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Community-acquired pneumonia (CAP) contributes substantially to morbidity and mortality in children under the age of 5 years. In examining bronchoalveolar lavages (BALs) of children with CAP, we found that interleukin-17 (IL-17) production was significantly increased in severe CAP. Immune profiling showed that mucosal-associated invariant T (MAIT) cells from the BALs, but not blood, of CAP patients actively produced IL-17 (MAIT17). Single-cell RNA-sequencing revealed that MAIT17 resided in a BAL-resident PLZF hi CD103 + MAIT subset with high expression of hypoxia-inducible factor 1α (HIF-1α), reflecting the hypoxic state of the inflamed tissue. CAP BALs also contained a T-bet + MAIT1 subset and a novel DDIT3 + (DNA damage-inducible transcript 3-positive) MAIT subset with low expression of HIF1A. Furthermore, MAIT17 differed from T-helper type 17 (Th17) cells in the expression of genes related to tissue location, innateness, and cytotoxicity. Finally, we showed that BAL monocytes were hyper-inflammatory and elicited differentiation of MAIT17. Thus, tissue-resident MAIT17 cells are induced at the infected respiratory mucosa, likely influenced by inflammatory monocytes, and contribute to IL-17-mediated inflammation during CAP.Mucosal Immunology _#####################_ ; https://doi.

Background: Strict countermeasures for coronavirus disease (COVID-19) were undertaken in China without knowing their influence on asthma.Objective: To investigate the associations between the frequencies of asthma exacerbations and respiratory infections and air pollutants before and during the COVID-19 pandemic, which were direct consequences of countermeasures undertaken for the pandemic.Methods: Asthma exacerbations and respiratory infections among hospitalized children in the permanent population of Guangzhou City, China, from February to June 2016-2019 (before the pandemic) to February to June 2020 (during the pandemic) were collected in this cross-sectional study in Guangzhou.Results: The number of asthma exacerbation cases per month documented in the Guangzhou Women and Children's Hospital before (median: 13.5; range: 0-48) and during (median: 20; range: 0-34) the mitigative response to the COVID-19 pandemic was similar. The frequency of severe asthma exacerbation cases per month decreased, whereas that of mild asthma exacerbation cases per year increased (p = .004). The number of patients hospitalized with infectious respiratory diseases decreased from 146 (range: 90-172) per month before the pandemic to 42 (range: 33-57) per month during the pandemic (p = .004). Most pathogens and air pollutants decreased during the COVID-19 pandemic. The frequency of severe asthma exacerbations positively correlated to that of respiratory infections in children, but did not correlate to air pollutants. Conclusion:Strict countermeasures undertaken for the pandemic were associated with a decreased the frequency of infectious respiratory diseases and severe asthma exacerbations among urban children.

Human adenovirus (HAdV) infection causes serious pneumonia in children, leading to significant morbidity and mortality rates. However, diagnostic biomarkers for HAdV-associated pneumonia are unavailable. Serum microRNAs (miRNAs/miRs) have been recently reported as diagnostic biomarkers for several diseases. The present study performed microRNA sequencing to identify potential biomarkers among serum exosomal miRNAs, with the aim of identifying candidate biomarkers for the diagnosis of pneumonia in adenovirus-infected children. To validate the biomarker candidates, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was performed to determine the relative expression levels of miRNAs. As there is no endogenous reference RNA for serum miRNAs, pairwise analysis of RT-qPCR was used in the present study to narrow down the number of biomarker candidates among all the serum exosomal miRNAs to a set of four miRNAs. As a result, the identified miRNAs (namely, miR-450a-5p-miR-103a-3p and miR-103b-5p-miR-98-5p) from 59 samples were considered as potential diagnostic biomarkers in adenovirus-infected children. The results indicated that this four miRNA set could distinguish adenovirus-infected patients from healthy controls. In conclusion, the four exosomal miRNAs identified in the present study could be considered as candidate diagnostic biomarkers for pneumonia in adenovirus-infected children.