Exploring the relationship between early cognitive ability and age-60 sleep quality: The Newcastle Thousand Families Study birth cohort.

OBJECTIVES: Poor sleep quality has been linked to adverse health outcomes. It is important to understand factors contributing to sleep quality. Previous research has suggested increased cognition and education duration have a protective effect on sleep quality in old age. This study aimed to assess the hypothesis that age-11 intelligence quotient and highest achieved education level are associated with subjective sleep quality at age 60. METHODS: Participants are members of the Newcastle Thousand Families Study birth cohort, all born in 1947. Data included a calculated intelligence quotient score based on participant's 11-plus exam results, highest achieved education level, social class at ages 25 and 50 and global Pittsburgh Sleep Quality Index (PSQI) at age 60. Multivariable regression analysis was used to investigate effect sizes of variables on global PSQI, which formed the basis of a path analysis model. RESULTS: After excluding participants with incomplete data, and those who had been diagnosed with sleep apnea, 251 participants were included in the path analysis model. Education level was associated with global PSQI (R=-0.653; 95% CI -1.161, -0.145; P = .012) but age-11 intelligence quotient was not. While a similar association was seen for women in the stratified analysis, no such associations were seen for men. CONCLUSIONS: The results of this study show an inverse relationship between education level, but not childhood intelligence quotient, and sleep quality in later life, in women only. Future research is needed to examine the mechanism underlying this relationship.

Host control of the microbiome: Mechanisms, evolution, and disease.

Many species, including humans, host communities of symbiotic microbes. There is a vast literature on the ways these microbiomes affect hosts, but here we argue for an increased focus on how hosts affect their microbiomes. Hosts exert control over their symbionts through diverse mechanisms, including immunity, barrier function, physiological homeostasis, and transit. These mechanisms enable hosts to shape the ecology and evolution of microbiomes and generate natural selection for microbial traits that benefit the host. Our microbiomes result from a perpetual tension between host control and symbiont evolution, and we can leverage the host's evolved abilities to regulate the microbiota to prevent and treat disease. The study of host control will be central to our ability to both understand and manipulate microbiotas for better health.

Computational framework for the generation of one-dimensional vascular models accounting for uncertainty in networks extracted from medical images.

One-dimensional (1D) cardiovascular models offer a non-invasive method to answer medical questions, including predictions of wave-reflection, shear stress, functional flow reserve, vascular resistance and compliance. This model type can predict patient-specific outcomes by solving 1D fluid dynamics equations in geometric networks extracted from medical images. However, the inherent uncertainty in in vivo imaging introduces variability in network size and vessel dimensions, affecting haemodynamic predictions. Understanding the influence of variation in image-derived properties is essential to assess the fidelity of model predictions. Numerous programs exist to render three-dimensional surfaces and construct vessel centrelines. Still, there is no exact way to generate vascular trees from the centrelines while accounting for uncertainty in data. This study introduces an innovative framework employing statistical change point analysis to generate labelled trees that encode vessel dimensions and their associated uncertainty from medical images. To test this framework, we explore the impact of uncertainty in 1D haemodynamic predictions in a systemic and pulmonary arterial network. Simulations explore haemodynamic variations resulting from changes in vessel dimensions and segmentation; the latter is achieved by analysing multiple segmentations of the same images. Results demonstrate the importance of accurately defining vessel radii and lengths when generating high-fidelity patient-specific haemodynamics models. KEY POINTS: This study introduces novel algorithms for generating labelled directed trees from medical images, focusing on accurate junction node placement and radius extraction using change points to provide haemodynamic predictions with uncertainty within expected measurement error. Geometric features, such as vessel dimension (length and radius) and network size, significantly impact pressure and flow predictions in both pulmonary and aortic arterial networks. Standardizing networks to a consistent number of vessels is crucial for meaningful comparisons and decreases haemodynamic uncertainty. Change points are valuable to understanding structural transitions in vascular data, providing an automated and efficient way to detect shifts in vessel characteristics and ensure reliable extraction of representative vessel radii.

Salmonella-driven intestinal edema in mice is characterized by tensed fibronectin fibers.

