Robust antibody and T cell responses tracked longitudinally in patients with long COVID

After severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, a minority of patients experience persistent or emerging symptoms, termed 'long coronavirus disease (COVID)' or post-acute sequelae of COVID-19. The molecular causes of long COVID remain unclear, but disrupted immune functions, such as inflammation and immune deficit, have been posited as factors. In this retrospective cohort study, we measured markers of immune function in a group of patients with long COVID up to 40 months post infection. As proxies for immune function, we measured serum antibody levels, antibody neutralizing capability and production of IFN gamma (IFN-γ) and IL-2 against SARS-CoV-2 and other viral peptides. As expected, serum antibody levels increased over time with vaccinations and reinfections with later variants of SARS-CoV-2. Patients also showed corresponding increasing SARS-CoV-2-specific IL-2 responses and stable IFN-γ responses. We observed no significant differences in immune responses among patients with ongoing long COVID, those who had recovered from it or individuals who recovered from acute COVID-19. Overall, we found no indication of a reduction in these aspects of immune function after SARS-CoV-2 infection. This study provides a valuable foundation for further research aimed at understanding the causes of long COVID.