Single-cell RNA sequencing of blood immune cells reveals type I interferon–associated hyper-inflammation in severe COVID-19.

Biomarkers have been actively investigated to supplement functional and imaging modalities to predict the severity, therapeutic responsiveness, and progression of connective tissue disease-associated interstitial lung disease (CTD-ILD). This study aimed to evaluate Krebs von den Lungen 6 (KL-6) as a potential biomarker reflecting the severity of CTD-ILD as assessed through computed tomography (CT) and pulmonary function test (PFT) parameters. This retrospective study included 549 Korean patients with rheumatoid arthritis, systemic sclerosis, inflammatory myositis, and other CTDs with or without concurrent ILD. Serum KL-6 concentration (U/mL) was measured using the latex-enhanced immunoturbidimetric assay method. CT and PFT results were collected within 1 year of serum collection. A semiquantitative grade of ILD extent was evaluated through CT scan (grade 1, 0–25%; grade 2, 26–50%; grade 3, 51–75%; grade 4, 76–100%). CTD-ILD patients (n = 165) had elevated serum KL-6 levels compared to CTD patients without ILD (n = 384) (p < 0.001), and those findings were preserved after adjusting for age, sex, and CTD type. The semiquantitative grade of ILD on CT scan was significantly proportional to the KL-6 level, and the optimal cut-off KL-6 value effectively differentiated each ILD grade. The percent diffusing capacity of the lung for carbon monoxide (DLCO) (p < 0.001) and forced vital capacity (FVC) (p < 0.001) parameters had a moderate, negative correlation with the KL-6 level. Serum KL-6 levels were increased in CTD-ILD patients and had a positive correlation with CT grade and a negative correlation with FVC and DLCO. Serum KL-6 levels may reflect CTD-ILD severity.

Few studies have used a longitudinal approach to describe the immune response to SARS-CoV-2 infection. Here, we perform single-cell RNA sequencing of bronchoalveolar lavage fluid cells longitudinally obtained from SARS-CoV-2-infected ferrets. Landscape analysis of the lung immune microenvironment shows distinct changes in cell proportions and characteristics compared to uninfected control, at 2 and 5 days post-infection (dpi). Macrophages are classified into 10 distinct subpopulations with transcriptome changes among monocyte-derived infiltrating macrophages and differentiated M1/M2 macrophages, notably at 2 dpi. Moreover, trajectory analysis reveals gene expression changes from monocyte-derived infiltrating macrophages toward M1 or M2 macrophages and identifies a macrophage subpopulation that has rapidly undergone SARS-CoV-2-mediated activation of inflammatory responses. Finally, we find that M1 or M2 macrophages show distinct patterns of gene modules downregulated by immune-modulatory drugs. Overall, these results elucidate fundamental aspects of the immune response dynamics provoked by SARS-CoV-2 infection.

Objective: To investigate the impact of tumor necrosis factor inhibitor (TNFi) treatment and inflammation control on radiographic progression in early ankylosing spondylitis (AS) over 4 years.Methods: We included a total of 215 patients with early AS (symptom duration <10 years) treated with TNFi (the TNFi group; n = 135) or with nonsteroidal antiinflammatory drugs (NSAIDs) (the control group; n = 80). Two blinded readers assessed radiographic progression using the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS). Inflammation control was inferred from C‐reactive protein (CRP) levels time‐averaged between 2 radiologic assessments. Linear mixed modeling was used to estimate mSASSS changes over radiographic intervals as well as the impact of clinical factors on outcomes.Results: The TNFi group had longer disease duration, a higher baseline CRP level, and a higher Bath Ankylosing Spondylitis Disease Activity Index than did controls. The time‐averaged CRP level over radiographic intervals was lower with TNFi treatment than with NSAID treatment (mean ± SD 0.27 ± 0.30 mg/dl versus 0.61 ± 0.68 mg/dl; P < 0.001). Overall, mean ± SD mSASSS change over the 2‐year interval was 1.30 ± 2.97 units. In the multivariable model adjusted for age, smoking status, baseline CRP level, and the presence of syndesmophytes at baseline, the TNFi group showed less mSASSS change over the 2‐year interval (β = −0.90 [95% confidence interval {95% CI} −1.51, −0.29]). However, when a time‐averaged CRP level was additionally included, it significantly influenced the mSASSS change (β = 1.02 [95% CI 0.32, 1.71]), decreasing the estimated group difference (β = −0.52 [95% CI −1.17, 0.14]). NSAID indices of both groups were not associated with either time‐averaged CRP levels or mSASSS changes.Conclusion: Effective suppression of inflammation by TNFi treatment decreases radiographic progression in early AS.

To analyze clinical characteristics of interstitial lung disease (ILD) associated with rheumatoid arthritis (RA), especially in patients with poor prognosis. Seventy-seven RA patients with ILD and 231 age, sex, and disease duration-matched RA patients without ILD were enrolled in this retrospective study. Epidemiologic, clinical, and laboratory information were obtained through a medical chart review. Logistic regression analysis was used to estimate the risk of mortality in RA patients with ILD. Compared to the RA without ILD group, the RA with ILD group had significantly higher titers of rheumatoid factor and the anti-cyclic citrullinated peptide (p = 0.001 for both), higher levels of C-reactive protein (CRP) at the time of RA diagnosis (p = 0.014), and a higher erythrocyte sedimentation rate (p = 0.022) and CRP levels (p < 0.001) throughout the 10-year follow-up period. These patients also received a higher mean daily dose of corticosteroids (p < 0.001). In the subgroup analysis of RA patients with ILD, 28 patients (36.4%) died during follow-up. Multivariate analysis revealed that older age at the time of ILD diagnosis was significantly associated with mortality. Usual interstitial pneumonia (UIP) subtype on high-resolution computed tomography (HRCT) was also suggested as a poor prognostic factor. The survival of RA patients with ILD is adversely affected by age at the time of ILD diagnosis. RA-ILD patients diagnosed after age 65 or with a UIP subtype on HRCT may have a poor prognosis.