Biology subjects

Pellerin, M.

Publications and source records attributed to Pellerin, M..

8 recordsLinked to original sources

bioRxiv2025

An optimized model for HEV infection in the HepaRG cell line

Hepatitis E virus (HEV) causes acute hepatitis that can progress to fulminant or chronic hepatitis. For decades, the lack of a pertinent and robust cell culture system for HEV has delayed our understanding on this hepatotropic virus. HepaRG cells are one of the few hepatocyte-derived cell lines able to replicate HEV. These cells can differentiate (dHepaRG) into hepatocytes and cholangiocytes upon treatment with dimethyl sulfoxyde (DMSO) and are very relevant to study interactions between pathogens and hepatocyte innate immunity. However, the suitability of the HepaRG model to study HEV need to be further investigated. In this study, we found that HEV can infect proliferating HepaRG cells and that DMSO-induced differentiation is not necessary for HEV infection. Moreover, even if treatment with DMSO is needed to maintain optimal differentiation and polarization of dHepaRG, its presence is detrimental for HEV infection. Overall, this study shows that dHepaRG cells cultured without DMSO is a suitable model to study HEV and its interaction with the hepatocyte innate system.

microbiology↗

bioRxiv2025

Evaluating camera trap methods for monitoring population trends in ungulates: insights from simulation

Camera traps have been widely used in the last decade to monitor abundance of unmarked animal populations. Most estimation methods rely either on the number of times animals pass through the detection zones, like random encounter models (REM) or on the number of capture occasions in a time-lapse program when animals were seen on the pictures, like the instantaneous sampling approach (IS). Yet, the ability of these two popular method classes to both reliably detect population trends and estimate population size has rarely been evaluated. We filled this gap by simulating a setup of either 100 or 25 camera traps randomly distributed on a 2600-ha area (respectively {approx} 4 and 1 trap/km2), along with the movements of a fictional population of 300 roe deer (Capreolus capreolus). Simulations were informed by field data on habitat, habitat selection and activity patterns of GPS-monitored roe deer. Under idealized conditions (e.g., perfect knowledge of day range and visibility), both IS and REM provided unbiased population estimates, though uncertainty remained substantial (CV from 15% to 30% with 4 and 1 trap/km2 respectively). However, our results show that neglecting imperfect detectability leads to severe biases in absolute density estimation. Moreover, despite idealized conditions and large sampling efforts, a simulated 20% population decline over 5 years went undetected by both approaches in 65-75% of simulations at high trap density and 80% at low trap density. Testing other sampling strategies to improve sensitivity either led to an unchanged population size estimation precision (stratified sampling) or to biased estimated trends (sampling only in high-quality habitats). Simulating animals with a 10 times larger home-range, led to miss the decline less frequently (5% - 40% at high trap density, 33% - 67% at low trap density). These results suggest that the key metric for camera trap use is the average number of different traps visited per animal, which in turn depends on trap density, home-range size and space use heterogeneity. We provide a R package allowing the reader to reproduce these simulations, and carry out their own.

ecology↗

bioRxiv2025

Likely circulation of a coronavirus in roe deer (Capreolus capreolus) populations suggested by SARS-CoV-2 serological investigation in France

The risk of viral transmissions from domestic/wild animals to humans is a major public health concern. Humans can also transmit viruses back to domestic and wild animals, acting as reservoir for virus maintenance and sources of epidemic diseases re-emergence. The SARS-CoV-2, causing COVID-19, likely originated from wildlife and has been evidenced to transmit from humans to captive, domestic and wild animals. White-tailed deer (Odocoileus virginianus) show high SARS-CoV-2 prevalence following human contamination, suggesting they could act as an emerging virus reservoir. We completed recent research on European cervid species by investigating whether SARS-CoV-2 had emerged in longitudinally-monitored European roe deer (Capreolus capreolus) populations in direct contact with humans in France. We performed indirect tests (serological ELISAs and seroneutralization) on sera collected before and after the virus emergence in humans, and direct RT-PCR tests on nasal swabs collected in 2022. We also investigated the virus exposure and prevalence in three other cervid species. ELISA tests were positive for 2.20% of sera, pre- and post-pandemic, but seroneutralization and PCR tests were negative. Although one population showed increased seroprevalence post-2020, results suggest that SARS-CoV-2 has not emerged in those populations, and that ELISA cross-reaction with one or several unidentified circulating coronaviruses is possible.

immunology↗

bioRxiv2024

Early-life glucocorticoids accelerate lymphocyte count senescence in roe deer

Immunosenescence corresponds to the progressive decline of immune functions with increasing age. Although it is critical to understand what modulates such a decline, the ecological and physiological drivers of immunosenescence remain poorly understood in the wild. Among them, the level of glucocorticoids (GCs) during early life are good candidates to modulate immunosenescence patterns because these hormones can have long-term consequences on individual physiology. Indeed, GCs act as regulators of energy allocation to ensure allostasis, are part of the stress response triggered by unpredictable events and have immunosuppressive effects when chronically elevated. We used longitudinal data collected over two decades in two populations of roe deer (Capreolus capreolus) to test whether higher baseline GC levels measured within the first year of life were associated with a more pronounced immunosenescence and parasite susceptibility. We first assessed immunosenescence trajectories in these populations facing contrasting environmental conditions. Then, we found that juvenile GC levels can modulate lymphocyte trajectory. Lymphocyte depletion was accelerated late in life when FGMs were elevated early in life. Although the exact mechanism remains to be elucidated it could involve a role of GCs on thymic characteristics. In addition, elevated GC levels in juveniles were associated with a higher abundance of lung parasites during adulthood for individuals born during bad years, suggesting short-term negative effects of GCs on juvenile immunity, having in turn long-lasting consequences on adult parasite load, depending on juvenile environmental conditions. These findings offer promising research directions in assessing the carry-over consequences of GCs on life-history traits in the wild.

