The Monocyte Chemotactic Protein 1 as a Potential Indicator for SARS-CoV-2 Infected Mild COVID-19 Patients

The authors compare chemokines and their receptors in mild and severe cases of COVID-19 to healthy controls, suggesting that mild (and severe) disease is associated with increased serum levels of MCP-1, but only severe disease is characterized by increased IL-8 and IP-10. They show that mild cases do have elevated PBMC expression of the MCP-1 receptor CCR2 and that MCP-1 upregulation is associated with reduced levels of IRF3 and a reduced IFN-b response. 

Research Highlights

1. Mild (and severe) cases of COVID-19 show higher serum levels of MCP-1 than healthy controls 

2. Levels of IP-10 and IL-8 are high in severe but low in mild cases 

3. Levels of CCR2 but not CXCR3 and CXCR2 are elevated in PBMC in mild disease compared to healthy controls 

4. Levels of IRF3 and IFN-b are reduced in mild disease compared to healthy controls 

5. IRF3 downregulation is negatively correlated with MCP-1  

Impact for COVID-19 research:  

Low 

Methodologies: 

• In vitro 

• Key Techniques: ELISA, real-time PCR 

Limitations: 

• The authors focus on the difference in serum chemokines between mild COVID-19 and healthy controls. It would be more useful to investigate differences between mild and severe cases. 

• Chemokines were only measured in serum, not in lung fluid. 

• The authors conclude that MCP-1 may be an effective indicator in mild patients, which is wrong as MCP-1 levels are elevated in severe patients to the same extend. 

• The authors conclude that early use of interferon has a good antiviral therapeutic effect which they did not test. A downregulation of IFN-b in mild cases compared to healthy controls does not necessarily mean increasing IFN-b would be beneficial. The  difference of IFN-b in mild compared to severe cases was not investigated.