The quantity of SARS-CoV-2 antigen found in the blood of those hospitalised with COVID-19 is associated with the severity of the disease and other clinical outcomes, according to a recent study published in the Annals of Internal Medicine.
After the ACTIV-3 trial of COVID-19 therapeutics in patients hospitalised with COVID-19, researchers from the National Institute of Allergy and Infectious Diseases (NIAID), a division of the National Institutes of Health, and their collaborators assessed the levels of SARS-COV-2 antigen in blood samples taken from study participants and evaluated the association of those levels with disease progression. Higher viral antigen levels in the blood were associated with more severe illness, which may indicate continuous SARS-CoV-2 replication.
SARS-CoV-2 Antigenas a Biomarker
SARS-CoV-2 antigen levels appear to have potential as a biomarker, or quantifiable component, to identify COVID-19 hospital patients who are more likely to have unfavourable outcomes.
The ACTIV-3 study included patients who were hospitalised with COVID-19 between August 2020 and November 2021. Participants were randomly randomised to receive either a COVID-19 investigational treatment or a placebo after submitting a baseline blood sample. All participants got the antiviral remdesivir, barring medical necessity. In this follow-up investigation, the researchers assessed the SARS-CoV-2 antigen levels in baseline blood samples from 2540 individuals.
The pulmonary symptoms of each participant were assessed on Day 5 of the experiment to determine if they had persisted, grown worse, or improved since enrolment.
Additionally, they assessed the connection between each participant’s SARS-CoV-2 blood antigen levels and the date of their hospital release. With all of this information at hand, the researchers conducted statistical analyses to determine whether plasma antigen levels were associated with the participants’ pulmonary function at the time the blood sample was given, as well as to determine whether they could predict how the participants would fare over time. The relationship between the quantity of participants, virus, and antigen levels was also examined by the researchers.
Higher SARS-CoV-2 antigen levels and lower lung function at enrolment were significantly correlated, according to the analyses (1000 nanograms per litre). Importantly, individuals with greater SARS-CoV-2 antigen levels in the blood at enrollment frequently had lower pulmonary function on Day 5 and required longer to be released from the hospital, independent of the severity of their sickness at the time of study entrance. Furthermore, recognised risk factors for more severe disease were connected with both being a male and having high blood antigen levels.
Three other participant characteristics—the existence of SARS-CoV-2 antibodies, past remdesivir exposure, and greater length of hospital stay—were also found to be related with lower antigen levels.
Antigen levels were also greater in delta variant-infected participants than in those with earlier circulating strains. The authors of the study came to the conclusion that blood antigen levels are probably an indication of ongoing viral replication and may aid in predicting the course of a patient’s illness and expected consequences following hospitalisation. The authors conclude that the results suggest a possible advantage of a precision medicine approach in prospective antiviral treatment clinical trials. For example, antigen levels might be utilised to pinpoint the patients most likely to gain from virus-fighting therapies.