The composition of the upper respiratory tract (URT) microbiota is shaped by both anatomical niches and host immune defenses. Older adults (>65 years) are at greatest risk of acquiring severe URT infections. However, very little is known about whether age-related changes in the composition of the URT microbiota and host innate immunity contribute to this susceptibility to respiratory infection. We aimed to characterize age-related changes to the composition of the URT microbiota and investigate the modulation of host immune gene expression by microbiota community composition.The mid-turbinate microbiotas of 270 adults between 20 and 100 years old were interrogated by 16S rRNA sequencing of nasal swabs. We identified dominant microbial subcommunities by latent Dirichlet allocation topic modeling. Dominant microbes, age, and nasal epithelium gene expression were correlated by mixed-effect models. Gene clusters examined include core macrophage markers, inflammatory macrophage genes, chemotaxis and migration genes, and neutrophil-associated genes.Topic alignment identified 10 subcommunities in the URT microbiome dominated by the following species: Staphylococcus aureus, Staphylococcus caprae, Corynebacterium accolens 1, C. accolens 2, C. accolens 3, Corynebacterium propinquum, Moraxella catarrhalis, Moraxella catarrhalis, Corynebacterium tuberculostearicum, and Peptoniphilus grossensis. Subcommunities dominated by S. aureus and C. accolens had decreasing relative abundance with increasing age, though this was not statistically significant. The C. accolens 2-dominated subcommunity was more likely to be dominant and had higher relative abundance with increasing age. The nasal epithelium became more secretory and structurally robust with age, with a reduced expression of cellular plasticity and immune regulation genes. Inflammatory cytokine gene (IL1B, IL16, OSM, and SRGN) expression was significantly upregulated in microbial communities dominated by S. aureus, C. accolens 2, C. accolens 3, and C. propinquum. S. aureus- and C. propinquum-dominated communities also demonstrated significant upregulation of macrophage- and neutrophil-associated genes. In contrast, significant downregulation of macrophage- and neutrophil-associated genes was seen in S. caprae-dominated communities. We conclude that increasing age is associated with compositional changes in the adult URT microbiota, which further alter host innate immunity. Understanding age-related changes to the URT microbiota and immune defenses is essential to reduce susceptibility to respiratory infections.

People with immune-mediated inflammatory diseases (IMIDs) may be more vulnerable to severe COVID-19 outcomes. COVID-19 vaccination is a key element in mitigating this risk. Anti-SARS-CoV-2 antibodies (Ab), including anti-spike (S) and anti-receptor binding domain (RBD) Ab, are metrics of seroconversion following COVID-19 vaccination in the general population. We assessed if anti-S and anti-RBD antibodies were negatively correlated with COVID-19 infection in IMID. SUCCEED, a prospective Canada-wide study, was conducted in 2 phases. First, between Feb 2021-Jul 2023, adult IMID participants provided dried blood spot samples for anti-S and anti-RBD ELISA testing at intervals of 1, 3, 6, and 12 months following each COVID-19 vaccine dose. Second, between Sep 2022-Aug 2023, consenting participants from 4 academic centers in British Columbia, Ontario and Quebec (2) also provided monthly saliva samples for PCR detection of SARS-CoV-2. We studied subjects receiving at least their primary series (3+ doses) of a COVID-19 vaccine. Multivariable general estimating equation (GEE) models (accounting for repeated measures) evaluated PCR SARS-CoV-2 detection in saliva, assessing the effects of anti-S or anti-RBD levels (in separate models) within the 6 months preceding a given saliva sample. We controlled for recent COVID-19 infection, sex, age, medications (conventional immunosuppressives, biologics, and prednisone), and time since last COVID vaccine. 366 participants contributed 1,266 saliva samples. Participants were 79.8% female and 85.5% White, with median age 56.7 (standard deviation: 13.8) years. Most participants were taking immunosuppressants (N=252, 68.9%). The majority (N=356, 97.3%) of participants displayed seroconversion at the first saliva sample, defined as ≥11.3 Binding Antibody Units (BAU)/ml for anti-S or ≥31 BAU/ml for anti-RBD. In the GEE models of positive saliva PCR for SARS-CoV-2, (Table 1) a 1000 BAU/ml increase in anti-S was associated with an adjusted odds ratio (aOR) of 0.66 (95% confidence interval [CI] 0.45-0.97). Anti-RBD Ab levels had a similar effect (aOR 0.91, 95% CI 0.81-1.02). Table 1: Odds Ratios, OR (95% confidence intervals, CI) for Having a Positive COVID-19 Saliva Test in Univariable and Multivariable GEE Models In this large, multi-center sample of COVID-19-vaccinated individuals with IMIDs, most of whom were immunosuppressed, we demonstrated that anti-S Ab levels were associated with lower odds of positive saliva PCR test for SARS-CoV-2, with a similar trend for anti-RBD Ab. This highlights clear benefits for vaccination against SARS-CoV-2 in IMID.

