Biology subjects

Baldari, C. T.

Publications and source records attributed to Baldari, C. T..

10 recordsLinked to original sources

bioRxiv2026

Human CD8-iTreg are potent GVHD suppressors and tumoricidal effectors by release of Granzyme-K+ Supramolecular Attack Particles

Regulatory CD8+ T-cells (CD8+ Treg) are a distinct yet understudied T-cell subset capable of simultaneous immunosuppression and cytolysis. Here, we characterized induced human CD8+ Treg (CD8-iTreg) generated from peripheral blood CD8+CD25- T-cells using anti-CD3e mAb-loaded artificial antigen presenting cells, IL-2, TGF{beta}, and Rapamycin. These CD8-iTreg differentiated into a stable, highly proliferative bifunctional population with suppressive activity comparable to CD4-iTreg while retaining cytolytic capacity similar to conventional CD8 cytotoxic T lymphocytes (CTL). Multi-parameter spectral flow cytometry and single-cell RNA-seq revealed a distinct immunoregulatory signature: a predominantly Treg-like profile marked by tissue-residency marker CD103 with increased canonical Treg markers (FoxP3, HELIOS, CD25, CD39, CTLA-4, CCR4, and IL-10) and reduced pro-inflammatory cytokines. A unique cytotoxic program was marked by elevated Granzyme-K (GzmK) and Thrombospondin-4 (Tsp-4), a thrombospondin family extracellular matrix glycoprotein upregulated in activated CD8+ T-cells. Cytolysis was primarily mediated by Perforin (Prf) and multiple Granzymes packaged into Tsp-4 supramolecular attack particles (SMAPs), with GzmK contributing to both cytotoxic and suppressive functions. After anti-CD19scFv CAR (CAR19) transduction, CAR19+ CD8-iTreg showed superior in vivo anti-tumor efficacy compared with CAR19-CTLs, significantly reducing tumor burden and prolonging survival in a CD19+ Nalm-6 human leukemia xenograft model while maintaining low pro-inflammatory cytokine production. In a xenogeneic graft-versus-host disease (GVHD) model with residual human leukemia, CAR19 CD8-iTreg inhibited GVHD lethality and controlled tumor growth without increasing systemic inflammation. Together, these findings support CD8-iTreg-based CAR therapies as a strategy to retain potent anti-leukemic activity while limiting inflammatory toxicities of conventional CAR T-cells, properties particularly beneficial in treating auto- and allo-immune diseases. One sentence summaryCD8-iTreg drive parallel tumoricidal and immunoregulatory functions mediated by releasing Tsp-4+ SMAPs containing granzyme K.

immunology↗

bioRxiv2026

Interferon-γ promotes SMAP production by cytotoxic T lymphocytes in a thrombospondin 4 dependent manner

Cytotoxic T lymphocytes (CTLs) eliminate infected and cancerous cells by exocytosing cytotoxic granules, either as single-core granules (SCGs) releasing diffusible Granzyme B and Perforin, or as multi-core granules (MCGs) releasing these effectors as thrombospondin-1/4-encapsulated supramolecular attack particles (SMAPs). How CTLs differentially deploy these granule types remains unclear. We demonstrate that prolonged in vitro expansion and restimulation selectively enhance SMAP release, correlating with increased MCG maturation and thrombospondin-4 expression. Using high-resolution imaging, we identify fusion-competent MCG intermediates lacking SMAPs but releasing granzyme B diffusively. Mechanistically, interferon-{gamma} upregulates thrombospondin-4, driving MCG maturation and SMAP biogenesis, enhancing late-phase CTL killing efficiency against resistant targets. Consistent with this, THBS1 and THBS4 transcript levels appear elevated in melanoma-infiltrating CTLs compared with those during acute adenovirus infection. These findings define a stimulus-dependent, interferon-{gamma}-driven pathway tailoring CTL responses to chronic pathology and highlight opportunities for SMAP-targeted immunotherapies.

immunology↗

bioRxiv2024

Thrombospondins 1 and 4 undergo coordinated transport to multicore cytotoxic granules to regulate SMAP biogenesis and function in CTL-mediatedcytotoxicity

