Immunoglobulin (1g) variable regions are tumor associated antigens of B cell lymphomas and meyelomas. Vaccination with intact Ig has induced tumor specified immunity, but this approach has produced variable results and has led to the outgrowth of tumor variants. We hypothesize that the variable results seen may be due to the elicitation of a limited immune response to single or very restricted set of immunodominant epitopes when whole Ig is used as the vaccine. Our goal is therefor to define discrete VH peptides representing subdominant or cryptic epitopes from both the hyper variable and conserved framework regions to design a vaccination strategy that could provoke a broader response. In addition a vaccine that provokes protective immunity against epitopes within more conserved regions including framework regions of VH could be utilized for multiple patients. Our strategy is to identify peptides from he entire VH region with predicted binding affinities for H-2Kd, and test them for their ability to generate MHC-restricted CTL. Mice are immunized with dendritic cells pulsed with synthetic peptides, with dendritic cells transfected to express the selected peptides, or with dendritic cells transfected with the entire VH region. Our rational is that by using dendritic cells and focusing upon selected peptides it will be possible to generate CTL responses to areas of the VH that would otherwise be ignored due to the suppressive effects of more dominate epitopes. To test our hypothesis, antibody forming clones derived from the immune response of BALB/c mice to dextran and to the hapten phthalate have been immortalized as hybridomas and associated VH region peptides will be used to assess the specificity of the T cell repertoire and the hybridoma cells used as tumor models. The strengths of these two models are that (a) each hybidoma represents a dominant clonotype in the primary or secondary response, and (b) the Vh regions of these hybidomas have been sequenced and MHC binding peptides from these regions have been identified. While we expect to see tumor specific MHC-restricted CTL responses to both germ line and somatically mutated peptides an attempt being made to enhance the responses by linking peptides to heat shock proteins, by the local release of cytokines from biodegradable micro spheres and by treatment of dendritic cells with CpG-containing oligodeoxynucleotides. The efficacy of vaccination is evaluated in vitro and also tested in vivo by assessing the ability of immunized mice to withstand a tumor challenge or to prevent the outgrowth of tumor in remission. Finally, the effect of vaccination upon the normal B-cell repertoire expression is assessed.