Intestinal edema is a common manifestation of numerous gastrointestinal diseases and is characterized by the accumulation of fluid in the interstitial space of the intestinal wall. Technical advances in laser capture microdissection and low-biomass proteomics now allow us to specifically characterize the intestinal edema proteome. Using advanced proteomics, we identify peptides derived from antimicrobial factors with high signal intensity, but also highlight major contributions from the blood clotting system, extracellular matrix (ECM) and protease-protease inhibitor networks. The ECM is a complex fibrillar network of macromolecules that provides structural and mechanical support to the intestinal tissue. One abundant component of the ECM observed in Salmonella-driven intestinal edema is the glycoprotein fibronectin, recognized for its structure-function interplay regulated by mechanical forces. Using mechanosensitive staining of fibronectin fibers reveals that they are tensed in the edema, despite the high abundance of proteases able to cleave fibronectin. In contrast, fibronectin fibers increasingly relax in other cecal tissue areas as the infection progresses. Co-staining for fibrin(ogen) indicates the formation of a provisional matrix in the edema, similar to what is observed in response to skin injury, while collagen staining reveals a sparse and disrupted collagen fiber network. These observations plus the absence of low tensional fibronectin fibers and the additional finding of a high number of protease inhibitors in the edema proteome could indicate a critical role of stretched fibronectin fibers in maintaining tissue integrity in the severely inflamed cecum. Understanding these processes may also provide valuable functional diagnostic markers of intestinal disease progression in the future.

Cumulative methotrexate dose is not associated with liver fibrosis in patients with a history of moderate-to-severe psoriasis.

BACKGROUND: There are established risk factors for liver fibrosis (LF), but data on the impact of methotrexate on LF in patients with psoriasis are lacking. OBJECTIVES: This cross-sectional study aimed to determine the prevalence of LF in patients with psoriasis and to evaluate the relationship between LF, cumulative methotrexate dose and other LF risk factors. METHODS: Adults with a history of moderate-to-severe chronic plaque psoriasis were recruited between June 2020 and March 2021. Patients underwent transient elastography to evaluate LF. Three values for liver stiffness measurement (LSM) were assessed, indicating mild or worse LF (≥ 7 kPa), moderate or worse LF (≥ 7.9 kPa) and advanced LF (≥ 9.5kPa). Cumulative methotrexate dose and other potential risk factors for LF were assessed. RESULTS: Overall, 240 patients were recruited and 204 participants with valid LSM values were included in the analysis [median age 48 years [interquartile range (IQR) 37-57]; 51% female sex; 56% body mass index (BMI) ≥ 30 (kg m-2) and a median Alcohol Use Disorders Identification Test (AUDIT) score of 4 (IQR 1-7, 23% score ≥ 8)]. In total, 91% had received methotrexate [median duration 36 months (IQR 14-78)]. Prevalence of LF was 36%, 25% and 17% using LSM ≥ 7 kPa, ≥ 7.9 kPa and ≥ 9.5 kPa, respectively. There was no association between cumulative methotrexate dose [median 2.16 (IQR 0.93-5.2)] and continuous LSM values [unstandardized coefficient 0.16, 95% confidence interval (CI) -0.49 to 0.82, P = 0.626] or using the categorical LSM cutoff values: ≥ 7 kPa [unadjusted odds ratio 1.06 (95% CI 0.97-1.15), P = 0.192], ≥ 7.9 kPa [unadjusted odds ratio 1.03 (95% CI 0.94-1.12), P = 0.577] and ≥ 9.5 kPa (unadjusted odds ratio 1.01, 95% CI 0.91-1.12; P = 0.843). The following risk factors were associated with higher LSM values: BMI (P ≤ 0.001), waist circumference (P ≤ 0.001), metabolic syndrome (P ≤ 0.001), AUDIT score (P = 0.020) and FIB-4 score (P = 0.03). BMI ≥ 28, diabetes and metabolic syndrome were shown to be better predictors of LF compared with FIB-4 score. CONCLUSIONS: This study confirms a high prevalence of significant LF in patients with psoriasis. Cumulative methotrexate dose was not associated with LF. Patients with BMI ≥ 28, metabolic syndrome and diabetes are at higher risk for LF. These risk factors may help to identify when a more detailed liver health assessment is needed.

