Psychological stress can cause diminished immune response to infectious challenges. The extent this holds true during severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the modifying effect of vaccination status is untested. We explored these relationships in a non-random sample standardized to the US adult population. Across 2178 participants in the Aegis study (2021-2022), we identified 507 eligible laboratory-confirmed SARS-CoV-2 infections. We estimated the natural log of nucleocapsid-binding antibody absorbance (N-antibody) at study visits up to 225 days following a positive SARS-CoV-2 test. Linear mixed effects models were fit to estimate the association of baseline perceived stress and, separately, allostatic load with N-antibody trajectories. Standardization was performed using iterative post-stratification weighting. Consistently, lower stress groups had higher N-antibody response. Low perceived stress was associated with greater antibody response up to 26 days post-positive test (P = .047) while low allostatic load was associated with greater antibody response up to 24 days (P = .049). Pre-infection vaccination modified the relationship between stress and N-antibody trajectories, where the observed relationships attenuated to the null for vaccinated individuals (P = .031). Overall, we found consistent evidence that high stress was associated with reduced N-antibody response following SARS-CoV-2 infection and that vaccination may narrow the antibody response across high versus low stress groups.

Sterile alpha motif and histidine-aspartate domain-containing protein 1 (SAMHD1) restricts a broad spectrum of viruses through multifaceted mechanisms. It also limits spontaneous- and virus-induced innate immune responses by suppressing proinflammatory cytokine and type-I interferon (IFN-I) production. Some viruses escape SAMHD1 restriction and utilize SAMHD1-mediated innate immune suppression to establish effective infection through IFN antagonism. Our previous studies showed that SAMHD1 is a proviral factor facilitating replication of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) in human macrophages, monocytic THP-1 and epithelial-like HEK293T cell lines by suppressing IFN responses. However, it is unclear about the function of SAMHD1 in lung epithelial cells during SARS-CoV-2 infection. Here, we report that SAMHD1 knockout (KO) restricts SARS-CoV-2 replication in lung epithelial Calu-3 cells by suppressing endogenous expression of the viral receptor angiotensin-converting enzyme 2 (ACE2) via hepatocyte nuclear factor 1-alpha (HNF1α) and HNF1β. Using pseudotyped SARS-CoV-2 and lentiviral vectors, we found that SARS-CoV-2 spike protein-mediated viral entry was suppressed in SAMHD1 KO Calu-3 cells. SAMHD1 KO repressed ACE2 expression in Calu-3 cells at mRNA and protein levels. Functional analyses revealed that HNF1α and HNF1β were crucial for the endogenous ACE2 expression in Calu-3 cells. Additionally, SAMHD1 KO led to a reduction in the expression levels and ACE2-promoting function of HNF1α and HNF1β. Inhibition of IFN antiviral response by baricitinib, a Janus kinase 1 and 2 (JAK 1/2) inhibitor, did not revert the suppression of SARS-CoV-2 in SAMHD1 KO Calu-3 cells. SAMHD1 knock-in and deoxynucleoside supplementation experiments indicated that SAMHD1 expression and dNTP pool balance collectively regulated HNF1-mediated ACE2 expression in Calu-3 cells. Our findings demonstrate that SAMHD1 depletion hinders HNF1-mediated ACE2 expression and SARS-CoV-2 replication in Calu-3 cells via a novel mechanism beyond its IFN-suppressive function.