Supramolecular Attack Particles (SMAPs) are particulate entities, characterized by a cytotoxic core enriched in granzymes and perforin surrounded by a glycoproteic shell, released by CTLs and NK cells. Prior proteomic analysis identified thrombospondin-1 (TSP-1) and thrombospondin-4 (TSP-4) as putative components of SMAPs. While TSP-1 has been validated as a component of the SMAP shell and shown to contribute significantly to CTL-mediated killing, the expression and function of TSP-4 in CTLs, and its interplay with TSP-1 in SMAP biogenesis and function, has not been investigated as yet. Here we demonstrate that TSP-4 and TSP-1 have a complementary expression profile during in vitro human CD8+ T cell differentiation to CTLs and sequentially localize to lytic granules (LG), with TSP-4 being required for TSP-1 association with LGs. Correlative light microscopy identified the TSP-enriched LGs as the SMAP-containing multicore granules. We show by STED microscopy a heterogeneity among TSP-enriched LGs, the most abundant population being positive for both TSP-4 and TSP-1. We also show that TSP-1 and TSP-4 are co-released in association with SMAPs at immune synapses formed on planar supported lipid bilayers, as assessed by dSTORM imaging. Finally, we provide evidence that TSP-4 is required for CTL- and SMAP-mediated cell killing. Of note, we found that chronic lymphocytic leukemia (CLL) cell supernatants, which suppress CTL mediated killing, also suppress expression of TSP-4 as well as of cytolytic effectors and impair SMAP biogenesis. These results identify TSP-4 as a key player in SMAP structure and activity and suggest that SMAPs may be a new target for immune suppression by CLL.

immunology↗

bioRxiv2023

Human monoclonal antibodies reveal subdominant gonococcal and meningococcal cross-protective antigens

Gonococcus (Gc), a bacterium resistant to most antibiotics causing more than 80 million cases of gonorrhea annually, is a WHO high priority pathogen. Recently, vaccine development prospects were boosted by reports that licensed meningococcus serogroup B (MenB) vaccines provided partial protection against Gc infection. To determine antigens responsible for cross-protection, memory B cells from 4CMenB vaccinated volunteers were single-cell sorted to identify antibodies that kill Gc in a bactericidal assay. Nine different antibodies, all deriving from the IGHV4-34 germline carrying unusually long HCDR3s, recognized the PorB protein, four recognized the lipooligosaccharide (LOS), and four unknown antigens. One of the PorB antibodies, tested in vivo, provided protection from Gc infection. The identification of PorB and LOS as key antigens of gonococcal and meningococcal immunity provides a mechanistic explanation of the cross-protection observed in the clinic and shows that isolating human monoclonal antibodies from vaccinees can be instrumental for bacterial antigen discovery.

immunology↗

bioRxiv2023

Leukemic cell-secreted interleukin-9 suppresses cytotoxic T cell-mediated killing in chronic lymphocytic leukemia

The tumor microenvironment (TME) plays a central role in the pathogenesis of chronic lymphocytic leukemia (CLL), contributing to disease progression and chemoresistance. Leukemic cells shape the TME into a pro-survival and immunosuppressive niche through contact-dependent and contact-independent interactions with the cellular components of the TME. Immune synapse (IS) formation is defective in CLL. Here we asked whether soluble factors released by CLL cells contribute to their protection from cytotoxic T cell (CTL)-mediated killing by interfering with this process. We found that healthy CTLs cultured in media conditioned by leukemic cells from CLL patients or E-TCL1 mice upregulate the exhaustion marker PD-1 and become unable to form functional ISs and kill target cells. These defects were more pronounced when media were conditioned by leukemic cells lacking p66Shc, a proapoptotic adaptor whose deficiency has been implicated in disease aggressiveness both in CLL and in the E-TCL1 mouse model. Multiplex ELISA assays showed that leukemic cells from E-TCL1 mice secrete abnormally elevated amounts of CCL22, CCL24, IL-9 and IL-10, which are further upregulated in the absence of p66Shc. Among these, IL-9 and IL-10 were also overexpressed in leukemic cells from CLL patients, where they inversely correlated with residual p66Shc. Using neutralizing antibodies or the recombinant cytokines we show that IL-9, but not IL-10, mediates both the enhancement in PD-1 expression and the suppression of effector functions in healthy CTLs. Our results demonstrate that IL-9 secreted by leukemic cells negatively modulates the anti-tumor immune abilities of CTLs, highlighting a new suppressive mechanism and a novel potential therapeutical target in CLL.