Psoriasis is a common inflammatory skin disease affecting 3% of the UK population. People with psoriasis appear to have higher rates of liver fibrosis (scarring in the liver from injury or inflammation) compared with people without psoriasis. There are several risk factors for increasing chances of developing liver fibrosis, including obesity, alcohol and diabetes; however, there have been some concerns that methotrexate (a medicine used to treat psoriasis) could also contribute to liver fibrosis. The majority of people needing systemic therapy (such as oral medicines) will try methotrexate first as per National Institute for Health and Care Excellence (NICE) guidance. In this study carried out in the UK, we aimed to look at the relationship between the cumulative dose (total over time) of methotrexate and liver fibrosis and the relationship between other risk factors and liver fibrosis (e.g. body mass index (BMI) (a measure that uses your height and weight to work out whether your weight is healthy), diabetes, alcohol intake and metabolic syndrome (a combination of diabetes, high blood pressure and obesity)). Liver fibrosis was measured using transient elastography, which is a non-invasive technique similar to an ultrasound. We also aimed to find out whether the clinical risk factors for liver fibrosis and a simple test called a 'FIB-4 score' (measured using blood test values and age) can predict a person's chance of developing liver fibrosis, in order to determine which people will benefit most from transient elastography. From our results, we were able to confirm that liver scarring is prevalent in our patients with psoriasis. We did not find an association between cumulative methotrexate and liver scarring. However, BMI, diabetes, metabolic syndrome and FIB-4 score were associated with liver scarring. We found that BMI ≥ 28, metabolic syndrome and diabetes can be used to identify patients who require a liver health assessment. Overall, the study findings suggest that cumulative methotrexate dose is not associated with liver fibrosis in people with a history of moderate-to-severe psoriasis.

Computational framework for the generation of one-dimensional vascular models accounting for uncertainty in networks extracted from medical images.

One-dimensional (1D) cardiovascular models offer a non-invasive method to answer medical questions, including predictions of wave-reflection, shear stress, functional flow reserve, vascular resistance, and compliance. This model type can predict patient-specific outcomes by solving 1D fluid dynamics equations in geometric networks extracted from medical images. However, the inherent uncertainty in in-vivo imaging introduces variability in network size and vessel dimensions, affecting hemodynamic predictions. Understanding the influence of variation in image-derived properties is essential to assess the fidelity of model predictions. Numerous programs exist to render three-dimensional surfaces and construct vessel centerlines. Still, there is no exact way to generate vascular trees from the centerlines while accounting for uncertainty in data. This study introduces an innovative framework employing statistical change point analysis to generate labeled trees that encode vessel dimensions and their associated uncertainty from medical images. To test this framework, we explore the impact of uncertainty in 1D hemodynamic predictions in a systemic and pulmonary arterial network. Simulations explore hemodynamic variations resulting from changes in vessel dimensions and segmentation; the latter is achieved by analyzing multiple segmentations of the same images. Results demonstrate the importance of accurately defining vessel radii and lengths when generating high-fidelity patient-specific hemodynamics models.

Surface Cross-Linking by Macromolecular Tethers Enhances Virus-like Particles' Resilience to Mucosal Stress Factors.

Virus-like particles (VLPs) are emerging as nanoscaffolds in a variety of biomedical applications including delivery of vaccine antigens and cargo such as mRNA to mucosal surfaces. These soft, colloidal, and proteinaceous structures (capsids) are nevertheless susceptible to mucosal environmental stress factors. We cross-linked multiple capsid surface amino acid residues using homobifunctional polyethylene glycol tethers to improve the persistence and survival of the capsid to model mucosal stressors. Surface cross-linking enhanced the stability of VLPs assembled from Acinetobacter phage AP205 coat proteins in low pH (down to pH 4.0) and high protease concentration conditions (namely, in pig and mouse gastric fluids). Additionally, it increased the stiffness of VLPs under local mechanical indentation applied using an atomic force microscopy cantilever tip. Small angle X-ray scattering revealed an increase in capsid diameter after cross-linking and an increase in capsid shell thickness with the length of the PEG cross-linkers. Moreover, surface cross-linking had no effect on the VLPs' mucus translocation and accumulation on the epithelium of in vitro 3D human nasal epithelial tissues with mucociliary clearance. Finally, it did not compromise VLPs' function as vaccines in mouse subcutaneous vaccination models. Compared to PEGylation without cross-linking, the stiffness of surface cross-linked VLPs were higher for the same length of the PEG molecule, and also the lifetimes of surface cross-linked VLPs were longer in the gastric fluids. Surface cross-linking using macromolecular tethers, but not simple conjugation of these molecules, thus offers a viable means to enhance the resilience and survival of VLPs for mucosal applications.

