Predicting SARS-CoV-2-specific CD4⁺ and CD8⁺ T-cell responses elicited by inactivated vaccines in healthy adults...

The ongoing evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants highlights the importance of monitoring immune responses to guide vaccination strategies. Although neutralizing antibodies (NAbs) have garnered increasing attention, T-cells are crucial for conferring long-lasting immunity, especially their resilience against viral mutations. However, assessing T-cell responses clinically has been hindered by cost and complexity. In this study, we recruited a cohort of 134 healthy adults, who had been immunized with three doses of the SARS-CoV-2 inactivated vaccine. Cellular immunity elicited by a comprehensive array of overlapping peptides covering the entire sequence of the virus's structural proteins was assessed by intracellular cytokine staining (ICS). Additionally, a dataset including demographic information, routine blood indices, and immune cell indicators comprising 32 variables was collected. Multivariate analysis revealed age and days post-vaccination as key factors influencing the strength of the T-cell response. Importantly, random forest (RF) and classification and regression tree (CART) algorithms were employed, along with 8 easily accessible indicators to formulate predictive models for the SARS-CoV-2-specific CD4⁺ and CD8⁺ T-cell responses. Besides, these models demonstrated substantial accuracy (r > 0.9) in both the training and testing sets. Our findings offer an efficient and economical methodology for evaluating the T-cell reactions in healthy adults following inactivated SARS-CoV-2 vaccination, which is visualizable and easy to use, providing a novel strategy for assessing cellular immunity after vaccination.