Spike glycoprotein and host cell determinants of SARS-CoV-2 entry and cytopathic effects.

SARS-CoV-2, a betacoronavirus, is the cause of the COVID-19 pandemic. The SARS-CoV-2 spike (S) glycoprotein trimer mediates virus entry into host cells and cytopathic effects (syncytium formation). We studied the contribution of several S glycoprotein features to these functions, focusing on those that differ among related coronaviruses. Acquisition of the furin cleavage site by the SARS-CoV-2 S glycoprotein decreased virus stability and infectivity, but greatly enhanced syncytium-forming ability. Notably, the D614G change found in globally predominant SARS-CoV-2 strains increased infectivity, modestly enhanced responsiveness to the ACE2 receptor and susceptibility to neutralizing sera, and tightened association of the S1 subunit with the trimer. Apparently, these two features of the SARS-CoV-2 S glycoprotein, the furin cleavage site and D614G, have evolved to balance virus infectivity, stability, cytopathicity and antibody vulnerability. Although the endodomain (cytoplasmic tail) of the S2 subunit was not absolutely required for virus entry or syncytium formation, alteration of palmitoylated cysteine residues in the cytoplasmic tail decreased the efficiency of these processes. As proteolytic cleavage contributes to the activation of the SARS-CoV-2 S glycoprotein, we evaluated the ability of protease inhibitors to suppress S glycoprotein function. Matrix metalloprotease inhibitors suppressed S-mediated cell-cell fusion, but not virus entry. Synergy between inhibitors of matrix metalloproteases and TMPRSS2 suggests that both host proteases can activate the S glycoprotein during the process of syncytium formation. These results provide insights into SARS-CoV-2 S glycoprotein-host cell interactions that likely contribute to the transmission and pathogenicity of this pandemic agent.IMPORTANCE The development of an effective and durable SARS-CoV-2 vaccine is essential for combating the growing COVID-19 pandemic. The SARS-CoV-2 spike (S) glycoprotein is the main target of neutralizing antibodies elicited during virus infection or following vaccination. Knowledge of the spike glycoprotein evolution, function and interactions with host factors will help researchers to develop effective vaccine immunogens and treatments. Here we identify key features of the spike glycoprotein, including the furin cleavage site and the D614G natural mutation, that modulate viral cytopathic effects, infectivity and sensitivity to inhibition. We also identify two inhibitors of host metalloproteases that block S-mediated cell-cell fusion, a process that contributes to the destruction of the virus-infected cell.

Quality of Life and Its Associated Factors Among Cancer Patients Receiving Chemotherapy at Oncology Hospitals in Vietnam After the Third Wave of the COVID-19 Pandemic.

Purpose: This study aimed to evaluate the health-related quality of life (HRQOL) of cancer patients receiving chemotherapy and identify associated factors affecting the HRQOL after the third wave of the COVID-19 pandemic in Vietnam. Patients and Methods: Patients with solid cancers receiving chemotherapy at two oncology hospitals in Vietnam during April and May 2021 were included. The European Organisation for Research and Treatment of Cancer Core Quality of Life Questionnaire version 3 was used to measure the HRQOL. Three questions were asked to explore patients' concern levels about contracting COVID-19, delaying chemotherapy, or not controlling cancer well. One question was used to explore whether patients were concerned about cancer progression or COVID-19 infection more, or equally, or had no concern about both. Multiple regression models were conducted to examine factors associated with the global health status (GHS) score. Results: Of 270 included patients, mean (Standard deviation [SD]) GHS was 56.7 (20.8). Among the functional statuses, social functioning (SF) had the lowest score of 63.6 (29.2). The symptoms with the highest means were insomnia and fatigue, obtaining the score of 38.5 (31.7) and 37.3 (29.2), respectively. The mean of financial difficulties was 54.1 (32.2). In univariate analysis, high concerns about contracting COVID-19, delaying chemotherapy, not controlling cancer well, or more concern about either cancer or COVID-19 over the other were associated with worse GHS, physical functioning, emotional functioning, and SF. In multivariate analysis, those concerns and no income were significantly related to lower GHS scores besides the non-modifiable factors, such as female gender and some cancer types. Conclusion: Patients at the high concern levels, or with more concern about either cancer or COVID-19 over the other had poorer HRQOL. Interventions to address the concerns are required to improve their HRQOL, particularly for women, those without income, or with some specific cancers.