Possible long COVID biomarker: identification of SARC-CoV-2 related protein(s) in Serum Extracellular Vesicles, 2025, Abbasi et al

[forestglip]

Possible long COVID biomarker: identification of SARC-CoV-2 related protein(s) in Serum Extracellular Vesicles

Asghar Abbasi, Ritin Sharma, Nathaniel Hansen, Patrick Pirrotte & William W. Stringer

[Snippets from correspondence with no abstract, bolding added]

Blood samples were collected from 14 adults (aged ≥ 18 years) with a documented history of SARS-CoV-2 infection (confirmed via PCR or patient report) and persistent long COVID symptoms proposed by CDC and WHO (> 12 weeks since initial SARS-CoV-2 infection) including fatigue, dyspnea, exercise intolerance, or post-exertional malaise (PEM). The cohort was demographically and clinically diverse, including 43% women and 43% Hispanic/Latino participants. The majority (79%) were not hospitalized during their initial infection, and only one participant was unvaccinated at the time of study entry. Obesity was common (mean BMI 32.5 ± 8.4), and baseline physical activity levels were predominantly sedentary or limited to walking. The mean duration between initial SARS-CoV-2 infection and study enrollment was 17 ± 10 months. For further details about methods, see our previous publication [7].

Blood samples were collected from individuals with long COVID in response to an acute exercise test (both at rest and peak exercise), before (visit 2) and after (visit 24) completing an exercise training program.

Sequence analysis (pBLAST) confirmed that these peptides were specific to SARS-CoV-2 and did not overlap with human proteins. Importantly, each subject exhibited one or more SARS-CoV-2 peptides in their EV cargo, suggesting the persistence of viral components over time (Fig. 1B). Pp1ab is encoded by the ORF1ab gene and plays a crucial role in viral RNA transcription and replication.

To assess whether the peptides identified in long COVID EVs were also present in individuals without COVID-19 exposure (control group), we analyzed 20 serum EV samples collected prior to the COVID-19 pandemic (before 2019). These EV samples, obtained at rest and at peak incremental exercise from ex-smokers, showed no detectable viral peptide in any of the pre-pandemic specimens.

Overall, our targeted analysis confirmed the presence of the Pp1ab peptide in at least one sample in all long COVID subjects, while absent in controls.

Web | PDF | Infection | Open Access

 

[forestglip]

Why use control samples from before COVID? Of course they won't have SARS-CoV-2 proteins. We're interested in whether people who have had COVID but didn't get long COVID have those proteins.

 

[Jonathan Edwards]

Why use control samples from before COVID? Of course they won't have SARS-CoV-2 proteins.

But they might contain the same peptides, since any one peptide can originate from various proteins

 

[forestglip]

But they might contain the same peptides, since any one peptide can originate from various proteins

True, good as a control to be sure they're testing what they want to be testing. But would it have been so hard/expensive to find 20 more samples from the 5 years since?

 

[forestglip]

I was probably being too hard on them. It is definitely necessary to verify these are SARS-CoV-2 peptides. And maybe they do plan on comparing to recovered controls. This is only a correspondence, not a full paper, so maybe they just wanted to get their initial results out quickly in case others want to look at EVs themselves.