Killer T cells against Covid: study points to more broadly protective vaccines
Patients with mild Covid-19 showed stronger CD8 T-cell responses to certain virus fragments. US researchers see a chance for vaccines that hold up better against new variants.
Graphic: TERRA WORLD NEWS (own graphic based on the sources listed)
Unvaccinated Covid-19 patients with mild illness mounted stronger CD8 killer T-cell responses to certain fragments of the coronavirus than those who became severely ill. That is the finding of a study published in the journal iScience by Kazuya Masuda of Columbia University and immunologist Moriya Tsuji of Texas A&M University, science portal scinexx reported. The authors stress that this is an association, not proof of protection.
The team analysed blood samples from 42 unvaccinated patients from 2020, all carrying the immune marker HLA-A2 – 26 with mild, 8 with moderate and 8 with severe disease. Their immune cells were exposed to 11 segments of viral proteins (epitopes). In 20 of the 26 mild cases a response to at least one epitope was measurable, while severe cases mostly responded weakly. A detailed profile of 8,402 virus-reactive T cells from 11 patients found more cells with immediate antiviral features and long-lived memory cells in mild cases. Responses remained detectable up to about four months after diagnosis.
Many of the epitopes come from internal viral proteins that change relatively little between variants. The authors suggest they could complement the changeable spike protein in future vaccines, offering broader and possibly more durable T-cell protection. "Showing that these T-cell responses directly contribute to protection will be crucial," Tsuji said. Limitations include the small sample, samples from early in the pandemic and open questions over whether the results apply to vaccinated people, current variants and other HLA types.