SARS-CoV-2 antigen levels correlate with patient outcomes

According to published in Annals of Internal Medicine . Following the ACTIV-3 trial of COVID-19 therapy in hospitalized patients with COVID-19, researchers at the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, and their collaborators analyzed levels of SARS-COV -2 antigen in blood samples taken from study participants and assess the association of these levels with disease progression. Higher levels of viral antigens in blood may indicate ongoing SARS-CoV-2 replication, associated with more severe disease. The authors believe that SARS-CoV-2 antigen levels hold promise as a biomarker or measurable substance to predict which COVID-19 hospitalized patients are at higher risk for poor prognosis.

ACTIV-3 trial enrolled people hospitalized with COVID-19 between August 2020 and November 2021 . Participants provided baseline blood samples and were then randomized to receive either an experimental COVID-19 treatment or a placebo. All participants received the antiviral drug remdesivir unless contraindicated. In this follow-up analysis, the researchers examined SARS-CoV-2 antigen levels in baseline blood samples from 2,540 participants.

The researchers assessed each participant’s SARS-CoV-2 blood antigen levels between their time to hospital discharge affiliated hospitals, and their pulmonary symptoms on day 5 of the trial—whether they had remained the same, worsened, or improved since enrollment. Armed with all this information, the researchers performed statistical analyses to determine whether plasma antigen levels correlated with lung function when participants provided blood samples, and whether they could predict how participants would perform over time. In addition, the researchers examined the relationship between some participants and viral signatures and antigen levels.

Analysis showed higher SARS-CoV-2 antigen levels at enrollment (≥1000 ng/L) There is a strong correlation with poorer lung function. Importantly, participants with higher blood levels of SARS-CoV-2 antigen at enrollment generally had decreased lung function by day 5, regardless of their disease severity at the start of the study, and took longer to be discharged from the hospital . High blood antigen levels are also associated with some known risk factors for disease progression, such as being male. Three additional participant characteristics were found to be associated with lower antigen levels: presence of SARS-CoV-2 antibodies, remdesivir exposure prior to enrollment, and longer hospitalization prior to enrollment. Finally, participants infected with the delta variant had higher levels of the antigen than those infected with previously circulating strains. The researchers concluded that antigen levels in the blood may be a marker of ongoing viral replication and can be used to predict disease progression and likely outcomes after admission in patients. The authors note that these results suggest that a precision medicine approach may aid future clinical trials of antiviral treatments. For example, antigen levels can help identify those patients most likely to benefit from therapy to fight the virus.