ABSTRACT SARS-CoV-2 is the causative agent of COVID-19. The ancestral SARS-CoV-2 Washington-1 (WA1) strain does not infect standard laboratory mouse strains, necessitating the use of mouse-adapted (MA) viruses. A MA SARS-CoV-2, SARS-CoV-2-N501Y MA30 (hereafter MA30), has been developed to allow infection of wild-type (WT) mice. However, SARS-CoV-2 MA30 cannot be tracked in vitro , ex vivo , or in vivo . To address this problem, we generated recombinant (r)SARS-CoV-2 MA30 expressing fluorescent (mCherry) and nanoluciferase (Nluc) reporter genes, alone or in combination, that enable tracking viral infections in WT C57BL/6 and BALB/c mice. Insertion of the reporter genes resulted in minor viral attenuation in vitro , with ~0.5–1.0 log lower titers than rSARS-CoV-2 MA30 WT in A549 hACE2 cells, while maintaining similar plaque morphology and replication kinetics in Vero AT cells. In vivo , reporter-expressing rSARS-CoV-2 MA30 caused transient weight loss, contrasting with lethal rSARS-CoV-2 MA30 WT infection. Bioluminescence imaging of rSARS-CoV-2 MA30 Nluc in C57BL/6 and BALB/c mice revealed peak pulmonary replication at 2 days post-infection, with resolution by day 4, and correlated with tissue viral loads. Our results demonstrate the feasibility of using rSARS-CoV-2 MA30 expressing reporter genes to track viral infection in vitro, ex vivo , and in vivo without a need for secondary approaches to monitor viral infection required for rSARS-CoV-2 MA30 WT. Our system is highly suitable to evaluate prophylactic vaccines and therapeutic antibodies or antiviral approaches in WT or transgenic C57BL/6 and BALB/c mice without the shortcomings of K18-hACE2 mice and with the added advantage of non-invasive monitoring of treatment efficacy. IMPORTANCE Mouse-adapted (MA) SARS-CoV-2 that infect wild-type (WT) mice are critical tools for preclinical studies. While the previously described SARS-CoV-2-N501Y MA30 enables infection of WT mice, it does not allow non-invasive tracking of viral infections. Recombinant viruses expressing reporter genes enable real-time monitoring of infection dynamics, opening an avenue to study viral tropism and easily evaluate prophylactic and therapeutic approaches. They furthermore support longitudinal studies, which reduces the number of research animals required. Here, we show that a recombinant (r)SARS-CoV-2 expressing fluorescent (mCherry) and nanoluciferase (Nluc) reporter genes, alone or in combination, can be used to track viral infections in vitro , ex vivo , and in vivo without the need for secondary approaches that are required to detect SARS-CoV-2 MA30 in WT mice. These reporter-expressing rSARS-CoV-2 MA30 may accelerate vaccine development and antiviral drug discovery in WT or transgenic mice bypassing the need for hACE2 overexpression in K18-hACE2 transgenic mice.

Middle East respiratory syndrome coronavirus (MERS-CoV) remains a low-incidence but high-consequence zoonotic coronavirus threat. Since its identification in Saudi Arabia in 2012, more than 2600 laboratory-confirmed cases have been reported from 27 countries, most from the Arabian Peninsula; the reported case fatality ratio is high but probably overestimates infection fatality because mild and asymptomatic infections are under-detected. Dromedary camels across the Middle East, North Africa, East Africa, the Horn of Africa, and parts of the Sahel show extensive evidence of MERS-CoV infection or exposure, yet PCR-confirmed human disease has rarely been reported from Africa. This "Africa paradox" is one of the most important unresolved issues in MERS-CoV epidemiology. We propose a dromedary camel-centered One Health framework for the connected Middle East-Africa dromedary belt. The framework is organized around two linked barriers: an upstream barrier that detects and reduces zoonotic spillover at the camel-human interface, and a downstream healthcare barrier that prevents amplification after human infection occurs. Preparedness should include sentinel surveillance for severe acute respiratory infection and atypical pneumonia in camel-exposed populations, linked animal-human genomic surveillance, culturally respectful and occupationally practical risk reduction, rapid diagnostic pathways, healthcare infection prevention and control, mass-gathering and travel preparedness, and preapproved research platforms. A Middle East-Africa preparedness compact aligned with the International Health Regulations, One Health governance, and equitable pathogen access and benefit sharing could transform fragmented surveillance into a standing transregional system for early detection, prevention, and research-ready response.

