Sumary of Majority of population likely has pre-existing immunity to SARS-CoV-2, claim researchers:
- A team of researchers has conducted a study suggesting that the majority of the global population is likely to have pre-existing T-cell immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) – the agent responsible for the coronavirus disease 2019 (COVID-19) pandemic..
- The team – from the United States and India – says many people who have not yet been exposed to the virus probably already have SARS-CoV-2-reactive T cells as a result of previous exposure to viruses such as influenza and cytomegalovirus (CMV)..
- The researchers say the study demonstrates that strong immunity among unexposed individuals can arise through cross-reactive T cell receptors (TCRs) against common CMV and influenza antigens that mount an early CD8 T-cell response to clear SARS-CoV-2..
- “This finding is in contrast to multiple published studies in which pre-existing T-cell immunity is suggested to arise from shared epitopes between SARS-CoV-2 and other common cold-causing coronaviruses,”.
- SARS-CoV-2 disease phenotypes vary widely Since the first cases of COVID-19 were identified in Wuhan, China, late last year (2019), a range of disease phenotypes have been observed, ranging from asymptomatic or mild, to severe clinical outcomes and death..
- Delays in CD8 T-cell activation and the production of interferon-g (IFN-g) results in high viral loads that trigger overactivation of the innate and adaptive immune responses..
- “Therefore, an early wave of strong CD8 T-cell response may delay viral titer build-up, allowing rapid clearance of the virus by the immune system without perturbing immune homeostasis,”.
- Studies have shown that healthy individuals not yet exposed to SARS-CoV-2 exhibit pre-existing CD4 and CD8 T-cell immunity to the virus..
- Some studies have also suggested that a pool of SARS-CoV-2-reactive T-cells arises in unexposed individuals who have previously been infected with human coronaviruses that cause the common cold..
- However, whether this pre-existing immunity protects against SARS-CoV-2 infection or contributes to a faster recovery following infection, remains unclear..
- It also remains unclear whether such pre-existing immunity, involving either CD4 or CD8 T-cells, or both, is required for maximal protection, adds the team..
- T-cell reactivity to Spike-S1, S2 pools and 11-peptide-mix in asymptomatic, mild-moderate and severe disease after in vitro stimulation for 48 h..
- Related Stories Chaudhuri and colleagues developed a novel TCR-binding algorithm called OncoPeptVAC that predicts CD8 T-cell activating epitopes across the SARS-CoV-2 proteome..
- The algorithm identified many CD8 T-cell epitopes in a small pool of 11 peptides that are used in assays of T-cell activation..
- This 11-peptide pool was tested for T-cell activation in healthy individuals from the United States and India who had not been exposed to SARS-CoV-2…