Environmentally persistent free radicals enhance SARS-CoV-2 replication in respiratory epithelium.

Epidemiological evidence links lower air quality with increased incidence and severity of COVID-19; however, mechanistic data have yet to be published. We hypothesized air pollution-induced oxidative stress in the nasal epithelium increased viral replication and inflammation. Nasal epithelial cells (NECs), collected from healthy adults, were grown into a fully differentiated epithelium. NECs were infected with the ancestral strain of SARS-CoV-2. An oxidant combustion by-product found in air pollution, the environmentally persistent free radical (EPFR) DCB230, was used to mimic pollution exposure four hours prior to infection. Some wells were pretreated with antioxidant, astaxanthin, for 24 hours prior to EPFR-DCB230 exposure and/or SARS-CoV-2 infection. Outcomes included viral replication, epithelial integrity, surface receptor expression (ACE2, TMPRSS2), cytokine mRNA expression (TNF-α, IFN-ß), intracellular signaling pathways, and oxidative defense enzymes. SARS-CoV-2 infection induced a mild phenotype in NECs, with some cell death, upregulation of the antiviral cytokine IFN-ß, but had little effect on intracellular pathways or oxidative defense enzymes. Prior exposure to EPFR-DCB230 increased SARS-CoV-2 replication, upregulated TMPRSS2 expression, increased secretion of the proinflammatory cytokine TNF-α, inhibited expression of the mucus producing MUC5AC gene, upregulated expression of p21 (apoptosis pathway), PINK1 (mitophagy pathway), and reduced levels of antioxidant enzymes. Pretreatment with astaxanthin reduced SARS-CoV-2 replication, downregulated ACE2 expression, and prevented most, but not all EPFR-DCB230 effects. Our data suggest that oxidant damage to the respiratory epithelium may underly the link between poor air quality and increased COVID-19. The apparent protection by antioxidants warrants further research.

Absence of antibody responses to SARS-CoV-2 N protein in COVID-19 vaccine breakthrough cases.

Understanding the risk factors for breakthrough coronavirus disease 2019 (COVID-19) (BC19) is critical to inform policy. Herein, we assessed Delta (Lineage B.1.617.2) variant-specific effectiveness of the BNT162b2 (Pfizer) vaccine and characterized Delta-driven BC19 cases (fully vaccinated individuals who get infected) with known-time-since-vaccination. In this longitudinal prospective study (January 21-October 30, 2021), 90 naïve and 15 convalescent individuals were enrolled at the initiation of vaccination. Samples from 27 unvaccinated individuals with previous laboratory-confirmed COVID-19 diagnosis were collected at a single time point. Longitudinal serology profile (antibodies against severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2] S and N proteins) and live-virus-based neutralization capacities were assessed while controlling for age. Sex, age, history of reactions to the COVID-19 vaccine, and viral neutralization capacities were identified as significant risk factors for breakthrough COVID-19. At 8 months postvaccination, male sex, individuals ⩾65 years of age, and individuals who experienced noticeable side effects with the COVID-19 vaccine were at 5.47 (p-value = 0.0102), 4.33 (p-value = 0.0236), and 4.95 (p-value = 0.0159) fold greater risk of BC19 as compared to their peers, respectively. Importantly, every five-fold increase in viral neutralization capacities (by live-virus-based assays) was significantly associated with ~4-fold reduction in the risk occurrence of breakthrough COVID-19 (p-value = 0.045). Vaccine boosting remarkably increased these viral neutralization capacities by 16.22-fold (p- value = 0.0005), supporting the importance of the BNT162b2 booster in efforts to control the incursion of future variants into the population at large. Strikingly, BC19 cases exhibited a delayed/absent antibody response to the N protein, suggesting limited exposure to the virus. Since antibodies against N protein are widely used to evaluate the extent of virus spread in communities, our finding has important implications on the utility of existing serological diagnostic and surveillance for COVID-19.