cancer biology↗

bioRxiv2023

Human colorectal cancer: upregulation of the adaptor protein Rai in TILs leads to cell dysfunction by sustaining GSK-3 activation and PD-1 expression

BackgroundThe immunosuppressive tumor microenvironment (TME) of colorectal cancer (CRC) is a major hurdle for immune checkpoint inhibitor-based therapies. Hence characterization of the signaling pathways driving T cell exhaustion within TME is a critical need for the discovery of novel therapeutic targets and the development of effective therapies. We previously showed that i) the adaptor protein Rai is a negative regulator of T cell receptor signaling and T helper 1 (Th1)/Th17 cell differentiation; and ii) Rai deficiency is implicated in the hyperactive phenotype of T cells in autoimmune diseases. MethodsThe expression level of Rai was measured by qRT-PCR in paired peripheral blood T cells and T cells infiltrating tumor tissue and the normal adjacent tissue in CRC patients. The impact of HIF-1 on Rai expression was evaluated in T cells exposed to hypoxia and by performing chromatin immunoprecipitation assays and RNA interference assays. The mechanism by which upregulation of Rai in T cells promotes T cell exhaustion were evaluated by flow cytometric, qRT-PCR and western blot analyses. ResultsWe show that Rai is a novel HIF-1-responsive gene that is upregulated in tumor infiltrating lymphocytes of CRC patients compared to patient-matched circulating T cells. Rai upregulation in T cells promoted PD-1 expression and impaired antigen-dependent degranulation of CD8+ T cells by inhibiting phospho-inactivation of glycogen synthase kinase (GSK)-3, a central regulator of PD- 1 expression and T cell-mediated anti-tumor immunity. ConclusionsOur data identify Rai as a hitherto unknown regulator of the TME-induced exhausted phenotype of human T cells. What is already known on this topicO_LITumor hypoxia contributes to establish an immunosuppressive microenvironment that unleashes T cell function and limits the efficacy of immunotherapy in CRC. C_LIO_LIThe molecular mechanisms underlying the impact of hypoxia on the signaling pathways controlling PD-1 expression are unknown. C_LI What this study addsO_LIA Rai/Akt/GSK-3 axis regulates PD-1 expression following TCR/CD28 co-stimulation C_LIO_LIThis study uncovers the signaling pathway controlling hypoxia-dependent T cell exhaustion. C_LI How this study might affect research, practice or policyRai expression levels in TILs of CRC patients might be explored as a potential new biomarker of T cell exhaustion and a predictive biomarker for anti-PD-1 response.

cancer biology↗

bioRxiv2022

SARS-CoV-2 Spike protein suppresses CTL-mediated killing by inhibiting immune synapse assembly

CTL-mediated killing of virally infected or malignant cells is orchestrated at a specialized intercellular junction, the immune synapse (IS). We hypothesized that SARS-CoV-2 may target IS assembly in CTLs to escape killing. We show that primary human CD8+ T cells strongly upregulate the expression of ACE2, the Spike protein receptor, during differentiation to CTLs. CTL pre-incubation with the Wuhan or Omicron Spike variants inhibits IS assembly and function, as shown by defective synaptic accumulation of TCRs and tyrosine phosphoproteins as well as defective centrosome and lytic granule polarisation to the IS, resulting in impaired target cell killing. These defects were reversed by anti-Spike antibodies that interfere with ACE2 binding and were reproduced by ACE2 engagement with Angiotensin-II or an anti-ACE2 antibody, but not by the ACE2 product Ang (1-7). These results highlight a new strategy of immune evasion by SARS-CoV-2 based on the Spike-dependent, ACE2-mediated targeting of the lytic IS to prevent the elimination of infected cells. Summary statementWe report a new mechanism of immune evasion by SARS-CoV-2 based on direct disabling CTLs to form immune synapses through Spike protein binding to ACE2. This mechanism could contribute to the failure of the immune system to control SARS-CoV-2 infection.

immunology↗

bioRxiv2020

The Bardet-Biedl Syndrome complex component BBS1 regulates proteasome-dependent F-actin clearance from the centrosome to enable its translocation to the T cell immune synapse