Post-acute sequelae of COVID-19 (PASC) encompasses persistent neurological disease, including olfactory and cognitive dysfunction. The basis for this dysfunction is poorly understood. Here, we report neurological dysfunction for at least 120 d postinfection in mice infected with a virulent nonneurotropic mouse-adapted SARS-CoV-2. Long after recovery from nasal infection, we observed diminished tyrosine hydroxylase expression in olfactory bulb glomeruli and in substantia nigra. Similar changes were observed in brains of COVID-19 deceased patients. Vulnerability of dopaminergic neurons in these brain areas was accompanied by increased proinflammatory cytokines, and neurobehavioral changes. RNAseq analysis unveiled persistent microglia activation, similar to human neurodegenerative diseases. Treatment with antivirals (nirmatrelvir and molnupiravir) at the time of infection minimally prevented neurological abnormalities, consistent with patient data. In contrast, antivirals plus corticosteroids resulted in nearly complete recovery of neurological function. Remarkably, initiation of combined therapy even three days after infection improved outcomes. Together these results demonstrate that neurological dysfunction in SARS-CoV-2 infected mice resembles human neurodegenerative disease and indicate that minimizing inflammation early after SARS-CoV-2 infection may be critical for decreasing neurological PASC. The requirement for decreasing inflammation soon after infection may also explain why antiviral therapy has had inconsistent effects in patients.

Transgenic K18-hACE2 mice are a standard model for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), albeit with limitations. A mouse-adapted 30 (MA30) SARS-CoV-2 has been developed to allow infection of wild-type (WT) mice strains. However, SARS-CoV-2 MA30 cannot be easily tracked in vitro , ex vivo , or in vivo . To address the problem, we developed a recombinant (r)SARS-CoV-2 based on the MA30 strain expressing fluorescent (mCherry) and luciferase (nanoluciferase, Nluc) reporter genes, alone or in combination, that enable tracking of viral infection in WT C57BL/6 and BALB/c mice. Insertion of the reporter genes resulted in minor viral attenuation in vitro , with ∼0.5-1.0-log lower titers than rSARS-CoV-2 MA30 WT in A549 hACE2 cells, while maintain similar plaque morphology and replication kinetics in Vero AT cells. In vivo , reporter-expressing rSARS-CoV-2 MA30 caused transient weight loss, contrasting with lethal rSARS-CoV-2 MA30 WT infection. Bioluminescence imaging of rSARS-CoV-2 MA30 Nluc in C57BL/6 and BALB/c mice revealed peak pulmonary replication at 2 days post-infection, with resolution by day 4, and correlated with tissue viral loads. Our results demonstrate the feasibility of using rSARS-CoV-2 MA30 expressing reporter genes to track viral infection in vitro, ex vivo , and in vivo without a need for secondary approaches to monitor viral infection as are required for rSARS-CoV-2 MA30 WT. Our system is highly suitable to evaluate prophylactic vaccines and therapeutic antibodies or antiviral approaches in WT or transgenic C57BL/6 and BALB/c mice without the shortcomings of K18-hACE2 mice and with the added advantage of non-invasive monitoring of treatment efficacy. Importance:The K18-hACE2 transgenic mouse model limits the capability to study SARS-CoV-2. While a mouse adapted 30 (MA30) has been developed to study SARS-CoV-2 in wild-type (WT) mice, it does not allow non-invasive tracking of viral infections. Recombinant viruses expressing reporter genes enable real-time monitoring of infection dynamics, opening an avenue to study viral tropism and easily evaluate prophylactic and therapeutic approaches. They furthermore support longitudinal studies, which reduces the number of research animals required. Here, we show that a recombinant (r)SARS-CoV-2 expressing fluorescent (mCherry) and nanoluciferase (Nluc) reporter genes, alone or in combination, can be used to track viral infections in vitro, ex vivo , and in vivo without the need for secondary approaches that are required to detect SARS-CoV-2 MA30 in WT mice. These reporter-expressing rSARS-CoV-2 MA30 may accelerate vaccine development and antiviral drug discovery in WT or transgenic mice bypassing the need for hACE2 overexpression in K18-hACE2 transgenic mice.

