Oxford-AstraZeneca COVID-19 Vaccine Induces Robust T Cell-ba
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A study has revealed that the Oxford-AstraZeneca COVID-19 vaccine, AZD1222, is capable of inducing strong spike-specific CD4+ T cell helper type 1 (Th1) and CD8+ T-cell responses in vaccinated individuals. The scientists have characterized functional CD4+ and CD8+ T-cell responses in healthy adults after administering 1st and 2nd doses of the AZD1222 vaccine.

A total of 280 participants who received two doses of AZD1222 vaccine were analyzed for spike-specific cytokine secretion and T cell receptor sequencing. To determine spike-specific T cell response in vaccinated individuals, the scientists experimentally stimulated cytokine production in participant-derived peripheral blood mononuclear cells with peptide pools that cover the entire spike sequence of SARS-CoV-2.

The findings revealed that compared to the baseline (day 0), the total spike-specific CD4+ T cell helper type 1 (Th1) response increased significantly at days 28 and 56 post-vaccination. The cytokines produced by Th1 cells primarily included TNF, followed by Interleukin-2 (IL-2), and Interferon-gamma (IFN). However, no Th2 response was observed in AZD1222-vaccinated individuals.

In contrast to CD4+ Th1 responses, a significantly lower frequency of spike-specific CD8+ T cells was detected in vaccinated individuals at days 28 and 56 post-vaccination. A significant difference in cytokine production pattern was also observed between CD4+ and CD8+ T cells, with CD8+ T cells primarily producing IFN, followed by TNF and IL-2. Together, these observations suggest that AZD1222 induces robust Th1 responses and significant expansion of CD8+ T cell responses.

To determine the diversity and specificity of spike-specific T cell responses, the scientists performed sequencing of T cell receptor beta chain on peripheral blood mononuclear cells derived from AZD1222-vaccinated individuals at day 0 and day 28 post second dose. The findings revealed that after receiving the 2nd vaccine dose at 4 weeks or 12 weeks interval, the participants had significantly increased fractions of spike-specific total T cell receptors and unique T cell receptors.

The study reveals that the AZD1222 vaccine could provide long-lasting protection against COVID-19 by significantly inducing polyfunctional Th1-dominated T cell responses to SARS-CoV-2 spike protein. Moreover, the vaccine causes a significant expansion of spike-specific CD4+ and CD8+ T cells with unique T cell receptor sequences that map to multiple spike epitopes.

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