Biology subjects

Petrovas, C.

Publications and source records attributed to Petrovas, C..

8 recordsLinked to original sources

bioRxiv2026

An eicosanoid-enriched follicular microenvironment shapes germinal centre immune dynamics in antiretroviral-treated PLWH

Delineating the follicular (F) cellular and molecular landscape in HIV infection is essential for understanding neutralizing antibody responses and HIV reservoir maintenance. Multiplex imaging analysis revealed a less differentiated profile for follicular helper CD4 T cells (TFH) and significantly increased follicular CD25lo/hiFoxp3hi T cells in lymph nodes (LNs) from antiretroviral treated (cART) compared to viremic (Vir) people living with HIV (PLWH). Spatial transcriptomics identified distinct inflammatory follicular microenvironments in Vir and cART LNs, characterized by interferon and eicosanoid enrichment, respectively. In an independent cohort, scRNA-sequencing analysis of LN-derived cells revealed an enrichment of eicosanoid-related pathways in follicular immune cell types in non-neutralizers compared to neutralizers PLWH. In vitro infection and in situ multimodal investigation of HIV DNA+ cell microenvironments suggested a potential role of PGE2/Eicosanoids in maintaining viral reservoirs in cART LNs. Our data highlight cellular and molecular factors that could regulate both antibody responses and viral reservoir persistence in PLWH.

immunology↗

bioRxiv2025

Targeting PD-1+ T-cells with Chimeric Antigen Receptors to reduce the HIV Reservoir

The unique ability of chimeric antigen receptor (CAR) T-cells to infiltrate tissues is revolutionizing our perspectives for tackling severe-refractory and otherwise untreatable diseases. In HIV, CAR-T-cells have been designed to target viral biomarkers, with limited success so far. Here, we investigated the possibility of redirecting CAR-T-cells against a cellular biomarker of the HIV reservoir, PD-1. We designed two second-generation 4-1BB-CARs using the scFv of either a blocking (bPD1-CAR) or a nonblocking (nbPD1-CAR) anti-PD-1 monoclonal antibody. The CAR avidity modulated T-cell sensitivity, trogocytosis, and effector functions, independently of the PD-1 signalling domain. Both anti-PD-1 CAR T-cells could persist for 70 days in HIV-infected humanized mice, correlating with viral protection and a disruption of the lymphoid architecture in the white pulp of the spleen. Altogether, our results open new strategic avenues for reducing the HIV reservoir as we demonstrate the feasibility of depleting specific T-cell subpopulations. SummaryT cells can be redirected against cellular rather than viral-specific biomarkers to reduce the HIV reservoir.

immunology↗

bioRxiv2025

Redirecting TCR specificity in regulatory T cells toward class I HLA antigens mediates tissue-specific homing

Type 1 diabetes (T1D) is marked by the overexpression of class I major histocompatibility complex (MHC) antigens in pancreatic islets, which are targeted by islet-specific CD8+ T cells. Here, we aimed to improve regulatory T cell (Treg) infiltration into pancreatic islets by redirecting their specificity toward class I-restricted islet antigens. We functionally validated two public islet specific HLA-A2 (*02:01) restricted TCRs, one specific for ZnT8186-194 (clone D222D), the second for IGRP265-273 (clone 32) by dual locus (TRAC/CD4) homology-directed editing. Clone D222D was peptide-specific and CD8{beta} dependent while clone 32 exhibited antigen promiscuity and showed CD8 dependency. Engineered CD4to8 TCR Tregs maintained stable phenotypes, suppressed significantly better than their polyclonal counterpart, and showed co-receptor-dependent migration in vivo. This approach demonstrates that TCR specificity, reflected by its functional activity, is crucial for tissue-specific trafficking, paving the way to improve the efficacy of Treg therapies for T1D.

immunology↗

bioRxiv2024

Follicular Bcl6 reactivity is associated with a unique immune landscape and spatial transcriptome in COVID-19

The regulation of follicular (F) and germinal center (GC) immune reactivity in human lymph nodes (LNs), particularly during the early stages of viral infections, remains poorly understood. We have analyzed lung-draining lymph nodes (LD-LNs) from COVID-19 autopsies using multiplex imaging and spatial transcriptomics to examine the immune landscape and with respect to the aging. We identified three subgroups of Reactive Follicles (RFs) based on Bcl6 prevalence, RF-Bcl6no/low, RF-Bcl6int and RF-Bcl6high. RF-Bcl6high tissues express a distinct B/TFH immune landscape associated with increased prevalence of proliferating B- and TFH-cell subsets. Comparison between LD-LNs and matched subdiaphragmatic LNs revealed a disconnected Bcl6 reactivity between the two anatomical sites. LD-LNs Bcl6 reactivity was associated with a distinct spatial transcriptomic profile. TH1-associated genes/pathways (e.g. CXCR3, STAT5, TNF signaling) were significantly upregulated in RF-Bcl6no/low tissues while the RF-Bcl6high tissues exhibited significant upregulation of GC-promoting genes/pathways (e.g. CXCL13, B cell receptor signaling). Despite the similar prevalence, the in-situ transcriptome profiling indicates a higher monocyte/macrophage functionality in "Aged" compared to "Young" follicles from donors with comparable Bcl6 reactivity. Our findings reveal a heterogeneous F/GC landscape in COVID-19 LD-LNs and highlight specific molecular targets and pathways that could regulate human F/GC immune dynamics during early viral infections.

