ABSTRACT
Background: It has been widely acknowledged that severe acute respiratory syndrome coronavirus 2 (SARS-CoV- 2) infects host cells via the angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) entry mechanism. However, ACE2 and TMPRSS2 cannot explain the Toll-like receptor driven response of monocytes since there is no ACE2 expressed on monocytes, suggesting alternative receptor(s) on these cells. Here, we report cell surface glucose-regulated protein 78 (csGRP78) which is abundantly expressed on monocytes to function as an alternative receptor for SARS-CoV- 2 internalization. Method(s): Blood from COVID-19 patients and healthy donors were collected for csGRP78 and monocyte activation marker as well as cytokine concentration. In vitro SPR, GST pull-down and Co-IP assay were used to determine interaction between SARS-CoV- 2 spike protein and GRP78. Cytokine mixture of IL-1beta, IL-6, TNF and IFN-gamma were used to stimulated csGRP78 upregulation on human monocytic cell line THP-1. GRP78-overexpressing- THP- 1 was also established. pseudo-typed virus expressing spike protein was used to infect mock or GRP78 over-expressing THP-1 cells. Result(s): Our results show that csGRP78 is upregulated on the monocyte of COVID-19 patients. Moreover, in vitro cell culture experiments revealed that stimulation of wtTHP-1 and GRP78 over-expressing THP-1 with the relevant cytokines IL-1beta, IL-6, TNF and IFN-gamma induces similar csGRP78 and activation marker upregulation on cell surface as found on patients' monocytes. In vitro spike protein and GRP78 interaction tests, confirmed direct binding of spike protein and GRP78. Finally, pseudo-typed virus infection assay showed that virus entered GRP78 over-expressing THP-1 cells but not control THP-1 cells. Conclusion(s): Our results demonstrate that csGRP78 acts as a potential functional receptor for SARS-CoV- 2 spike protein and mediates ACE2 independent SARS-CoV- 2 entry into monocytes. These findings provide insight into role of monocytes in the pathophysiology of COVID-19, and suggest a new therapeutic target candidate for anti-SARS- CoV- 2 treatment.
ABSTRACT
It has been widely acknowledged that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects host cells via the angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) entry mechanism. However, ACE2 and TMPRSS2 cannot explain the Toll-like receptor driven response of monocytes since there is no ACE2 expressed on monocytes, suggesting alternative receptor(s) on these cells. Here, we report cell surface glucose-regulated protein 78 (csGRP78) which is abundantly expressed on monocytes to function as an alternative receptor for SARS-CoV-2 internalization. Our results show that csGRP78 is upregulated on the monocyte of COVID-19 patients. Moreover, in vitro cell culture experiments revealed that GRP78 over-expressing THP-1 cells and stimulation of wtTHP-1 cells with the relevant cytokines IL-1beta, IL-6, TNF and IFN-gamma induces similar csGRP78 and activation marker upregulation on cell surface as found on patients' monocytes. In vitro spike protein and GRP78 interaction tests (SPR assay, GST-pull down and Co-IP), confirmed direct binding of spike protein and GRP78. Finally, pseudo-typed virus expressing spike protein was used to infect mock or GRP78 over-expressing THP-1 cells. We found that pseudo-typed virus entered GRP78 over-expressing THP-1 cells but not control THP-1 cells. Our results demonstrate that csGRP78 acts as a potential functional receptor for SARS-CoV-2 spike protein and mediates ACE2 independent SARS-CoV-2 entry into monocytes. These findings provide insight into role of monocytes in the pathophysiology of COVID-19, and suggest a new therapeutic target candidate for anti-SARS-CoV2 treatment.
ABSTRACT
Background Considering the vaccine hesitancy recorded among healthcare workers (HCW) during the 2009/10 influenza pandemic, we aimed to examine the COVID-19 vaccination intent of HCW at one of the largest hospitals in Germany and to identify associated factors. Methods We conducted a cross-sectional anonymous survey at LMU University Hospital in Munich, Germany, between February 25 and March 20, 2021. Data was collected on COVID-19 vaccination intent as main outcome and on potential associated factors. Results In total, 2555 HCW completed the survey;48,3% (n = 1325) of them had already received at least one COVID-19 vaccine dose. Of those not yet vaccinated 51,7% (n = 1320), 83,6% (n = 1104) reported intention to get vaccinated, while 10,2% (n = 134) were undecided and further 6,2% (n = 82) reported refusal. Disagreeing that everyone should receive the generally recommended vaccines was associated with refusal (RR = 529,500, p = 0,000) while being vaccinated against influenza in the 2020/21 season was linked with lower likelihood of refusal or indecisiveness (RR = 0,124, p = 0,000;RR = 0,182, p = 0,000). Low or partial conviction of the effectiveness and safety of COVID-19 vaccines were linked to refusal (effectiveness;RR = 485,471, p = 0,000;RR = 9,247, p = 0,000;safety: RR = 116,829, p = 0,000;RR = 5,423, p = 0,025). Feeling ill informed about COVID-19 vaccines was associated with refusal and indecisiveness (RR = 25,900, p = 0,000;RR = 21,104, p = 0,000). Conclusions At the beginning of the vaccination campaign in Germany, a small proportion of HCW at LMU University hospital was hesitant on receiving a COVID-19 vaccine. Factors associated with refusal or indecisiveness were a sceptical attitude towards vaccines in general as well as feeling ill informed about COVID-19 vaccines, especially regarding their effectiveness and safety. Having received an influenza vaccine was associated with COVID-19 vaccination intent. Key messages • The presented results provide insight into the reasons for hesitancy of HCW against COVID-19 vaccines, indicating a pattern-like behaviour in the acceptance of novel vaccines by HCW. • The evidence from our analysis can help inform the communication aims and emphases of vaccination campaigns among HCW within similar organizational contexts or in future outbreak scenarios.