IL-1ß Promotes Expansion of IL-33+ Lung Epithelial Stem Cells after Respiratory Syncytial Virus Infection during Infancy.

Respiratory syncytial virus (RSV)-induced immunopathogenesis and disease severity in neonatal mice and human infants have been related to elevated pulmonary IL-33. Thus, targeting IL-33 has been suggested as a potential therapy for respiratory viral infections. Yet, the regulatory mechanisms on IL-33 during early life remain unclear. Here, using a neonatal mouse model of RSV, we demonstrate that IL-1ß positively regulates but is not required for RSV-induced expression of pulmonary IL-33 in neonatal mice early after the initial infection. Exogenous IL-1ß upregulates RSV-induced IL-33 expression by promoting the proliferation of IL-33+ lung epithelial stem/progenitor cells. These cells are exclusively detected in RSV-infected neonatal rather than adult mice, partially explaining the IL-1ß-independent IL-33 expression in RSV-infected adult mice. Furthermore, IL-1ß aggravates IL-33-mediated T-helper cell type 2-biased immunopathogenesis upon reinfection. Collectively, our study demonstrates that IL-1ß exacerbates IL-33-mediated RSV immunopathogenesis by promoting the proliferation of IL-33+ epithelial stem/progenitor cells in early life.

Reduced turnaround times through multi-sectoral community collaboration during the first surge of SARS-CoV-2 and associated effect on patient care and hospital operations.

BACKGROUND: In March 2020, an influx of admissions in COVID-19 positive patients threatened to overwhelm healthcare facilities in East Baton Rouge Parish, Louisiana. Exacerbating this problem was an overall shortage of diagnostic testing capability at that time, resulting in a delay in time-to-result return. An improvement in diagnostic testing availability and timeliness was necessary to improve the allocation of resources and ultimate throughput of patients. The management of a COVID-19 positive patient or patient under investigation requires infection control measures that can quickly consume personal protective equipment (PPE) stores and personnel available to treat these patients. Critical shortages of both PPE and personnel also negatively impact care in patients admitted with non-COVID-19 illnesses. METHODS: A multisectoral partnership of healthcare providers, facilities and academicians created a molecular diagnostic lab within an academic research facility dedicated to testing inpatients and healthcare personnel for SARS-CoV-2. The purpose of the laboratory was to provide a temporary solution to the East Baton Rouge Parish healthcare community until individual facilities were self-sustaining in testing capabilities. We describe the partnership and the impacts of this endeavor by developing a model derived from a combination of data sources, including electronic health records, hospital operations, and state and local resources. FINDINGS: Our model demonstrates two important principles: the impact of reduced turnaround times (TAT) on potential differences in inpatient population numbers for COVID-19 and savings in PPE attributed to the more rapid TAT.

Deficiency in ST2 signaling ameliorates RSV-associated pulmonary hypertension.

Pulmonary hypertension (PH) observed during respiratory syncytial virus (RSV) bronchiolitis is associated with morbidity and mortality, especially in children with congenital heart disease. Yet, the pathophysiological mechanisms of RSV-associated PH remain unclear. Therefore, this study aimed to investigate the pathophysiological mechanism of RSV-associated PH. We used a translational mouse model of RSV-associated PH, in which wild-type (WT) and suppression of tumorigenicity 2 (ST2) knockout neonatal mice were infected with RSV at 5 days old and reinfected 4 wk later. The development of PH in WT mice following RSV reinfection was evidenced by elevated right ventricle systolic pressure, shortened pulmonary artery acceleration time (PAT), and decreased PAT/ejection time (ET) ratio. It coincided with the augmentation of periostin and IL-13 expression and increased arginase bioactivity by both arginase 1 and 2 as well as induction of nitric oxide synthase (NOS) uncoupling. Absence of ST2 signaling prevented RSV-reinfected mice from developing PH by suppressing NOS uncoupling. In summary, ST2 signaling was involved in the development of RSV-associated PH. ST2 signaling inhibition may be a novel therapeutic target for RSV-associated PH.NEW & NOTEWORTHY We report that the pathogenic role of ST2-mediated type 2 immunity and mechanisms contribute to RSV-associated pulmonary hypertension. Inhibiting ST2 signaling may be a novel therapeutic target for this condition.

