Comparing T-cell responses between different groups of COVID-19 patients, researchers from Duke-NUS found that people who had mild symptoms produced the strongest virus-specific T cells early on in their infections. The researchers, who published their findings in Cell Reports, also noted that the immune response in people who had more severe disease was dominated by a rapid appearance of large quantities of antibodies.
The secretion of interferon-gamma-secreting SARS-CoV-2-specific T cells, in particular, characterised the immune response in those with mild infections. Interferon gamma (IFN-γ) is the primary activator of macrophages, which play a key role in fighting foreign pathogens including viruses. It also recruits other immune cells, including a type of T cell, known as natural killer cells, and neutrophils.
“Our data supports the idea that SARS-CoV-2-specific T cells play an important role in the rapid control of viral infection and eventual clearance of the disease,” said Dr Martin Linster, a then-senior research fellow with Duke-NUS’ Emerging Infectious Diseases Programme and the co-author of this study in a media statement at the time.
The quantity of these IFN-γ-secreting T cells also increased progressively while the SARS-CoV-2 infection resolved. Their peak was detected within 15 days after onset of symptoms in eight of the twelve patients studied.
The most robust functional T-cell response, further, was detected in patients with mild symptoms who cleared the virus early.
When the study was published, Professor Antonio Bertoletti, the corresponding author of this study, called for more efforts to adopt a more holistic view of immune responses to SARS-CoV-2: “It is time that T-cell monitoring should be considered in providing a comprehensive understanding of the immune response against SARS-CoV-2. This would also mean that a vaccine will likely be more effective if a concurrent induction of both antibodies and T cells occurs.”