immunology↗

bioRxiv2024

Neutralization activity in chronic HIV infection is characterized by a distinct programming of follicular helper CD4 T cells

A subset of people living with HIV (PLWH) can produce broadly neutralizing antibodies (bNAbs) against HIV, but the lymph node (LN) dynamics that promote the generation of these antibodies are poorly understood. Here, we explored LN-associated histological, immunological, and virological mechanisms of bNAb generation in a cohort of anti-retroviral therapy (ART)-naive PLWH. We found that participants who produce bNAbs, termed neutralizers, have a superior LN-associated B cell follicle architecture compared with PLWH who do not. The latter was associated with a significantly higher in situ prevalence of Bcl-6hi follicular helper CD4 T cells (TFH), expressing a molecular program that favors their differentiation and stemness, and significantly reduced IL-10 follicular suppressor CD4 T cells. Furthermore, our data reveal possible molecular targets mediating TFH-B cell interactions in neutralizers. Together, we identify cellular and molecular mechanisms that contribute to the development of bNAbs in PLWH.

immunology↗

bioRxiv2022

Multilevel human secondary lymphoid immune system compartmentalization revealed by complementary multiplexing and mass spectrometry imaging approaches

Secondary human lymphoid tissue immune reactions take place in a highly coordinated environment with compartmentalization representing a fundamental feature of this organization. In situ profiling methodologies are indispensable for the understanding of this compartmentalization. Here, we propose a complementary experimental approach aiming to reveal different aspects of this process. The analysis of human tonsils, using a combination of single cell phenotypic analysis based on flow cytometry and multiplex imaging and mass spectrometry-based methodologies, revealed a compartmentalized organization at cellular and molecular level. More specifically, the skewed distribution of highly specialized immune cell subsets and relevant soluble mediators was accompanied by a compartmentalized localization of several lipids across different anatomical areas of the tonsillar tissue. The performance of such combinatorial experimental approaches could lead to the identification of novel in situ interactions and molecular targets for the in vivo manipulation of lymphoid organ, particularly the germinal center, immune reactions.

immunology↗

bioRxiv2021

IL-10 driven memory T cell survival and Tfh differentiation promote HIV persistence

Mechanisms regulating HIV persistence are complex and not well understood. Increased IL-10 levels were positively associated with HIV reservoir in blood and lymph nodes (LN) of treated HIV aviremic individuals. In LNs, B cells, regulatory T cells, follicular T helper cells (Tfh), monocytes and macrophages contributed to the frequencies of IL10+ cells. Cells with HIV DNA in LNs were in close proximity to IL-10+ cells and/or had the active form of STAT3, the transcription downstream of IL-10. Gene signatures and proteins associated to cell survival, Co-inhibitory receptors expression, maintenance of memory T cells, immune metabolism and Tfh frequencies were all modulated by IL-10 and associated with HIV reservoir persistence. In vitro, STAT3 knockout or neutralization of IL-10, reverted all the aforementioned pathways and resulted in 10-fold decay in HIV reservoir. Collectively, these results provide strong evidence for a pivotal role of IL-10 in HIV persistence, and a potential therapeutic strategy for HIV cure.

immunology↗

bioRxiv2020

Human follicular CD4 T cell function is defined by specific molecular, positional and TCR dynamic signatures.

The orchestrated interaction between follicular helper CD4 T cells (TFH) and germinal center (GC) B cells is crucial for optimal humoral immunity. However, the regulatory mechanisms behind spatial distribution and function of TFH is not well understood. Here, we studied human TFH cells and found that transitioning to a CD57hi TFH status was associated with distinct positioning in the GC, phenotype, transcriptional signatures, function and downregulation of their T-cell receptor (TCR). Single cell TCR clonotype analysis indicated a unidirectional transition towards the CD57hi TFH status, which was marked with drastic changes in the nature of immunological synapse formation where peripheral microclusters become dominant. Lack of central supra molecular activation cluster (cSMAC) formation in TFH synapse was associated with enhanced ubiquitination/proteasome activity in these cells. Our data reveal significant aspects of the tissue organization and heterogeneity of follicular adaptive immunity and suggest that CD57hi TFH cells are endowed with distinctive programming and spatial positioning for optimal GC B cell help. One Sentence Summaryhuman TFH cell heterogeneity

immunology↗