Unraveling the long-term effect of influenza vaccines.

The past decade has witnessed the emergence of highly sophisticated vaccines; still their mechanism of action is not fully understood. Wimmers et al. use advanced techniques to evaluate the immune landscape induced by flu vaccines and show that their effect on the immune system can last even 6 months from administration.

Gone with the Antibody.

Bacterial metabolites can reach distant organs, and in this issue of Immunity, Uchimura et al. (2018) show a fast systemic distribution of microbiota metabolites. This distribution is controlled by antibodies that accelerate bacterial transit through the small intestine, resulting in reduced local and systemic metabolite penetration and attenuation of immune responses.

The gut-brain vascular axis in neuroinflammation.

The multifaceted microbiota characterizing our gut plays a crucial role in maintaining immune, metabolic and tissue homeostasis of the intestine as well as of distal organs, including the central nervous system. Microbial dysbiosis is reported in several inflammatory intestinal diseases characterized by the impairment of the gut epithelial and vascular barriers, defined as leaky gut, and it is reported as a potential danger condition associated with the development of metabolic, inflammatory and neurodegenerative diseases. Recently, we pointed out the strict connection between the gut and the brain via a novel vascular axis. Here we want to deepen our knowledge on the gut-brain axis, with particular emphasis on the connection between microbial dysbiosis, leaky gut, cerebral and gut vascular barriers, and neurodegenerative diseases. The firm association between microbial dysbiosis and impairment of the vascular gut-brain axis will be summarized in the context of protection, amelioration or boosting of Alzheimer, Parkinson, Major depressive and Anxiety disorders. Understanding the relationship between disease pathophysiology, mucosal barrier function and host-microbe interaction will foster the use of the microbiome as biomarker for health and disease as well as a target for therapeutic and nutritional advances.

COVID-19 vaccines and a perspective on Africa.

Vaccines have dramatically changed the COVID-19 pandemic. Over 30 vaccines that were developed on four main platforms are currently being used globally, but a deep dissection of the immunological mechanisms by which they operate is limited to only a few of them. Here, we review the evidence describing specific aspects of the modes of action of COVID-19 vaccines; these include innate immunity, trained innate immunity, and mucosal responses. We also discuss the use of COVID-19 vaccines in the African continent which is ridden with inequality in its access to vaccines and vaccine-related immunological research. We argue that strengthening immunology research in Africa should inform on fundamental aspects of vaccination, including the relevance of genetics, trained innate immunity, and microbiome diversity.

Observation of the most H2-dense filled ice under high pressure.

Hydrogen hydrates are among the basic constituents of our solar system's outer planets, some of their moons, as well Neptune-like exo-planets. The details of their high-pressure phases and their thermodynamic conditions of formation and stability are fundamental information for establishing the presence of hydrogen hydrates in the interior of those celestial bodies, for example, against the presence of the pure components (water ice and molecular hydrogen). Here, we report a synthesis path and experimental observation, by X-ray diffraction and Raman spectroscopy measurements, of the most H[Formula: see text]-dense phase of hydrogen hydrate so far reported, namely the compound 3 (or C[Formula: see text]). The detailed characterisation of this hydrogen-filled ice, based on the crystal structure of cubic ice I (ice I[Formula: see text]), is performed by comparing the experimental observations with first-principles calculations based on density functional theory and the stochastic self-consistent harmonic approximation. We observe that the extreme (up to 90 GPa and likely beyond) pressure stability of this hydrate phase is due to the close-packed geometry of the hydrogen molecules caged in the ice I[Formula: see text] skeleton.

MSIpixel: a fully automated pipeline for compound annotation and quantitation in mass spectrometry imaging experiments.

Mass spectrometry imaging (MSI) is commonly used to map the spatial distribution of small molecules within complex biological matrices. One of the major challenges in imaging MS-based spatial metabolomics is molecular identification and metabolite annotation, to address this limitation, annotation is often complemented with parallel bulk LC-MS2-based metabolomics to confirm and validate identifications. Here we applied MSI method, utilizing data-dependent acquisition, to visualize and identify unknown molecules in a single instrument run. To reach this aim we developed MSIpixel, a fully automated pipeline for compound annotation and quantitation in MSI experiments. It overcomes challenges in molecular identification, and improving reliability and comprehensiveness in MSI-based spatial metabolomics.

Opening the doors of precision medicine: novel tools to assess intestinal barrier in inflammatory bowel disease and colitis-associated neoplasia.

