ABSTRACT
Background: A significant portion of individuals experience persistent symptoms months after SARS-CoV-2 infection, broadly referred to as Long COVID (LC). Although the frequencies of subsets of SARS-CoV-2-specific T cells have been shown to differ in individuals with LC relative to those with complete recovery, a deep dive into phenotypic and functional features of total and SARSCoV- 2-specific T cells from individuals with LC has yet to be performed. Method(s): Here, we used CyTOF to characterize the phenotypes and effector functions of T cells from LIINC cohort. The median age was 46, the cohort was 55.8% female, and 9/43 had been hospitalized. Participants were reported a median of 7 LC symptoms at 8 months. SARS-CoV-2-specific total antibody levels were also measured in concurrent sera. Manual gating was used to define T cell subsets, SPICE analyses for polyfunctionality, T cell clustering for phenotypic features, and linear regression for correlation. Permutation tests, Student's t tests, and Welch's t test were used for statistical analysis. Result(s): SARS-CoV-2 total antibody responses were elevated in the LC group (p=0.043), and correlated with frequencies of SARS-CoV-2-specific T cells in those without LC (r=0.776, p< 0.001) but not those with LC. While the frequencies of total SARS-CoV-2-specific CD4+ and CD8+ T cells were similar between individuals with and without LC, those from individuals without LC tended to be more polyfunctional (co-expressing IFNgamma, TNFalpha, IL2, and/or MIP1beta). CD4+ T cells from individuals with LC harbored higher frequencies of Tcm (p=0.003), Tfh (p=0.037), and Treg subsets (p=0.0412), and preferentially expressed a variety of tissue homing receptors including CXCR4 and CXCR5 (p=0.037). SARS-CoV-2-specific CD4+ T cells producing IL6, albeit rare, were observed exclusively among those with LC (p=0.016). In addition, participants with LC harbored significantly higher frequencies of SARS-CoV-2-specific CD8+ T cells co-expressing exhaustion markers PD1 and CTLA4 (p=0.018). Conclusion(s): Long COVID is characterized by global phenotypic differences in the CD4+ T cell compartment in ways suggesting preferential migration of these cells to inflamed mucosal tissues. Individuals with LC also harbor higher numbers of exhausted SARS-CoV-2-specific CD8+ T cells, potentially implicating viral persistence. Finally, our data additionally suggest that individuals with LC may uniquely exhibit an uncoordinated T cell and antibody response during COVID-19 convalescence.
ABSTRACT
Background: There is mounting evidence regarding the frequency and spectrum of post-acute sequelae of SARS-CoV-2 infection (PASC), but a search for causes has been elusive. Recently, a plasma-based assay for SARS-CoV-2 antigen has been developed, which in initial use revealed that a high fraction of severely affected patients with PASC had circulating antigen. It is unknown whether detectable SARS-CoV-2 antigen is specific for PASC or how the assay performs in a broader clinical spectrum of patients with PASC. Method(s): We evaluated a cohort of patients with RNA-confirmed SARS-CoV-2 infection enrolled >=3 weeks following initial symptoms. Participants, both with and without PASC at enrollment, were identified via facility- and communitybased advertising and examined every 4 months. An interviewer-administered questionnaire ascertained presence of 30 different symptoms (new or worse compared to pre-COVID) in the prior 2 days at each exam. Using the single molecule array (Simoa) assay, we measured spike, S1, and nucleocapsid SARSCoV- 2 antigens in plasma collected at time of symptom assessment. Result(s): We examined 172 participants (50% men, 46% non-white, median age 46 years) who contributed 667 timepoints from 0.7 to 15.4 months following infection, at which 66% featured report of >=1 symptom. Sixty-one of 667 timepoints (9.1%) representing 24% of persons had >=1 detectable SARSCoV- 2 antigen. Among the 437 timepoints at which >=1 symptom was present, 9.8% had >=1 detectable antigen;this compares to 7.8% of timepoints at which symptoms were absent. In comparison to those without symptoms, individuals with several specific symptom complexes (gastrointestinal, musculoskeletal, and central neurologic) more commonly had detectable antigen (Figure). Hospitalization during acute COVID-19 was strongly related to antigen detection. Conclusion(s): Among a diverse group of SARS-CoV-2-infected persons in the post-acute phase of infection, SARS-CoV-2 antigen is detectable in plasma in both those with and without symptoms but more commonly in those with gastrointestinal, musculoskeletal, and central neurologic complaints. The findings indicate that antigen persists in at least some persons and suggest (but do not prove) that antigen is causally related to symptoms. That antigen is found in only a fraction of those with PASC indicates either that not all symptoms are driven by antigen, current plasma antigen detection is insensitive relative to tissue, or nominal PASC symptoms are sometimes unrelated to SARS-CoV-2. (Figure Presented).
ABSTRACT
Background. The biological determinants of post-acute sequelae of SARS-CoV-2 infection (PASC), defined as the persistence or recurrence of symptoms not explained by an alternative medical diagnosis, are poorly understood. We assessed viral and immunological determinants during acute SARS-CoV-2 infection for an association with PASC at 4 to 8 months. Methods. From September 2020 to February 2022, symptomatic nonhospitalized individuals with laboratory-confirmed SARS-CoV-2 infection were identified within 5 days of symptom onset. We used anterior nasal biospecimens to measure the magnitude and duration of RNA and infectious viral shedding as well as blood samples to measure soluble markers of inflammation during the acute phase (first 28 days post-enrollment). PASC was defined as self-report of 1 or more COVID-19 attributed symptoms between 4 and 8 months after initial illness. We compared virologic and inflammatory markers, GFAP (a marker of neuronal damage) and neutralizing antibody levels from the acute phase between those with and without PASC using Mann-Whitney U tests or repeated measures mixed effects linear models. Results. Among 71 SARS-CoV-2-positive participants with a completed follow-up visit between 4 to 8 months, we included 69 with virologic data and 61 with inflammatory marker data. Median age was 37 (IQR: 29 to 48) Overall, 16/72 (23%) reported at least one qualifying PASC symptom. Report of PASC was associated with >9 days of RNA shedding (p=0.04);all participants stopped RNA shedding by day 20. During acute illness, those with subsequent PASC had increased levels of INF-alpha, INF-gamma, IP-10, IL-10, and MCP-1;these differences were greatest in the early period and normalized over 2 to 3 weeks post-illness onset. Compared to those without PASC, during the acute illness those with PASC had increased levels of GFAP and decreased levels of neutralizing antibodies but these differences were not statistically significant. Conclusion. We found indications that viral and immunological factors during acute illness may be associated with PASC, suggesting acute immunologic response to SARS-CoV-2 may have longer term effects and play a role in PASC. Further understanding of the clinically significance of these observations is needed.