Biology subjects

Kloet, S. L.

Publications and source records attributed to Kloet, S. L..

6 recordsLinked to original sources

bioRxiv2026

Ageing of the Upper Airway Epithelial Niche Limits Tissue-Resident T Cell Immunity

Respiratory tract infections are a major cause of morbidity and mortality among older adults worldwide. Yet, how ageing shapes protective immunity within the upper respiratory tract (URT) remains poorly understood. Here, we profiled the nasal immune landscape of young adults and older adults with and without frailty, using high-dimensional cytometry, proteomics, single-cell transcriptomics and T cell receptor (TCR) sequencing. Ageing was associated with a selective reduction of tissue-resident memory T (Trm) cells, independent of effector T cell numbers, inflammageing levels or frailty and was accompanied by a decline in T cell receptor repertoire stability. Trm cells from older adults also showed decreased steady-state IFN{gamma} expression, accompanied by reduced antiviral transcriptional programs in the mucosa. Mechanistically, in vitro PBMC-epithelium co-culture models revealed that older adults have a reduced capacity for Trm differentiation, which was associated with a diminished epithelial TGF-{beta} secretion, driven by reduced expression in ciliated epithelial cells. Together, these findings reveal that URT immunity deteriorates with age due to disrupted epithelial-immune crosstalk. This identifies the epithelial niche as a key regulator of mucosal immune ageing and suggests that enhancing TGF{beta} signaling may improve the effectiveness of mucosal airway vaccination strategies in older populations.

immunology↗

bioRxiv2026

Distinct transcriptional programs define human IgG4+ memory B cells

Human immunoglobulin G4 (IgG4) shapes both protective and pathogenic immunity, influencing conditions ranging from allergy and autoimmunity to cancer. However, subclass-specific targeting of memory B cells remains challenging due to limited knowledge of their phenotypic and functional heterogeneity. Here, we show that IgG4+ memory B cells are overrepresented in a niche of FCER2+BAFFR+ memory B cells, can be classified in several subtypes, have a distinct transcription factor profile and are the only memory B cell subset to express sterile IGHE transcripts. While IgG4+ B cells display a unique transcriptional profile, only BAFFR, IL5Rb and the B cell receptor were upregulated on protein level on IgG4+ cells. IgG4+ B cells have normal repertoire diversity, but a distinct germline V-gene usage, suggesting IgG4 responses are driven by specific antigens. By labeling autoreactive B cells, we confirmed that MuSK myasthenia gravis (an archetypal IgG4-mediatedautoimmune disease) patients have a normal memory B cell profile and that autoreactive IgG4+ memory B cells are extremely rare. These results highlight the unique features of IgG4+ B cells, provide insight on potential subclass-specific therapeutic targets and point towards an antigen-driven IgG4 response within a largely non-autoreactive memory B cell pool.

immunology↗

bioRxiv2024

Metagenomic global survey and in-depth genomic analyses of Ruminococcus gnavus reveal differences across host lifestyle and health status

Ruminococcus gnavus is a highly prevalent gut bacterium (present in >90% of healthy individuals), of which increased abundance is associated with chronic inflammatory diseases, most notably Crohns disease. Nevertheless, its global distribution has not been investigated and little is known about intraspecies genomic variation. Through a large-scale survey of 12,791 gut metagenomes, we recapitulated known associations with metabolic diseases and inflammatory bowel disease. We uncover a higher prevalence and abundance of R. gnavus in Westernized populations and observe relative abundances of up to 83% in newborns and infants. Next, we built a collection of existing and newly cultured R. gnavus isolates (N = 45) from both healthy individuals and Crohns disease patients and subjected these to PacBio circular consensus sequencing to greatly expand the number of complete R. gnavus genomes. Analysis of these genomes as well as publicly available high quality draft genomes (total > 300 genomes) revealed multiple clades which separated Crohns-derived isolates from healthy-derived isolates. Functional analyses of genes predicted to constitute R. gnavus virulence factors could not explain this separation. Bacterial GWAS revealed that Crohns-derived isolates were enriched in genes related to mobile elements and putative mucin foraging. Together, we present one of the largest complete genome collections of any commensal gut microbe and provide novel biological insights into the global distribution and genomic variation of R. gnavus.

