle base of 5'GGC3'+5'GCC3' sites although these sites represent only 8% of the G:C base pairs in the genome. SOS-induced transversions were also DNA strand biased, occurring, on average, 2- to 4- times more often when the purine was on the leading strand template and the pyrimidine on the lagging strand template than in the opposite orientation. However, the strand bias was also sequence specific, and even of reverse orientation at some sites. By eliminating constraints on the mutations that can be recovered, the MA/WGS protocol revealed new complexities to the nature of SOS "untargeted" mutations. HighlightsO_LIThe SOS response to DNA damage induces "untargeted" mutations C_LIO_LISOS-mutations are revealed by mutation accumulation and whole genome sequencing C_LIO_LISOS-mutations are both sequence and DNA-strand biased C_LIO_LIG:C to C:G transversions are particularly highly induced by SOS C_LIO_LIG:C to C:G transversions are extremely sequence and DNA-strand biased C_LI

genetics↗