Iterative Machine Learning for Classification and Discovery of Single-Molecule Unfolding Trajectories from Force Spectroscopy Data.

We report the application of machine learning techniques to expedite classification and analysis of protein unfolding trajectories from force spectroscopy data. Using kernel methods, logistic regression, and triplet loss, we developed a workflow called Forced Unfolding and Supervised Iterative Online (FUSION) learning where a user classifies a small number of repeatable unfolding patterns encoded as images, and a machine is tasked with identifying similar images to classify the remaining data. We tested the workflow using two case studies on a multidomain XMod-Dockerin/Cohesin complex, validating the approach first using synthetic data generated with a Monte Carlo algorithm and then deploying the method on experimental atomic force spectroscopy data. FUSION efficiently separated traces that passed quality filters from unusable ones, classified curves with high accuracy, and identified unfolding pathways that were undetected by the user. This study demonstrates the potential of machine learning to accelerate data analysis and generate new insights in protein biophysics.

Mapping Mechanostable Pulling Geometries of a Therapeutic Anticalin/CTLA-4 Protein Complex.

We used single-molecule AFM force spectroscopy (AFM-SMFS) in combination with click chemistry to mechanically dissociate anticalin, a non-antibody protein binding scaffold, from its target (CTLA-4), by pulling from eight different anchor residues. We found that pulling on the anticalin from residue 60 or 87 resulted in significantly higher rupture forces and a decrease in koff by 2-3 orders of magnitude over a force range of 50-200 pN. Five of the six internal anchor points gave rise to complexes significantly more stable than N- or C-terminal anchor points, rupturing at up to 250 pN at loading rates of 0.1-10 nN s-1. Anisotropic network modeling and molecular dynamics simulations helped to explain the geometric dependency of mechanostability. These results demonstrate that optimization of attachment residue position on therapeutic binding scaffolds can provide large improvements in binding strength, allowing for mechanical affinity maturation under shear stress without mutation of binding interface residues.

Direct Comparison of Lysine versus Site-Specific Protein Surface Immobilization in Single-Molecule Mechanical Assays.

Single-molecule force spectroscopy (SMFS) is powerful for studying folding states and mechanical properties of proteins, however, it requires protein immobilization onto force-transducing probes such as cantilevers or microbeads. A common immobilization method relies on coupling lysine residues to carboxylated surfaces using 1-ethyl-3-(3-dimethyl-aminopropyl) carbodiimide and N-hydroxysuccinimide (EDC/NHS). Because proteins typically contain many lysine groups, this strategy results in a heterogeneous distribution of tether positions. Genetically encoded peptide tags (e.g., ybbR) provide alternative chemistries for achieving site-specific immobilization, but thus far a direct comparison of site-specific vs. lysine-based immobilization strategies to assess effects on the observed mechanical properties was lacking. Here, we compared lysine- vs. ybbR-based protein immobilization in SMFS assays using several model polyprotein systems. Our results show that lysine-based immobilization results in significant signal deterioration for monomeric streptavidin-biotin interactions, and loss of the ability to correctly classify unfolding pathways in a multipathway Cohesin-Dockerin system. We developed a mixed immobilization approach where a site-specifically tethered ligand was used to probe surface-bound proteins immobilized through lysine groups, and found partial recovery of specific signals. The mixed immobilization approach represents a viable alternative for mechanical assays on in vivo-derived samples or other proteins of interest where genetically encoded tags are not feasible.

Utility of basophil activation test for predicting the outcome of wheezing in children: a pilot study.

