Figure 5. Skin vaccination seeds tissue-resident memory CD8⁺ T cells in multiple distant tissues to confer host protection.

(A-B) Relative viral DNA amount measured by qPCR in the brain (day 2 post-WR; A) and weight measurements (B) of wild-type (WT) and T-cell deficient (Tcra^−/−) mice immunized subcutaneously with MVA three weeks prior to intranasal WR challenge. Arbitrary units, a.u. (WT values set to 1) (A). Error bars, SD (n = 5) in A, and SEM (n = 7) in B. *; Student’s t-test p-value < 0.05.

(C-E) Flow cytometry analysis of Vaccinia virus peptide B8R-specific (H2-K^b B8R_20–27) memory CD8α⁺ T cells (gated on live CD3ε⁺CD44⁺CD62L⁻ cells) from indicated tissues from mice vaccinated at skin with MVA 3 weeks (C), 3 months (E, left) or 15 months (E, right) earlier, and quantifications in percentage of parent gate (%) and absolute count per 10⁵ live cells (cells) (D). Error bars, SD (n = 5).

(F) Flow cytometry analysis of vascular and parenchymal B8R-specific memory CD8α⁺ T cells (gated on live CD3ε⁺CD44⁺CD62L⁻ cells) by intravascular staining with CD45 (CD45 i.v.). Bar graphs show quantifications in percentage of parent gate (%) and absolute count per 10⁵ live cells (cells). Error bars, SD (n = 3). *; Student’s t-test p-value < 0.05.

(G-H) Timed parabiosis experiments show the role of tissue-resident cells in host protection. One parabiont (CD45.2) was immunized at skin with MVA at indicated days before (−28, −14, −1) or after (+14) joining with the other parabiont (CD45.1) (G). For groups −28, −14 and −1, mice were joined for 2 weeks before splitting, whereas for group +14, mice were joined for 2 weeks before immunization of one parabiont and split after another 2 weeks. Weight measurements of immunized (dark grey) and naïve (light grey) parabionts after WR challenge are shown in panel H. Data are representative of two to three independent experiments. Error bars, SEM (n = 5). *; Student’s t-test p-value < 0.05.

See also Figure S5.