Mounting evidence underscores the pivotal role of the intestinal barrier and its convoluted network with diet and intestinal microbiome in the pathogenesis of inflammatory bowel disease (IBD) and colitis-associated colorectal cancer (CRC). Moreover, the bidirectional association of the intestinal barrier with the liver and brain, known as the gut-brain axis, plays a crucial role in developing complications, including extraintestinal manifestations of IBD and CRC metastasis. Consequently, barrier healing represents a crucial therapeutic target in these inflammatory-dependent disorders, with barrier assessment predicting disease outcomes, response to therapy and extraintestinal manifestations.New advanced technologies are revolutionising our understanding of the barrier paradigm, enabling the accurate assessment of the intestinal barrier and aiding in unravelling the complexity of the gut-brain axis. Cutting-edge endoscopic imaging techniques, such as ultra-high magnification endocytoscopy and probe-based confocal laser endomicroscopy, are new technologies allowing real-time exploration of the 'cellular' intestinal barrier. Additionally, novel advanced spatial imaging technology platforms, including multispectral imaging, upconversion nanoparticles, digital spatial profiling, optical spectroscopy and mass cytometry, enable a deep and comprehensive assessment of the 'molecular' and 'ultrastructural' barrier. In this promising landscape, artificial intelligence plays a pivotal role in standardising and integrating these novel tools, thereby contributing to barrier assessment and prediction of outcomes.Looking ahead, this integrated and comprehensive approach holds the promise of uncovering new therapeutic targets, breaking the therapeutic ceiling in IBD. Novel molecules, dietary interventions and microbiome modulation strategies aim to restore, reinforce, or modulate the gut-brain axis. These advancements have the potential for transformative and personalised approaches to managing IBD.

The gut-brain axis: Correlation of choroid plexus volume and permeability with inflammatory biomarkers in Crohn's disease.

BACKGROUND: The dysregulation of the gut-brain axis in chronic inflammatory bowel diseases can cause neuro-psychological disturbances, but the underlying mechanisms are still not fully understood. The choroid plexus (CP) maintains brain homeostasis and nourishment through the secretion and clearance of cerebrospinal fluid. Recent research has demonstrated the existence of a CP vascular barrier in mice which is modulated during intestinal inflammation. This study investigates possible correlations between CP modifications and inflammatory activity in patients with Crohn's disease (CD). METHODS: In this prospective study, 17 patients with CD underwent concomitant abdominal and brain 3 T MRI. The volume and permeability of CP were compared with levels of C-reactive protein (CRP), fecal calprotectin (FC), sMARIA and SES-CD scores. RESULTS: The CP volume was negatively correlated with CRP levels (R = -0.643, p-value = 0.024) and FC (R = -0.571, p-value = 0.050). DCE metrics normalized by CP volume were positively correlated with CRP (K-trans: R = 0.587, p-value = 0.045; Vp: R = 0.706, p-value = 0.010; T1: R = 0.699, p-value = 0.011), and FC (Vp: R = 0.606, p-value = 0.037). CONCLUSIONS: Inflammatory activity in patients with CD is associated with changes in CP volume and permeability, thus supporting the hypothesis that intestinal inflammation could affect the brain through the modulation of CP vascular barrier also in humans.

Adipose tissue macrophage dysfunction is associated with a breach of vascular integrity in NASH.

BACKGROUND & AIMS: In non-alcoholic fatty liver disease (NAFLD), monocytes infiltrate visceral adipose tissue promoting local and hepatic inflammation. However, it remains unclear what drives inflammation and how the immune landscape in adipose tissue differs across the NAFLD severity spectrum. We aimed to assess adipose tissue macrophage (ATM) heterogeneity in a NAFLD cohort. METHODS: Visceral adipose tissue macrophages from lean and obese patients, stratified by NAFLD phenotypes, underwent single-cell RNA sequencing. Adipose tissue vascular integrity and breaching was assessed on a protein level via immunohistochemistry and immunofluorescence to determine targets of interest. RESULTS: We discovered multiple ATM populations, including resident vasculature-associated macrophages (ResVAMs) and distinct metabolically active macrophages (MMacs). Using trajectory analysis, we show that ResVAMs and MMacs are replenished by a common transitional macrophage (TransMac) subtype and that, during NASH, MMacs are not effectively replenished by TransMac precursors. We postulate an accessory role for MMacs and ResVAMs in protecting the adipose tissue vascular barrier, since they both interact with endothelial cells and localize around the vasculature. However, across the NAFLD severity spectrum, alterations occur in these subsets that parallel an adipose tissue vasculature breach characterized by albumin extravasation into the perivascular tissue. CONCLUSIONS: NAFLD-related macrophage dysfunction coincides with a loss of adipose tissue vascular integrity, providing a plausible mechanism by which tissue inflammation is perpetuated in adipose tissue and downstream in the liver. IMPACT AND IMPLICATIONS: Our study describes for the first time the myeloid cell landscape in human visceral adipose tissue at single-cell level within a cohort of well-characterized patients with non-alcoholic fatty liver disease. We report unique non-alcoholic steatohepatitis-specific transcriptional changes within metabolically active macrophages (MMacs) and resident vasculature-associated macrophages (ResVAMs) and we demonstrate their spatial location surrounding the vasculature. These dysfunctional transcriptional macrophage states coincided with the loss of adipose tissue vascular integrity, providing a plausible mechanism by which tissue inflammation is perpetuated in adipose tissue and downstream in the liver. Our study provides a theoretical basis for new therapeutic strategies to be directed towards reinstating the endogenous metabolic, homeostatic and cytoprotective functions of ResVAMs and MMacs, including their role in protecting vascular integrity.