Influenza vaccination saves lives, reduces short-term and long-term health consequences, decreases healthcare utilization, and improves pregnancy outcomes and infant health. Consequently, many, although not all, high-income countries have influenza vaccination policies that recognize both the direct (prevention of infection) and indirect (e.g., reduction in transmission and absenteeism, exacerbations of other health conditions) benefits of vaccination. Vaccination policies for COVID-19 are less consistent, even though COVID-19 continues to cause more infections than influenza. Indeed, some countries recommend COVID-19 vaccination only for older adults and individuals who are severely immunocompromised. Herein we compare influenza and COVID-19 vaccination effectiveness against both acute infection and indirect effects of infection. We find that COVID-19 vaccines are equivalent to, or outperform, influenza vaccines when comparing protection from symptomatic infection, reduction in severe disease, safety profiles, and real-world effectiveness. We propose that expansion of COVID-19 vaccination policies would reduce disruptions to school, work, and healthcare systems, in addition to preventing hospitalizations and severe disease.

Background:Common cold coronaviruses were a frequent cause of respiratory infections in older adults living in congregate care homes before the coronavirus disease 2019 pandemic, which may influence immune responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination and infection. We investigated humoral and cellular immune responses to prior common cold coronaviruses and SARS-CoV-2, how they are affected by SARS-CoV-2 vaccination and infection, and their associations with Omicron BA.1 SARS-CoV-2 infections in residents of long-term care and retirement homes. Methods:In SARS-CoV-2 infection-naive residents with 3 monovalent messenger RNA SARS-CoV-2 vaccinations, we measured serum anti-receptor binding domain (RBD) immunoglobulin (Ig) G and IgA antibody titers against SARS-CoV-2 and common cold human coronavirus (HCoV) NL63, HCoV-OC43, and HCoV-229E; ancestral and Omicron BA.1 neutralizing antibodies; and CD4+ and CD8+ T-cell activation responses to membrane, nucleocapsid, and spike proteins. We examined the relationships of common cold coronavirus and SARS-CoV-2 humoral immune responses, whether antibody and T-cell responses changed after SARS-CoV-2 messenger RNA vaccination or infection, and their associations with Omicron BA.1 infection. Results:Anti-RBD IgG HCoV-OC43 titers were positively correlated with SARS-CoV-2 anti-RBD IgG and neutralizing antibody titers. Common cold coronavirus anti-RBD IgA titers, but not anti-RBD IgG titers, increased after SARS-CoV-2 vaccination or infection, and many residents had cross-reactive T cells. Common cold coronavirus humoral immunity was similar in residents without and those with subsequent Omicron BA.1 infection. Conclusions:Despite frequent exposure, and associations of common cold coronavirus and vaccine-induced SARS-CoV-2 humoral immunity, preexisting common cold coronavirus immunity was not associated with Omicron BA.1 infection in residents of long-term care and retirement communities.

