Biology subjects

Garcia-Beltran, W. F.

Publications and source records attributed to Garcia-Beltran, W. F..

6 recordsLinked to original sources

bioRxiv2026

HIV-1 promotes cell-to-cell interactions enabling spread from CD4+ T cells to microglia

HIV-1 infection of the brain occurs early in acute infection and results in neuroinflammation and - when untreated - in cognitive impairment, yet the mechanisms by which microglia become infected remain poorly defined. Evidence from simian immunodeficiency virus (SIV) studies supports a model in which infected CD4+ T cells disseminate HIV-1 to tissue macrophages, but this has not yet been confirmed for human microglia. Here, we used human monocyte-derived microglia (MDMi) and autologous HIV-1-infected primary CD4+ T cells to investigate viral transmission and immune cell interactions. Transcriptional profiling of MDMi confirmed microglia signature genes such as CX3CR1, P2RY12 and C1QB, and surface staining showed expression of CD4 and the HIV-1 coreceptor CCR5. Compared to cell-free infection, direct cell-to-cell contact between MDMi and HIV-1-infected CD4+ T cells markedly enhanced productive infection of MDMi. HIV-1 infection downmodulated the "dont-eat-me" signal CD47 and increased phosphatidylserine on the surface of primary CD4+ T cells. Consequently, HIV-1 infection of primary CD4+ T cells increased microglia-CD4+ T cell interactions and resulted in enhanced phagocytosis by MDMi. Together, this supports a mechanism where HIV-1 facilitates cell-to-cell spread from primary CD4+ T cells to microglia, which has important implications for therapeutic targeting of HIV-1 brain reservoir seeding.

immunology↗

bioRxiv2025

Control of antigen presentation on MHC-I by a bacterial secretion system

Mycobacterium tuberculosis (Mtb) remains one of the worlds leading infectious killers. Although CD8{square} T cells contribute to immune control of tuberculosis, the pathways through which bacterial antigens access major histocompatibility complex class I (MHC-I) antigen presentation remain incompletely defined. Here, we show that the activity of an Mtb secretion system actively promotes antigen presentation on MHC-I. Using quantitative immunopeptidomics, host and bacterial genetic perturbations, and T cell activation assays, we demonstrate that presentation of Mtb-derived peptides on MHC-I requires the ESX-1 type VII secretion system. Presentation of these peptides proceeds in a manner dependent on the transporter associated with antigen processing (TAP) but independent of host cell mechanisms such as autophagy or MPEG1-mediated pore formation. Chemical induction of phagosomal membrane damage fails to restore antigen presentation in the absence of ESX-1 activity, suggesting that pathogen-encoded secretion, not nonspecific membrane rupture, governs access to MHC-I antigen processing pathways. These findings reveal a secretion system-driven mechanism of antigen presentation, redefining how mycobacteria interface with host MHC-I pathways, potentially informing tuberculosis vaccine design strategies, and highlighting a potential route for synthetic antigen delivery to the cytosol in therapeutics and vaccination. One-sentence summaryPresentation of Mycobacterium tuberculosis antigens on MHC class I through a cytosolic pathway depends on a bacterial secretion system rather than host response and cross-presentation pathways.

immunology↗

bioRxiv2025

SLAMF6 enables efficient attachment, synapse formation, and killing of HIV-1-infected CD4+ T cells by virus-specific CD8+ T cells

Efficient recognition and elimination of HIV-1-infected CD4+ T cells by cytotoxic CD8+ T cells (CTLs) require target cell engagement and the formation of a well-organized immunological synapse. Surface proteins belonging to the SLAM family are known to be crucial for stabilizing the immunological synapse and regulating antiviral responses during lymphotropic viral infections. In the context of HIV-1, there have been reports of SLAMF6 down-regulation in HIV-1-infected CD4+ T cells; however, the significance of this modulation for CTL function remains unclear. In this investigation, we used CTL lines from People living with HIV (PLWH) to examine the impact of SLAMF6 blockade on three pivotal processes: (1) the formation of CD8+-CD4+ T-cell conjugates, (2) the establishment of the immunological synapse, and (3) the killing and cytokine production capacity of HIV-1-specific CTLs during HIV-1 infection. Our findings reveal that the inability to form CD8+-CD4+ T-cell conjugates following incubation with an anti-SLAMF6 blocking antibody is primarily attributable to a defect in actin ring formation at the immunological synapse. Furthermore, SLAMF6 blockade leads to a reduction in the killing efficiency of HIV-1-infected CD4+ T cells by HIV-1-specific CTLs, underscoring the critical role of SLAMF6 in cytolytic function. This study highlights the importance of SLAMF6 receptors in modulating cytotoxic antiviral responses, shedding light on potential avenues for manipulation and enhancement of this pathway in the context of HIV and other lymphotropic viral infections.

