Long COVID Immune Profiling

COVID-19 infections can cause a disabling syndrome that persists beyond the 3-month convalescence period. The term post-acute COVID-19 syndrome or Long COVID is coined to describe a cluster of symptoms consisting of fatigue, chest pain, reduced exercise tolerance, tachycardia, and cognitive impairment.

Persistent tachycardia remains one of the most common complaints, reported in 9% of patients at 6 months post-infection. These symptoms overlap with those present in patients with Postural orthostatic tachycardia syndrome (POTS). It is noteworthy that about half of POTS patients also report a history of viral infection prior to the development of these symptoms.

Post-COVID-19 tachycardia syndrome, POTS variant: It present with chronic tachycardia with symptoms of orthostatic intolerance (OI) without any other identifiable cause. In addition, non-specific symptoms such as fatigue, headache, and "brain fog", commonly described in POTS patients are also present in this novel condition.

Elevated levels of inflammatory markers CRP,D-dimer and IL-6 are found in Long COVID patients. Data in POTS, which resembles post-COVID tachycardia syndrome, shows increased cytokines including IL-6, IL-1b, and TNF-a.

Notably, stimulation of the efferent vagus nerve (PNS), has been shown to reduce proinflammatory markers production and systemic inflammation. Hence, decreased PNS function, as reported with acute SARS-CoV-2 infection and in post-COVID-19 POTS patients, may render these patients prone to persistent inflammation. To determine the link between PNS activity and immune activation in post-COVID-19 POTS, the study aims to evaluate immune cell activation in post-COVID-19 POTS and patients with history of COVID-19 infection without sequelae and correlate this with the degree of decreased PNS activity.

Rationale and Specific Aims:

Preliminary data shows that post-COVID-19 POTS patients have reduced parasympathetic (PNS) function. Given that the PNS protects against inflammation, we hypothesize that post-COVID-19 POTS is caused by reduced PNS activity, which in turn, contributes to persistent inflammation, orthostatic intolerance, and OI symptoms.

Primary Aim: Test the hypothesis that reduced PNS activity is associated with persistent inflammation in patients with post-COVID-19 POTS.

Study Participants:

This is a cross-sectional study conducted, up to 150 patients will be enrolled, 50 POTS without Long-COVID, 50 POTS with Long-COVID and 50 controls with history of COVID-19 infection without sequelae.

Study Procedures

Recruitment: Subjects will be recruited from referrals to the Vanderbilt Autonomic Dysfunction Center (ADC)

Study visit:

Assessments:

• Autonomic symptoms assessment questionnaire (COMPASS-31)
• Quality of life EQ-5D
• PROMIS scale (Functional Activities Questionnaire in Older Adults with Dementia),
• OHQ (Orthostatic Hypotension Questionnaire)
• CBS (Cambridge Brain sciences: Web based cognitive assessment platform, Optional), and neuropsychological tests Blood sample collection: CBC, CMP, C-reactive protein (CRP), D-dimer, Flow cytometry study, PBMC isolation Autonomic function tests: Testing performed at Vanderbilt ADC within 10 years of the study visit will be utilized. Testing will not be repeated solely for the purposes of this study.

Statistical Considerations

Biostatistical Section The primary endpoint serum IL-6. The proposed sample size of 150 (50 POTD, 50 Long COVID POTS patients and 50 controls) provides more than 90% power to detect an effect size of 0.62 for the mean difference in IL-6 between post-COVID-19 POTS (cases) and controls (COVID-19 infected w/o sequelae), with the two-sided type I error = 5%. This calculation is based on the preliminary data of mean difference of IL-6 ≈ 1.82 and the SD ≈ 2.94 in POTS.16 The effect size is defined as the ratio of mean IL-6 difference between cases and controls to standard deviation.

Data analysis plan: Demographic information will be tabulated. Descriptive statistics, including means, standard deviations, and ranges for continuous parameters, as well as percent and frequencies for categorical parameters, will be presented. T-test or Mann-Whitney (as appropriate) will be applied to examine the mean differences between cases and control with respect to the outcomes. The conditional logistic regression model will be applied for the multivariable data analysis. The adjusted p-values and the adjusted 95% confidence intervals (CIs) will be reported.