Description:
<jats:title>Abstract</jats:title><jats:p>Adoptive transfer of <jats:italic>in vitro</jats:italic> generated antigen‐specific T cells has been successfully used to treat viral infections in immunodeficient patients. Therefore, methods for the rapid <jats:italic>in vitro </jats:italic>expansion of antigen‐specific T cells are needed. Influenza virus efficiently infects dendritic cells, and peptides derived from viral proteins are processed and presented to CD8<jats:sup>+</jats:sup> cytotoxic T cells. However, both, CD4<jats:sup>+</jats:sup> and CD8<jats:sup>+</jats:sup> T cells are necessary for the efficient control of viral infections, and it is becoming increasingly clear that a T helper cell response is very important for the maintenance and strength of the immune response. Here we show that recombinant influenza virus efficiently infects a wide range of professional antigen‐presenting cells and does not interfere with antigen presentation pathways. Using T cell clones for three different MHC class II‐restricted antigens we demonstrate that peptides derived from these antigens are efficiently presented on MHC class II molecules. Importantly, it was possible to generate and expand antigen‐specific CD4<jats:sup>+</jats:sup> T cells following <jats:italic>in vitro</jats:italic> infection of professional antigen‐presenting cells with recombinant influenza virus. These findings support the notion that recombinant influenza virus is a valuable tool for the expansion of antigen‐specific CD4<jats:sup>+</jats:sup> T cells <jats:italic>in vitro</jats:italic>.</jats:p>