Blood Tests May Help Monitor SARS-CoV-2 Infection

Truncated ACE2 levels served to discriminate patients infected with SARS-CoV-2 and influenza A.

A recent study conducted by investigators from the Spanish National Research Council (CSIC) has discovered that a blood test that quantifies the ACE2 protein could be a simple and effective way to monitor a SARS-CoV-2 infection.

Results from the study were published in The FASEB Journal.

“Our approach to this research line was the possibility that soluble ACE2 protein can serve as a read-out during infection with COVID-19,” Javier Sáez-Valero, lead investigator on the study said. “This hypothesis originates from our expertise in Alzheimer's disease.”

For the study, the team of investigators analyzed data from 49 patients with a positive reverse transcription polymerase chain reaction (RT-PCR) test for SARS-CoV-2 in nasopharyngeal swabs. Two other groups were also included in the study. The first included 17 participants with influenza A virus pneumonia and the second included 26 disease free controls.

The investigators then used immunoprecipitation and western blotting to identify ACE2 species in the participants plasma.

Findings showed that patients in the acute phase of a COVID-19 infection had significantly reduced plasma levels of the full-length ACE2 protein when compared to the controls. They also found that the plasma levels of a lower molecular mass (70 kDa) ACE2 fragment were increased.

When patients recovered, the levels of ACE2 and truncated ACE2 in their plasma returned to normal. These findings suggest that both forms of ACE2 present in plasma could be used as a good biomarker of the evolution of coronavirus infection.

"In this work we have studied the plasma levels of the coronavirus receptor, the ACE2 protein, and we have been able to determine that there are different forms of the protein in plasma, and that part of the soluble ACE2 are proteolytic fragments of the ACE2 receptor, generated subsequently to interaction with the virus,” Sáez-Valero said. “The full-length protein is also found in plasma, which provides information about tissue affection during infection.”