IntroductionLittle is known about the acute and long-term sequelae of COVID-19 and its pathophysiology in African patients, who are known to have a distinct immunological profile compared to Caucasian populations. Here, we established protein signatures to define severe outcomes of acute COVID-19 and determined whether unique protein signatures during the first week of acute illness predict the risk of post-acute sequelae of COVID-19 (Long COVID) in a low-income country (LIC) setting.MethodUsing the Olink inflammatory panel, we measured the abundance of 92 proteins in the plasma of COVID-19 patients (n=55) and non-COVID-19 individuals (n=23). We investigated distinct inflammatory protein signatures in acute severe COVID-19 individuals (n=22) compared to asymptomatic or mild/moderate COVID-19 cases (n=33), and non-COVID-19 controls.ResultsLevels of SLAMF1, CCL25, IL2RB, IL10RA, IL15RA, IL18 and CST5 were significantly upregulated in patients with critical COVID-19 illness compared to individuals negative for COVID-19. The cohort was followed for an average of 20 months, and 23 individuals developed Long COVID, based on the WHO’s case definition, while 32 COVID-19 patients recovered fully. Whereas upregulated levels of SLAMF1, TNF, TSLP, IL15RA, IL18, ADA, CXCL9, CXCL10, IL17C, and NT3 at the acute phase of the illness were associated with increased Long COVID risk, upregulated TRANCE was associated with a reduced risk of developing Long COVID. Protein levels of SLAMF1, IL15RA, and IL18 associated with critical illness during the acute phase of COVID-19 also predicted Long COVID risk.DiscussionPatients with severe COVID-19 and Long COVID outcomes exhibited distinct proteomic signatures. Unravelling the pathophysiology of severe acute COVID-19 and Long COVID before its advent may contribute to designing novel interventions for diagnosing, treating, and monitoring of SARS-CoV-2 infection and its associated acute and long-term consequences.

Background The use of cannabis during pregnancy is rising following its widespread legalization. Cannabidiol (CBD) is gaining popularity due to the public perception that it is safer than the psychoactive cannabis component Δ9-tetrahydrocannabinol (THC). However, while evidence underpins the harm of THC and cannabis smoke on fetal development, there is minimal research on the safety of CBD and oral cannabis. The current study aims to decipher the safety of oral CBD and THC use during pregnancy. Methods Using a mouse model, we directly compared the effects of oral CBD and THC oil exposure (20 mg/kg body weight) from early to mid-gestation on implantation site remodelling and fetal growth. We examined offspring behaviour and metabolic activity using both traditional and automated cage systems. Lastly, using human and mouse immune cells we assessed how CBD and THC influence angiogenic factor production. Findings We observed impaired maternal spiral artery remodelling in cannabis exposed mice and found that CBD and THC disrupt immune cell angiogenic factor production. Oral consumption of THC or CBD oil also resulted in significant fetal growth impairment and led to long-lasting sex-dependent consequences as male offspring exhibited altered aggression and metabolic activity while females had impaired spatial learning. Interpretation Our results show that oral consumption of either CBD or THC oil during pregnancy in mice results in harm to the developing fetus and causes behavioural changes after birth. Funding The Michael G. DeGroote Centre for Medicinal Cancer Research, the Canadian Institutes of Health Research, and the Canadian Foundation for Innovation.

BACKGROUND:Antibiotic use during the coronavirus disease 2019 (Covid-19) pandemic was common in the outpatient setting, but was not supported by guidelines. We sought to evaluate the role of this antibiotic use on downstream antibiotic resistance. METHODS:We performed a population-wide cohort study of all nonhospitalized adults 66 years of age or older in Ontario, Canada, from January 1, 2020, to June 30, 2021, with a first identification of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We evaluated the relationship between outpatient peri-Covid-19 antibiotic exposure (within a period of 7 days before or after index SARS-CoV-2 reporting) and downstream isolation of an antibiotic-resistant organism from clinical culture within 6 months. We calculated adjusted odds ratios of the association between peri-Covid-19 prescribing and antibiotic-resistant organism detection, as well as the adjusted attributable fractions of downstream antibiotic-resistant organisms. RESULTS:Of the 53,533 eligible individuals included, 8228 (15%) were prescribed a peri-Covid-19 antibiotic, and 1477 (3%) had a downstream antibiotic-resistant organism identified. The adjusted odds ratio for the presence of any antibiotic-resistant organism with peri-Covid-19 antibiotic use was 1.24 (95% confidence interval [CI], 1.09 to 1.41), while the adjusted odds ratio for the presence of gram-negative antibiotic-resistant organisms was 1.27 (95% CI, 1.11 to 1.46) and for gram-positive antibiotic-resistant organisms it was 1.02 (95% CI, 0.70 to 1.48). Among all individuals who received an antibiotic within 7 days of SARS-CoV-2 diagnosis, the attributable fraction of downstream antimicrobial resistance related to peri-Covid-19 antibiotic use was 17% (95% CI, 7 to 26%). Among all individuals with a SARS-CoV-2 diagnosis, the population-attributable fraction of downstream antimicrobial resistance related to peri-Covid-19 antibiotic use was 4% (95% CI, 2 to 7%). CONCLUSIONS:Peri-Covid-19 antibiotic use was associated with downstream antimicrobial resistance, and particularly the presence of gram-negative antibiotic-resistant organisms. (Funded by the Canadian Institutes of Health Research Operating Grant [grant number 179461] and others).

