Porcine Deltacoronavirus Utilizes Sialic Acid as an Attachment Receptor and Trypsin Can Influence the Binding Activity.

Porcine deltacoronavirus (PDCoV) is a novel coronavirus that causes diarrhea in nursing piglets. Studies showed that PDCoV uses porcine aminopeptidase N (pAPN) as an entry receptor, but the infection of pAPN-knockout cells or pigs with PDCoV revealed that pAPN might be not a critical functional receptor, implying there exists an unidentified receptor involved in PDCoV infection. Herein, we report that sialic acid (SA) can act as an attachment receptor for PDCoV invasion and facilitate its infection. We first demonstrated that the carbohydrates destroyed on the cell membrane using NaIO4 can alleviate the susceptibility of cells to PDCoV. Further study showed that the removal of SA, a typical cell-surface carbohydrate, could influence the PDCoV infectivity to the cells significantly, suggesting that SA was involved in the infection. The results of plaque assay and Western blotting revealed that SA promoted PDCoV infection by increasing the number of viruses binding to SA on the cell surface during the adsorption phase, which was also confirmed by atomic force microscopy at the microscopic level. In in vivo experiments, we found that the distribution levels of PDCoV and SA were closely relevant in the swine intestine, which contains huge amount of trypsin. We further confirmed that SA-binding capacity to PDCoV is related to the pre-treatment of PDCoV with trypsin. In conclusion, SA is a novel attachment receptor for PDCoV infection to enhance its attachment to cells, which is dependent on the pre-treatment of trypsin on PDCoV. This study paves the way for dissecting the mechanisms of PDCoV-host interactions and provides new strategies to control PDCoV infection.

Inactivation of SARS-CoV-2 and HCoV-229E in vitro by ColdZyme® a medical device mouth spray against the common cold.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic calls for effective and safe treatments. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing COVID-19 actively replicates in the throat, unlike SARS-CoV, and shows high pharyngeal viral shedding even in patients with mild symptoms of the disease. HCoV-229E is one of four coronaviruses causing the common cold. In this study, the efficacy of ColdZyme® (CZ-MD), a medical device mouth spray, was tested against SARS-CoV-2 and HCoV-229E in vitro. The CZ-MD provides a protective glycerol barrier containing cod trypsin as an ancillary component. Combined, these ingredients can inactivate common cold viruses in the throat and mouth. The CZ-MD is believed to act on the viral surface proteins that would perturb their entry pathway into cells. The efficacy and safety of the CZ-MD have been demonstrated in clinical trials on the common cold. METHOD OF STUDY: The ability of the CZ-MD to inactivate SARS-CoV-2 and HCoV-229E was tested using an in vitro virucidal suspension test (ASTM E1052). RESULTS: CZ-MD inactivated SARS-CoV-2 by 98.3% and HCoV-229E by 99.9%. CONCLUSION: CZ-MD mouth spray can inactivate the respiratory coronaviruses SARS-CoV-2 and HCoV-229E in vitro. Although the in vitro results presented cannot be directly translated into clinical efficacy, the study indicates that CZ-MD might offer a protective barrier against SARS-CoV-2 and a decreased risk of COVID-19 transmission.

Quantifying the effect of trypsin and elastase on in vitro SARS-CoV infections.

The SARS coronavirus (SARS-CoV) has the potential to cause serious disease that can spread rapidly around the world. Much of our understanding of SARS-CoV pathogenesis comes from in vitro experiments. Unfortunately, in vitro experiments cannot replicate all the complexity of the in vivo infection. For example, proteases in the respiratory tract cleave the SARS-CoV surface protein to facilitate viral entry, but these proteases are not present in vitro. Unfortunately, proteases might also have an effect on other parts of the replication cycle. Here, we use mathematical modeling to estimate parameters characterizing viral replication for SARS-CoV in the presence of trypsin or elastase, and in the absence of either. In addition to increasing the infection rate, the addition of trypsin and elastase causes lengthening of the eclipse phase duration and the infectious cell lifespan.