microbiology↗

bioRxiv2022

Design and performance of a long-read sequencing panel for pharmacogenomics

Pharmacogenomics (PGx)-guided drug treatment is one of the cornerstones of personalized medicine. However, the genes involved in drug response are highly complex and known to carry many (rare) variants. Current technologies (short-read sequencing and SNP panels) are limited in their ability to resolve these genes and characterize all variants. Moreover, these technologies cannot always phase variants to their allele of origin. Recent advance in long-read sequencing technologies have shown promise in resolving these problems. Here we present a long-read sequencing panel-based approach for PGx using PacBio HiFi sequencing. A capture based approach was developed using a custom panel of clinically-relevant pharmacogenes including up- and downstream regions. A total of 27 samples were sequenced and panel accuracy was determined using benchmarking variant calls for 3 Genome in a Bottle samples and GeT-RM star(*)-allele calls for 21 samples.. The coverage was uniform for all samples with an average of 94% of bases covered at >30x. When compared to benchmarking results, accuracy was high with an average F1 score of 0.89 for INDELs and 0.98 for SNPs. Phasing was good with an average of 68% the target region phased (compared to ~20% for short-reads) and an average phased haploblock size of 6.6kbp. Using Aldy 4, we compared our variant calls to GeT-RM data for 8 genes (CYP2B6, CYP2C19, CYP2C9, CYP2D6, CYP3A4, CYP3A5, SLCO1B1, TPMT), and observed highly accurate star(*)-allele calling with 98.2% concordance (165/168 calls), with only one discordance in CYP2C9 leading to a different predicted phenotype. We have shown that our long-read panel-based approach results in high accuracy and target phasing for SNVs as well as for clinical star(*)-alleles.

genetics↗

bioRxiv2022

Clostridioides difficile PCR ribotype 151 is polyphyletic and includes pathogenic isolates from cryptic clade C-II with mono-toxin pathogenicity loci that can escape routine diagnostics

We report a patient case with pseudomembranous colitis associated with a mono-toxin producing Clostridioides difficile belonging to the very rarely diagnosed PCR ribotype (RT) 151. The infection was difficult to diagnose, since the isolate and the feces sample tested negative for toxin-encoding genes using a routine commercial test. This prompted us to sequence n = 11 RT151s from various geographical regions to study their genomic characteristics and relatedness. By including whole genome sequence data from other sources, we could further place these isolates into the phylogenetic tree of C. difficile and assign them to their respective clades. These analyses revealed that 1) RT151s are polyphyletic with isolates falling into clades 1, and cryptic clades C-I and C-II 2) RT151 contains both non-toxigenic and toxigenic isolates and 3) RT151 C-II isolates contained mono-toxin pathogenicity loci (PaLoc). Additional analysis with PacBio circular consensus sequencing revealed that the isolate from our patient case report contains a novel PaLoc insertion site, lacked tcdA and a had significantly divergent tcdB sequence that might explain the failure of the diagnostic test. The study is noteworthy as 1) RT151 encompasses both typical and cryptic clades and 2) conclusive evidence for CDI due to clade C-II isolates was hitherto lacking.

microbiology↗

bioRxiv2022

Carriage of three plasmids in a single human clinical isolate of Clostridioides difficile

A subset of clinical isolates of Clostridioides difficile contains one or more plasmids and these plasmids can harbor virulence and antimicrobial resistance determinants. Despite their potential importance, C. difficile plasmids remain poorly characterized. Here, we describe a human clinical isolate that carries three plasmids from three different plasmid families that are therefore compatible. For two of these, we identify a region capable of sustaining plasmid replication in C. difficile. Together, our data advance our understanding of C. difficile plasmid biology. HighlightsThe complete circular genome sequence is provided for a C. difficile isolate harboring three plasmids These three plasmids (pJMR5-1, pJMR5-4 and pJRM5-W) are therefore compatible in a single strain Sequence analysis suggest a modular nature of plasmid families to which the pJMR-plasmids belong A functional replicon was cloned from pJMR5-1 (pCD-ECE1 family) and pJMR5-W (pCD-WTSI1 family) and plasmids carrying this replicon are compatible with plasmid pCD630

microbiology↗