Optimizing abemaciclib-induced diarrhea management in patients with breast cancer: a pragmatic 2-group study using a postbiotic microbiota stabilizer.

BACKGROUND: Abemaciclib-induced diarrhea is a relevant concern in clinical practice. Postbiotics have emerged as a promising option for managing it. MATERIALS AND METHODS: We conducted a retrospective-prospective, 2-group, observational study to assess the impact of the postbiotic PostbiotiX-Restore, derived by Lactobacillus paracasei CNCM I-5220, on abemaciclib-induced diarrhea in patients with hormone receptor-positive HER2-negative breast cancer. The prospective population (Postbio group) received postbiotic during the first cycle of abemaciclib, while the retrospective one received standard care (Standard group). Diarrhea grading was defined according to the National Cancer Institute's Common Terminology Criteria for Adverse Events. RESULTS: During the first cycle, diarrhea occurred in 78.9% of patients in the Standard cohort and 97.1% in the Postbio one, with most cases being G1-G2. Severe (G3) diarrhea was significantly less frequent in the Postbio group (0%) compared to the Standard one (7.9%; P = .029). Over the entire study period, while the grading difference was not statistically significant, G3 events were less frequent in the Postbio population (5.9%) than the Standard one (15.4%). Moreover, Postbio patients required fewer dose reductions due to diarrhea compared to the Standard group (P = .002). Notably, in the Postbio population, G1 and G2 events had short median durations (3 and 1 days, respectively) and, for the 2 patients experiencing G3 events during the second abemaciclib cycle (off postbiotic), diarrhea lasted only 1 day. CONCLUSIONS: Our study demonstrates the effect of PostbiotiX-Restore in mitigating abemaciclib-induced diarrhea, resulting in reduced severity, fewer dose reductions, and shorter duration. Further exploration and validation in larger cohorts are needed.

Training the microbiota to increase immune checkpoint blockade and to reduce toxicity.

There is no doubt that immunotherapy, particularly immune checkpoint blockade (ICB), has drastically improved treatment of metastatic cancer patients. Microbiota composition has been proposed to be one of the reasons for failure or success. ICB works via the activation or reactivation of T cells that are "switched off" by tumor cells or by the tumor microenvironment. Even advanced metastatic disease, previously considered as untreatable, can benefit from cancer immunotherapy. However, still a good proportion of patients does not respond to therapy or acquires resistance during treatment. Some genera or species of bacteria have been associated with treatment response or toxicity, but as the composition of the microbiota is not static, rather, it is very dynamic there is promise that by changing the microbiota composition, or by harnessing the microbiota 'secrete' tricks, one can improve treatment efficacy or reduce toxicity. Several players, including diet, prebiotics, probiotics, and postbiotics, have been proposed to shape the microbiota. In this minireview, we summarize very recent data on how to train the microbiota to increase ICB efficacy and reduce toxicity.

BALB/c and C57BL/6 Mice Differ in Polyreactive IgA Abundance, which Impacts the Generation of Antigen-Specific IgA and Microbiota Diversity.

The interrelationship between IgAs and microbiota diversity is still unclear. Here we show that BALB/c mice had higher abundance and diversity of IgAs than C57BL/6 mice and that this correlated with increased microbiota diversity. We show that polyreactive IgAs mediated the entrance of non-invasive bacteria to Peyer's patches, independently of CX3CR1(+) phagocytes. This allowed the induction of bacteria-specific IgA and the establishment of a positive feedback loop of IgA production. Cohousing of mice or fecal transplantation had little or no influence on IgA production and had only partial impact on microbiota composition. Germ-free BALB/c, but not C57BL/6, mice already had polyreactive IgAs that influenced microbiota diversity and selection after colonization. Together, these data suggest that genetic predisposition to produce polyreactive IgAs has a strong impact on the generation of antigen-specific IgAs and the selection and maintenance of microbiota diversity.

Association Between Duration of SARS-CoV-2 Positivity and Long COVID.

In an observational study, we analyzed 1293 healthcare workers previously infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), of which 34.1% developed postacute sequelae of SARS-CoV-2 infection (also known as long COVID). Using a multivariate logistic regression model, we demonstrate that the likelihood of developing long COVID in infected individuals rises with the increasing of duration of infection and that 3 doses of the BNT162b2 vaccine are protective, even during the Omicron wave.

