Recombinant expression of vaccinia virus-encoded TAP1 and TAP2 promotes MHC class I-restricted antigen presentation in a Syrian hamster cell line.

Transporter associated with antigen presentation (TAP) molecules supply small peptides to the lumen of the endoplasmic reticulum for assembly with MHC class I glycoproteins. Here we report that a Syrian hamster cell line, BHK, which is commonly used in cell biological and virological investigations, is deficient in antigen presentation in a xenogeneic model. Thus when the mouse MHC class I restriction element, Kd, is expressed in BHK cells via a vaccinia virus (VV) recombinant, no significant recognition by VV-immune and Kd-restricted cytotoxic T cells is induced. This defect is apparently a consequence of a deficiency in TAP-dependent peptide transport and can be repaired when rat TAP1 and TAP2 are provided by recombinant VV expression.