Objective To estimate the relative effectiveness of vaccination (0, 1, 2, ≥3 doses) and prior infection, in combination, on risk of SARS-CoV-2 infection/reinfection.Design Prospective cohort study.Participants We recruited participants for the Aegis Study from nine clinics across five US states. Participants must have been 18 years or older, had a history of a positive PCR for SARS-CoV-2, SARS-CoV-2 antigen or antibody test for SARS-CoV-2 with documentation or had no suspected or documented prior SARS-CoV-2 infection, intended to remain in study area for the next 12 months, and had elevated risk of future SARS-CoV-2 exposure. Exclusion criteria included acute illness, contraindication to phlebotomy, use of immunosuppressants or receipt of systemic immunoglobulins.Methods We used extended Cox regression with robust standard errors to estimate the association between time-varying number of vaccine doses and baseline prior infection on risk of infection/reinfection among a prospective cohort of US adults between February 2021 and January 2023, accounting for censoring using inverse probability of censoring weights. Additionally, to quantify possible exposure misclassification of prior infection by comparing prior infection operationalised as (1) documented/self-reported prior infection and (2) documented/self-reported prior infection plus nucleocapsid antibody indication of prior infection.Results Of n=2178 who completed enrolment, n=1887 adults (63% female; 65% non-Latino White) contributed 366 905 days of observation. Participants contributed an average of 7.2 months of follow-up between February 2021 and January 2023. 28% (n=533) of individuals were infected or reinfected during the study period. Similar relative effectiveness was observed between the two different operationalisations of prior infection. After correction for prior infection status in the nearly 16% of those without study documentation of prior infection who had nucleocapsid antibody levels comparable to documented cases, relative to the unvaccinated with no prior infection, estimated effectiveness generally increased with increasing vaccine doses and prior infection (without prior infection: one (17%, 95% CI −31% to 47%), two (49%, 95% CI 31% to 63%), ≥three (71%, 95% CI 58% to 80%) vaccine doses; with prior infection: none (56%, 95% CI 30% to 72%), one (71%, 95% CI 42% to 86%), two (65%, 95% CI 49% to 76%), ≥three (80%, 95% CI 68% to 88%) vaccine doses). Pairwise comparisons at each vaccine dose (ref: no prior infection) revealed that prior infection provided additional protection, with stronger relationships for no and one dose (none: 56% (95% CI 30% to 72%), one: 66% (95% CI 28% to 84%), two: 31% (95% CI 7% to 49%), ≥three 31% (95% CI 0% to 53%)). There was a marked decrease in the protection offered by vaccination, prior infection, or both in the Omicron period versus pre-Omicron period.Conclusion In our real-world observational sample, vaccination (with two and ≥three vaccine doses of any Food and Drug Administration Emergency Use Authorization approved vaccine) and prior infection conferred benefits for protection against infection/reinfection. Re-classification of prior infection status based on antibody levels had little effect on results.

Over the past half-century, perceptions of human coronaviruses have evolved from their initial characterisation as causes of the common cold to recognition of their capacity to trigger severe disease and global epidemics. The emergence of three zoonotic coronaviruses—severe acute respiratory syndrome coronavirus (SARS-CoV) in 2002, Middle East respiratory syndrome coronavirus (MERS-CoV) in 2012, and SARS-CoV-2 in 2019, has had profound health, economic, and societal consequences and continues to influence global epidemic-preparedness strategies. All three viruses remain on the WHO Blueprint of priority pathogens for research and development. This Review summarises current knowledge on human coronaviruses, drawing lessons from the past 25 years of epidemic outbreaks. The shared and divergent features of SARS-CoV, MERS-CoV, and SARS-CoV-2, including their origins, evolution, transmission determinants, zoonotic transmission, viral entry pathways, pathogenesis, spectrum of clinical manifestations, long-term sequelae, and case-fatality profiles are highlighted. The full range of clinical manifestations, from asymptomatic or atypical presentations to severe acute respiratory and multisystem disease, are outlined together with risk factors for progression and populations with the greatest susceptibility. Diagnostic approaches, including molecular assays, antigen-based tests, and imaging modalities are described alongside current therapeutics, antiviral strategies, immunomodulators, supportive care principles, and evidence from clinical trials. Advances in diagnostics, vaccines, therapeutics, and infection-control practices are examined together with persistent challenges in early recognition, particularly in resource-limited settings. Strengthening multinational clinical trial capacity, leveraging digital innovations, and embedding One Health approaches are essential to mitigating spillover risks and improving global readiness. We review the latest data, identify gaps and opportunities, and outline forward-looking strategies to anticipate and prepare for the threat of future coronaviruses, and other existing or new respiratory pathogens with epidemic potential. Clinicians and other health-care workers play a central role in detecting and reporting possible lethal coronavirus infection including atypical presentations, enabling rapid, coordinated infection control and management responses.

