T cell hybridomas define the class II MHC-restricted response to vesicular stomatitis virus infection

T cell hybridomas with specificity for VSV (vesicular stomatitis virus)-infected cells were generated in an attempt to better define the la-restricted helper T cell response to VSV. The hybridomas were created by fusing BALB/c (H-2^d) anti-VSV immune spleen cells to the murine thymoma BW 5147. These hybridomas produce IL-2 when stimulated with VSV-infected spleen cells. They were found to recognize viral antigens in association with I-A^d and, in addition, could also be stimulated by VSV-infected A20 cells (an la-positive B cell lymphoma of H-2^d origin). The purified viral membrane glycoprotein, G protein, and Gs (secreted G protein that lacks the hydrophobic and intracytoplasmic domains) both stimulated IL-2 production when added to cultures of A20 and the hybridomas. These hybridomas therefore recognize a viral antigenic determinant on G protein. Since chemically-fixed antigen-presenting cells fail to stimulate the hybridomas after exogenous addition of purified G protein we can conclude that these T cell hybridomas recognize a processed form of the G protein. Stimulator cells created by expression in A20 of a transfected cDNA encoding G protein were also recognized. Recognition in this case was I-A^d-restricted, as anti-I-A^d monoclonal antibodies blocked stimulation, and an la-negative cell (P815) expressing a transfected G protein gene failed to stimulate the hybridomas. Even after paraformaldehyde fixation, G gene-transfected, la-positive cells could stimulate the hybridomas, suggesting that processing of this endogenously-synthesized antigen has occurred.