CHARACTERIZATION OF TAP-INDEPENDENT AND BREFELDIN A-RESISTANT PRESENTATION OF SENDAI VIRUS-ANTIGEN TO CD8(-LYMPHOCYTES() CYTOTOXIC T)

H-2K(b)-transfected T2 cells, which lack both TAP1/2 and LMP2/7 genes, are able to efficiently process and present Sendai virus Antigen to K -b-restricted Sendai virus-specific CTL. This presentation is not inhi bited by Brefeldin A (BFA). Here we extend our analysis of this novel antigen presentation pathway. We show that presentation of Sendai viru s antigen was not due to sensitization of T2K(b) cells by peptides in the virus preparation or peptides released from virus infected cells. Also, the ability to present Sendai virus in a BFA resistant fashion w as specific for cells of the T2 lineage. Re-expression of TAP1/2 genes in T2K(b) cells did not alter the capability to present antigen in a BFA resistant fashion, i.e. the presence of a functional TAP transport er complex did not relocate (all) peptides to the classical pathway fo r antigen processing and presentation. We found that co-infection of T 2K(b) cells with either Sendai virus plus influenza virus or Sendai vi rus plus VSV did not relocate presentation of influenza or VSV antigen to the TAP independent BFA resistant antigen presentation pathway. Pe ptide elution experiments and studies with peptide-specific CTL firmly demonstrated that the antigen presented by T2K(b) cells after infecti on with Sendai virus was the natural Sendai virus epitope NP324-332. T he same epitope, when expressed as a minigene in vaccinia virus, could be presented also by T2K(b) cells but this presentation could be bloc ked by BFA. Thus, the TAP independent BFA resistant presentation of an tigen seem cell (T2 lineage) and virus (Sendai virus) specific, but no t epitope specific. The ability of T2K(b) cells to present Sendai viru s antigen in a TAP independent BFA resistant fashion was only partiall y blocked by lysosomal inhibitors such as methylamine, ammonium chlori de and chloroquine. These findings demonstrate that TAP1/2-independent and BFA-resistant class I processing is only expressed in certain cel l types, in parallel with classical MHC class I processing, and that S endai virus selectively can enter this pathway. Hypothetical models fo r the TAP-independent class I processing are discussed.