Prolonged effects of adenoviral vector priming on T-cell cytokine production in heterologous adenoviral vector/mRNA COVID-19 vaccination regimens

Abstract

mRNA and adenoviral vector vaccine platforms were used for the primary series of COVID-19 vaccines in many countries. However, the distinct immunogenic properties on these platforms remain less understood. We traced neutralizing antibodies, memory B cells, and T cells longitudinally in cohorts that received either mRNA (BNT162b2 or mRNA-1273) or adenoviral vector (ChAdOx1) vaccines with homologous or heterologous regimens (total 9 groups, n = 26-28 for each group) at 4 weeks interval. The priming and boosting effects on various immune parameters were comparably assessed between mRNA and adenoviral vector platforms. We found that initial priming by adenoviral vector vaccine elicited robust T cell responses, but B cell responses, including antibody titers, were relatively lower than those elicited by mRNA priming. The dissociation between T cell and antibody responses were exaggerated at greater extents after the homologous booster with the adenoviral vector vaccine, resulting in 5-19-fold lower antibody titers despite comparable spike-specific T cell numbers at day 28 after the boost. Robust IFN-γ and few IL-2 and IL-5 production characterized T cell functionality primed by adenoviral vector. Boosting with mRNA vaccines restored their IL-2 and IL-5 production at some extents, but the IL-5 T cell responses elicited by adenoviral vector/mRNA heterologous regimen waned faster than those by mRNA homologous regimen. Thus, our data revealed that the cytokine production of helper T cells was skewed by adenoviral vector priming, leading to the attenuated IL-2 and IL-5 responses which were prolonged even after mRNA boosting, suggesting an imprinting of T-cell functionality depending on the vaccine platform used for initial priming. These results highlight the importance of selecting vaccine platforms based on the immunogenic properties.

Fig. 1

Study design.

Fig. 2

Robust T-cell responses but attenuated antibody and B-cell responses following adenoviral vector priming. Immune responses were analyzed at 28 days after primary vaccination with BNT162b2, mRNA-1273, and ChAdOx1. Subjects with ≥ 40 years of age were analyzed. (A) Serum anti-spike titers were measured with ECLIA. (B) Neutralization titers against authentic SARS-CoV-2 virus were measured. (C) Frequencies of CD19 + CD20 + IgG + B cells which bind SARS-CoV-2 spike RBD were measured with flow cytometry. (D) Frequencies of spike-specific CD4 and CD8 T cells were measured using AIM assay. (E) Indicated humoral immune parameters were normalized to spike⁺ CD4 T cell frequencies. (F) Indicated humoral immune parameters were normalized to spike⁺ CD8 T cell frequencies. Data were analyzed by Kruskal-Wallis test and subsequent Dunn’s multiple comparison test (*P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001).

Fig. 3

Immune responses induced by primary vaccination in young and aged subjects. Immune responses were analyzed at 28 days after primary vaccination with BNT162b2, mRNA-1273, and ChAdOx1. For mRNA vaccinees, subjects were classified into < 40 and ≥ 40 years of age were analyzed. (A) Serum anti-spike titers were measured with ECLIA. (B) Neutralization titers against authentic SARS-CoV-2 virus were measured. (C) Frequencies of CD19⁺CD20⁺IgG⁺ B cells which bind SARS-CoV-2 spike RBD were measured with flow cytometry. (D) Frequencies of spike-specific CD4 and CD8 T cells were measured using AIM assay. (E) Indicated humoral immune parameters were normalized to spike⁺ CD4 T cell frequencies. (F) Indicated humoral immune parameters were normalized to spike⁺ CD8 T cell frequencies. Data were analyzed by Kruskal-Wallis test and subsequent Dunn’s multiple comparison test (*P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001).

Fig. 4

Comparable T-cell responses but attenuated antibody responses following adenoviral vector priming and boosting. (A–D) Overall kinetics of spike-specific CD4 and CD8 T cells (A), RBD-reactive IgG B cells (B), serum anti-spike titers (C), and neutralization titers (D) were analyzed. Medians and IQRs were depicted. (E–H) Serum anti-spike titers (E, G) and neutralization titers (F, H) at 56 and 168 days after the primary vaccination (28 and 140 days after the booster vaccination, respectively) were analyzed. Data were analyzed by Mixed-effects analysis of time points (Time) and vaccine combination (Vac.) (A–D) and Kruskal-Wallis test followed by Dunn’s multiple comparison test (E–H) (*P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001). Differences in ages were included in as fixed effects the mixed-effects model.

Fig. 5

Cytokine profiling of T cells. (A and B) Frequencies of spike-specific cTfh cells at 28 days after the primary (A) and booster (B) vaccination were analyzed. (C and E) Cytokines secreted into supernatants of AIM culture at 28 days after the primary (C) and booster (E) vaccination were analyzed. (D) Ratio of indicated cytokines were calculated for data from 28 days after the primary vaccination. In (A, C, and D), subjects with ≥ 40 years of age were analyzed. Data were analyzed by Kruskal-Wallis test and subsequent Dunn’s multiple comparison test (*P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001). In (E), the analyses were performed between the homologous ChAdOx1 group and the others.

Fig. 6

Durability of the IL-5-producing T cells is imprinted by the primary vaccine. (A) Overall kinetics of IL-5 secreted into supernatants of AIM culture were analyzed. Medians and IQRs were depicted. (B) IL-5 secreted into supernatants of AIM culture at 168 days after the primary vaccination (140 days after the booster vaccination) were analyzed. (C and D) Overall kinetics of cTfh cell frequencies (C) and IL-2 secreted into supernatants of AIM culture (D) were analyzed. Medians and IQRs were depicted. Data were analyzed by Mixed-effects analysis of time points (Time) and vaccine combination (Vac.) (A, C, and D, *P < 0.05, **P < 0.01, ****P < 0.0001) and Kruskal-Wallis test followed by Dunn’s multiple comparison test (B, groups not sharing a common letter are significantly different (P < 0.05)). Differences in ages were included in as fixed effects the mixed-effects model.