Greater than twenty percent of HIV-1 infected will eventually develop a B-cell lymphoma. Historically, this incidence has been attributed to immune dysfunction and not to direct infection and transformation of B- cells by HIV. However, through the use of limiting dilution PCR (Polymerase Chain Reaction), a relatively new technique not previously applied to AIDS lymphomas, we have obtained evidence of a high load of HIV provirus in a subset (3 of 14) of AIDS-related B-cell lymphomas. These 3 tumors are all non-translocation cases. In addition, we have obtained evidence that these tumors are polyclonal which raises the possibility that transformation may be mediated by an HIV-specific protein. Furthermore, we have recently found that HIV can infect and malignantly transform B-cells populations in vitro (1,2), provided that at least some cells in the target population contain EBV. Our transformed line, B-HIV, contains one HIV provirus per cell and one EBV genome, grows in 1% serum, clones in soft agar, and forms malignant tumors in SCID mice. These results have led to the hypothesis that HIV infection of B- cells may in concert with EBV, can be a direct cause of a subset of AIDS- related lymphomas. Because this hypothesis is important and novel as well as controversial, the 4 aims of this proposal range from a more thorough analysis of B-cell tumor material, to the application of in situ hybridization for testing for the parallel presence of both HIV and EBV sequences, through to direct testing of the ability of HIV gene products to cause, in conjunction with EBV, the malignant transformation of B- cells. Our specific aims are: a. Analysis of additional AIDS B-cell lymphomas. b. Determination of the clonality of B-cell lymphomas containing a high load of HIV provirus. c. Detection of HIV and EBV in transformed cells and tumor cells by in situ hybridization. d. Use of a B-cell transformation assay to determine the gene(s) involved in malignant conversion in EBV infected B-cell populations. AIDS-related lymphomas represent a major cause of death for HIV-infected individuals. Our experiments are novel and have the potential of providing evidence of a mechanism by which HIV could transform B-cells in vivo generating lymphoma.