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Artificial antigen‐presenting cells engineered by recombinant vaccinia viruses expressing antigen, MHC class II, and costimulatory molecules elicit proliferation of CD4+ lymphocytes in vitro

The current study was designed to test the ability of recombinant Vaccinia virus (rVV) encoding essential components of an artificial antigen‐presenting cell to activate antigen‐specific T cells in vitro. We have constructed a set of rVV encoding separately or in combination a CD4+ T cell‐specific epitope (the 133–145 peptide of chicken conalbumin), the MHC class II molecule I‐Ak, and costimulatory molecules (mB7‐1 and mB7‐2). Cultured cells infected with rVV encoding both the antigen and the presenting MHC, but not either one alone, could activate cloned CD4+ T cells specific for the virus‐encoded epitope. Additional co‐expression of mB7‐1 and mB7‐2 resulted in further enhancement of T cell response. Thus, our rVV vector expressing four different foreign gene products elicited the highest proliferation rates of antigen‐specific cloned T cells.