Nasopharyngeal Expression of Angiotensin-Converting Enzyme 2 and Transmembrane Serine Protease 2 in Children within SARS-CoV-2-Infected Family Clusters.

Lower levels of angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) in the nasal epithelium of children may be related to a lower incidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, compared to adults. However, no direct evidence is available to support this hypothesis. In this study, we compared the transcript levels of ACE2 and TMPRSS2 in nasopharyngeal swab samples (n = 234) from children and adult family members within SARS-CoV-2-exposed families and assessed the association with SARS-CoV-2 infection status. Transcript levels for ACE2, but not TMPRSS2, were higher in adults than in children (n = 129 adults and 105 children; P < 0.05). The expression of the two genes was not significantly different between SARS-CoV-2 positive and SARS-CoV-2 negative patients within the same age groups. However, in families with one or more SARS-CoV-2 positive adult family members, expression of both genes was significantly higher in SARS-CoV-2 positive children than in SARS-CoV-2 negative children (P < 0.05). By multivariate analysis, ACE2 expression adjusted for age and sex was significantly associated with SARS-CoV-2 infection in the overall population (odds ratio [OR], 1.112 [95% confidence interval [CI], 1.012 to 1.229]; P < 0.05). The degree of this association was higher (OR, 1.172 [95% CI, 1.034 to 1.347]; P < 0.05) in the subgroup of families with only SARS-CoV-2 positive adult family members. Our results suggest that children with lower levels of nasal ACE2 and TMPRSS2 are more likely to remain SARS-CoV-2 negative despite being exposed to a SARS-CoV-2 positive adult family member. IMPORTANCE ACE2 and TMPRSS2 are well established in the literature as SARS-CoV-2 entry factors. Recent data suggest that lower levels of nasal ACE2 in children may be associated with their lower incidence of coronavirus disease 2019 (COVID-19). In this study, using data from nasopharyngeal swab specimens from adult and pediatric members of families in which one or more members of the family had laboratory-confirmed SARS-CoV-2 infection, we show that children with lower levels of ACE2 and TMPRSS2 are more likely to remain SARS-CoV-2 negative despite being exposed to a SARS-CoV-2 positive adult family member. These results provide new insights into the roles of nasopharyngeal ACE2 and TMPRSS2 in acquiring SARS-CoV-2 infection, and they show that the differential expression of these genes in adults versus children may contribute to differential rates of SARS-CoV-2 infection in these populations.

Thrombotic and Hypercoagulability Complications of COVID-19: An Update.

The current COVID-19 pandemic emerged in December 2019, in China, affecting millions of people worldwide. COVID-19 is mainly a disease of the respiratory system, yet systematic complications have also been reported among SARS-CoV-2 infected patients. Thrombotic complications are one of the severe clinical outcomes of COVID-19, especially among critically ill patients, and are associated with poor prognosis. To date, many studies have concluded that COVID-19 increases the incidence of thrombotic events and coagulopathies; however, the exact mechanism behind such a disease outcome is not well known. Various pathophysiological mechanisms for thrombotic events in COVID-19 have been proposed, these include virus-induced endothelial cell damage, inflammation, and excess production of pro-inflammatory cytokines. As a result, most critically diseased COVID-19 patients are managed with prophylactic anticoagulant, yet some still develop thrombotic episodes. Therefore, better understanding of the mechanisms behind the thrombotic complications is needed to develop treatments that specifically target such pathways, which may aid in better disease management and improve the prognosis.

Evaluation of automated molecular tests for the detection of SARS-CoV-2 in pooled nasopharyngeal and saliva specimens.

BACKGROUND: Pooling of samples for SARS-CoV-2 testing in low-prevalence settings has been used as an effective strategy to expand testing capacity and mitigate challenges with the shortage of supplies. We evaluated two automated molecular test systems for the detection of SARS-CoV-2 RNA in pooled specimens. METHODS: Pooled nasopharyngeal and saliva specimens were tested by Qiagen QIAstat-Dx Respiratory SARS-CoV-2 Panel (QIAstat) or Cepheid Xpert Xpress SARS-CoV-2 (Xpert), and the results were compared to that of standard RT-qPCR tests without pooling. RESULTS: In nasopharyngeal specimens, the sensitivity/specificity of the pool testing approach, with 5 and 10 specimens per pool, were 77%/100% (n = 105) and 74.1%/100% (n = 260) by QIAstat, and 97.1%/100% (n = 250) and 100%/99.5% (n = 200) by Xpert, respectively. Pool testing of saliva (10 specimens per pool; n = 150) by Xpert resulted in 87.5% sensitivity and 99.3% specificity compared to individual tests. Pool size of 5 or 10 specimens did not significantly affect the difference of RT-qPCR cycle threshold (CT ) from standard testing. RT-qPCR CT values obtained with pool testing by both QIAstat and Xpert were positively correlated with that of individual testing (Pearson's correlation coefficient r = 0.85 to 0.99, p < 0.05). However, the CT values from Xpert were significantly stronger (p < 0.01, paired t test) than that of QIAstat in a subset of SARS-CoV-2 positive specimens, with mean differences of -4.3 ± 2.43 and -4.6 ± 2 for individual and pooled tests, respectively. CONCLUSION: Our results suggest that Xpert SARS-CoV-2 can be utilized for pooled sample testing for COVID-19 screening in low-prevalence settings providing significant cost savings and improving throughput without affecting test quality.

Deciphering the Role of Filamin B Calponin-Homology Domain in Causing the Larsen Syndrome, Boomerang Dysplasia, and Atelosteogenesis Type I Spectrum Disorders via a Computational Approach.

Filamins (FLN) are a family of actin-binding proteins involved in regulating the cytoskeleton and signaling phenomenon by developing a network with F-actin and FLN-binding partners. The FLN family comprises three conserved isoforms in mammals: FLNA, FLNB, and FLNC. FLNB is a multidomain monomer protein with domains containing an actin-binding N-terminal domain (ABD 1-242), encompassing two calponin-homology domains (assigned CH1 and CH2). Primary variants in FLNB mostly occur in the domain (CH2) and surrounding the hinge-1 region. The four autosomal dominant disorders that are associated with FLNB variants are Larsen syndrome, atelosteogenesis type I (AOI), atelosteogenesis type III (AOIII), and boomerang dysplasia (BD). Despite the intense clustering of FLNB variants contributing to the LS-AO-BD disorders, the genotype-phenotype correlation is still enigmatic. In silico prediction tools and molecular dynamics simulation (MDS) approaches have offered the potential for variant classification and pathogenicity predictions. We retrieved 285 FLNB missense variants from the UniProt, ClinVar, and HGMD databases in the current study. Of these, five and 39 variants were located in the CH1 and CH2 domains, respectively. These variants were subjected to various pathogenicity and stability prediction tools, evolutionary and conservation analyses, and biophysical and physicochemical properties analyses. Molecular dynamics simulation (MDS) was performed on the three candidate variants in the CH2 domain (W148R, F161C, and L171R) that were predicted to be the most pathogenic. The MDS analysis results showed that these three variants are highly compact compared to the native protein, suggesting that they could affect the protein on the structural and functional levels. The computational approach demonstrates the differences between the FLNB mutants and the wild type in a structural and functional context. Our findings expand our knowledge on the genotype-phenotype correlation in FLNB-related LS-AO-BD disorders on the molecular level, which may pave the way for optimizing drug therapy by integrating precision medicine.