Neurological and neuropsychiatric symptoms, collectively termed neuroPASC, are among the most prevalent Post-Acute Sequelae of COVID-19 (PASC). Neuroinflammation - particularly microglia reactivity - has been implicated in neuroPASC. We previously established a PASC model in which SARS-CoV-2-infected mice developed persistent behavior alterations and prolonged neuroinflammation for up to 120 days post-infection (dpi). Here, we extend these results to a longitudinal single-cell RNA sequencing analysis of brain immune cells collected at 0, 6, 30, and 100 dpi. We identify a coordinated contribution of infiltrating and resident myeloid cells to the initiation and persistence of neuroinflammation. In specific, microglia display sustained expansion of subclusters characterized by inflammatory, stress response, and metabolic signatures. Border-associated macrophages upregulate monocyte attractants during acute infection. Concurrently, peripherally derived monocytes and neutrophils mount transient inflammatory responses, potentially triggering long-term microglial reactivity. Together, these findings provide a high-resolution atlas of brain myeloid immune dynamics during neuroPASC and highlight a central role for microglia in sustaining chronic neuroinflammation.

SARS-CoV-2 continues to accumulate spike mutations that erode the efficacy of antibody therapeutics. The Q493E mutation in the spike RBD, present in recent Omicron subvariants, enables escape from many antibodies and nanobodies, including our Nanosota-9A nanobody, which neutralizes Omicron JN.1 (Q493) but not KP.3 (E493). To address this, we applied a structure-guided in vitro evolution strategy to engineer Nanosota-9A, generating Nanosota-9B, which binds the KP.3 RBD with high affinity but shows reduced binding to JN.1 RBD. To regain breadth, we engineered a bispecific nanobody combining Nanosota-9A and -9B, which effectively neutralizes both JN.1 and KP.3 in infection assays. Our results provide proof of concept for an "update and reuse" strategy: applying structure-guided engineering to update and reuse validated nanobodies to overcome variant escape. This strategy offers a practical path to maintain therapeutic coverage as the virus evolves, supporting more efficient use of research resources and faster responses to emerging variants.

The risk of developing melanoma increases with age. Although immune checkpoint blockade (ICB) therapy has shown considerable success, a significant portion of melanoma patients either fail to respond to ICB or eventually develop resistance. This leads to the urgent need for exploring novel treatments. Phospholipase A2 group IID (PLA2G2D) is an inducible enzyme found in myeloid cells, especially in aging dendritic cells (DCs), that exert an immunosuppressive effect by producing anti- or proinflammatory small lipid molecules, including prostaglandin D2 (PGD2). An aging-related increase of PLA2G2D-PGD2 expression makes this signaling a promising target for treating aging-associated diseases. The overexpression of hematopoietic PGD2 synthase identified in both human and mouse melanoma tissue further highlights the potential of PLA2G2D-PGD2-targeting therapy. In this study, we show that the absence of PLA2G2D or the PGD2 receptor, PTGDR, restricts primary tumor growth and lung metastasis of subcutaneously implanted melanoma, as demonstrated using middle-aged Pla2g2d-/- and Ptgdr-/- mice. These therapeutic benefits are linked to increased tumor infiltration of activated γδ T cells, which can be amplified in B16F10-bearing wild-type mice through the adoptive transfer of Ptgdr-/- DCs. These tumor-restraining effects were also confirmed in DC-specific PTGDR-deficient (zDCcrePtgdrfloxp) mice. Mechanistically, the enhanced production of IL-1β by Ptgdr-/- DCs contributes to the activation and accumulation of γδ T cells in tumor tissue. In summary, our findings highlight the effectiveness of targeting the PLA2G2D-PGD2/PTGDR axis to reprogram aging dendritic cells, thereby inhibiting melanoma progression and presenting a promising therapeutic target, particularly for elderly patients.