BACKGROUND: No reliable biological marker for the diagnosis of asthma in younger children is currently available. In this study, we analyzed the differences in basophil activation test (BAT) results among children with recurrent wheezing episodes who had different asthma outcomes. RESULTS: A prospective cohort study was conducted in children aged under 5 years who visited our pediatric respiratory clinic and ward for wheezing. After enrollment, the participants provided samples for a CD63-based BAT performed using an inhalant allergen mixture as a stimulant. Histories of personal allergic diseases and family allergic diseases were evaluated by using a questionnaire. All participants were followed up for 2 years, and their asthma outcomes were evaluated at the end of the follow-up period. The correlation between the BAT results and asthma outcomes was analyzed. Of the 45 originally enrolled children, 38 completed both the follow-up and a BAT. After stimulation with the inhalant mixture, the CD63 expression on basophils and the rate of positive CD63-based BAT results in children diagnosed with asthma were both significantly higher than those in children who were not diagnosed with asthma (p < 0.05 and p < 0.01, respectively). For the prediction of asthma, the positive predictive value and negative predictive value of CD63-based BAT was 71.8 and 69.2%, respectively. The positive likelihood ratio and negative likelihood ratio of CD63-based BAT were 1.70 and 0.3, respectively. CONCLUSIONS: Our pilot study indicates that CD63-based BAT has potential clinical value for predicting asthma outcome in young children with wheezing episodes.

A bacterial stimulation assay for bronchoalveolar lavage immune cells from young children with cystic fibrosis.

Cystic Fibrosis (CF) is primarily a progressive lung disease, characterized by chronic pulmonary infections with opportunistic pathogens. Such infections typically commence early in life, producing an inflammatory response marked by IL-8 chemokine production and neutrophilic infiltration, major contributory factors in CF progression. Studying this inflammation, especially early in life, is critical for developing new strategies for preventing or slowing disruption to the structural integrity of the CF airways. However, evaluating the immune responses of bronchoalveolar lavage (BAL) cells from children with CF faces technical challenges, including contamination carried from the lung due to pre-existing infections and low cell number availability. Here, we describe a technique for preparing BAL cells from young children with CF and using those cells in a bacterial stimulation assay. Initial antibiotic treatment proved essential for preventing resident bacteria from overgrowing BAL cell cultures, or non-specifically activating the cells. ACTB, identified as an optimal reference gene, was validated for accurate analysis of gene expression in these cells. Pseudomonas aeruginosa and Staphylococcus aureus were used as bacterial stimulants to evaluate the immune response of BAL cells from young children with CF. Addition of gentamicin prevented bacterial overgrowth, although if added after 3 hours of culture an extremely variable response resulted, with the bacteria causing a suppressive effect in some cultures. Addition of gentamicin after 1 hour of culture completely prevented this suppressive effect. This technique was then able to reproducibly measure the IL-8 response to stimulation with S. aureus and P. aeruginosa, including co-stimulation with both bacteria.

A pilot study to evaluate the role of circulation CD4+ CCR6+ CRTh2+ cell in predicting risk of asthma in wheezing children.

BACKGROUND: Wheezing is common in younger children and often related to viral infection. It is lack of reliable indicators for asthma prediction. OBJECTIVE: To evaluate the relationship between circulation CD4+CCR6+CRTh2+ memory Th2 cells and asthma diagnosis in wheezing children. METHODS: A prospective study was performed in children under 5 years old presented with wheezing or at last one episode of documented wheezing history. After inclusion, the level of serum allergen-specific serum IgE (sIgE) and circulating CD4+CCR6+CRTh2+cells were detected. The patients' personal and family histories of allergic disease were acquired by questionnaire. The children were followed up over 2 years. Diagnosis of asthma was assessed at the end follow-up. The risk factors in predicting asthma diagnosis were evaluated. RESULTS: A total of 43 children completed follow-up. Higher wheezing frequency were found in children with asthma diagnosis. The mean of circulating CD4+CCR6+CRTh2+cells in children diagnosed with or without asthma was 1.6 %±0.8 and 0.8 %±0.6 %, respectively, and was significantly higher in children diagnosed with asthma (p < 0.01). There was no significant difference between children with and without allergic diseases history or family allergic diseases in level of circulating CD4+CCR6+CRTh2+ cells. Logistic regression analysis indicated that circulating CD4+CCR6+CRTh2+ cells (EXP, 8.986; 95 % CI,1.886-42.816) and wheezing frequency(EXP, 0.127; 95 % CI, 0.023-0.703)were high risk factors for asthma. CONCLUSIONS: Our exploratory study shown that circulating CD4+CCR6+CRTh2+ memory Th2 cells increased in asthma diagnosed children and it was a high-risk factor for asthma. Detection of this type of cells could be helpful in predicting the risk of asthma in wheezing children.

