The relative abundance of two measles virus fusion protein peptide-DR1 complexes expressed by B cells is independent of the form of the antigen

The relative processing and presentation efficiency of two DR1-restricted d eterminants from the fusion protein (F protein) of measles virus (MV) was d etermined using three forms of antigen (Ag): MV, an F protein recombinant v accinia virus, and a chimerical polypeptide between the glutathione S-trans ferase and the F protein (GST-F protein). First, it was shown that these di fferent preparations of F protein have distinct processing requirements. In MV-infected B cells, the F254 determinant (contained within the F protein sequence 254-268) relies on protein synthesis for its presentation, while t he F314 determinant (contained within the F protein sequence 314-328) is al so presented in the absence of protein synthesis. By contrast, in GST-F pro tein-pulsed B cells, presentation of both determinants is dependent on prot ein synthesis. Then, it was established that, independently of the form of the Ag, the F314 determinant was considerably more (18- to 36-fold) efficie ntly processed and presented than the F254 determinant, These results indic ate that determinants from the same protein are displayed by antigen-presen ting cells at widely different levels and they may also suggest that this i s an intrinsic characteristic of the determinants, rather than a feature co ntrolled by the processing pathways followed by the Ag, (C) 1999 Academic P ress.