Biology subjects

Besbassi, H.

Publications and source records attributed to Besbassi, H..

4 recordsLinked to original sources

bioRxiv2026

Longitudinal Profiling of CD4⁺ T Cell Responses Following de novo Yellow Fever Vaccination

The yellow fever 17D vaccine is one of the most successful live-attenuated viral vaccines, yet the cellular mechanisms underlying its long-term protection remain not fully understood. This study provides a longitudinal analysis of the human CD4+ T cell and IgG response following de novo yellow fever vaccination by focusing. Peripheral blood mononuclear cells (PBMCs) from 49 vaccinated individuals were stimulated with yellow fever (YF) and control peptide pools across four timepoints: pre-vaccination/baseline (D1), day 22 (D22), day 43 (D43), and one year (D365) post-vaccination. Activation-induced marker (AIM) assays confirmed robust activation of CD4+ T cells following yellow fever peptide stimulation, peaking at day 22 post-vaccination and subsequently declining. T-cell receptor (TCR{beta}) sequencing of AIM-sorted CD4+ T cells showed a transient increase in clonal diversity at D22, consistent with broad epitope targeting and early polyclonal expansion. This was followed by repertoire contraction, which could indicate the persistence of a limited set of dominant clonotypes responsible for immune memory formation. TCR repertoires remained largely private over time, indicating a mostly individualized immune response. Next, serological analyses revealed a robust and highly yellow fever virus (YFV)-specific IgG response. Antibody levels peaked within the D22-D43 window and remained elevated at one year post-vaccination. Cross-reactivity toward other flaviviruses was limited, suggesting an antigen-specific humoral response. Together, these findings characterize the longitudinal dynamics of the CD4+ T cell and IgG response following de novo yellow fever vaccination and provide insights into the mechanisms contributing to durable antiviral immunity.

immunology↗

bioRxiv2026

The T cell receptor repertoire captures healthy aging and CMV independently from epigenetic clocks

Human aging is the process through which numerous biological changes occur during life, affecting various processes. In some elderly individuals, this functional decline becomes more pronounced, leading to frailty, a condition characterised by reduced physiological reserves and increased vulnerability to stress. With the global rise of life expectancy, identification of biomarkers for healthspan and frailty are becoming more important. In this study, we directly compare two molecular readouts, namely the T cell receptor (TCR) repertoire and epigenetic clocks, on their ability to discern healthy aging. On blood samples from sixteen individuals, across age-matched healthy elderly and frail individuals, both TCR sequencing and epigenetic profiling were performed. A significantly higher TCR repertoire diversity in the CD4+ T cells differentiated the healthy elderly individuals from the frailty ones. Epigenetic clock signatures of biological relative to chronological ageing rate, did not show a clear difference between both groups. However, when taking into account the CMV-serostatus, a significant increase in epigenetic aging could be observed in the CMV-seropositive individuals. Our results support a clear hypothesis on the role of CMV infection in the healthy aging of the immune system. In healthy elderly, CMV is typically controlled by CD4+ T cells, however, in the frail elderly, the burden of managing the infection shifts to the CD8+ T cells. This change is marked by two key changes: a decrease in TCR diversity for seropositive individuals compared to seronegative individuals, as well as an increase in the fraction of CMV-associated TCRs within the CD8+ T cells. These findings contribute to our understanding of aging and provide insight into how CMV-infection may affect healthy aging and frailty. They also underline the crucial role of the immune system in healthy aging and the value of further investigating ageing-related health/disease patterns in the TCR repertoire to determine healthspan/lifespan.

immunology↗

bioRxiv2025

T cell-microbiome associations captured through T cell receptor convergence analysis

The gut microbiome modulates mucosal immunity, yet how specific bacterial taxa shape the diversity and specificity of T cell receptor (TCR) repertoires remains poorly understood. Existing approaches emphasize single-species effects or broad immune features, without pinpointing which microbes drive specific T cell clonotypes. We present AIRRWAS, a computational framework that integrates TCR-microbiome interaction analysis with targeted in vitro validation to detect genus-level TCR convergence. Applied to three independent cohorts, AIRRWAS identified reproducible associations between convergent TCR clusters and 21 bacterial genera spanning core commensals, probiotics and taxa with immunomodulatory roles. Predicted clonotypes were enriched within the TCR-microbiome interaction network and preferentially activated by genus-matched stimuli, eliciting different functional T cell responses. These findings demonstrate that distinct repertoires can share genus-specific TCR motifs, enabling detection of shared immune signatures. AIRRWAS can map these TCR- microbiome interactions, laying the groundwork for biomarker discovery immune monitoring and the development of microbiome-targeted therapies.

bioinformatics↗

bioRxiv2023

Modeling Antigen-Specific T Cell Dynamics Following Hepatitis B Vaccination indicates differences between conventional and regulatory T cell dynamics

Our study aims to investigate the dynamics of conventional memory T cells (Tconv) and regulatory T cells (Treg) following activation, and to explore potential differences between these two cell types. To achieve this, we developed advanced statistical mixed models based on mathematical models of ordinary differential equations (ODE), which allowed us to transform post-vaccination immunological processes into mathematical formulas. These models were applied on in-house data from a de novo Hepatitis B vaccination trial. By accounting for inter- and intra-individual variability, our models provided good fits for both antigen-specific Tconv and Treg cells, overcoming the challenge of studying these complex processes. Our modeling approach provided a deeper understanding of the immunological processes underlying T cell development after vaccination. Specifically, our analysis revealed several important findings regarding the dynamics of Tconv and Treg cells, as well as their relationship to seropositivity for HSV-1 and EBV, and the dynamics of antibody response to vaccination. Firstly, our modeling indicated that Tconv dynamics suggest the existence of two T cell types, in contrast to Treg dynamics where only one T cell type is predicted. Secondly, we found that individuals who converted to a positive antibody response to the vaccine earlier had lower decay rates for both Tregs and Tconv cells, which may have important implications for the development of more effective vaccination strategies. Additionally, our modeling showed that HSV-1 seropositivity negatively influenced Tconv cell expansion after the second vaccination, while EBV seropositivity was associated with higher Treg expansion rates after vaccination. Overall, this study provides a critical foundation for understanding the dynamic processes underlying T cell development after vaccination.

immunology↗