Background: The Safety and Immunogenicity of COVID-19 Vaccines in Systemic Autoimmune-Mediated Inflammatory Diseases (SUCCEED) study was created to better understand COVID-19 vaccination in immune-mediated inflammatory disease (IMID). Knowing the frequency of COVID-19 breakthrough infections is important, particularly in IMID. Our objective was to assess these events in IMID. Methods: We prospectively studied IMID participants who had received ≥three COVID-19 vaccine doses. Individuals provided saliva samples monthly (September 2022 to August 2023). These were evaluated by polymerase chain reaction (PCR) for SARS-CoV-2. We also assessed antibodies against SARS-CoV-2 (anti-spike, SmT1, receptor binding domain, RBD, and nucleocapsid, NP) based on dried blood spots. Multivariable general estimating equation regression produced odd ratios (OR) for PCR SARS-CoV-2 positivity, related to demographics, immunosuppressives, and antibody levels. Results: Diagnoses included rheumatoid arthritis RA (N = 161, 44% of the total), systemic lupus, psoriatic arthritis, spondylarthritis, vasculitis, systemic sclerosis, and inflammatory bowel disease. Of the 366 participants, most were taking immunosuppressive medication. Of 1266 saliva samples, 56 (5.1%) were positive for SARS-CoV-2 on PCR. Higher anti-SmT1 antibodies were inversely associated with SARS-CoV-2 detection on PCR (adjusted OR 0.66, 95% confidence interval 0.45–0.97). Antibodies to SmT1, RBD, and NP were correlated and thus could not be included in a single model, but when anti-RBD was used in place of anti-SmT1, the results were similar. No other factor (including prior COVID-19 infection) was clearly associated with SARS-CoV-2 detection. Conclusions: This is the first study of SARS-CoV-2 in a large prospective cohort of triple (or more) vaccinated individuals with IMIDs. Anti-SmT1 antibodies appeared to be protective against later SARS-CoV-2 positivity, although recent past infection was not clearly related. This suggests the importance of maintaining robust vaccine-induced immunity through vaccination in IMID.

[This corrects the article DOI: 10.1371/journal.pgph.0003490.].

Chronic low-level inflammation or "inflammaging" is hypothesized to contribute to sarcopenia and frailty. Resident microbiota are thought to promote inflammaging, frailty, and loss of skeletal muscle mass. We tested immunity and frailty in male C57BL6/N germ-free (GF), specific pathogen-free (SPF) mice, and mice that were born germ-free and colonized (COL) with an SPF microbiota. Male and female GF mice had lower systemic cellular inflammation indicated by lower blood Ly6Chigh monocytes across their lifespan. Male GF mice had lower body mass, but relative to body mass, GF mice had smaller hindlimb muscles and smaller muscle fibers compared with SPF mice across the lifespan. Male and female GF mice had increased frailty at 18 mo or older. Colonization of female GF mice increased blood Ly6Chigh monocytes but did not affect frailty at 18 mo or older. Colonization of male GF mice increased blood Ly6Chigh monocytes, skeletal muscle size, myofiber fiber size, and decreased frailty at 18 mo or older. Transcriptomic analysis of the tibialis anterior muscle revealed a microbiota-muscle axis with over 550 differentially expressed genes in COL male mice at 18 mo or older. Colonized male mice had transcripts indicative of lower tumor necrosis factor (TNF)-α signaling via nuclear factor κB (NF-κB). Our findings show that microbiota can increase systemic cellular immunity while decreasing muscle inflammation, thereby protecting against muscle loss and frailty. We also found sex differences in the role of microbiota regulating frailty. We propose that microbiota components protect against lower muscle mass and frailty across the lifespan in mice.NEW & NOTEWORTHY Germ-free mice had increased frailty, lower muscle mass, and lower circulating inflammatory monocytes. Therefore, lower systemic inflammation coincided with worse frailty and muscle loss. Microbial colonization decreased frailty, restored muscle mass, and increased circulating inflammatory monocytes while lowering transcripts in inflammatory TNF and NF-κB pathways within muscle. Hence, microbiota can increase circulating inflammation but decrease muscle inflammation to protect against frailty. This microbiota-muscle axis should be investigated for therapeutic potential in muscle wasting and sarcopenia.

