Trends in Viral Respiratory Culture: Impacts of the SARS-CoV-2 Pandemic

Introduction Due to the increasing ease and availability of molecular assays, viral culture is rarely employed for the diagnosis of respiratory illnesses. Despite lower sensitivity than molecular techniques, viral culture may detect a wider array of viral pathogens at a lower cost relative to multiplex molecular panels. In this study, we examined the effects of the SARS-CoV-2 pandemic on viral respiratory culture ordering and trends in the rates of pathogen detection. Methods Viral respiratory culture results from Jan 1st, 2017 to February 28th, 2022 were analyzed for changes in the number of monthly orders, positivity rate, and incidence of individual pathogens. To determine changes in seasonal incidence and viral etiology, a comparison was made between winter (Dec-Feb) and summer (June-Aug) months as well as acute (Influenza A/B, RSV) and chronic (HSV, CMV) infections. Given SARS-CoV-2's classification as a BSL-3 pathogen, our viral culture assay was not designed to detect this virus. As a surrogate method to measure rates of SARS-CoV-2 in viral culture specimens, we performed NAAT testing with the ThermoFisher TaqPath COVID-19, Flu A/B, RSV assay on negative specimens. Results Following the pandemic, testing volume decreased by 46.7% with the overall positivity rate decreasing from 6.67% to 4.85%. Among the 46 states for which more than ten orders were placed, monthly testing decreased in 38 states. Of the eight states with increased average monthly testing, the greatest increases were seen in Rhode Island, Nevada, and Montana. During the pre-pandemic timeframe, acute respiratory pathogens demonstrated a typical winter peak with low summer detection. Post-pandemic, there was an atypical increase of acute respiratory pathogens, driven primarily by RSV. The positivity rate for chronic viral infections increased from 3.43% pre-pandemic to 4.09% post-pandemic. Following the pandemic, HSV has replaced influenza as the most commonly detected pathogen during winter months. Molecular studies of 229 negative viral culture specimens identified 36 (15.7%) samples positive for SARS-CoV-2, 9 (3.9%) for RSV, and none for influenza A or B. Median cycle threshold values for SARS-CoV-2 samples were 21.3 (range: 9.1-36.5). Conclusions Following the SARS-CoV-2 pandemic, the number of respiratory virus cultures ordered significantly decreased. There has also been a statistically significant decrease in the positivity rate driven by the absence of acute viral respiratory pathogens, including influenza A/B and RSV. We also observed an offseason increase of RSV during the summer months of 2021. Detection rates of chronic viral pathogens including CMV and HSV have remained relative stable. The presence of SARS-CoV-2 in negative specimens raises concerns for inappropriate test utilization. While less sensitive than molecular methods, viral culture has the potential to offer a lower cost alternative for monitoring a broad range of viral pathogens.

Anti-SARS-CoV-2 Antibody Levels Measured by the AdviseDx SARS-CoV-2 Assay Are Concordant with Previously Available Serologic Assays but Are Not Fully Predictive of Sterilizing Immunity.

With the availability of widespread SARS-CoV-2 vaccination, high-throughput quantitative anti-spike protein serological testing will likely become increasingly important. Here, we investigated the performance characteristics of the recently FDA-authorized semiquantitative anti-spike protein AdviseDx SARS-CoV-2 IgG II assay compared to the FDA-authorized anti-nucleocapsid protein Abbott Architect SARS-CoV-2 IgG, Roche Elecsys anti-SARS-CoV-2-S, EuroImmun anti-SARS-CoV-2 enzyme-linked immunosorbent assay (ELISA), and GenScript surrogate virus neutralization assays and examined the humoral response associated with vaccination, natural protection, and vaccine breakthrough infection. The AdviseDx assay had a clinical sensitivity at 14 days after symptom onset or 10 days after PCR detection of 95.6% (65/68; 95% confidence interval [CI], 87.8 to 98.8%), with two discrepant individuals seroconverting shortly thereafter. The AdviseDx assay demonstrated 100% positive percent agreement with the four other assays examined using the same symptom onset or PCR detection cutoffs. Using a recently available WHO international standard for anti-SARS-CoV-2 antibody, we provide assay unit conversion factors to international units for each of the assays examined. We performed a longitudinal survey of healthy vaccinated individuals, finding that median AdviseDx immunoglobulin levels peaked 7 weeks after first vaccine dose at approximately 4,000 IU/ml. Intriguingly, among the five assays examined, there was no significant difference in antigen binding level or neutralizing activity between two seropositive patients protected against SARS-CoV-2 infection in a previously described fishing vessel outbreak and five health care workers who experienced vaccine breakthrough of SARS-CoV-2 infection, all with variants of concern. These findings suggest that protection against SARS-CoV-2 infection cannot currently be predicted exclusively using in vitro antibody assays against wild-type SARS-CoV-2 spike. Further work is required to establish protective correlates for SARS-CoV-2 infection.

