Parent tRNA Modification Status Determines the Induction of Functional tRNA-Derived RNA by Respiratory Syncytial Virus Infection.

tRNA-derived RNA fragments (tRFs) are a recently discovered family of small noncoding RNAs (sncRNAs). We previously reported that respiratory syncytial virus (RSV) infection induces functional tRFs, which are derived from a limited subset of parent tRNAs, in airway epithelial cells. Such induction is also observed in nasopharyngeal wash samples from RSV patients and correlates to RSV genome copies, suggesting a clinical significance of tRFs in RSV infection. This work also investigates whether the modification of parent tRNAs is changed by RSV to induce tRFs, using one of the most inducible tRFs as a model. We discovered that RSV infection changed the methylation modification of adenine at position 57 in tRNA glutamic acid, with a codon of CTC (tRNA-GluCTC), and the change is essential for its cleavage. AlkB homolog 1, a previously reported tRNA demethylase, appears to remove methyladenine from tRNA-GluCTC, prompting the subsequent production of tRFs from the 5'-end of tRNA-GluCTC, a regulator of RSV replication. This study demonstrates for the first time the importance of post-transcriptional modification of tRNAs in tRF biogenesis following RSV infection, providing critical insights for antiviral strategy development.

Numerical Investigation on the Droplet Dispersion inside a Bus and the Infection Risk Prediction

COVID-19 can be easily transmitted to passengers by inhaling exhaled droplets from the infected person in a bus. Therefore, studying droplet dispersion would provide further insight into the mechanism of virus transmission and predict the risk of infection among passengers on a bus. In this research, a bus equipped with air-conditioning was employed as the research object. To determine the dispersion path, concentration distribution, and escape time of the droplets, computational fluid dynamic (CFD) was applied to simulate the flow field and the droplets' dispersion. The effect of the air supply rate, the location of vents, and the location of infected persons on the dispersion were discussed. Based on the distribution of droplets in the cabin calculated by CFD, a superposition method was used to determine the number of virus particles inhaled by every individual passenger over a four-hour journey. Then, infection risk was assessed by the Wells-Riley equation for all the passengers in the cabin after the whole journey. The results show that the distribution of droplets in the cabin is greatly influenced by the location of the infected person, and the airflow pattern is highly associated with the air supply rate and the location of vents. The infection risk of passengers located at the droplet dispersion path and the distance from the infected persons less than 2.2 m is over 10%. The increase in the air supply rate could speed up the spread of the droplets but at the same time, it could reduce the infection risk.

Changes of hematological and immunological parameters in COVID-19 patients.

The aim of this study was to identify the changes of hematologic and immunological parameters in COVID-19 patients. We collected and analyzed the data of 117 patients who were laboratory confirmed as SARS-CoV-2 infection. The cases were divided into regular group, severe group and critically ill group according to the sixth edition scheme for COVID-19 diagnosis and treatment of China. The laboratory tests included blood routine, cellular and humoral immunity indices, biochemical detections and inflammatory biomarker. Compared with regular patients, severe and critically ill patients had significantly lower lymphocyte count (p < 0.01), decreased red blood cell and hemoglobin (p < 0.01), low levels of immunoglobulin G (p < 0.05) and significantly higher in D-dimer (p < 0.0001), fibrinogen (p < 0.01), white blood cell count (p < 0.01), neutrophil count (p < 0.0001), interleukin-6 (p < 0.05), C-reactive protein (p < 0.01), procalcitonin (p < 0.01), erythrocyte sedimentation rate (p < 0.05), ferritin (p < 0.01) and lactate dehydrogenase (p < 0.0001). The specific immunoglobulin G antibodies to the SARS-CoV-2 in severe and critically ill patients were significantly lower than that in regular patients (p < 0.05). Our findings suggest that the lymphocyte counts, red blood cell counts and the immunoglobulin G antibodies of COVID-19 patients were impaired to varying degrees and the blood was in a state of hypercoagulation, which were more obvious in critically ill patients.