During the early phase of the COVID-19 pandemic, the province of Ontario enacted restrictions and recommendations that changed over time. These measures were effective in reducing COVID-19-related illness and deaths, but adherence to these non-pharmaceutical interventions may be modified by individual factors including demographics and health status which shape exposure risk behaviors. A total of 348 participants completed baseline questionnaires (to assess demographics, pre-pandemic exposure risk, and health status), weekly illness reports, and monthly social distancing behavior questionnaires to evaluate exposure risk over time in response to changing levels of government restrictions. Exposure risk behaviors were calculated using seven categories: attendance at social events, receiving care (hospital, etc.), visiting or volunteering at care facilities, public transportation use, hours working outside of the home, hours volunteering outside of the home, and handwashing frequency. The impact of individual and environmental factors on exposure risk over time was evaluated by a Poisson family generalized linear mixed model. Participants across all age groups and health statuses adapted their behaviors in response to evolving regulations, but older individuals and those with pre-existing conditions had the largest change in behavior. These individuals also had the most severe symptoms when they developed COVID-19 or other influenza-like illnesses. Participants who were older or had pre-existing health conditions had lower levels of exposure risk overall, and this was largely driven by a lower prevalence and frequency of in-person work. Female participants also had lower levels of exposure risk overall, consistent with an increased frequency of handwashing in this group. Unexpectedly, we found no effect of vaccination on total exposure risk. Participant behavior was generally responsive to government-imposed restrictions, with increased stringency coinciding with decreased exposure risk among participants. Demographic-associated differences in exposure risk behaviors appear to be driven by systemic factors (i.e., a return to in-person work) to a greater extent than personal choices (i.e., social gatherings). These findings emphasize the interplay between demographic factors and government interventions in shaping individual behaviors over the course of the pandemic. Understanding these dynamics is crucial for informing interventions and mitigating the impact of future pandemics.

Frequent SARS-CoV-2 vaccination in vulnerable populations has raised concerns that this may contribute to T cell exhaustion, which could negatively affect the quality of immune protection. Herein, we examined the impact of repeated SARS-CoV-2 vaccination on T cell phenotypic and functional exhaustion in frail older adults in long-term care (n = 23), individuals on immunosuppressive drugs (n = 10), and healthy adults (n = 43), in Canada. Spike-specific CD4+ and CD8+ T cell levels did not decline in any cohort following repeated SARS-CoV-2 vaccination, nor did the expression of exhaustion markers on spike-specific or total T cells increase. T cell production of multiple cytokines (i.e. polyfunctionality) in response to the spike protein of SARS-CoV-2 did not decline in any cohort following repeated vaccination. None of the cohorts displayed elevated levels of terminally differentiated T cells following multiple SARS-CoV-2 vaccinations. Thus, repeated SARS-CoV-2 vaccination was not associated with increased T cell exhaustion in older frail adults, immunosuppressed individuals, or healthy adults.

BACKGROUND:Aging is a well-established risk factor for the development and progression of atherosclerosis, but the molecular mechanisms underlying this relationship remain poorly defined, and its role in atherosclerosis regression is unknown. To uncover age-related alterations that may impair atherosclerosis regression, we investigated the response of young and old macrophages to atherogenic lipoproteins in vitro and in vivo.METHODS:Metabolic and proteomic studies were performed in vitro using macrophages differentiated from the bone marrow of young or old mice. To test the role of immune cell aging in atherosclerosis regression, bone marrow from young and old donors was transplanted into irradiated young recipient mice expressing gain-of-function AAV-PCSK9 (adeno-associated virus-proprotein convertase subtilisin/kexin type 9). Following 14 weeks of Western diet feeding, atherosclerosis regression was induced by switching to a standard laboratory diet for 4 weeks.RESULTS:Compared with young macrophages, old macrophages accumulated more lipid droplets upon lipid loading with the pro-atherogenic lipoprotein aggregated LDL (low-density lipoprotein), accompanied by a failure to proportionally induce autophagy and cholesterol efflux. Proteomic analysis of bone marrow-derived macrophages revealed that pathways related to endocytosis, engulfment, and phagocytosis were downregulated in old lipid-loaded macrophages. Functional studies confirmed a reduction in efferocytic capacity in old macrophages. In recipient mice transplanted with old bone marrow, atherosclerosis regression was impaired, as evidenced by inefficient resolution of circulating inflammatory cell levels, reduced activation of plaque autophagy and apoptotic cell clearance, and persistent plaque CD45+ and CD68+ content.CONCLUSIONS:Aging impairs macrophage function through reduced efferocytosis and autophagy activation, limiting atherosclerosis regression. These results highlight the need to better define the mechanisms linking aging to atherosclerosis to develop targeted therapies for the aging population.