From microbiome composition to functional engineering, one step at a time.

SUMMARYCommunities of microorganisms (microbiota) are present in all habitats on Earth and are relevant for agriculture, health, and climate. Deciphering the mechanisms that determine microbiota dynamics and functioning within the context of their respective environments or hosts (the microbiomes) is crucially important. However, the sheer taxonomic, metabolic, functional, and spatial complexity of most microbiomes poses substantial challenges to advancing our knowledge of these mechanisms. While nucleic acid sequencing technologies can chart microbiota composition with high precision, we mostly lack information about the functional roles and interactions of each strain present in a given microbiome. This limits our ability to predict microbiome function in natural habitats and, in the case of dysfunction or dysbiosis, to redirect microbiomes onto stable paths. Here, we will discuss a systematic approach (dubbed the N+1/N-1 concept) to enable step-by-step dissection of microbiome assembly and functioning, as well as intervention procedures to introduce or eliminate one particular microbial strain at a time. The N+1/N-1 concept is informed by natural invasion events and selects culturable, genetically accessible microbes with well-annotated genomes to chart their proliferation or decline within defined synthetic and/or complex natural microbiota. This approach enables harnessing classical microbiological and diversity approaches, as well as omics tools and mathematical modeling to decipher the mechanisms underlying N+1/N-1 microbiota outcomes. Application of this concept further provides stepping stones and benchmarks for microbiome structure and function analyses and more complex microbiome intervention strategies.

Associations between early infections and childhood cognition in the Newcastle Thousand Families Study birth cohort.

Childhood infections have been shown to stunt growth, contribute to malnutrition and reduce cognition in early adulthood. This study aimed to assess relationships between early life infections and childhood cognition at age 11 years in the Newcastle Thousand Families Study (NTFS). The analysis included 741 members from the NTFS who had complete data for infections between birth and 5 years, and the 11-plus examinations. School records from the 11-plus examinations showed cognitive (IQ), English (EQ) and arithmetic (AQ) abilities. Housing conditions, overcrowding, birth order and social class were recorded at birth. Helicobacter pylori seropositivity was measured at age 49-51 years. Multivariable linear regression was used to examine relationships between infections and cognition. The total number of infections in the first 5 years of life was not significantly associated with IQ, EQ or AQ, nor were there significant relationships between cognitive outcomes and most infections. Tonsillitis did display a positive, significant association with IQ after adjustment for confounders (b = 6.43, 95% CI 0.92, 11.94, p = 0.022). Lower respiratory tract infections (LRTIs) showed significant negative relationships with all cognitive outcomes. H. pylori seropositivity at age 50 exhibited negative, significant relationships with EQ (p = 0.014) and AQ (p = 0.024) after adjustment for confounders. Although no significant relationship between overall infections and cognition were found, there were indications that LRTIs and gastrointestinal system infections may limit cognitive development. Given these infections remain prevalent, further research regarding severity and recurrence of infections and how they affect childhood cognition is needed.

Identifying, synthesising and appraising existing evidence relating to myalgic encephalomyelitis/chronic fatigue syndrome and pregnancy: a mixed-methods systematic review.