Influence of Fluorination on Single-Molecule Unfolding and Rupture Pathways of a Mechanostable Protein Adhesion Complex.

We investigated the influence of fluorination on unfolding and unbinding reaction pathways of a mechanostable protein complex comprising the tandem dyad XModule-Dockerin bound to Cohesin. Using single-molecule atomic force spectroscopy, we mapped the energy landscapes governing the unfolding and unbinding reactions. We then used sense codon suppression to substitute trifluoroleucine in place of canonical leucine globally in XMod-Doc. Although TFL substitution thermally destabilized XMod-Doc, it had little effect on XMod-Doc:Coh binding affinity at equilibrium. When we mechanically dissociated global TFL-substituted XMod-Doc from Coh, we observed the emergence of a new unbinding pathway with a lower energy barrier. Counterintuitively, when fluorination was restricted to Doc, we observed mechano-stabilization of the non-fluorinated neighboring XMod domain. This suggests that intramolecular deformation is modulated by fluorination and highlights the differences between equilibrium thermostability and non-equilibrium mechanostability. Future work is poised to investigate fluorination as a means to modulate mechanical properties of synthetic proteins and hydrogels.

Small RNA, Transcriptome and Degradome Analysis of the Transgenerational Heat Stress Response Network in Durum Wheat.

Heat stress is a major limiting factor of grain yield and quality in crops. Abiotic stresses have a transgenerational impact and the mechanistic basis is associated with epigenetic regulation. The current study presents the first systematic analysis of the transgenerational effects of post-anthesis heat stress in tetraploid wheat. Leaf physiological traits, harvest components and grain quality traits were characterized under the impact of parental and progeny heat stress. The parental heat stress treatment had a positive influence on the offspring for traits including chlorophyll content, grain weight, grain number and grain total starch content. Integrated sequencing analysis of the small RNAome, mRNA transcriptome and degradome provided the first description of the molecular networks mediating heat stress adaptation under transgenerational influence. The expression profile of 1771 microRNAs (733 being novel) and 66,559 genes was provided, with differentially expressed microRNAs and genes characterized subject to the progeny treatment, parental treatment and tissue-type factors. Gene Ontology and KEGG pathway analysis of stress responsive microRNAs-mRNA modules provided further information on their functional roles in biological processes such as hormone homeostasis, signal transduction and protein stabilization. Our results provide new insights on the molecular basis of transgenerational heat stress adaptation, which can be used for improving thermo-tolerance in breeding.

Fundamental Characteristics of Neuron Adhesion Revealed by Forced Peeling and Time-Dependent Healing.

A current bottleneck in the advance of neurophysics is the lack of reliable methods to quantitatively measure the interactions between neural cells and their microenvironment. Here, we present an experimental technique to probe the fundamental characteristics of neuron adhesion through repeated peeling of well-developed neurite branches on a substrate with an atomic force microscopy cantilever. At the same time, a total internal reflection fluorescence microscope is also used to monitor the activities of neural cell adhesion molecules (NCAMs) during detaching. It was found that NCAMs aggregate into clusters at the neurite-substrate interface, resulting in strong local attachment with an adhesion energy of ∼0.1 mJ/m2 and sudden force jumps in the recorded force-displacement curve. Furthermore, by introducing a healing period between two forced peelings, we showed that stable neurite-substrate attachment can be re-established in 2-5 min. These findings are rationalized by a stochastic model, accounting for the breakage and rebinding of NCAM-based molecular bonds along the interface, and provide new insights into the mechanics of neuron adhesion as well as many related biological processes including axon outgrowth and nerve regeneration.

Removal of a Conserved Disulfide Bond Does Not Compromise Mechanical Stability of a VHH Antibody Complex.