Coronaviruses, both known and yet to emerge, pose persistent zoonotic and pandemic threats. While current parenteral COVID-19 mRNA vaccines effectively mitigate severe disease caused by SARS-CoV-2, they primarily elicit systemic immunity restricted to specific variants within clade 1b of the sarbecovirus subgenus and provide limited mucosal protection. Addressing these shortcomings, Cheang et al. developed a DC-targeting intranasal boostervaccine that induces robust and durable mucosal and systemic immunity across sarbecovirus clades 1a and 1b. This study highlights a promising strategy for pan-sarbecovirus vaccines by leveraging mucosal immune induction to preventviral transmission and enhance pandemic preparedness.

Pathogenic Middle East respiratory syndrome CoV (MERS-CoV), first identified in Saudi Arabia in 2012, continues to pose a threat to public health. The trimeric spike (S) protein of MERS-CoV binds to the cellular receptor through the receptor-binding domain (RBD) in the S1 subunit to initiate virus entry and infection. Therefore, both the S protein and its RBD are targets for the development of MERS-CoV vaccines. Nevertheless, a direct comparison of the immune efficiency of S- and RBD-based MERS-CoV vaccines has not been made. Here, we compared two mRNA vaccines, respectively, targeting the S (S-mRNA) and RBD (RBD-mRNA) of MERS-CoV for their durable immunogenicity, neutralizing activity, and protective efficacy in a mouse model. Both mRNAs encapsulated with lipid nanoparticles (LNPs) maintained strong stability at various temperatures during the detection period. LNP-encapsulated RBD-mRNA elicited significantly higher and more durable antibodies than LNP-encapsulated S-mRNA, maintaining stronger and broadly neutralizing activity against the MERS-CoV original strain, as well as multiple variants containing key mutations within the RBD region. Importantly, RBD-mRNA provided durable protective efficacy against MERS-CoV infection in middle-aged mice, and this protection was associated positively with serum neutralizing antibody titers. Overall, this study identifies RBD-mRNA as an effective vaccine against MERS-CoV, with great potential for further development.

Background: Preceding respiratory tract infections (RTIs) caused by bacteria or viruses are associated with worse stroke outcomes, likely due to an exaggerated inflammatory immune response, endothelial dysfunction, platelet activation, and coagulopathy. Recent studies have revealed increased plasma von Willebrand factor (VWF) levels and reduced ADAMTS13 activity (the risk factors for stroke) in patients with RTIs, including COVID-19. However, it remains unclear whether an imbalance in the VWF–ADAMTS13 axis plays a causative role in the pathophysiology of S. aureus - or COVID-19-associated stroke severity or is merely an associative marker of disease status. Objective: To examine whether an imbalance in the VWF–ADAMTS13 axis is a causal link between RTIs and stroke severity. Methods: Wild-type (WT) mice (3–4 months old) were infected intranasally with sublethal doses of S. aureus (on days 0, 2, and 5) or mouse-adapted SARS-CoV-2 (on day 0). On day 6 ( S. aureus ) or day 3 (SARS-CoV-2), the infection was confirmed to be localized in the lungs (but not in the brain) and the plasma VWF levels and ADTMTS13 activity were quantified. In another set of experiments, WT, Vwf −/− , and Adamts13 −/− mice (3–4 months old) with respective littermate controls were subjected to transient (30 or 45 min) cerebral ischemia (filament stroke model) followed by reperfusion. For the S. aureus experiments, brain infarcts were assessed on day 2 post-reperfusion and functional outcomes (corner test, wire hanging test, modified neurological severity score, and rotarod test) on week 1 and 4 post-reperfusion. For the SARS-CoV-2 experiments, brain infarcts and functional outcomes (the Bederson score) were assessed on day 1 post-reperfusion. Result: We demonstrated that S. aureus or SARS-CoV-2 infection localized to the lungs in the WT mice resulted in increased (2–3 fold) plasma VWF levels and reduced ADAMTS13 activity, concomitant with larger infarcts and worse functional outcomes (P<0.05 vs. mock-infected mice) up to day 28 post-reperfusion. S. aureus - or SARS-CoV-2-infected VWF-deficient mice exhibited reduced infarcts and improved functional outcomes (P<0.05 vs. infected Vwf +/+ ). In contrast, S. aureus or SARS-CoV-2-infected ADAMTS13-deficient mice displayed greater stroke severity (P<0.05 vs. infected Adamts13 +/+ ). Conclusion: In the experimental models of RTI preceding stroke, VWF plays a causal role in worsening stroke outcomes, while ADAMTS13 is protective.

