Biology subjects

Dallaire, F.

Publications and source records attributed to Dallaire, F..

6 recordsLinked to original sources

bioRxiv2026

HIV-1 Vpu complements HLA-A downregulation by Nef and impairs TCR-mediated recognition of HIV-infected cells through distinct mechanisms

Many viruses, including HIV-1, target the human leukocyte antigen (HLA) class I molecules HLA-A, HLA-B, and HLA-C to evade immune surveillance. HIV-1 Nef selectively downregulates HLA-A and HLA-B, whereas Vpu variants from primary strains reduce cell-surface HLA-C expression. Whether HIV-1 also uses Vpu to target other HLA molecules has remained unclear. Here, we show that Vpu from primary strains reduces HLA-A, including the globally prevalent HLA-A2, on infected cells. Although Nef is the principal modulator of these molecules, Vpu acts independently of Nef and impairs TCR-mediated recognition of infected cells in co-culture systems. However, the reduction in TCR signaling is also dependent on the presence of BST2/tetherin, a restriction factor that retains nascent virions and targets them for degradation. HLA-A2-restricted, HIV-specific CTL responses were lowest when both Nef and Vpu were present. Vpu variants from chronic and transmitted/founder strains, but not from the prototypical recombinant strain NL4.3, were sufficient to reduce cell-surface HLA-A2, although activity varied widely among variants and appears to have arisen independently in different hosts. Coimmunoprecipitation and immunofluorescence analyses showed that Vpu interacts with HLA-A2 and redirects it to a perinuclear compartment which is probably the trans-Golgi network through a mechanism governed by the Vpu N-terminus/transmembrane domain. Overall, our findings reveal a previously unrecognized function of Vpu and show how HIV-1 uses Nef and Vpu to limit HLA-A-mediated viral antigen presentation and promote immune evasion.

immunology↗

bioRxiv2024

Texture-Analysis Classification of Intraductal Carcinoma of the Prostate Using Label-Free Multimodal Nonlinear Optical Imaging

Intraductal carcinoma of the prostate (IDC-P) is a very aggressive histopathological subtype of prostate cancer (PCa) for which no accurate biomarkers exist. In our work, we apply a multimodal nonlinear optical imaging approach that uses second-harmonic generation (SHG) and stimulated Raman scattering (SRS) imaging to distinguish IDC-P from regular PCa and benign prostate tissue. Images from each tissue type were classified using support vector machine (SVM). The technique classified the images from each region based on first-order statistics and texture-based second-order statistics derived from the gray-level co-occurrence matrix (GLCM) of the images. Our results demonstrate that SVM models trained on either SHG or SRS images accurately classify IDC-P as well as high-grade PCa, low-grade PCa, and benign tissue with a mean classification accuracy of over 89%. Furthermore, a classification model combining both SHG and SRS imaging modalities can accurately classify all tissue types with a mean classification accuracy of 98%.

pathology↗

bioRxiv2022

Generation of Functional Human T Cell Development in NOD/SCID/IL2rγnull Humanized Mice Without Using Fetal Tissue: Application as a Model of HIV Infection and Persistence

Generating humanized mice with fully functional T cells currently relies on co-implantation of hematopoietic stem cells from fetal liver and autologous fetal thymic tissue (BLT mouse). However, access to such tissues has ethical and logistical challenges. Herein, we show that NOD/SCID/IL2r{gamma}null mice humanized with cord blood-derived CD34+ cells and implanted in quadriceps with pediatric thymic tissues excised during cardiac surgeries (CCST mice) are an alternative to BLT mice. Our data revealed a strong immune reconstitution in CCST mice, with T cells originating from CD34+ progenitor cells, proliferating efficiently in response to mitogenic stimulation ex vivo and capable of rejecting allogeneic human leukemic cells in vivo. Despite having less T cells than BLT mice, CCST mice were equally susceptible to mucosal or intraperitoneal HIV infection. Importantly, HIV-specific T cell responses were significantly higher in CCST-mice (median: 10.4% vs. 0.7%; p<0.0001 for CD8+cells and 3.9% vs. 0.7%; p<0.01 for CD4+ cells). As well, antiretroviral therapy (ART) robustly suppressed viremia and reduced the frequencies of cells carrying integrated HIV DNA by up to 2 logs in various CCST mouse tissues. As in BLT mice, we observed a complete viral rebound in 67% of the animals by 2-4 weeks following ART interruption, suggesting the presence of HIV reservoirs. In conclusion, CCST mice represent an ethical and practical alternative to BLT mice, broadening the feasibility of utilizing humanized mice for research on HIV and other human diseases. One Sentence SummaryWe herein report a new humanized mouse model implanted with human cord blood hematopoietic stem cells and allogenic pediatric thymic tissue that develops a functional T cell compartment and supports efficient HIV infection and persistence during antiretroviral therapy.