Elevated Levels of Type 2 Respiratory Innate Lymphoid Cells in Human Infants with Severe Respiratory Syncytial Virus Bronchiolitis.

Rationale: Studies of the immune responses at the site of respiratory syncytial virus (RSV) infection are sparse despite nearly five decades of research into understanding RSV disease.Objectives: To investigate the role of mucosal innate immune responses to RSV and respiratory viral load in infants hospitalized with the natural disease.Methods: Cytokines, viral load, and type 2 innate lymphoid cell (ILC2) levels in nasal aspirates, collected within 24 hours of enrollment, from infants hospitalized with RSV infection were quantified.Measurements and Main Results: RSV severity in infants was categorized based on admission to the general ward (moderate) or the pediatric ICU (severe). Evaluable subjects included 30 patients with severe and 63 patients with moderate disease (median age, 74 d; range, 9-297 d). ILC2s were found in the nasal aspirates of patients with severe disease (0.051% of total respiratory CD45+ cells) to a significantly greater extent than in patients with moderate disease (0.018%, P = 0.004). Levels of IL-4, IL-13, IL-33, and IL-1ß were significantly higher in nasal aspirates of patients with severe disease compared with those of patients with moderate disease. Factors associated with disease severity were gestational age (odds ratio, 0.49; 95% confidence interval, 0.29-0.82; P = 0.007) and IL-4 (odds ratio, 9.67; 95% confidence interval, 2.45-38.15; P = 0.001).Conclusions: This study shows, for the first time, that elevated levels of ILC2s is associated with infant RSV severity. The findings highlight the dominance of type-2 responses to RSV infection in infants and suggest an important role of ILC2 in shaping the immune response early during RSV infection.

Role of Type I Interferon (IFN) in the Respiratory Syncytial Virus (RSV) Immune Response and Disease Severity.

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract disease in children <2 years of age. Increased morbidity and mortality have been reported in high-risk patients, such as premature infants, patients with cardiac disease, and severely immune compromised patients. Severe disease is associated with the virulence of the virus as well as host factors specifically including the innate immune response. The role of type I interferons (IFNs) in the response to RSV infection is important in regulating the rate of virus clearance and in directing the character of the immune response, which is normally associated with protection and less severe disease. Two RSV non-structural proteins, NS1 and NS2, as well as the envelope G glycoprotein are known to suppress type I IFN production and a robust type I IFN response to RSV does not occur in human infants or neonatal mouse models of RSV infection. Additionally, presence of type I IFNs are associated with mild symptoms in infants and administration of IFN-α prior to infection of neonatal mice with RSV reduces immunopathology. This evidence has driven RSV prophylaxis and therapeutic efforts to consider strategies for enhancing type I IFN production.

Type I Interferon Potentiates IgA Immunity to Respiratory Syncytial Virus Infection During Infancy.

Respiratory syncytial virus (RSV) infection is the most frequent cause of hospitalization in infants and young children worldwide. Although mucosal RSV vaccines can reduce RSV disease burden, little is known about mucosal immune response capabilities in children. Neonatal or adult mice were infected with RSV; a subset of neonatal mice received interferon alpha (IFN-α) (intranasal) prior to RSV infection. B cells, B cell activating factor (BAFF) and IgA were measured by flow cytometry. RSV specific IgA was measured in nasal washes. Nasal associated lymphoid tissue (NALT) and lungs were stained for BAFF and IgA. Herein, we show in a mouse model of RSV infection that IFN-α plays a dual role as an antiviral and immune modulator and age-related differences in IgA production upon RSV infection can be overcome by IFN-α administration. IFN-α administration before RSV infection in neonatal mice increased RSV-specific IgA production in the nasal mucosa and induced expression of the B-cell activating factor BAFF in NALT. These findings are important, as mucosal antibodies at the infection site, and not serum antibodies, have been shown to protect human adults from experimental RSV infection.

