While considerable research has focused on characterizing the acute phase of COVID-19 following SARS-CoV-2 infection, less is understood about the pathogenesis of long COVID or post-acute sequelae of COVID-19 (PASC). Disentangling the complex biology of PASC will rely on the identification of biomarkers that enable classification of patient phenotypes.
Using ultra-sensitive single molecule array (Simoa) assays, we measured SARS-CoV-2 antigens, including S1, spike, and nucleocapsid (N), in plasma samples collected from PASC and COVID-19 patients (n = 63) at multiple time points up to 12 months after initial SARS-CoV-2 infection.
In approximately 65% of the patients diagnosed with PASC, we were able to detect either S1, spike or N at any given time point several months after SARS-CoV-2 infection. Most interestingly, we detected spike most often in 60% of the PASC patients, whereas we did not detect spike at all in the COVID-19 patients.
The detection of spike in a majority of PASC patient samples analyzed provides strong support for the use of spike as a biomarker for PASC. Additionally, the presence of circulating spike up to 12 months post-diagnosis suggests that SARS-CoV-2 viral reservoirs persist in the body.