Single-domain VHH antibodies are promising reagents for medical therapy. A conserved disulfide bond within the VHH framework region is known to be critical for thermal stability, however, no prior studies have investigated its influence on the stability of VHH antibody-antigen complexes under mechanical load. Here, we used single-molecule force spectroscopy to test the influence of a VHH domain's conserved disulfide bond on the mechanical strength of the interaction with its antigen mCherry. We found that although removal of the disulfide bond through cysteine-to-alanine mutagenesis significantly lowered VHH domain denaturation temperature, it had no significant impact on the mechanical strength of the VHH:mCherry interaction with complex rupture occurring at ∼60 pN at 103-104 pN/sec regardless of disulfide bond state. These results demonstrate that mechanostable binding interactions can be built on molecular scaffolds that may be thermodynamically compromised at equilibrium.

Integrated Analysis of Small RNA, Transcriptome, and Degradome Sequencing Reveals the Water-Deficit and Heat Stress Response Network in Durum Wheat.

Water-deficit and heat stress negatively impact crop production. Mechanisms underlying the response of durum wheat to such stresses are not well understood. With the new durum wheat genome assembly, we conducted the first multi-omics analysis with next-generation sequencing, providing a comprehensive description of the durum wheat small RNAome (sRNAome), mRNA transcriptome, and degradome. Single and combined water-deficit and heat stress were applied to stress-tolerant and -sensitive Australian genotypes to study their response at multiple time-points during reproduction. Analysis of 120 sRNA libraries identified 523 microRNAs (miRNAs), of which 55 were novel. Differentially expressed miRNAs (DEMs) were identified that had significantly altered expression subject to stress type, genotype, and time-point. Transcriptome sequencing identified 49,436 genes, with differentially expressed genes (DEGs) linked to processes associated with hormone homeostasis, photosynthesis, and signaling. With the first durum wheat degradome report, over 100,000 transcript target sites were characterized, and new miRNA-mRNA regulatory pairs were discovered. Integrated omics analysis identified key miRNA-mRNA modules (particularly, novel pairs of miRNAs and transcription factors) with antagonistic regulatory patterns subject to different stresses. GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis revealed significant roles in plant growth and stress adaptation. Our research provides novel and fundamental knowledge, at the whole-genome level, for transcriptional and post-transcriptional stress regulation in durum wheat.

Multi-Omics Analysis of Small RNA, Transcriptome, and Degradome in T. turgidum-Regulatory Networks of Grain Development and Abiotic Stress Response.

Crop reproduction is highly sensitive to water deficit and heat stress. The molecular networks of stress adaptation and grain development in tetraploid wheat (Triticum turgidum durum) are not well understood. Small RNAs (sRNAs) are important epigenetic regulators connecting the transcriptional and post-transcriptional regulatory networks. This study presents the first multi-omics analysis of the sRNAome, transcriptome, and degradome in T. turgidum developing grains, under single and combined water deficit and heat stress. We identified 690 microRNAs (miRNAs), with 84 being novel, from 118 sRNA libraries. Complete profiles of differentially expressed miRNAs (DEMs) specific to genotypes, stress types, and different reproductive time-points are provided. The first degradome sequencing report for developing durum grains discovered a significant number of new target genes regulated by miRNAs post-transcriptionally. Transcriptome sequencing profiled 53,146 T. turgidum genes, swith differentially expressed genes (DEGs) enriched in functional categories such as nutrient metabolism, cellular differentiation, transport, reproductive development, and hormone transduction pathways. miRNA-mRNA networks that affect grain characteristics such as starch synthesis and protein metabolism were constructed on the basis of integrated analysis of the three omics. This study provides a substantial amount of novel information on the post-transcriptional networks in T. turgidum grains, which will facilitate innovations for breeding programs aiming to improve crop resilience and grain quality.

Steered molecular dynamics simulations reveal the role of Ca2+ in regulating mechanostability of cellulose-binding proteins.