Aging-associated vulnerability to coronavirus disease 2019 (COVID-19) remains poorly understood. Here, we show that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected aged mice lacking SIRT2, a cytosolic NAD+-dependent deacetylase, develop more severe disease and show increased mortality, while treatment with an NAD+ booster, 78c, protects aged mice from lethal infection. Mechanistically, we demonstrate that SIRT2 modulates the acetylation of cyclic GMP-AMP synthase (cGAS), an immune sensor for cytosolic DNA, and suppresses aging-associated cGAS activation and inflammation. Furthermore, we show that SARS-CoV-2 infection-induced inflammation is mediated at least in part by ORF3a, which triggers mtDNA release and cGAS activation. Collectively, our study reveals a molecular basis for aging-associated susceptibility to COVID-19 and suggests therapeutic approaches to protect aged populations from severe SARS-CoV-2 infection.

Background Central nervous system (CNS) infections contribute to the development of neuroinflammation and neurodegenerative diseases. However, the mechanisms underlying the correlation between CNS infection and subsequent inflammatory course remain largely unknown. Methods Here, we addressed this question by infecting mice with a sublethal dose of a well-studied neurotropic coronavirus, mouse hepatitis virus (MHV), and investigated the effects of infection on the subsequent induction of a mouse multiple sclerosis (MS) model (myelin oligodendrocyte glycoprotein 35-55 (MOG35-55) peptide-induced experimental autoimmune encephalitis (EAE)). Results Unexpectedly, C57BL/6J mice that recovered from MHV infection showed alleviated clinical signs of induced EAE. Mechanistically, this protection is mediated by a novel CNS-resident Foxp3+ CD8 T cell population induced by interleukin (IL)-10, which was secreted by myeloid cells that infiltrated the MHV-infected CNS as part of the MHV-specific immune response. These Foxp3+ CD8 T cells ameliorated EAE severity by decreasing the quantity and function of autoreactive CD4 and CD8 T cell infiltrating CNS independent of antigen specificity, as well as by inhibiting the activation of microglia accumulating in the affected spinal cords (SCs). The persistence of these Foxp3+ CD8 T cells in the CNS may contribute to the long-term post-acute sequelae of infection. Conclusion This study reveals a novel post-infectious anti-inflammatory milieu that develops in MHV-infected CNS of MHV and leads to the generation of Foxp3+ CD8 regulatory T cells, thereby diminishing the progression of subsequent autoimmune disease.