Humoral and T-Cell Immune Response After 3 Doses of Messenger RNA Severe Acute Respiratory Syndrome Coronavirus 2 Vaccines in Fragile Patients: The Italian VAX4FRAIL Study.

BACKGROUND: Patients with solid or hematological tumors or neurological and immune-inflammatory disorders are potentially fragile subjects at increased risk of experiencing severe coronavirus disease 2019 and an inadequate response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination. METHODS: We designed a prospective Italian multicenter study to assess humoral and T-cell responses to SARS-CoV-2 vaccination in patients (n = 378) with solid tumors (ST), hematological malignancies (HM), neurological disorders (ND), and immunorheumatological diseases (ID). A group of healthy controls was also included. We analyzed the immunogenicity of the primary vaccination schedule and booster dose. RESULTS: The overall seroconversion rate in patients after 2 doses was 62.1%. Significantly lower rates were observed in HM (52.4%) and ID (51.9%) than in ST (95.6%) and ND (70.7%); a lower median antibody level was detected in HM and ID versus ST and ND (P < .0001). Similar rates of patients with a positive SARS-CoV-2 T-cell response were found in all disease groups, with a higher level observed in ND. The booster dose improved the humoral response in all disease groups, although to a lesser extent in HM patients, whereas the T-cell response increased similarly in all groups. In the multivariable logistic model, independent predictors of seroconversion were disease subgroup, treatment type, and age. Ongoing treatment known to affect the immune system was associated with the worst humoral response to vaccination (P < .0001) but had no effect on T-cell responses. CONCLUSIONS: Immunosuppressive treatment more than disease type per se is a risk factor for a low humoral response after vaccination. The booster dose can improve both humoral and T-cell responses.

Tfr cells and IgA join forces to diversify the microbiota.

How diversity of the microbiota is generated and maintained is an open question. In this issue of Immunity, Kawamoto et al. show that T follicular regulatory cells foster microbiota diversity via the regulation of IgA selection.

Oral tolerance can be established via gap junction transfer of fed antigens from CX3CR1⁺ macrophages to CD103⁺ dendritic cells.

Antigen-presenting cells (APCs) in the gut are apt at oral tolerance establishment at steady state and immunity after infection; complex tasks in an environment exposed to the inflammatory burden of the microbiota. Here we show an unanticipated division of labor among APCs for the establishment of oral tolerance. Chemokine receptor CX3CR1(+) macrophages were found to take up soluble fed antigens and quickly transfer them to CD103(+) dendritic cells (DCs). Antigen transfer occurred via a mechanism that was Connexin 43-dependent and required membrane transfer, indicating a physiological role of gap junctions in antigen presentation. Deletion of Connexin 43 in APCs affected antigen transfer and resulted in the inability of CD103(+) DCs to acquire and present antigens in vivo, to drive T regulatory cell differentiation and to induce tolerance to food antigens. This functional cooperation between intestinal phagocytes might be a mechanism to avoid the exposure of tolerogenic DCs to the intestinal microbiota.

Gut mucosa alterations and loss of segmented filamentous bacteria in type 1 diabetes are associated with inflammation rather than hyperglycaemia.

OBJECTIVE: Type 1 diabetes (T1D) is an autoimmune disease caused by the destruction of pancreatic ß-cells producing insulin. Both T1D patients and animal models exhibit gut microbiota and mucosa alterations, although the exact cause for these remains poorly understood. We investigated the production of key cytokines controlling gut integrity, the abundance of segmented filamentous bacteria (SFB) involved in the production of these cytokines, and the respective role of autoimmune inflammation and hyperglycaemia. DESIGN: We used several mouse models of autoimmune T1D as well as mice rendered hyperglycaemic without inflammation to study gut mucosa and microbiota dysbiosis. We analysed cytokine expression in immune cells, epithelial cell function, SFB abundance and microbiota composition by 16S sequencing. We assessed the role of anti-tumour necrosis factor α on gut mucosa inflammation and T1D onset. RESULTS: We show in models of autoimmune T1D a conserved loss of interleukin (IL)-17A, IL-22 and IL-23A in gut mucosa. Intestinal epithelial cell function was altered and gut integrity was impaired. These defects were associated with dysbiosis including progressive loss of SFB. Transfer of diabetogenic T-cells recapitulated these gut alterations, whereas induction of hyperglycaemia with no inflammation failed to do so. Moreover, anti-inflammatory treatment restored gut mucosa and immune cell function and dampened diabetes incidence. CONCLUSION: Our results demonstrate that gut mucosa alterations and dysbiosis in T1D are primarily linked to inflammation rather than hyperglycaemia. Anti-inflammatory treatment preserves gut homeostasis and protective commensal flora reducing T1D incidence.