IL-13 is a driver of COVID-19 severity.

Immune dysregulation is characteristic of the more severe stages of SARS-CoV-2 infection. Understanding the mechanisms by which the immune system contributes to COVID-19 severity may open new avenues to treatment. Here, we report that elevated IL-13 was associated with the need for mechanical ventilation in 2 independent patient cohorts. In addition, patients who acquired COVID-19 while prescribed Dupilumab, a mAb that blocks IL-13 and IL-4 signaling, had less severe disease. In SARS-CoV-2-infected mice, IL-13 neutralization reduced death and disease severity without affecting viral load, demonstrating an immunopathogenic role for this cytokine. Following anti-IL-13 treatment in infected mice, hyaluronan synthase 1 (Has1) was the most downregulated gene, and accumulation of the hyaluronan (HA) polysaccharide was decreased in the lung. In patients with COVID-19, HA was increased in the lungs and plasma. Blockade of the HA receptor, CD44, reduced mortality in infected mice, supporting the importance of HA as a pathogenic mediator. Finally, HA was directly induced in the lungs of mice by administration of IL-13, indicating a new role for IL-13 in lung disease. Understanding the role of IL-13 and HA has important implications for therapy of COVID-19 and, potentially, other pulmonary diseases. IL-13 levels were elevated in patients with severe COVID-19. In a mouse model of the disease, IL-13 neutralization reduced the disease and decreased lung HA deposition. Administration of IL-13-induced HA in the lung. Blockade of the HA receptor CD44 prevented mortality, highlighting a potentially novel mechanism for IL-13-mediated HA synthesis in pulmonary pathology.

Histopathology and ultrastructural findings of fatal COVID-19 infections in Washington State: a case series.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of an ongoing pandemic, with increasing deaths worldwide. To date, documentation of the histopathological features in fatal cases of the disease caused by SARS-CoV-2 (COVID-19) has been scarce due to sparse autopsy performance and incomplete organ sampling. We aimed to provide a clinicopathological report of severe COVID-19 cases by documenting histopathological changes and evidence of SARS-CoV-2 tissue tropism. METHODS: In this case series, patients with a positive antemortem or post-mortem SARS-CoV-2 result were considered eligible for enrolment. Post-mortem examinations were done on 14 people who died with COVID-19 at the King County Medical Examiner's Office (Seattle, WA, USA) and Snohomish County Medical Examiner's Office (Everett, WA, USA) in negative-pressure isolation suites during February and March, 2020. Clinical and laboratory data were reviewed. Tissue examination was done by light microscopy, immunohistochemistry, electron microscopy, and quantitative RT-PCR. FINDINGS: The median age of our cohort was 73·5 years (range 42-84; IQR 67·5-77·25). All patients had clinically significant comorbidities, the most common being hypertension, chronic kidney disease, obstructive sleep apnoea, and metabolic disease including diabetes and obesity. The major pulmonary finding was diffuse alveolar damage in the acute or organising phases, with five patients showing focal pulmonary microthrombi. Coronavirus-like particles were detected in the respiratory system, kidney, and gastrointestinal tract. Lymphocytic myocarditis was observed in one patient with viral RNA detected in the tissue. INTERPRETATION: The primary pathology observed in our cohort was diffuse alveolar damage, with virus located in the pneumocytes and tracheal epithelium. Microthrombi, where observed, were scarce and endotheliitis was not identified. Although other non-pulmonary organs showed susceptibility to infection, their contribution to the pathogenesis of SARS-CoV-2 infection requires further examination. FUNDING: None.