Figure 1.

In vivo antigen presentation and T-cell activation. (a) Schematic representation of the DNA vaccines and the corresponding protein domains of the haemagglutinin of influenza A virus (IAV) strain PR8. The single-chain antibody fragment variables were separated from the antigens by a [Gly4Ser]3-linker and all expression cassettes contain a C-terminal OLLAS-tag for detection purposes. (b) To assess the antigen presentation and activation of T-cell receptor (TCR)-specific T cells in vivo, BALB/c mice were immunized with 20 μg of DNA encoding either the DEC205-targeted antigens (DECsolHA/DEC-HACD8) or the control antigens (GL117-solHA/GL117-HACD8). Four days after immunization, 2 × 10⁶ CFSE-labelled TCR-transgenic CD8 T cells (CL4) or CD4 T cells (TCR-HA) were adoptively transferred and their proliferation was determined after 3 days by CFSE dilution. Lymphocytes from spleen and pooled lymph nodes (popliteal, inguinal) were analysed. Representative histograms are shown and percentages of proliferating cells are indicated for the marked region. (c) Mean values and standard errors of the means (SEM) for six animals per group out of two independent experiments are shown for CD4 T cells (left) and CD8 T cells (right), respectively. One-way analysis of variance, Tukey post test, *P < 0·05, **P < 0·01, ***P < 0·001.