Background: The demand for COVID-19 vaccines has diminished as the pandemic lingers. Understanding vaccine hesitancy among essential workers is important in reducing the impact of future pandemics by providing effective immunization programs delivered expeditiously. Method: Two surveys exploring COVID-19 vaccine acceptance in 2021 and 2022 were conducted in cohorts of health care providers (HCP) and education workers participating in prospective studies of COVID-19 illnesses and vaccine uptake. Demographic factors and opinions about vaccines (monovalent and bivalent) and public health measures were collected in these self-reported surveys. Modified multivariable Poisson regression was used to determine factors associated with hesitancy. Results: In 2021, 3 % of 2061 HCP and 6 % of 3417 education workers reported hesitancy (p < 0.001). In December 2022, 21 % of 868 HCP and 24 % of 1457 education workers reported being hesitant to receive a bivalent vaccine (p = 0.09). Hesitance to be vaccinated with the monovalent vaccines was associated with earlier date of survey completion, later receipt of first COVID-19 vaccine dose, no influenza vaccination, and less worry about becoming ill with COVID-19. Factors associated with hesitance to be vaccinated with a bivalent vaccine that were common to both cohorts were receipt of two or fewer previous COVID-19 doses and lower certainty that the vaccines were safe and effective. Conclusion: Education workers were somewhat more likely than HCP to report being hesitant to receive COVID-19 vaccines but reasons for hesitancy were similar. Hesitancy was associated with non-receipt of previous vaccines (i.e., previous behaviour), less concern about being infected with SARS-CoV-2, and concerns about the safety and effectiveness of vaccines for both cohorts. Maintaining inter-pandemic trust in vaccines, ensuring rapid data generation during pandemics regarding vaccine safety and effectiveness, and effective and transparent communication about these data are all needed to support pandemic vaccination programs.

Individuals with systemic sclerosis (SSc) are particularly susceptible to SARS-CoV-2 infections, yet it remains to be determined if they generate humoral and cellular responses comparable to controls following SARS-CoV-2 vaccinations. Herein, we collected blood and serum after second, third, and fourth SARS-CoV-2 vaccinations in patients with SSc and controls. Following each dose, participants with SSc mounted comparable serum anti-RBD IgG, anti-RBD IgA, and spike-specific CD4+ and CD8+ T cell responses to those found in controls. At 3 months post dose 2, the frequencies of Th1, Th2, Th17, and Treg spike-specific CD4+ T cells in participants with SSc did not differ from controls. At 2-6 weeks post dose 3, participants with SSc displayed reduced frequencies, but not numbers, of Th17-polarized spike-specific CD4+ T cells. Thus, participants with SSc did not display significantly weaker humoral or cellular responses to SARS-CoV-2 vaccination than controls, enabling reassurance of vaccine immunogenicity in participants with SSc.

Individuals with clonal hematopoiesis of indeterminate potential (CHIP) are at increased risk of aging related health conditions and all -cause mortality, but whether CHIP affects risk of infection is much less clear. Using UK Biobank data, we revealed a positive association between CHIP and incident pneumonia in 438,421 individuals. We show that inflammation enhanced pneumonia risk, as CHIP carriers with a hypomorphic IL6 receptor polymorphism were protected. To better characterize the pathways of susceptibility, we challenged hematopoietic Tet Methylcytosine Dioxygenase 2- knockout ( Tet2 -/- ) and floxed control mice ( Tet2 f l/ f l ) with Streptococcus pneumoniae . As with human CHIP carriers, Tet2 -/- mice had hematopoietic abnormalities resulting in the expansion of inflammatory monocytes and neutrophils in peripheral blood. Yet, these cells were insufficient in defending against S . pneumoniae and resulted in increased pathology, impaired bacterial clearance, and higher mortality in Tet2 -/- mice. We delineated the transcriptional landscape of Tet2 -/- neutrophils and found that, while inflammation -related pathways were upregulated in Tet2 -/- neutrophils, migration and motility pathways were compromised. Using live -imaging techniques, we demonstrated impairments in motility, pathogen uptake, and neutrophil extracellular trap (NET) formation by Tet2 -/- neutrophils. Collectively, we show that CHIP is a risk factor for bacterial pneumonia related to innate immune impairments.