physiology↗

bioRxiv2022

The environmental roots of the relationship between glucocorticoids and body mass in the wild

Environmental fluctuations force animals to adjust glucocorticoids (GCs) secretion and release to current conditions. GCs are a widely used proxy of an individual stress level. While short-term elevation in GCs is arguably beneficial for fitness components, previous studies have documented that the relationship between long-term baseline GCs elevation and fitness components can vary according to ecological and individual factors and according to the life-history of the species studied. Using longitudinal data on roe deer (Capreolus capreolus) from two populations facing markedly different environmental contexts, we tested whether baseline GC levels negatively correlate with body mass - a trait positively associated with demographic individual performance - on the short- to long-term. In support, higher baseline GC concentrations were associated to lighter body mass, both measured during the same capture event, in adults of both populations. Overall, we showed that despite the marked environmental and demographic differences between populations and despite the between-sex differences in life history (i.e. reproductive tactics), the relationship between body mass and GCs is consistent across environmental contexts, but might differ according to the life history stage of an individual. This work opens promising perspectives to further explore the relationship between GC and fitness-related traits according to life history stages in free-ranging mammals across seasonal and environmental contexts. The timing and context-dependence of GC levels highlight the complexity of studying stress responses in the wild.

ecology↗

bioRxiv2022

Body mass change over winter is consistently sex-specific across roe deer populations

In most polygynous vertebrates, males must allocate energy to growing secondary sexual characteristics, such as ornaments or weapons, that they require to attract and defend potential mates, impacting body condition and potentially entailing fitness costs. We investigated sex differences in over winter body mass change across five intensively monitored populations of roe deer (Capreolus capreolus) with markedly contrasting environmental conditions. At winter onset, males weighed, on average, 8.4% (from 4.7% in the most northerly population to 11.6% in the most southerly one) more than females. However, across all populations, males fared worse over the winter than females, losing more (Sweden) or gaining less (France) mass, so that sexual mass dimorphism was virtually absent prior to the onset of spring. Our findings reveal that the direction of over-winter change in mass of roe deer depends on winter severity, but that males are consistently more sensitive to this environmental constraint than females. As a result of this sex-specific change in body mass, sexual mass dimorphism is lowest at the onset of the territorial season. We suggest that allocation to antler growth and territory establishment drives this pattern, providing a likely explanation to account for the lower rates of male adult survival that are consistently reported in this weakly dimorphic species.

ecology↗

bioRxiv2022

Age and spatio-temporal variations in food resources modulate stress-immunity relationships in three populations of wild roe deer

Living in variable and unpredictable environments, organisms face recurrent stressful situations. The endocrine stress response, which includes the secretion of glucocorticoids, helps organisms to cope with these perturbations. Although short-term elevations of glucocorticoid levels are often associated with immediate beneficial consequences for individuals, long-term glucocorticoid elevation can compromise key physiological functions such as immunity. While laboratory works highlighted the immunosuppressive effect of long-term elevated glucocorticoids, it remains largely unknown, especially in wild animals, whether this relationship is modulated by individual and environmental characteristics. In this study, we explored the co-variation between baseline cortisol levels, assessed non-invasively using faecal cortisol metabolites (FCMs), and 12 constitutive indices of innate, inflammatory, and adaptive immune functions, in wild roe deer living in three populations with contrasting environmental conditions. Using longitudinal data on 564 individuals, we further investigated whether age and spatio-temporal variations in the quantity and quality of food resources affect the relationship between FCMs and immunity. Negative covariation with glucocorticoids was evident only for innate and inflammatory markers of immunity, while adaptive immunity appeared to be positively or not linked to glucocorticoids. In addition, the negative covariations were generally exacerbated, or revealed, in individuals facing harsh environmental constraints and in old individuals. Therefore, our results highlight the importance of measuring multiple immune markers of immunity in individuals from contrasted environments to unravel the complex relationships between glucocorticoids and immunity in wild animals. Our results also help explain conflicting results found in the literature and could improve our understanding of the long-term consequences of elevated glucocorticoid levels on disease spread and population dynamics.

ecology↗

bioRxiv2020

Epigenetic clock and DNA methylation studies of roe deer in the wild

DNA methylation-based biomarkers of aging (epigenetic clocks) promise to lead to new insights in the evolutionary biology of ageing. Relatively little is known about how the natural environment affects epigenetic aging effects in wild species. In this study, we took advantage of a unique long-term (>40 years) longitudinal monitoring of individual roe deer (Capreolus capreolus) living in two wild populations (Chize and Trois Fontaines, France) facing different ecological contexts to investigate the relationship between chronological age and levels of DNA methylation (DNAm). We generated novel DNA methylation data from n=90 blood samples using a custom methylation array (HorvathMammalMethylChip40). We present three DNA methylation-based estimators of age (DNAm or epigenetic age), which were trained in males, females, and both sexes combined. We investigated how sex differences influenced the relationship between DNAm age and chronological age through the use of sex-specific epigenetic clocks. Our results highlight that both populations and sex influence the epigenetic age, with the bias toward a stronger male average age acceleration (i.e. differences between epigenetic age and chronological ages) particularly pronounced in the population facing harsh environmental conditions. Further, we identify the main sites of epigenetic alteration that have distinct aging patterns across the two sexes. These findings open the door to promising avenues of research at the crossroad of evolutionary biology and biogerontology.

evolutionary biology↗