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The reverse transcriptase (RT) of the human immunodeficiency virus type 1 (HIV-1) is the major target for antiretroviral therapy of the acquired immunodeficiency syndrome (AIDS). While some inhibitors exhibit activity against most retroviral RTs, others are specific for the HIV-1 enzyme.To develop an animal model for the therapy of the HIV-1 infection with RT inhibitors, the RT of the simian immunodeficiency virus (SIV) was replaced by the RT of HIV-1.

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Herpesvirus saimiri has recently been shown to immortalize human T cels. It was unknown, however, whether Herpesvirus saimiri transformation affects T-cell receptor (TCR) expression and signal transduction. In the present study, we have transformed CD4+ human T-cell clones speciffc for human myelin basic protein. The transformed T cells were grown in interleukin 2 and divided in the absence of antigen and antigen-presenting ceUls. They retained the membrane phenotype of activated T ceUs and secreted the cytokines interferon y and lymphotoxin, but interleukin 4 was not detected. Further, the transformed T cells continued to express the original TCR as demonstrated by TCR variable-region-V(&specific monoclonal antibodies and TCR sequencing. Antigen-specific recognition and signal transduction by the TCR were demonstrated by myelin-basic-protein-induced HLA-DRrestricted secretion of interferon y and lymphotoxin and by myelin-basic-protein-speciflc proliferation. Antigen specificity and reactivity have been maintained for >1 year after transformation. Transformation with Herpesvirus saimiri now allows the production of virtually unlimited numbers of (auto)antigen-specific T cells expressing functional TCR and a stable membrane phenotype. This technology will facilitate studies of the pathogenesis of putative autoimmune diseases, such as multiple sclerosis, and may be of help in TCR-targeted immunotherapy.Autoantigen-specific autoaggressive T-cell clones have become indispensable tools to study the cellular and molecular mechanisms of autoimmunity. For example, studies using myelin-specific T-cell lines have provided insights into the details of demyelinating autoimmune responses and into the general organization of intracerebral immune reactivity and seem to provide a basis for additional therapeutic strategies (1). Once isolated from the donor organism, autoimmune T cells can be cultured for a few weeks in interleukin (IL) 2-containing medium in the absence of antigen. For prolonged culture, the cells must be restimulated at regular intervals with antigen and antigen-presenting cells (APCs) (2, 3). Even under optimal culture conditions, most human and rodent T-cell lines have finite life spans. This and the requirement of fresh human APCs form major obstacles limiting the duration and dimension of human T-cell studies.These problems could be overcome by virus transformation of antigen-specific T cells, in analogy to Epstein-Barr virus transformation of B cells. To be useful for broad application, the ideal T-cell-transforming agent should lead to permanent APC-and antigen-independent growth, whileThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.conserving the essential features of the nontransformed parental T cells. We show here that Herpesvirus saimiri (HVS), a lymphotropic -.2 herpesvirus (4), fulfills most, if not all, of these criteria. Using ce...

SummaryHerpes virus saimiri (HVS) immortalizes T lymphocytes from a variety of primates and causes acute T cell lymphomas and leukemias in nonnatural primate hosts. Here we have analyzed the requirements for growth of three HVS-transformed human T cell lines. The cells expressed the phenotype of activated T cells: two were CD4 + , and one was CD8 + . All three cells responded to all allogeneic human cell lines tested with enhanced proliferation, production of interleukin 2 (Ib2), and increased expression of the I1:2 receptor. Binding of CD2 to its ligand CD58 was the critical event mediating stimulation because: (a) monoclonal antibodies (mAbs) to CD2 and to CD58, but not to a variety of other surface structures, blocked induced and spontaneous proliferation and Ib2 production; (b) only anti-CD2 mAbs were stimulatory if crosslinked; (c) a nonstimulatory cell was rendered stimulatory by CD58 transfection; and (d) the cells responded specifically to CD58 on sheep red blood cells. Growth of the cells required activation because cyclosporin A and FK506 blocked stimulator cell-induced II:2 production and proliferation as well as the spontaneous growth of the lines. Antibodies to the I1:2 receptor reduced proliferation of the cells and blocked 11:2 utilization. Taken together, these results show that HVS-transformed T cells proliferate in response to CD2-mediated contact with stimulator cells or with each other in an I1:2-dependent fashion. They suggest that HVS transforms human T cells to an activationdependent autocrine growth. Herpes virus saimiri (HVS) is the prototype of the lymphotropic 3~-2 herpes viruses (rhadinoviruses). Natural hosts of the virus are the squirrel monkeys (Saimiri sciureus).By cocultivation with permissive monolayer cells, HVS can be isolated from PBL >80% of the population, and at least one in 106 T cells will yield virus (reviewed in reference 1). The virus persists in T cells for their lifetime. HVS is not pathogenic for squirrel monkeys, even after immunosuppression. In contrast to this benign behavior in its natural host, HVS has a high oncogenic potential in numerous other New World primates (1). It causes acute lymphoproliferative syndromes, leukemias, and lymphomas. After infection, the animals die within a few weeks from rapidly progressing neoplasias. Cell lines can be established from infected animals that initially produce virus in "~1-10% of the cells, but after prolonged cultivation the ability to produce virus is lost (2), HVS is able to transform T lymphoeytes of nonhuman primates as well as human PBL and thymocytes to continuous growth (2, 3). The molecular basis of T cell stimulation and transformation is unknown.In this study we show that transformation with HVS induces human T cells to respond to cell-cell contact with each other and with other cells leading to I1:2-dependent autocrine growth. The critical stimulating signal in this contact is given by binding of the CD2 molecule to its natural ligand. These HVS-transformed T cells are the first example of an activation-de...