OBJECTIVES: To identify, synthesise and appraise evidence relating to myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and pregnancy. DESIGN: Mixed-methods systematic review, using convergent segregated design. DATA SOURCES: MEDLINE, EMBASE, Scopus, PsycINFO, CINAHL, MedRxiv, PROSPERO and grey literature sources through 6 August 2023. ELIGIBILITY CRITERIA: We included original research studies, expert opinion and grey literature reporting on ME/CFS and pregnancy/post partum (up to 2 years), risk of pregnancy outcomes with ME/CFS or experiences during pregnancy for mother, partner or health and social care professionals following ME/CFS during pregnancy, all where the evidence was relevant to a confirmed ME/CFS diagnosis prior to pregnancy. DATA EXTRACTION AND SYNTHESIS: Three independent reviewers completed all screening, data extraction and quality assessment. Risk of bias was assessed using the mixed-methods appraisal tool V.2018. Qualitative and quantitative literature was analysed separately using thematic and descriptive syntheses. Findings were integrated through configuration. RESULTS: Searches identified 3675 articles, 16 met the inclusion criteria: 4 quantitative (1 grey), 11 qualitative (9 grey) and 1 grey mixed-methods study. Of the four quantitative studies that reported on ME/CFS severity during pregnancy, two suggested pregnancy negatively impacted on ME/CFS, one found most women had no change in ME/CFS symptoms and one found ME/CFS improved; this difference in symptom severity across studies was supported by the qualitative evidence. The qualitative literature also highlighted the importance of individualised care throughout pregnancy and birth, and the need for additional support during family planning, pregnancy and with childcare. Only one quantitative study reported on pregnancy outcomes, finding decreased vaginal births and higher rates of spontaneous abortions and developmental and learning delays associated with pregnancies in those with ME/CFS. CONCLUSIONS: Current evidence on ME/CFS in pregnancy is limited and findings inconclusive. More high-quality research is urgently needed to support the development of evidence-based guidelines on ME/CFS and pregnancy.

Non-invasive monitoring of microbiota and host metabolism using secondary electrospray ionization-mass spectrometry.

The metabolic "handshake" between the microbiota and its mammalian host is a complex, dynamic process with major influences on health. Dissecting the interaction between microbial species and metabolites found in host tissues has been a challenge due to the requirement for invasive sampling. Here, we demonstrate that secondary electrospray ionization-mass spectrometry (SESI-MS) can be used to non-invasively monitor metabolic activity of the intestinal microbiome of a live, awake mouse. By comparing the headspace metabolome of individual gut bacterial culture with the "volatilome" (metabolites released to the atmosphere) of gnotobiotic mice, we demonstrate that the volatilome is characteristic of the dominant colonizing bacteria. Combining SESI-MS with feeding heavy-isotope-labeled microbiota-accessible sugars reveals the presence of microbial cross-feeding within the animal intestine. The microbiota is, therefore, a major contributor to the volatilome of a living animal, and it is possible to capture inter-species interaction within the gut microbiota using volatilome monitoring.

License to Clump: Secretory IgA Structure-Function Relationships Across Scales.

Secretory antibodies are the only component of our adaptive immune system capable of attacking mucosal pathogens topologically outside of our bodies. All secretory antibody classes are (a) relatively resistant to harsh proteolytic environments and (b) polymeric. Recent elucidation of the structure of secretory IgA (SIgA) has begun to shed light on SIgA functions at the nanoscale. We can now begin to unravel the structure-function relationships of these molecules, for example, by understanding how the bent conformation of SIgA enables robust cross-linking between adjacent growing bacteria. Many mysteries remain, such as the structural basis of protease resistance and the role of noncanonical bacteria-IgA interactions. In this review, we explore the structure-function relationships of IgA from the nano- to the metascale, with a strong focus on how the seemingly banal "license to clump" can have potent effects on bacterial physiology and colonization.

The microbiota conditions a gut milieu that selects for wild-type Salmonella Typhimurium virulence.

Salmonella Typhimurium elicits gut inflammation by the costly expression of HilD-controlled virulence factors. This inflammation alleviates colonization resistance (CR) mediated by the microbiota and thereby promotes pathogen blooms. However, the inflamed gut-milieu can also select for hilD mutants, which cannot elicit or maintain inflammation, therefore causing a loss of the pathogen's virulence. This raises the question of which conditions support the maintenance of virulence in S. Typhimurium. Indeed, it remains unclear why the wild-type hilD allele is dominant among natural isolates. Here, we show that microbiota transfer from uninfected or recovered hosts leads to rapid clearance of hilD mutants that feature attenuated virulence, and thereby contributes to the preservation of the virulent S. Typhimurium genotype. Using mouse models featuring a range of microbiota compositions and antibiotic- or inflammation-inflicted microbiota disruptions, we found that irreversible disruption of the microbiota leads to the accumulation of hilD mutants. In contrast, in models with a transient microbiota disruption, selection for hilD mutants was prevented by the regrowing microbiota community dominated by Lachnospirales and Oscillospirales. Strikingly, even after an irreversible microbiota disruption, microbiota transfer from uninfected donors prevented the rise of hilD mutants. Our results establish that robust S. Typhimurium gut colonization hinges on optimizing its manipulation of the host: A transient and tempered microbiota perturbation is favorable for the pathogen to both flourish in the inflamed gut and also minimize loss of virulence. Moreover, besides conferring CR, the microbiota may have the additional consequence of maintaining costly enteropathogen virulence mechanisms.