immunology↗

bioRxiv2021

Implications of Spike-glycoprotein processing at S1/S2 by Furin, at S2' by Furin and/or TMPRSS2 and shedding of ACE2: cell-to-cell fusion, cell entry and infectivity of SARS-CoV-2

Disclaimer StatementThe author has withdrawn this manuscript due to a duplicate posting of manuscript number 423106. Therefore, the author does not wish this work to be cited as reference for the project. If you have any questions, please contact the corresponding author (Nabil G. Seidah at seidahn@ircm.qc.ca.

biochemistry↗

bioRxiv2021

Identification of Cell-Free DNA Methylation Patterns Unique to the Human Left Ventricle as a Potential Indicator of Acute Cellular Rejection

Increased levels of donor-derived cell-free DNA (dd-cfDNA) in recipient plasma have been associated with rejection after transplantation. DNA sequence differences have been used to distinguish between donor and recipient but epigenetic differences could also potentially identify dd-cfDNA. This pilot study aimed to identify ventricle-specific differentially methylated regions of DNA (DMRs) that could be detected in cfDNA. We identified 24 ventricle-specific DMRs and chose two for further study, one on chromosome 9 and one on chromosome 12. The specificity of both DMRs for the left ventricle was confirmed using genomic DNA from multiple human tissues. Serial matched samples of myocardium (n=33) and plasma (n=24) were collected from stable adult heart transplant recipients undergoing routine endomyocardial biopsy for rejection surveillance. Plasma DMR levels increased with biopsy-proven rejection grade for individual patients. Mean cellular apoptosis in biopsy samples increased significantly with rejection severity (2.4%, 4.4% and 10.0% for ACR 0R, 1R and 2R, respectively) but did not show a consistent relationship with DMR levels. We identified multiple DNA methylation patterns unique to the human ventricle and conclude that epigenetic differences in cfDNA populations represent a promising alternative strategy for the non-invasive detection of rejection.

genetics↗

bioRxiv2020

Furin cleaves SARS-CoV-2 spike-glycoprotein at S1/S2 and S2'for viral fusion/entry: indirect role for TMPRSS2

The spike (S)-protein of SARS-CoV-2 binds ACE2 and requires proteolytic "priming" at PRRAR685{downarrow} into S1 and S2 (cleavage at S1/S2), and "fusion-activation" at a S2 site for viral entry. In vitro, Furin cleaved peptides mimicking the S1/S2 cleavage site more efficiently than at the putative S2, whereas TMPRSS2 inefficiently cleaved both sites. In HeLa cells Furin-like enzymes mainly cleaved at S1/S2 during intracellular protein trafficking, and S2 processing by Furin at KPSKR815{downarrow} was strongly enhanced by ACE2, but not for the optimized S2 KRRKR815{downarrow} mutant (S2), whereas individual/double KR815AA mutants were retained in the endoplasmic reticulum. Pharmacological Furin-inhibitors (Boston Pharmaceuticals, BOS-inhibitors) effectively blocked endogenous S-protein processing in HeLa cells. Furthermore, we show using pseudotyped viruses that while entry by a "pH-dependent" endocytosis pathway in HEK293 cells did not require Furin processing at S1/S2, a "pH-independent" viral entry in lung-derived Calu-3 cells was sensitive to inhibitors of Furin (BOS) and TMPRSS2 (Camostat). Consistently, these inhibitors potently reduce infectious viral titer and cytopathic effects, an outcome enhanced when both compounds were combined. Quantitative analyses of cell-to-cell fusion and spike processing revealed the key importance of the Furin sites for syncytia formation. Our assays showed that TMPRSS2 enhances fusion and proteolysis at S2 in the absence of cleavage at S1/S2, an effect that is linked to ACE2 shedding by TMPRSS2. Overall, our results indicate that Furin and TMPRSS2 play synergistic roles in generating fusion-competent S-protein, and in promoting viral entry, supporting the combination of Furin and TMPRSS2 inhibitors as potent antivirals against SARS-CoV-2. IMPORTANCESARS-CoV-2 is the etiological agent of COVID-19 that resulted in >5 million deaths. The spike protein (S) of the virus directs infection of the lungs and other tissues by binding the angiotensin-converting enzyme 2 (ACE2) receptor. For effective infection, the S-protein is cleaved at two sites: S1/S2 and S2. Cleavage at S1/S2, induces a conformational change favoring the recognition of ACE2. The S2 cleavage is critical for cell-to-cell fusion and virus entry into host cells. Our study contributes to a better understanding of the dynamics of interaction between Furin and TMPRSS2 during SARS-CoV-2 entry and suggests that the combination of a non-toxic Furin inhibitor with a TMPRSS2 inhibitor could significantly reduce viral entry in lung cells, as evidenced by an average synergistic [~]95% reduction of viral infection. This represents a powerful novel antiviral approach to reduce viral spread in individuals infected by SARS-CoV-2 or future related coronaviruses.

biochemistry↗