Myb proteins regulate the expression of diverse target genes.

Hematopoiesis, the process by which mature blood cells arise, is controlled by multiple transcription factors, which act in stage- and lineage-specific complexes. It is a major goal to elucidate the genes regulated by these transcription factors, in order to obtain a full understanding of the process and its malignant counterpart, leukemia. Myb family transcription factors play a central role in hematopoiesis. To identify new Myb family target genes, we have used an inducible dominant-negative protein for a subtraction cloning protocol in a model cell system (FDCP-Mix) with many characteristics of normal hematopoiesis. We present here a novel group of 29 validated Myb family target genes of diverse functions.

Immunization with a recombinant adenovirus encoding a lymphoma idiotype: induction of tumor-protective immunity and identification of an idiotype-specific T cell epitope.

The Ig Id of a B cell lymphoma is a tumor-specific Ag, although as a self-Ag it is likely to be a weak immunogen. Provision of a foreign gene may enhance the immunogenicity of the idiotype. Viral vectors allow highly efficient transfer of genetic material and are themselves innately immunogenic. We have investigated the ability of recombinant adenoviral vectors, encoding the idiotypic gene with or without fusion to the human Fc region, to produce anti-idiotypic Ab- and T cell-mediated responses in a syngeneic BALB/c A20 murine lymphoma model. The idiotypic V(H) and V(L) sequences were assembled as a single chain variable fragment (scFv) and adenoviral vectors encoding the A20 scFv (Ad.A20) and A20 scFv linked to the Fc fragment of human IgG1 (Ad.A20hFc) were constructed. A single immunization of BALB/c mice with Ad.A20hFc but not Ad.A20 induced a specific anti-idiotypic Ab response. T cell lines generated from mice vaccinated with either vector displayed specific cytotoxicity, proliferation, and IFN-gamma release against a syngeneic dendritic cell line transduced using a retroviral vector to express the A20 scFv idiotype (XS52.A1.A20). Importantly, both T cell lines lysed the A20 lymphoma cells. An immunodominant H-2K(d)-restricted CD8(+) T cell peptide, DYWGQGTEL (A20[106-114]), was identified as a naturally occurring A20 scFv epitope. A single immunization with Ad.A20hFc but not Ad.A20 provided protection in >40% of animals challenged with a lethal dose of the A20 tumor line and was more effective, in this model, than a previously optimized plasmid vaccine.