No indications for overt innate immune suppression in critically ill COVID-19 patients

At the end of March 2020, there were in excess of 800.000 confirmed cases of coronavirus disease 2019 (COVID-19) worldwide. Several reports suggest that, in severe cases, COVID-19 may cause a hyperinflammatory “cytokine storm”. However, unlike SARS-CoV infection, high levels of anti-inflammatory mediators have also been reported in COVID-19 patients. One study reported that 16% of COVID-19 patients who died developed secondary infection, which might indicate an immune-suppressed state. We explored kinetics of mHLA-DR expression, the most widely used marker of innate immune suppression in critically ill patients, in COVID-19 patients admitted to the ICU.

Twenty-four confirmed COVID-19 patients were included, of which 75% was male and 79% had comorbidities. All patients were mechanically ventilated and exhibited large high levels of inflammatory parameters such as CRP and PCT. mHLA-DR expression levels were mostly within the normal range of 15000-45000 mAb/cell and showed no change over time. COVID-19 patients displayed notably higher mHLA-DR expression levels compared with bacterial septic shock patients. None of the COVID-19 patients developed a secondary infection.

In conclusion, despite a pronounced inflammatory response, mHLA-DR expression kinetics indicate no overt innate immune suppression in COVID-19 patients. These data signify that innate immune suppression as a negative feedback mechanism following PAMP-induced inflammation appears not to be present in COVID-19.