Nanoscale clustering by O-antigen-Secretory Immunoglobulin-A binding limits outer membrane diffusion by encaging individual Salmonella cells.

Secreted immunoglobulins, predominantly SIgA, influence the colonization and pathogenicity of mucosal bacteria. While part of this effect can be explained by SIgA-mediated bacterial aggregation, we have an incomplete picture of how SIgA binding influences cells independently of aggregation. Here we show that akin to microscale crosslinking of cells, SIgA targeting the Salmonella Typhimurium O-antigen extensively crosslinks the O-antigens on the surface of individual bacterial cells at the nanoscale. This crosslinking results in an essentially immobilized bacterial outer membrane. Membrane immobilization, combined with Bam-complex mediated outer membrane protein insertion results in biased inheritance of IgA-bound O-antigen, concentrating SIgA-bound O-antigen at the oldest poles during cell growth. By combining empirical measurements and simulations, we show that this SIgA-driven biased inheritance increases the rate at which phase-varied daughter cells become IgA-free: a process that can accelerate IgA escape via phase-variation of O-antigen structure. Our results show that O-antigen-crosslinking by SIgA impacts workings of the bacterial outer membrane, helping to mechanistically explain how SIgA may exert aggregation-independent effects on individual microbes colonizing the mucosae.

"EvoVax" - A rationally designed inactivated Salmonella Typhimurium vaccine induces strong and long-lasting immune responses in pigs.

Salmonella enterica subspecies enterica serovar Typhimurium (S.Tm) poses a considerable threat to public health due to its zoonotic potential. Human infections are mostly foodborne, and pork and pork products are ranked among the top culprits for transmission. In addition, the high percentage of antibiotic resistance, especially in monophasic S.Tm, limits treatment options when needed. Better S.Tm control would therefore be of benefit both for farm animals and for safety of the human food chain. A promising pre-harvest intervention is vaccination. In this study we tested safety and immunogenicity of an oral inactivated S.Tm vaccine, which has been recently shown to generate an "evolutionary trap" and to massively reduce S.Tm colonization and transmission in mice. We show that this vaccine is highly immunogenic and safe in post-weaning pigs and that administration of a single oral dose results in a strong and long-lasting serum IgG response. This has several advantages over existing - mainly live - vaccines against S.Tm, both in improved seroconversion and reduced risk of vaccine-strain persistence and reversion to virulence.

Differences Between Self-Reported and Objectively Measured Hearing Loss at Age 61-63 Years: The Newcastle Thousand Families Birth Cohort.

PURPOSE: Hearing loss is most prevalent among older adults, yet underestimated by patients, clinicians, and research communities. This study aimed to assess the accuracy of self-reported hearing difficulties among a group of adults aged 61-63 years, against audiometric measures. METHOD: The analysis used a sample (N = 346) of the Newcastle Thousand Families Study birth cohort. Data from audiological examinations and self-reported hearing difficulties were used to compare subjective and objective hearing. Hearing aid use was also assessed. RESULTS: Over 40% of the participants had some level of hearing loss (n = 155, 44.8%), and 31% (n = 133) of these reported having hearing problems during subjective assessment. Only 18 (10%) of those with objectively measured hearing loss reported using hearing aids. CONCLUSIONS: There was an inconsistency between measured and self-perceived hearing loss among adults aged 61-63 years in this cohort. The small number of hearing aid users in the cohort is a concern, in that people in this age group appear not to be getting the help they need. The data also add to the research evidence that people at this age underestimate their hearing loss.

Microbiomes in Neverland.

Differentiating the effects of infant microbiota, developmental, and nutritional changes on immunological maturation during weaning is an ongoing challenge. In this issue of Cell Host & Microbe, Lubin and colleagues report a gnotobiotic mouse model that maintains neonatal-like microbiome composition into adulthood to help answer burning questions in this field.