BACKGROUND:Treatments available to prevent progression of virus-induced lung diseases, including coronavirus disease 2019 (COVID-19) are of limited benefit once respiratory failure occurs. The efficacy of approved and emerging cytokine signalling-modulating antibodies is variable and is affected by disease course and patient-specific inflammation patterns. Therefore, understanding the role of inflammation on the viral infectious cycle is critical for effective use of cytokine-modulating agents. METHODS:The role of the type 2 cytokine IL-13 on SARS-CoV-2 binding/entry, replication, and host response was investigated in primary HAE cells in vitro and in a model of mouse-adapted SARS-CoV-2 infection in vivo using single-cell and bulk RNA-sequencing approaches. Additionally, the responses were quantified using immunofluorescence, histopathology, immunohistochemistry and LC-MS/MS assays. FINDINGS:IL-13 protected airway epithelial cells from SARS-CoV-2 infection in vitro by decreasing the abundance of ACE2-expressing ciliated cells rather than by neutralisation in the airway surface liquid or by interferon-mediated antiviral effects. In contrast, IL-13 worsened disease severity in mice; the effects were mediated by eicosanoid signalling and were abolished in mice deficient in the phospholipase A2 enzyme PLA2G2D. INTERPRETATION:IL-13-induced inflammation differentially affects multiple steps of COVID-19 pathogenesis. IL-13-induced inflammation may be protective against initial SARS-CoV-2 airway epithelial infection; however, it enhances disease progression in vivo. Blockade of IL-13 and/or eicosanoid signalling may be protective against progression to severe respiratory virus-induced lung diseases. FUNDING:Carver Trust COVID-19 Grant; CF Foundation Iowa RDP; NIH 1R01HL163024; K01HL140261; NIH R01AI129269; NIH P01AI060699; NIH Grant P30 DK-54759; Cystic Fibrosis Foundation PEZZUL20A1-KB; Stead Family Foundation.

Respiratory tract infections (RTIs) caused by bacteria or viruses are associated with stroke severity. Recent studies have revealed an imbalance in the von Willebrand factor (VWF)-ADAMTS13 axis in patients with RTIs, including COVID-19. We examined whether this imbalance contributes to RTI-mediated stroke severity. Wild-type (WT), Vwf −/−, or Adamts13−/− mice with respective littermate controls (Vwf +/+, or Adamts13+/+) were infected intranasally with sublethal doses of S. aureus (on days 0, 2, and 5) or mouse-adapted SARS-CoV-2 (on day 0) and subjected to transient (30 or 45 min) cerebral ischemia followed by reperfusion. In S. aureus-infected mice, infarct volumes were assessed on day 2 and functional outcomes on weeks 1 and 4 post-reperfusion. In SARS-CoV-2-infected mice, infarct volumes and functional outcomes (Bederson score) were assessed on day 1 post-reperfusion. We demonstrated that S. aureus or SARS-CoV-2 RTI was accompanied by an imbalance in the VWF-ADAMTS13 axis and an increase in plasma levels of IL-6, CXCL1, and MCP-1, which was associated with larger infarcts and worse functional outcomes (P<0.05 vs. mock-infection). S. aureus- or SARS-CoV-2-infected Vwf −/− mice exhibited reduced infarcts and improved functional outcomes, while infected Adamts13−/− mice displayed greater stroke severity (P<0.05 vs. control). In the models of RTI preceding stroke, VWF contributes to stroke severity, while ADAMTS13 is protective.

The innate immune response involves interferons (IFNs), antiviral cytokines that upregulate numerous IFN-stimulated genes, many of which have uncharacterized functions and mechanisms. Here we performed transcriptomic profiling of lung tissues from wild-type and IFNAR-/- mice infected with SARS-CoV-2 and single-cell RNA sequencing of bronchoalveolar lavage fluid and peripheral blood mononuclear cells from patients with COVID-19. We identified O-GalNAc transferase 2 (GALNT2), an N-acetylgalactosaminyltransferase, as an antiviral IFN-stimulated gene restricting the replication of multiple coronaviruses and influenza A viruses in vitro and in vivo, contributing to viral clearance and reducing disease severity. Mechanistically, GALNT2-dependent O-linked glycosylation may regulate viral glycoprotein proteolytic processing and impair viral growth by blocking virus-cell fusion. In addition, we found that serine residues at 810/813 in the viral spike protein undergo O-glycosylation and function as the primary genetic determinants of sensitivity or evasion towards GALNT2. Human genetic data analysis revealed that individuals with GALNT2 variants that lost antiviral function had elevated risk of hospitalization following SARS-CoV-2 infection. This study establishes GALNT2 as an antiviral factor against some respiratory virus infections.