The following article is a part of conference coverage from the American Academy of Allergy, Asthma & Immunology Annual Meeting, being held in Phoenix, Arizona, from February 25 to 28, 2022. The team at Pulmonology Advisor will be reporting on the latest news and research conducted by leading experts in the field. Check back for more from the AAAAI 2022 Virtual Annual Meeting.

Survivors of severe COVID-19 with long-haul respiratory symptoms display activated T-cell signatures and marked immune perturbations. A cohort study was conducted among a group of patients who had survived severe SARS-CoV-2 infection. Results of the study were presented at the American Academy of Allergy, Asthma & Immunology (AAAAI) 2022 Annual Meeting, held in Phoenix, Arizona, February 25 to 28.

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The investigators sought to explore the long-term evolution of T cells following COVID-19 infection among patients with long-haul symptoms. They tracked circulating T cells in a group of 88 individuals who had been hospitalized with COVID-19 and subsequently experienced persistent respiratory symptoms. The T cells were obtained during severe acute COVID-19, at 6 weeks after hospital discharge, and between 6 and 11 months following hospital discharge. High-dimensional immunophenotyping with spectral flow cytometry was used to analyze the participants’ T cells. The Tracking Responders Expanding (T-REX) algorithm was used to identify longitudinal changes in complex T-cell signatures. ImmunoCAP assay was utilized to evaluate patients for antibodies to SARS-CoV-2 proteins.

Participants with long-haul respiratory symptoms who were sampled at 6 weeks following hospital discharge had higher rates of activated and tissue-homing CD4+ and CD8+ T cells, compared with healthy individuals and patients who had experienced a mild acute COVID-19 infection. A higher number of terminally differentiated CD8+ T cells were also detected in these individuals.

The T-REX algorithm identified multiple CD4+ and CD8+ T-cell signatures that expanded or contracted by 95% or more up to 6 months following acute infection, including highly activated subtypes. Fluctuations in T-cell signatures were observed several months following acute infection, even in the presence of decreasing antibodies to SARS-CoV-2 proteins.

The researchers concluded that the activated T-cell signatures and marked immune perturbations detected following severe COVID-19 infection were consistent with trafficking of T cells with dysregulated homeostasis and pathogenic potential. They postulate that activated T cells may contribute to airway inflammation long after an acute illness has resolved.


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Canderan G, Muehling L, Kadl A, et al. Survivors of COVID-19 with long-haul respiratory symptoms display enhanced activation of circulating T cells. Presented at: American Academy of Allergy, Asthma & Immunology (AAAAI) 2022 Annual Meeting; February 25–28, 2022; Phoenix, AZ. Abstract 175.