Biology subjects

Affandi, A. J.

Publications and source records attributed to Affandi, A. J..

4 recordsLinked to original sources

bioRxiv2025

Identification of allo- or orthosteric VHH/single-domain antibodies that enhance or block pathogen binding to Siglec-1 on dendritic cells

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=87 SRC="FIGDIR/small/695420v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@e85819org.highwire.dtl.DTLVardef@1eff6b4org.highwire.dtl.DTLVardef@12daa92org.highwire.dtl.DTLVardef@11959e5_HPS_FORMAT_FIGEXP M_FIG C_FIG BackgroundSiglec-1 (Sialoadhesin/CD169) is expressed on myeloid cells and plays a key role in host defences by capturing incoming sialylated-pathogens such as Campylobacter jejuni. However, binding to Siglec-1 has also been exploited by pathogens such as SARS-CoV-2 for further dissemination. ResultsHere we identified high-affinity VHHs also known as single-domain antibodies or Nanobodies that bind to Siglec-1 and allo- or orthosterically modulate ligand binding. VHH 2C2 was shown to bind directly to the ligand binding site of Siglec-1 and blocked binding of ganglioside liposomes and Campylobacter jejuni to monocyte-derived dendritic cells (moDCs) and ex vivo Siglec-1+ DCs. VHH 2C2 also blocked SARS-CoV-2 binding of moDCs. In contrast, the VHHs 1B5 and 1C1 interacted with Siglec-1 outside the ligand binding site and acted as positive allosteric modulators of Siglec-1 ligand interactions, as was illustrated by increased ganglioside liposome and Campylobacter jejuni binding by moDCs. Our data suggests that mechanistically, the VHH 1B5 and 1C1 interfere with the cis-binding sialic acids present on the Siglec-1-expressing cell and thereby enhance trans-interactions with ligands. ConclusionIn conclusion, we have isolated VHH that enhance or block Siglec-1 ligand binding to a variety of sialylated-pathogens enabling further interrogation of Siglec-1 function. Moreover, unlike conventional blocking antibodies targeting specific pathogens, Siglec-1 binding VHH could potentially serve as broad-spectrum pathogen blocking agents.

immunology↗

bioRxiv2025

Histone methyltransferase DOT1L differentially affects the development of dendritic cell subsets

Dendritic cells (DCs) are important orchestrators of immune responses. Their development in the bone marrow is controlled by transcription factors, but epigenetic mechanisms remain poorly understood. DOT1L is emerging as a key epigenetic regulator in immune cells. By mapping DOT1L-mediated histone H3K79 methylation in canonical DC subsets, we observed that DOT1L modified common as well as DC subset-specific genes. In vitro- or in vivo-induced deletion of Dot1l followed by in vitro cell culture resulted in a decrease in myeloid progenitors and plasmacytoid DCs (pDCs) and an increase in cDC2s, while cDC1s remained unchanged. In vitro generated Dot1l-KO DCs were unable to produce IFN upon stimulation. Moreover, transcriptomes of Dot1l-KO DC subsets exhibited enrichment of antigen presentation pathways and MHC class II surface levels were upregulated in pDCs. Mechanistically, inhibition of DOT1L linked the observed effects to its methyltransferase activity. Together, our data indicate that in DCs DOT1L differentially affects the development of canonical subsets and suppresses antigen presentation pathways.

cell biology↗

bioRxiv2021

Impaired LAIR-1-mediated immune control due to collagen degradation in fibrosis

Tissue repair is disturbed in fibrotic diseases like systemic sclerosis (SSc), where the deposition of large amounts of extracellular matrix components such as collagen interferes with organ function. LAIR-1 is an inhibitory collagen receptor highly expressed on tissue immune cells. We questioned whether in SSc, impaired LAIR-1-collagen interaction is contributing to the ongoing inflammation and fibrosis. We found that SSc patients do not have an intrinsic defect in LAIR-1 expression or function. Instead, fibroblasts from SSc patients deposit disorganized collagen products in vitro, which are dysfunctional LAIR-1 ligands. This can be mimicked in healthy fibroblasts stimulated by soluble factors that drive inflammation and fibrosis in SSc and is dependent of matrix metalloproteinases and platelet-derived growth factor receptor signaling. In support of a non-redundant role of LAIR-1 in the control of fibrosis, we found that LAIR-1-deficient mice have increased skin fibrosis in response to repeated injury and in the bleomycin mouse model for SSc. Thus, LAIR-1 represents an essential control mechanism for tissue repair. In fibrotic disease, excessive collagen degradation may lead to a disturbed feedback loop. The presence of functional LAIR-1 in patients provides a therapeutic opportunity to reactivate this intrinsic negative feedback mechanism in fibrotic diseases.

immunology↗

bioRxiv2021

Nuclear receptor subfamily 4A signaling as a key disease pathway of CD1c+ dendritic cell dysregulation in systemic sclerosis

ObjectivesTo identify key disease pathways driving conventional dendritic cell (cDC) alterations in Systemic Sclerosis (SSc). MethodsTranscriptomic profiling was performed on peripheral blood CD1c+ cDCs (cDC2s) isolated from 12 healthy donors and 48 SSc patients with all major disease subtypes. Differential expression analysis comparing the different SSc subtypes and healthy donors was performed to uncover genes dysregulated in SSc. To identify biologically relevant pathways, a gene co-expression network was built using Weighted Gene Correlation Network Analysis. We validated the role of key transcriptional regulators using ChIP-sequencing and in vitro functional assays. ResultsWe identified 17 modules of co-expressed genes in cDC2s that correlated with SSc subtypes and key clinical traits including auto-antibodies, skin score, and occurrence of interstitial lung disease. A module of immune regulatory genes was markedly down regulated in patients with the diffuse SSc subtype characterized by severe fibrosis. Transcriptional regulatory network analysis performed on this module predicted NR4A (nuclear receptor 4A) subfamily (NR4A1, NR4A2, NR4A3) genes as the key transcriptional mediators of inflammation. Indeed, ChIP-sequencing analysis supported that these NR4A members target numerous differentially expressed genes in SSc cDC2s. Inclusion of NR4A receptor agonists in culture-based experiments provided functional proof that dysregulation of NR4As affects cytokine production by cDC2s and modulates downstream T-cell activation. ConclusionsNR4A1, NR4A2 and NR4A3 are important regulators of immunosuppressive and fibrosis-associated pathways in SSc cDC2s. Thus, the NR4A family represent novel potential targets to restore cDC homeostasis in SSc. KEY MESSAGESO_ST_ABSWhat is already known about this subject?C_ST_ABSO_LICD1c+ conventional dendritic cells (cDC2s) are implicated as key players in Systemic Sclerosis (SSc), but key molecular mechanisms underlying their dysregulation were unknown. C_LI What does this study add?O_LITranscriptomic analysis and network analysis identified modules of coexpressed genes in cDC2s that correlated with SSc subtypes and key clinical traits. C_LIO_LIThe NR4A (nuclear receptor 4A) subfamily (NR4A1, NR4A2, NR4A3) genes act as master regulators of key immune regulatory genes dysregulated in SSc cDC2s, as shown by multi-omics integration analysis using transcriptomics and targeted ChIP-sequencing. C_LIO_LIPharmacological activation of NR4As inhibits pro-inflammatory cytokine production and CD4+ T-cell activation by cDC2s. C_LI How might this impact on clinical practice or future developments?O_LINR4As are attractive candidates for novel treatment options to attenuate pro-inflammatory and pro-fibrotic responses in SSc patients. C_LI

immunology↗