immunology↗

bioRxiv2022

Inhibition of major histocompatibility complex-I antigen presentation by sarbecovirus ORF7a proteins

Viruses employ a variety of strategies to escape or counteract immune responses, including depletion of cell surface major histocompatibility complex class I (MHC-I), that would ordinarily present viral peptides to CD8+ cytotoxic T cells. As part of a screen to elucidate biological activities associated with individual SARS-CoV-2 viral proteins, we found that ORF7a reduced cell surface MHC-I levels by approximately 5-fold. Nevertheless, in cells infected with SARS-CoV-2, surface MHC-I levels were reduced even in the absence of ORF7a, suggesting additional mechanisms of MHC-I downregulation. ORF7a proteins from a sample of sarbecoviruses varied in their ability to induce MHC-I downregulation and, unlike SARS-CoV-2, the ORF7a protein from SARS-CoV lacked MHC-I downregulating activity. A single-amino acid at position 59 (T/F) that is variable among sarbecovirus ORF7a proteins governed the difference in MHC-I downregulating activity. SARS-CoV-2 ORF7a physically associated with the MHC-I heavy chain and inhibited the presentation of expressed antigen to CD8+ T-cells. Speficially, ORF7a prevented the assembly of the MHC-I peptide loading complex and causing retention of MHC-I in the endoplasmic reticulum. The differential ability of ORF7a proteins to function in this way might affect sarbecovirus dissemination and persistence in human populations, particularly those with infection- or vaccine-elicited immunity.

microbiology↗

bioRxiv2020

Multi-Modal Profiling of Human Fetal Liver-Derived Hematopoietic Stem Cells Reveals the Molecular Signature of Engraftment Potential

The human hematopoietic stem cell (HSC) harbors remarkable regenerative potential that can be harnessed therapeutically. During early development, HSCs in the fetal liver (FL) undergo active expansion while simultaneously retaining robust engraftment capacity, yet the underlying molecular program responsible for their efficient engraftment remains unclear. We profiled 26,407 FL cells at both transcriptional and protein levels including over 7,000 highly enriched and functional FL HSCs to establish a detailed molecular signature of engraftment potential. Integration of transcript and linked cell surface marker expression revealed a generalizable signature defining functional FL HSCs and allowed for the stratification of enrichment strategies with high translational potential. This comprehensive, multi-modal profiling of engraftment capacity connects a critical biological function at a key developmental timepoint with its underlying molecular drivers, serving as a useful resource for the field.

cell biology↗

bioRxiv2019

Applying CRISPR-based genetic screens to identify drivers of tumor-cell sensitivity towards NK-cell attack

Natural killer (NK) cells distinguish cancer cells from healthy cells using an array of germline-encoded receptors that interact with ligands expressed on target cells. A balance of inhibitory and activating signals transduced by these receptors regulate NK cell function to provide anti-tumor immunity while maintaining self-tolerance. However, knowledge of the spectrum of factors regulating NK-cell-mediated cytotoxicity, including the contribution of specific ligands and regulatory mechanisms for their expression on tumor cells, remains incomplete. Here, we apply a genome-wide loss-of-function screen in tumor cells using CRISPR/Cas9 technology to identify the factors that promote NK-cell cytotoxicity towards tumor cells. We established the drivers of tumor-cell sensitivity towards NK-cell attack (TuSeNKA) screening approach using the chronic myeloid leukemia (CML) cell line, K562. Interestingly, we identified B7H6, the ligand for the activating NK cell receptor NKp30, as the single factor whose loss resulted in increased resistance of K562 cells towards NK cells. Our study shows that combination of CRISPR-based genetic screens with NK-cell cytotoxicity assays is a valuable tool for identifying functionally relevant NK cell-tumor cell interactions, paving the way for further investigations that unravel the complexity of signals that promote NK-cell recognition of transformed cells and develop therapies that target these modes of tumor-cell killing.

immunology↗