The conversion of cellulosic biomass into biofuels requires degradation of the biomass into fermentable sugars. The most efficient natural cellulase system for carrying out this conversion is an extracellular multi-enzymatic complex named the cellulosome. In addition to temperature and pH stability, mechanical stability is important for functioning of cellulosome domains, and experimental techniques such as Single Molecule Force Spectroscopy (SMFS) have been used to measure the mechanical strength of several cellulosomal proteins. Molecular dynamics computer simulations provide complementary atomic-resolution quantitative maps of domain mechanical stability for identification of experimental leads for protein stabilization. In this study, we used multi-scale steered molecular dynamics computer simulations, benchmarked against new SMFS measurements, to measure the intermolecular contacts that confer high mechanical stability to a family 3 Carbohydrate Binding Module protein (CBM3) derived from the archetypal Clostridium thermocellum cellulosome. Our data predicts that electrostatic interactions in the calcium binding pocket modulate the mechanostability of the cellulose-binding module, which provides an additional design rule for the rational re-engineering of designer cellulosomes for biotechnology. Our data offers new molecular insights into the origins of mechanostability in cellulose binding domains and gives leads for synthesis of more robust cellulose-binding protein modules. On the other hand, simulations predict that insertion of a flexible strand can promote alternative unfolding pathways and dramatically reduce the mechanostability of the carbohydrate binding module, which gives routes to rational design of tailormade fingerprint complexes for force spectroscopy experiments.

Inhibition of transient receptor potential melastatin 8 alleviates airway inflammation and remodeling in a murine model of asthma with cold air stimulus.

Cold air stimulus is an important environmental factor that exacerbates asthma. At the molecular level, the transient receptor potential melastatin 8 (TRPM8) plays a crucial part in cold detection. The roles of TRPM8 in airway inflammation and remodeling in a murine model of asthma with cold stimulus and the related molecular mechanism are largely unknown. In this study, C57BL/6 mice were randomly divided into four groups: phosphate-buffered saline control group (control), ovalbumin (OVA)-induced asthma group (OVA), OVA with cold air stimulus group (OVA+cold), and OVA+cold+shTRPM8 (TRPM8 short hairpin RNA) group. We showed that cold air stimulus-induced TRPM8 upregulation in the OVA+cold group. Moreover, TRPM8 knockdown significantly attenuated cold-induced inflammation and infiltration, decreased levels of immunoglobulin E, restored the Th1/Th2 balance, and reduced inflammatory cell accumulation and airway remodeling. Furthermore, we demonstrated that TRPM8 knockdown dramatically inhibited mitogen-activated protein kinase and nuclear factor-κB pathways. Collectively, these results revealed that cold air stimulus induced an airway inflammatory response and remodeling by increasing TRPM8 expression and that downregulation of TRPM8 alleviated these responses.

Water-deficit stress-responsive microRNAs and their targets in four durum wheat genotypes.

MicroRNAs (miRNAs) guide regulation at the post-transcriptional level by inducing messenger RNA (mRNA) degradation or translational inhibition of their target protein-coding genes. Durum wheat miRNAs may contribute to the genotypic water-deficit stress response in different durum varieties. Further investigation of the interactive miRNA-target regulatory modules and experimental validation of their response to water stress will contribute to our understanding of the small RNA-mediated molecular networks underlying stress adaptation in durum wheat. In this study, a comprehensive genome-wide in silico analysis using the updated Triticum transcriptome assembly identified 2055 putative targets for 113 conserved durum miRNAs and 131 targets for four novel durum miRNAs that putatively contribute to genotypic stress tolerance. Predicted mRNA targets encode various transcription factors, binding proteins and functional enzymes, which play vital roles in multiple biological pathways such as hormone signalling and metabolic processes. Quantitative PCR profiling further characterised 43 targets and 5 miRNAs with stress-responsive and/or genotype-dependent differential expression in two stress-tolerant and two stress-sensitive durum genotypes subjected to pre-anthesis water-deficit stress. Furthermore, a 5' RLM-RACE approach validated nine mRNA targets cleaved by water-deficit stress-responsive miRNAs, which, to our knowledge, has not been previously reported in durum wheat. The present study provided experimental evidence of durum miRNAs and target genes in response to water-deficit stress in contrasting durum varieties, providing new insights into the regulatory roles of the miRNA-guided RNAi mechanism underlying stress adaptation in durum wheat.

MicroRNA167-Directed Regulation of the Auxin Response Factors GmARF8a and GmARF8b Is Required for Soybean Nodulation and Lateral Root Development.

