Coronavirus disease 2019 (COVID‐19) caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) has become a worldwide pandemic since it emerged in December, 2019. Previous studies have reported rapid antibody response to SARS‐CoV‐2 with the first 2‐3 weeks after symptom onset. Here, we retrospectively described the dynamic changes of serum IgM and IgG specifically against SARS‐CoV‐2 in later weeks (mainly 4‐10 weeks) in 97 hospitalized patients with COVID‐19. We observed that serum IgM and IgG, especially in patients with moderate‐to‐high levels, declined significantly between week 4‐10 after illness onset. Notably, IgG levels in high percentage of patients (77.5%, 31/40) rapidly declined by half, from 212.5 (range, 163.7‐420.3) to 96.3 (range, 75.0‐133.4) AU/ml, within 1‐2 weeks in the second month and then sustained around 100 AU/ml until discharge from hospital. Significant reduction of IgM was also observed as SARS‐CoV‐2 nucleic acid converted to negative (p=0.002). In the recovery stage, serum IgG declined significantly (early vs. late recovery stage, n=16, p=0.003) with a median reduction of 50.0% (range, 3.7‐77.0%). Our results suggested the decline of IgM may be an indicator of virus clearance and recovery patients may have robust immunity against reinfection within at least 3 months after illness onset. Yet, the rapid reduction of IgG by half arises serious concerns on the robustness and sustainability of humoral immune response in the future period after discharge, which is crucial for immunity strategy and developing vaccine. This article is protected by copyright. All rights reserved.

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BackgroundOxidative stress (OS) and reduced nitric oxide (NO) bioavailability contribute to the pathogenesis of pulmonary hypertension (PH). Whether there are associations between OS and NO signaling biomarkers and whether these biomarkers are associated with the severity of PH remain unclear.MethodsBlood samples were collected from 35 healthy controls and 35 patients with pulmonary arterial hypertension (PAH, n = 12) or chronic thromboembolic pulmonary hypertension (CTEPH, n = 23). The mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance index (PVRI) were measured by right heart catheterization. We measured the derivative of reactive oxygen molecules (d-ROMs), biological antioxidant potential (BAP) and superoxide dismutase (SOD) by automatic biochemical analyzer, malondialdehyde (MDA) and asymmetric dimethylarginine (ADMA) by enzyme-linked immunosorbent assay. The relationship between oxidative-antioxidative biomarkers and ADMA, as well as their association with pulmonary hemodynamics, were analyzed.ResultsCompared with age- and gender-matched controls, there was no significant difference of d-ROMs in PAH and CTEPH patients; MDA was increased in CTEPH patients (P = 0.034); BAP and SOD were decreased in PAH (P = 0.014, P < 0.001) and CTEPH patients (P = 0.015, P < 0.001); ADMA level was significantly higher in PAH (P = 0.007) and CTEPH patients (P < 0.001). No association between oxidative-antioxidative biomarkers and ADMA was found. Serum ADMA concentration was correlated with mPAP (r = 0.762, P = 0.006) and PVRI (r = 0.603, P = 0.038) in PAH patients.ConclusionsThe antioxidative potential and NO signaling are impaired in PAH and CTEPH. Increased serum ADMA level is associated with unfavorable pulmonary hemodynamics in PAH patients. Thus, ADMA may be useful in the severity evaluation and risk stratification of PAH.

Lung microbiome ecosystem homeostasis in idiopathic pulmonary fibrosis (IPF) remains uncharacterized. The aims of this study were to identify unique microbial signatures of the lung microbiome and analyze microbial gene function in IPF patients. DNA isolated from BALF samples was obtained for high-throughput gene sequencing. Microbial metagenomic data were used for principal component analysis (PCA) and analyzed at different taxonomic levels. Shotgun metagenomic data were annotated using the KEGG database and were analyzed for functional and metabolic pathways. In this study, 17 IPF patients and 38 healthy subjects (smokers and non-smokers) were recruited. For the PCA, the first and the second principal component explained 16.3 and 13.4% of the overall variability, respectively. The β diversity of microbiome was reduced in the IPF group. Signature of IPF's microbes was enriched of Streptococcus, Pseudobutyrivibrio, and Anaerorhabdus . The translocation of lung microbiome was shown that 32.84% of them were from oral. After analysis of gene function, ABC transporter systems, biofilm formation, and two-component regulatory system were enriched in IPF patients' microbiome. Here we shown the microbiology characteristics in IPF patients. The microbiome may participate in altering internal conditions and involving in generating antibiotic resistance in IPF patients.