New mouse model of pulmonary hypertension induced by respiratory syncytial virus bronchiolitis.

Pulmonary hypertension (PH) has been observed in up to 75% of infants with moderate to severe respiratory syncytial virus (RSV) bronchiolitis and is associated with significant morbidity and mortality in infants with congenital heart disease. The purpose of the present study was to establish a mouse model of PH secondary to RSV bronchiolitis that mimics the disease etiology as it occurs in infants. Neonatal mice were infected with RSV at 5 days of age and then reinfected 4 wk later. Serum-free medium was administered to age-matched mice as a control. Echocardiography and right ventricular systolic pressure (RVSP) measurements via right jugular vein catheterization were conducted 5 and 6 days after the second infection, respectively. Peripheral capillary oxygen saturation monitoring did not indicate hypoxia at 2-4 days post-RSV infection, before reinfection, and at 2-7 days after reinfection. RSV-infected mice had significantly higher RVSP than control mice. Pulsed-wave Doppler recording of the pulmonary blood flow by echocardiogram demonstrated a significantly shortened pulmonary artery acceleration time and decreased pulmonary artery acceleration time-to-ejection time ratio in RSV-infected mice. Morphometry showed that RSV-infected mice exhibited a significantly higher pulmonary artery medial wall thickness and had an increased number of muscularized pulmonary arteries compared with control mice. These findings, confirmed by RVSP measurements, demonstrate the development of PH in the lungs of mice infected with RSV as neonates. This animal model can be used to study the pathogenesis of PH secondary to RSV bronchiolitis and to assess the effect of treatment interventions. NEW & NOTEWORTHY This is the first mouse model of respiratory syncytial virus-induced pulmonary hypertension, to our knowledge. This model will allow us to decipher molecular mechanisms responsible for the pathogenesis of pulmonary hypertension secondary to respiratory syncytial virus bronchiolitis with the use of knockout and/or transgenic animals and to monitor therapeutic effects with echocardiography.

Specific inhibition of NLRP3 in chikungunya disease reveals a role for inflammasomes in alphavirus-induced inflammation.

Mosquito-borne viruses can cause severe inflammatory diseases and there are limited therapeutic solutions targeted specifically at virus-induced inflammation. Chikungunya virus (CHIKV), a re-emerging alphavirus responsible for several outbreaks worldwide in the past decade, causes debilitating joint inflammation and severe pain. Here, we show that CHIKV infection activates the NLRP3 inflammasome in humans and mice. Peripheral blood mononuclear cells isolated from CHIKV-infected patients showed elevated NLRP3, caspase-1 and interleukin-18 messenger RNA expression and, using a mouse model of CHIKV infection, we found that high NLRP3 expression was associated with peak inflammatory symptoms. Inhibition of NLRP3 activation using the small-molecule inhibitor MCC950 resulted in reduced CHIKV-induced inflammation and abrogated osteoclastogenic bone loss and myositis, but did not affect in vivo viral replication. Mice treated with MCC950 displayed lower expression levels of the cytokines interleukin-6, chemokine ligand 2 and tumour necrosis factor in joint tissue. Interestingly, MCC950 treatment abrogated disease signs in mice infected with a related arthritogenic alphavirus, Ross River virus, but not in mice infected with West Nile virus-a flavivirus. Here, using mouse models of alphavirus-induced musculoskeletal disease, we demonstrate that NLRP3 inhibition in vivo can reduce inflammatory pathology and that further development of therapeutic solutions targeting inflammasome function could help treat arboviral diseases.