Legume root nodules convert atmospheric nitrogen gas into ammonium through symbiosis with a prokaryotic microsymbiont broadly called rhizobia. Auxin signaling is required for determinant nodule development; however, the molecular mechanism of auxin-mediated nodule formation remains largely unknown. Here, we show in soybean (Glycine max) that the microRNA miR167 acts as a positive regulator of lateral root organs, namely nodules and lateral roots. miR167c expression was up-regulated in the vasculature, pericycle, and cortex of soybean roots following inoculation with Bradyrhizobium japonicum strain USDA110 (the microsymbiont). It was found to positively regulate nodule numbers directly by repressing the target genes GmARF8a and GmARF8b (homologous genes of Arabidopsis [Arabidopsis thaliana] AtARF8 that encode auxin response factors). Moreover, the expression of miR167 and its targets was up- and down-regulated by auxin, respectively. The miR167-GmARF8 module also positively regulated nodulation efficiency under low microsymbiont density, a condition often associated with environmental stress. The regulatory role of miR167 on nodule initiation was dependent on the Nod factor receptor GmNFR1α, and it acts upstream of the nodulation-associated genes nodule inception, nodulation signaling pathway1, early nodulin40-1, NF-YA1 (previously known as HAEM activator protein2-1), and NF-YA2. miR167 also promoted lateral root numbers. Collectively, our findings establish a key role for the miR167-GmARF8 module in auxin-mediated nodule and lateral root formation in soybean.

Engineering an artificial catch bond using mechanical anisotropy.

Catch bonds are a rare class of protein-protein interactions where the bond lifetime increases under an external pulling force. Here, we report how modification of anchor geometry generates catch bonding behavior for the mechanostable Dockerin G:Cohesin E (DocG:CohE) adhesion complex found on human gut bacteria. Using AFM single-molecule force spectroscopy in combination with bioorthogonal click chemistry, we mechanically dissociate the complex using five precisely controlled anchor geometries. When tension is applied between residue #13 on CohE and the N-terminus of DocG, the complex behaves as a two-state catch bond, while in all other tested pulling geometries, including the native configuration, it behaves as a slip bond. We use a kinetic Monte Carlo model with experimentally derived parameters to simulate rupture force and lifetime distributions, achieving strong agreement with experiments. Single-molecule FRET measurements further demonstrate that the complex does not exhibit dual binding mode behavior at equilibrium but unbinds along multiple pathways under force. Together, these results show how mechanical anisotropy and anchor point selection can be used to engineer artificial catch bonds.

Genetic analysis and functional study of novel CFTR variants in Chinese children with cystic fibrosis.

OBJECTIVES: To describe the clinical characteristics of Chinese cystic fibrosis (CF) patients and to investigate the variants of CFTR and their potential pathogenicity. STUDY DESIGN: Chinese patients with potential CF diagnosis were studied. Clinical data were reviewed retrospectively from medical records. Whole exome sequencing and genetic evaluation were conducted to explore potential gene variants. The disruption of the variants to protein structure and function was explored and validated using in vitro experiments and in silico analysis. RESULTS: Four patients were recruited to the study, three of them were diagnosed as CF, and one was diagnosed as CFTR-related disorder. The age at symptom onset for the patients in this study ranged from newborn to 6 years, while the age at diagnosis varied from 3 to 11 years. All four patients exhibited bilateral diffuse bronchiectasis with Pseudomonas aeruginosa infections, and three of them had malnutrition. Finger clubbing was observed in three patients, two of whom displayed mixed ventilatory dysfunction. The CFTR variants spectrum of Chinese children with CF differs from that of Caucasian. A total of six variants were identified, two of which were first reported (c.1219G > T [p.Glu407*] and c.1367delT [p.Ala457Leufs*12]). The nonsense variants c.1219G > T, c.1657C > T and c.2551C > T and the frameshift variant c.1367delT were predicted to introduce premature stop codon and produce shorten CFTR protein, which was also first validated by in vitro truncation assay in this study. The missense variant c.1810A > C was predicted to disrupt the function of the nucleotide-binding domain 1 (NBD1) in the CFTR protein. The splicing variant c.1766 + 5G > T caused skipping of exon 13 and damaged the integrity of CFTR protein. CONCLUSIONS: Our study expands the spectrum of phenotypes and genotypes for CF of Chinese origin, which differs significantly from that of Caucasian. Genetic analysis and counseling are crucial and deserve extensive popularization for the diagnosis ofCF in patients of Chinese origin.