Despite high vaccination rates, older adults are most susceptible to COVID-19 and severe disease.1 It is estimated that neutralizing antibodies provide protective immunity against symptomatic SARS-CoV-2 infection in young, healthy adults.2 Frailty is a potential modifier of vaccine immunogenicity and protective immunity in older adults.3 Prior studies with relatively small cohorts have provided mixed evidence regarding the association of frailty and SARS-CoV-2 neutralizing antibodies, with some observing frail older adults have poorer humoral immune responses to vaccinations, whereas others report no impact of frailty.

Chronic low-grade inflammation, particularly elevated tumor necrosis factor (TNF) levels, occurs due to advanced age and is associated with greater susceptibility to infection. One reason for this is age-dependent macrophage dysfunction (ADMD). Herein, we use the adoptive transfer of alveolar macrophages (AM) from aged mice into the airway of young mice to show that inherent age-related defects in AM were sufficient to increase the susceptibility to Streptococcus pneumoniae, a Gram-positive bacterium and the leading cause of community-acquired pneumonia. MAPK phosphorylation arrays using AM lysates from young and aged wild-type (WT) and TNF knockout (KO) mice revealed multilevel TNF-mediated suppression of kinase activity in aged mice. RNAseq analyses of AM validated the suppression of MAPK signaling as a consequence of TNF during aging. Two regulatory phosphatases that suppress MAPK signaling, Dusp1 and Ptprs, were confirmed to be upregulated with age and as a result of TNF exposure both ex vivo and in vitro. Dusp1 is known to be responsible for glucocorticoid-mediated immune suppression, and dexamethasone treatment increased Dusp1 and Ptprs expression in cells and recapitulated the ADMD phenotype. In young mice, treatment with dexamethasone increased the levels of Dusp1 and Ptprs and their susceptibility to infection. TNF-neutralizing antibody reduced Dusp1 and Ptprs levels in AM from aged mice and reduced pneumonia severity following bacterial challenge. We conclude that chronic exposure to TNF increases the expression of the glucocorticoid-associated MAPK signaling suppressors, Dusp1 and Ptprs, which inhibits AM activation and increases susceptibility to bacterial pneumonia in older adults.

BackgroundThe intestinal barrier encompasses physical and immunological components that act to compartmentalize luminal contents, such as bacteria and endotoxins, from the host. It has been proposed that an age-related decline of intestinal barrier function may allow for the passage of luminal contents into the bloodstream, triggering a low-grade systemic inflammation termed inflamm-aging. Although there is mounting evidence to support this hypothesis in model species, it is unclear if this phenomenon occurs in humans. In addition, despite being well-established that biological sex impacts aging physiology, its influence on intestinal barrier function and inflamm-aging has not been explored.ResultsIn this study, we observed sex differences in markers of intestinal barrier integrity, where females had increased epithelial permeability throughout life as compared to males. With age, females had an age-associated increase in circulating bacterial products and metabolites such as LPS and kynurenine, suggesting reduced barrier function. Females also had age-associated increases in established markers of inflamm-aging, including peripheral blood monocytes as well as TNF and CRP. To determine if impaired barrier function was driving inflamm-aging, we performed a mediation analysis. The results show that the loss of intestinal barrier integrity was not the mediator of inflamm-aging in humans. Instead, persistent, low-grade inflammation with age preceded the increase in circulating bacterial products, which we confirmed using animal models. We found, as in humans, that sex modified age-associated increases in circulating monocytes in mice, and that inflammation mediates the loss of intestinal barrier function.ConclusionTaken together, our results suggest that higher basal intestinal permeability in combination with age-associated inflammation, increases circulating LPS in females. Thus, targeting barrier permeability in females may slow the progression of inflamm-aging, but is unlikely to prevent it.