Long-COVID following mild SARS CoV-2 infection: characteristic T cell alterations and response to antihistamines
Abstract
Background
Long-COVID is characterised by the emergence of multiple debilitating symptoms following SARS CoV2 infection. Its aetiology is unclear, and it often follows a mild acute illness. Anecdotal reports of gradual clinical responses to histamine receptor antagonists (HRA) suggest a histamine-dependent mechanism distinct from anaphylaxis. Histamine is a paracrine regulator of T-cells: although T-cell perturbations are reported in acute COVID-19, the T-cell landscape in recovered patients and its relationship to long-COVID remains under-explored.
Objective
To survey T-cell populations in patients recovered from mild COVID-19, comparing those with long-COVID and asymptomatic individuals, and to analyse these data in light of symptoms and response to HRA.
Design
Prospective observational cohort study.
Setting
Single-site outpatient clinic
Participants
65 (87 to 408 days post mild COVID-19). None had sought treatment for acute COVID-19. 16 recovered uneventfully (asymptomatic group), 49 presented with long-COVID (symptomatic group), of whom 25 received HRA.
Measurements
Structured long-COVID symptom questionnaire; quantification of T-cell subsets using a standard diagnostic assay.
Results
HRA significantly reduced mean symptom burden. T-cell profiles distinguished asymptomatic and long-COVID groups, but did not predict response to HRA. Long-COVID patients had reduced CD4+ and CD8+ effector memory (EM) cells and increased PD-1 expression on central memory (CM) cells. Asymptomatic controls had reduced CD8+ EM cells and increased CD28 expression on CM cells.
Conclusion
HRA reduce long-COVID symptoms. T-cell perturbations persist for up to 400 days following mild acute COVID-19 irrespective of long-COVID symptoms.
Limitations
Preliminary, single health system study.
Primary Funding Source
Philanthropic donations from The Dominvs Group and Sir Peter Wood
Related articles
Related articles are currently not available for this article.