Changing clinical characteristics of pediatric inpatients with pneumonia during COVID-19 pandamic: a retrospective study.

BACKGROUND: The COVID-19 pandemic have impacts on the prevalence of other pathogens and people's social lifestyle. This study aimed to compare the pathogen, allergen and micronutrient characteristics of pediatric inpatients with pneumonia prior to and during the COVID-19 pandemic in a large tertiary hospital in Shanghai, China. METHODS: Patients with pneumonia admitted to the Department of Pediatric Pulmonology of Xinhua Hospital between March-August 2019 and March-August 2020 were recruited. And clinical characteristics of the patients in 2019 were compared with those in 2020. RESULTS: Hospitalizations for pneumonia decreased by 74% after the COVID-19 pandemic. For pathogens, virus, mycoplasma pneumoniae (MP) and mixed infection rates were all much lower in 2020 than those in 2019 (P < 0.01). Regarding allergens, compared with 2019, the positive rates of house dust mite, shrimp and crab were significantly higher in 2020 (P < 0.01). And for micronutrients, the levels of vitamin B2, B6, C and 25-hydroxyvitamin D (25(OH)D) in 2020 were observed to be significantly lower than those in 2019 (P < 0.05). For all the study participants, longer hospital stay (OR = 1.521, P = 0.000), milk allergy (OR = 6.552, P = 0.033) and calcium (Ca) insufficiency (OR = 12.048, P = 0.019) were identified as high-risk factors for severe pneumonia by multivariate analysis. CONCLUSIONS: The number of children hospitalized with pneumonia and incidence of common pathogen infections were both reduced, and that allergy and micronutrient status in children were also changed after the outbreak of the COVID-19 pandemic.

The analysis of risk factors for recurrent wheezing in infants and clinical intervention.

Background: Asthma is one of the most common chronic diseases affecting children's health, and recurrent wheezing in infants is closely related to childhood asthma. However, up to now, there is a lack of unified diagnostic criteria and interventions for recurrent wheezing in infants. By analyzing and discussing the risk factors of recurrent wheezing in infants and related intervention measures, we aim to take individualized treatment for different children and reduce the occurrence of recurrent wheezing in infants. Methods: From January 2017 to December 2020, children under 3 years old who were admitted to the Department of Pediatric Respiratory of Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine with the chief complaint of wheezing for the first time and were clinically diagnosed with bronchiolitis, asthmatic bronchopneumonia and asthmatic bronchitis were retrospectively analyzed through telephone questionnaires. These children were divided into two groups based on whether the wheezing occurred again after discharge. The demographic characteristics, clinical treatment, imaging characteristics, and related interventions and outcomes after discharge were analyzed in both groups. Results: Among the 523 children under 3 years old who were hospitalized due to wheezing, 264 (50.5%) did not have wheezing after discharge, and 259 (49.5%) still had wheezing after discharge. Both chi-squared test and multivariate analysis showed that male, history of eczema, history of rhinitis, history of wheezing before hospitalization, family smoke exposure, mycoplasma infection and inhalation allergen sensitization were risk factors for recurrent wheezing in infants and young children (P<0.05). Simultaneously, Cox survival curve showed that different intervention time and intervention methods would lead to different prognosis. Conclusions: (I) Male, with a history of eczema, rhinitis, wheezing before hospitalization, family environment smoke exposure, mycoplasma infection and a history of inhalation allergy are high risk factors for recurrent wheezing in the recurrent wheezing group, and are more likely to have recurrent wheezing after discharge, with shorter days of wheezing control; (II) there was a significant interaction between mycoplasma infection and a history of inhalation allergy in infants with the risk of recurrent wheezing; (III) long-term intervention for children with wheezing for 4 weeks or more after discharge can reduce the probability of recurrent wheezing; (IV) for children of male, with a history of eczema or rhinitis, the most effective intervention to reduce the probability of recurrent wheezing is long-term inhaled corticosteroids (ICS) treatment after discharge.