Fitness advantage of Bacteroides thetaiotaomicron capsular polysaccharide in the mouse gut depends on the resident microbiota.

Many microbiota-based therapeutics rely on our ability to introduce a microbe of choice into an already-colonized intestine. In this study, we used genetically barcoded Bacteroides thetaiotaomicron (B. theta) strains to quantify population bottlenecks experienced by a B. theta population during colonization of the mouse gut. As expected, this reveals an inverse relationship between microbiota complexity and the probability that an individual wildtype B. theta clone will colonize the gut. The polysaccharide capsule of B. theta is important for resistance against attacks from other bacteria, phage, and the host immune system, and correspondingly acapsular B. theta loses in competitive colonization against the wildtype strain. Surprisingly, the acapsular strain did not show a colonization defect in mice with a low-complexity microbiota, as we found that acapsular strains have an indistinguishable colonization probability to the wildtype strain on single-strain colonization. This discrepancy could be resolved by tracking in vivo growth dynamics of both strains: acapsular B.theta shows a longer lag phase in the gut lumen as well as a slightly slower net growth rate. Therefore, as long as there is no niche competitor for the acapsular strain, this has only a small influence on colonization probability. However, the presence of a strong niche competitor (i.e., wildtype B. theta, SPF microbiota) rapidly excludes the acapsular strain during competitive colonization. Correspondingly, the acapsular strain shows a similarly low colonization probability in the context of a co-colonization with the wildtype strain or a complete microbiota. In summary, neutral tagging and detailed analysis of bacterial growth kinetics can therefore quantify the mechanisms of colonization resistance in differently-colonized animals.

Mechanical tuning of virus-like particles.

HYPOTHESIS: Virus-like particles (VLPs) are promising scaffolds for developing mucosal vaccines. For their optimal performance, in addition to design parameters from an immunological perspective, biophysical properties may need to be considered. EXPERIMENTS: We investigated the mechanical properties of VLPs scaffolded on the coat protein of Acinetobacter phage AP205 using atomic force microscopy and small angle X-ray scattering. FINDINGS: Investigations showed that AP205 VLP is a tough nanoshell of stiffness 93 ± 23 pN/nm and elastic modulus 0.11 GPa. However, its mechanical properties are modulated by attaching muco-inert polyethylene glycol to 46 ± 10 pN/nm and 0.05 GPa. Addition of antigenic peptides derived from SARS-CoV2 spike protein by genetic fusion increased the stiffness to 146 ± 54 pN/nm although the elastic modulus remained unchanged. These results, which are interpreted in terms of shell thickness and coat protein net charge variations, demonstrate that surface conjugation can induce appreciable changes in the biophysical properties of VLP-scaffolded vaccines.

Active eosinophils regulate host defence and immune responses in colitis.

In the past decade, single-cell transcriptomics has helped to uncover new cell types and states and led to the construction of a cellular compendium of health and disease. Despite this progress, some difficult-to-sequence cells remain absent from tissue atlases. Eosinophils-elusive granulocytes that are implicated in a plethora of human pathologies1-5-are among these uncharted cell types. The heterogeneity of eosinophils and the gene programs that underpin their pleiotropic functions remain poorly understood. Here we provide a comprehensive single-cell transcriptomic profiling of mouse eosinophils. We identify an active and a basal population of intestinal eosinophils, which differ in their transcriptome, surface proteome and spatial localization. By means of a genome-wide CRISPR inhibition screen and functional assays, we reveal a mechanism by which interleukin-33 (IL-33) and interferon-γ (IFNγ) induce the accumulation of active eosinophils in the inflamed colon. Active eosinophils are endowed with bactericidal and T cell regulatory activity, and express the co-stimulatory molecules CD80 and PD-L1. Notably, active eosinophils are enriched in the lamina propria of a small cohort of patients with inflammatory bowel disease, and are closely associated with CD4+ T cells. Our findings provide insights into the biology of eosinophils and highlight the crucial contribution of this cell type to intestinal homeostasis, immune regulation and host defence. Furthermore, we lay a framework for the characterization of eosinophils in human gastrointestinal diseases.