Extended Data Figure 3: Systemic TLR7- and IFNAR-dependent activation of APCs and effector cells, IFNα production and strong expansion of fully functional antigen-specific T cells induced by RNA-LPX vaccines.

a, Localization of splenic CD11c^hi cells at baseline (top) and 6 h after i.v. injection of 40 μg HA-LPX (bottom) into BALB/c mice (n = 2). Nuclear staining in blue. Scale bar, 100 μm. RP, red pulp; WP, white pulp. b–e, Activation marker expression in splenic cell subsets and kinetics of IFNα serum levels after i.v. injection of mice (n = 3 per time point) with HA-LPX in Tlr3^−/−, Tlr4^−/− and Tlr9^−/− mice (b), in Ifnar1^−/− mice (c, d), or in BALB/c mice treated with 100 μg anti-IFNAR1 antibody or isotype i.p. 1 h before i.v. injection of HA-LPX (e). Ab, antibody. f, mRNA levels of IFNα isoforms in sorted splenic APC subsets of C57BL/6 mice (n = 3) 1 h after i.v. injection of HA-LPX determined by qRT–PCR. Data expressed as log₂-fold change, as compared to control animals. g, IFNα serum levels after i.v. injection of HA-LPX in BDCA2-DTR mice (n = 3 per time point) depleted (depl) of pDCs (left) and in C57BL/6 mice (n = 3 per time point) depleted of macrophages (right). h, CFSE proliferation profile of HA-specific CD4⁺ T cells in lymphoid compartments of BALB/c Thy1.1⁺ mice (n = 3) after adoptive transfer of HA-specific Thy1.2⁺ HA-TCR-transgenic CD4⁺ T cells and subsequent immunization with HA-LPX or control (untreated). Fraction of proliferated cells indicated. tg, transgenic. i, Priming of naive HA-specific CD8⁺ T cells ex vivo. BALB/c (n = 3) mice were immunized with 80 μg HA-LPX, irrelevant (eGFP)-LPX or NaCl (control). Splenocytes were prepared 12 h later and co-incubated with CFSE-labelled CL4-TCR-transgenic CD8⁺ T cells isolated using MACS magnetic microbeads coated with CD8 antibodies at an effector:target ratio of 1:6. Four days later, proliferation profiles were analysed by flow cytometry. Numbers indicate the percentage of proliferated cells. j, Fraction of cytokine-secreting CD8⁺ T cells within CD8⁺ T cells in the spleen upon de novo priming in C57BL/6 mice (n = 5) immunized i.v. (day 0, 3, 8) with OVA-LPX after in vitro restimulation with no (none), irrelevant VSV (irrelevant) or OVA peptide and intracellular cytokine staining (top). Spleen ex vivo ELISPOT assay upon de novo priming in BALB/c mice (n = 5) immunized i.v. (day 0, 3, 8) with gp70-LPX. Stimulation with no (none), irrelevant HA (irrelevant) or gp70 peptide (lower left). gp70-specific cytotoxicity in vivo (lower right). BALB/c mice (n = 5) were immunized i.v. (day 0, 3, 8) with 40 μg gp70-LPX. Naive splenocytes were labelled with 0.5 or 5 μM CFSE and pulsed with peptide (6 μg ml⁻¹) five days after the last immunization, and target cells (2 × 10⁷) were adoptively transferred into immunized recipients i.v. (irrelevant HA-loaded CFSE^low:gp70-loaded CFSE^high = 1:1). Recipient splenocytes were analysed by flow cytometry 18 h after transfer, and antigen-specific lysis was determined: specific lysis (%) = (1 − (percentage of cells pulsed with gp70/percentage of cells pulsed with HA)) × 100). k, Expression of memory markers CD127 and CD62L in gp70-specific, CD44⁺CD8⁺ T cells compared to non-specific CD8⁺ T cells in blood (day 19) and spleen (day 67) of BALB/c mice (n = 3) after priming with gp70-LPX (day 0, 7, 14). l, Fraction of gp70-specific CD8⁺ T cells within total CD8⁺ T cells in blood, bone marrow and lymph nodes determined by MHC class I tetramer staining after de novo priming of splenectomized BALB/c mice (n = 5–7) immunized with gp70-LPX (day 0, 7) or left untreated (control). Significance was determined using unpaired two-tailed Student’s t-test (b left, c), two-way ANOVA and Bonferroni’s multiple comparisons test (b right, g) and one-way ANOVA and Tukey’s multiple comparisons test (j, l). Error bars, mean ± s.d.