T-cell Responses in Long Covid Patients

June 28, 2023

In a research letter on long Covid and abnormal lung function and/or structure (pulmonary sequelae) following a COVID-19 infection, authors shared findings around the possibility of viral reservoirs causing a prolonged T-cell response in this patient population.

Researchers in Spain measured the subpopulations of CD8+ and CD4+ T lymphocytes in the blood of 40 patients who had been hospitalized with COVID-19 pneumonia, 6 and 12 months after hospital discharge. Eleven patients experienced long Covid, 17 had pulmonary sequelae, and 12 patients were fully recovered. Patients were followed after discharge if they presented with respiratory symptoms, fatigue, muscle pain, chest pain, joint pain, and headache, as well as neurocognitive or autonomic dysfunction. 

Researchers found that those with long Covid expressed less human leukocyte antigen-DR on their CD8+ T-cells, as well as a weaker Type 1 T-helper cell response than those who had fully recovered. These abnormalities indicate an exhaustion of the T-cells from prolonged infection. Researchers also tested patients’ immune responses to two different SARS-CoV-2 peptides. They found that 82% of patients with pulmonary sequelae and 72% of patients with long Covid conveyed an immune response, while only 50% of fully recovered patients did. Types of T-cell responses were also different between long Covid patients and those with pulmonary sequelae. 

Those with pulmonary sequelae also experienced decreased lung function between 6 and 12 months after hospital discharge; this correlated with SARS-CoV-2 specific T-cells. Researchers believe that this is likely an effect of a prolonged immune response to the SARS-CoV-2 virus leading to T-cell exhaustion and may be due to remaining viral reservoirs in these patients.