Blood tests can track the course of coronavirus infection

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Recreation of the SARS-CoV-2 virus. Credit: Pixabay

A blood test that quantifies ACE2 protein, the cellular protein that allows coronavirus to enter cells, as well as ACE2 fragments produced as a result of interaction with the virus, could be a simple and effective method. to control the SARS-CoV-2 infection, according to a study led by Javier Sáez-Valero, of the Institute of Neurosciences UMH-CSIC of Alicante, published in FASEB Magazine.

This study, conducted during the first wave of the pandemic, found that patients with COVID-19, in the acute phase of infection, have significantly reduced full-length ACE2 protein levels, which SARS-CoV-2 binds to cells, compared to uninfected controls. In addition, plasma levels of an ACE2 fragment of lower molecular mass (70 kDa), generated as a result of interaction with the virus, increase.

These abnormal truncated ACE2 and ACE2 levels (70 kDa fragment) return to normal after recovery from patients. This suggests that both forms of ACE2 present in plasma could be used as a good biomarker of the evolution of coronavirus infection. In addition, truncated ACE2 levels served to discriminate between patients infected with SARS-CoV-2 and those infected with influenza A virus.

“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 protein in plasma and that part of the soluble ACE2 are proteolytic fragments of the ACE2 receptor, generated after the interaction with the virus. The complete protein is also found in plasma, which provides information about tissue involvement during infection, “explains Javier Sáez-Valero, who led the study.

Although the main line of research of the Sáez-Valero group is Alzheimer’s disease, the “similarities” of ACE2 with basic proteins of Alzheimer’s disease pathology, such as the beta-amyloid precursor protein (APP), too resident proteins, made the expert think that perhaps ACE2 might be present in plasma, providing information about its interaction with the coronavirus.

“Our focus in this line of research was the possibility that soluble ACE2 protein could serve as a reading during COVID-19 infection. This hypothesis stems from our experience in Alzheimer’s disease. In this neurodegenerative disease we investigate proteins. , such as APP, APP is also a membrane protein that is processed by the same molecular tools as ACE2, enzymes called secretases, which process several membrane proteins into different fragments.This phenomenon was the clue that led us to to think that ACE2 fragments of proteins, but also of complete protein, are present in the plasma. Therefore, we have the possibility to investigate this protein as a possible biomarker “, explains Sáez-Valero.

Test participants

The samples and patient data included in this study were provided by the ISABIAL Biobank, integrated into the National Biobank Network and the Valencian Biobank Network. Fifty-nine patients with a SARS-CoV-2 positive reverse transcription polymerase (RT-PCR) chain reaction test were included in nasopharyngeal swabs, of which 24 were women and 35 men, with a mean age of 64 years. All were hospitalized 7 to 9 days after the onset of symptoms. Of these, 48 patients infected with SARS-CoV-2 suffered a moderate presentation of COVID-19 and 11 were considered severe as they suffered from respiratory failure requiring invasive mechanical ventilation and / or treatment of the unit. intensive care.

Two additional groups were also analyzed, one of the 17 participants (9 women and 8 men), which included people aged 34 to 85 years with influenza A pneumonia. The other group consisted of 26 disease-free controls ( 14 women and 12 men) aged 34-85 years. For the “influenza A” group, samples were also taken in the acute phase, prior to specific hospital treatment.

ACE2 species in human plasma were identified by immunoprecipitation and western blot, a technique that detects a specific protein in a blood or tissue sample, where there is a complex mixture of protein forms. Until now, plasma tests performed for coronavirus had mostly used another technique called ELISA, which does not allow to determine the different forms of proteins.

Changes in truncated and full-length ACE2 species in serum samples from humanized K18-hACE2 mice inoculated with a lethal dose of SARS-CoV-2 were also examined. These humanized mice carry the human gene that produces ACE2 , allowing SARS-CoV-2 infection, which does not occur naturally due to the lack of recognition of murine ACE2 by the virus.

Alterations in the forms of ACE2 present in plasma after SARS-CoV-2 infection observed in this study justify, according to the researchers, a further investigation of their potential as biomarkers of the disease process and also to evaluate the effectiveness of vaccination. The next step will be to investigate what happens to these proteins in asymptomatic individuals with positive or vaccinated PCR.


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More information:
Maria-Salut García-Ayllón et al, Plasma ACE2 species are differentially Altered in COVID-19 patients, The newspaper FASEB (2021). DOI: 10.1096 / fj.202100051R

Provided by the National Research Council

Citation: Blood test can track the evolution of coronavirus infection (2021, July 13) recovered on July 13, 2021 at https://medicalxpress.com/news/2021-07-blood- track-evolution-coronavirus-infection.html

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