Biology subjects

Blair, P.

Publications and source records attributed to Blair, P..

3 recordsLinked to original sources

bioRxiv2025

MSC-delivered High-Affinity Variants of soluble PD1 lead to tumour regression

Immune checkpoint therapies aim to restore anti-tumour immunity by blocking inhibitory signals that suppress T-cell activation. The most effective current strategies use humanised antibodies targeting PD1 or its ligand PDL1. However, due to their large size, antibodies often exhibit limited tissue diffusion, resulting in poor penetration into solid tumours. To address this challenge, we developed a novel checkpoint inhibitor approach that uses mesenchymal stromal cells (MSCs) to deliver a high-affinity, soluble PD1 receptor (sPD1HAC). We found that sPD1HAC produced as an IgG1-Fc fusion protein provided functional expression in MSCs. The sPD1HAC-IgG1-Fc fusion protein showed strong and specific binding to PDL1 and could outcompete recombinant PD1 and anti-PDL1 antibodies, including the clinically approved durvalumab. Although the sPD1HAC variant was designed to block human PD1-PDL1 signalling, it also bound murine PDL1 and blocked the binding of mouse-specific PD1 antibodies as well as recombinant murine PD1 protein. Accordingly, we found significant anti-tumour activity of intravenously administered MSCs.PD1HAC in an aggressive B16-F10 cancer model. This cell-based immune checkpoint approach offers a potential therapeutic option for targeting stroma-rich, treatment-resistant tumours.

cancer biology↗

bioRxiv2025

Multi-step antibody class switching in a primary human response is restricted after IGHG2 and dependent on B cell maturation stage.

Class switch recombination (CSR) allows the formation of functionally specialized antibodies. Understanding of CSR dynamics is key for better design and prediction of vaccines to protect mucosal surfaces. To investigate CSR in a primary human immune response under a controlled setting, we sampled healthy volunteers without COVID-19 history every other day during the first three weeks after SARS-CoV-2 vaccination, with additional time points up to six months. Leveraging bulk and single-cell B cell receptor repertoires, single-cell transcriptomics, and immunophenotyping, we uncover paradigm-shifting insights into CSR. Newly activated B cells produce sterile transcripts of all antibody isotype constant regions (IGHC) simultaneously up to IGHG2, challenging the view that sterile transcription occurs for only a single IGHC gene at a time. CSR follows a multistep progression along the IGHC locus; in this challenge vaccine-induced B cells switch from IGHM to IGHG3 and IGHG1, followed by a subsequent switching to IGHA1 and IGHG2 after secondary immunization. IGHA2 clones require pre-switching to IGHA1 clones. Notably, switching tendency, measured by IGHC sterile transcription, is memory B cell subtype dependent, particularly beyond IGHG2. Contrary to other vaccines, antigen-specific B cells are enriched in DN2, Cmem2 and DN4 subtypes after immunization. We also observe a temporal decoupling of CSR and somatic hypermutation (SHM), with the latter detectable only after six months post-immunization. Our data describes the dynamics between CSR, SHM, sterile transcription and B cell memory development during a human primary response, challenges textbook models of CSR and offers new insights to aid control of CSR direction. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=188 HEIGHT=200 SRC="FIGDIR/small/652638v1_ufig1.gif" ALT="Figure 1"> View larger version (49K): org.highwire.dtl.DTLVardef@785769org.highwire.dtl.DTLVardef@b2c54eorg.highwire.dtl.DTLVardef@b78c72org.highwire.dtl.DTLVardef@65b5aa_HPS_FORMAT_FIGEXP M_FIG C_FIG One Sentence SummaryClass switch recombination occurs independently of somatic hypermutation and in a multistep fashion up to IGHG2 during a primary response in humans.

immunology↗

bioRxiv2023

sciCSR infers B cell state transition and predicts class-switch recombination dynamics using single-cell transcriptomic data

Class-switch recombination (CSR) is an integral part of B cell maturation. Steady-state analyses of isotype distribution (e.g. B cell receptor [BCR] repertoire analysis of snapshots during an immune response) do not directly measure CSR dynamics, which is crucial in understanding how B cell maturation is regulated across time. We present sciCSR (pronounced scissor, single-cell inference of class switch recombination), a computational pipeline which analyses CSR events and dynamics of B cells from single-cell RNA-sequencing (scRNA-seq) experiments. sciCSR re-analyses transcriptomic sequence alignments to differentiate productive heavy-chain immunoglobulin transcripts from germline "sterile" transcripts. From a snapshot of B cell scRNA-seq data, a Markov state model is built by the pipeline to infer the dynamics and direction of CSR. Applying sciCSR on SARS-CoV-2 vaccination time-course scRNA-seq data, we observe that sciCSR predicts, using data from an earlier timepoint in the collected time-course, the isotype distribution of BCR repertoires of subsequent timepoints with high accuracy (cosine similarity [~] 0.9). sciCSR also recapitulates CSR patterns in mouse models where B cell maturation was perturbed using gene knockouts. sciCSR infers cell state transitions using processes specific to B cells, identifies transitions which are often missed by conventional RNA velocity analyses, and can reveal insights into the regulation of CSR and the dynamics of B cell maturation during an immune response.

bioinformatics↗