Components of the intraflagellar transport (IFT) system that regulates the assembly of the primary cilium are exploited by the non-ciliated T cell to orchestrate polarized endosome recycling to sustain signaling during immune synapse formation. Here we have investigated the potential role of BBS1, an essential core component of the Bardet-Biedl syndrome complex that cooperates with the IFT system in ciliary protein trafficking, in the assembly of the T cell synapse. We show that BBS1 allows for centrosome polarization towards the immune synapse by promoting its untethering from the nuclear envelope. This function is achieved through the clearance of centrosomal F-actin and its positive regulator WASH, a process that we demonstrate to be dependent on the proteasome. We show that BBS1 regulates this process by coupling the 19S proteasome regulatory subunit to the microtubule motor dynein for its transport to the centrosome. Our data identify the ciliopathy-related protein BBS1 as a new player in T cell synapse assembly that acts upstream of the IFT system to set the stage for polarized vesicular trafficking and sustained signaling.

immunology↗

bioRxiv2020

The intraflagellar transport protein IFT20 recruits ATG16L1 to early endosomes to promote autophagosome formation in T cells

Lymphocyte homeostasis, activation and differentiation crucially rely on basal autophagy. The fine-tuning of this process depends on autophagy-related (ATG) proteins and their interaction with the trafficking machinery that orchestrates the membrane rearrangements leading to autophagosome biogenesis. The underlying mechanisms are as yet not fully understood. The intraflagellar transport (IFT) system, known for its role in cargo transport along the axonemal microtubules of the primary cilium, has emerged as a regulator of autophagy in ciliated cells. Growing evidence indicates that ciliogenesis proteins participate in cilia-independent processes, including autophagy, in the non-ciliated T cell. Here we investigate the mechanism by which IFT20, an integral component of the IFT system, regulates basal T cell autophagy. We show that IFT20 interacts with the core autophagy protein ATG16L1 through its CC domain, which is also essential for its pro-autophagic activity. We demonstrate that IFT20 is required for the association of ATG16L1 with the Golgi complex and early endosomes, both of which have been identified as membrane sources for phagophore elongation. This involves the ability of IFT20 to interact with proteins that are resident at these subcellular localizations, namely the golgin GMAP210 at the Golgi apparatus and Rab5 at early endosomes. GMAP210 depletion, while leading to a dispersion of ATG16L1 from the Golgi, did not affect basal autophagy. Conversely, IFT20 was found to recruit ATG16L1 to early endosomes tagged for autophagosome formation by the BECLIN 1/VPS34/Rab5 complex, which resulted in the local accumulation of LC3. Hence IFT20 participates in autophagosome biogenesis under basal conditions by regulating the localization of ATG16L1 at early endosomes to promote autophagosome biogenesis. These data identify IFT20 as a new regulator of an early step of basal autophagy in T cells.

immunology↗

bioRxiv2019

Phosphoproteomics of CD2 signaling reveals an AMPK-dependent regulation of lytic granule polarization in cytotoxic T cells

The in-depth analysis of costimulatory signaling enhancing the activity of cytotoxic T cells (CTLs) represents a major approach towards immunotherapy development. Here we report that CD2 costimulation plays a critical role in killing by freshly isolated human CTLs, which represent a challenging but valuable study model to gain insight into CTL biology. We show that CD2 triggering critically aids signaling by the T cell receptor in the formation of functional immune synapses by promoting the polarization of lytic granules towards the microtubule-organizing center (MTOC). To gain insight into the underlying elusive mechanism, we explored the CD2 signaling network by phosphoproteomics, which revealed 616 CD2-regulated phosphorylation events in 373 proteins implicated in the regulation of vesicular trafficking, cytoskeleton organization, autophagy and metabolism. Strikingly, signaling by the master metabolic regulator AMP-activated protein kinase (AMPK) represents a functionally critical node of the CD2 network which regulates granule polarization towards the MTOC in CTLs. Granule trafficking is driven by active AMPK enriched on adjacent lysosomes, illustrating a novel signaling cross-talk between vesicular compartments in CTLs. Our results thus establish CD2 signaling as key for regulating cytotoxic killing and granule polarization in freshly isolated CTLs and strengthens the rationale to choose CD2 and AMPK as therapeutic targets to boost CTL activity.

immunology↗