In a recent study posted to the medRxiv* preprint server, researchers investigated the levels of circulating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) protein and viral ribonucleic acid (RNA) among patients hospitalized with acute coronavirus disease 2019 (COVID-19) and in patients with and without post-acute sequelae of COVID-19 (PASC).
Background
Considerable research progress pertaining to acute COVID-19 manifestations has occurred; however, PASC data are lacking. It is essential to elucidate the underlying mechanisms of PASC pathophysiology for identifying individuals most prone to develop PASC and for investigating targets for the development of potential anti-SARS-CoV-2 drugs.
About the study
In the present study, researchers investigated if the circulation of SARS-CoV-2 S or RNA was associated with the severity of acute COVID-19 and if the persistence of the viral components correlated with PASC manifestations.
The levels of SARS-CoV-2 S and RNA in plasma obtained from 151 acute COVID-19 (n=116, symptomatic and hospitalized) or PASC patients were analyzed, and their COVID-19 diagnosis was confirmed by polymerase chain reaction (PCR) tests. The acute COVID-19 patients were categorized on the basis of their World Health Organization (WHO) disease severity/clinical progression scores as (i) moderate COVID-19 without oxygen (O2) requirements (n=39), (ii) moderate COVID-19 requiring oxygen supplementation (n=40), and (iii) severe COVID-19 (n=37).
Individuals were considered to be PASC patients if they experienced ≥1 COVID-19 symptom for >8 weeks post-COVID-19 diagnosis. In addition, 12 patients of the acute COVID biorepository were included in the analysis. Samples from the acute COVID-19 group were obtained on the initial day of enrollment and every three days until hospital discharge or death.
PASC group samples were obtained on the day of recruitment ≥18 weeks post-acute COVID-19 period. SARS-CoV-2 RNA extracted from the samples was evaluated by reverse-transcription-droplet digital PCR (RT-ddPCR) tests. Plasma-derived small extracellular vesicles (SEVs) were isolated and analyzed, and SARS-CoV-2 S and SEV levels were measured by enzyme-linked immunosorbent assays (ELISA).
Data on demographics, comorbidities, body mass index (BMI), COVID-19 symptoms, and the duration between the most recent SARS-CoV-2-positive report and study recruitment were obtained from REDCap surveys and/or electronic medical records. The surveys were conducted at recruitment and three-monthly using WHO’s post-COVID conditions case report form (post-COVID-19 CRF).
Results
Among hospitalized patients with acute SARS-CoV-2 infections, positive correlations were observed for SARS-CoV-2 S and D-dimer, hospitalization duration, and WHO peak scores and between SARS-CoV-2 RNA levels and LDH (lactate dehydrogenase, tissue damage biomarker) levels. The comparison of 33 PASC patients with post-COVID-19 symptoms (PASC-positive) and 14 PASC-negative patients showed a greater likelihood of SARS-CoV-2 and viral RNA presence among PASC patients (with considerably higher levels in a few cases) in comparison to patients with acute SARS-COV-2 infections.
SARS-CoV-2 RNA positivity was higher among PASC patients with acute SARS-CoV-2 infections, whereas SARS-CoV-2 S was similar between the two groups. In addition, some SARS-CoV-2 S proteins were linked to EVs without SARS-CoV-2 RNA in vesicles. SARS-CoV-2 RNA was found in 33%, 35%, and 37% of patients with moderate COVID-19 without O2 needs, moderate COVID-19 with O2 need, and severe COVID-19, respectively, without significantly different levels among the groups.
The corresponding percentages for the three groups for SARS-CoV-2 S presence were 51%, 68%, and 68%, respectively. About 45%, 37%, and 50% of SARS-CoV-2 S-positive samples of the corresponding groups showed SARS-CoV-2 S in EVs. SARS-CoV-2 RNA levels correlated significantly with BMI values among patients with severe COVID-19.
The overall positivity for SARS-CoV-2 RNA and S protein were 35% and 62%, respectively, among symptomatic acute COVID-19 patients. About 34% and 6% of the acute COVID-19 group patients were positive for only SARS-CoV-2 S and only SARS-CoV-2 RNA only. PASC symptoms were more likely to develop among women with respiratory comorbidities such as obstructive sleep apnea or asthma.
PASC-negative patients were more likely to suffer from diabetes, renal diseases, and coronary artery diseases and had higher odds of being hospitalized due to acute COVID-19. SARS-CoV-2 RNA was present in 28% of PASC-negative patients (copy numbers between 0.1 to 2.1 copies/ul) and among 59% of PASC-positive patients (copy numbers between 0.1 and 12.7 copies/ul).
SARS-CoV-2 S was present in 14 and 21 PASC-negative and PASC-positive patients, respectively. Among PASC-positive patients, 33% (n=11) samples were SARS-CoV-2 S- and viral RNA-positive, 30% (n=10) were positive for SARS-CoV-2 S only and 18% (n=6) for SARS-CoV-2 RNA only. However, none of the PASC-negative patients were positive for both the viral components. Further, 53% (n=8) of PASC-positive patients showed positivity for EV-linked S, and the levels were similar to those found in acute COVID-19 patients, whereas EVs among PASC-negative patients were SARS-CoV-2 S-negative.
Conclusion
Overall, the study findings demonstrated the persistence of circulating SARS-CoV-2 S and RNA fragments among PASC patients (>1 year of COVID-19 diagnosis in a few cases), irrespective of their absence or presence in the acute phase of COVID-19. The findings also showed that SARS-CoV-2 S but not RNA was present in SEVs of plasma obtained from acute COVID-19 or long COVID patients.
*Important notice
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.
