Throughout this application various publications are referenced, many in parenthesis. Full citations for each of these publications are provided at the end of the Detailed Description. The disclosures of each of these publications in their entireties are hereby incorporated by reference in this application.
Recent studies have shown the presence of DNA sequences belonging to a novel herpesvirus in Kaposi's sarcoma (KS) tissues (Chang et al. 1994). This virus has been called KS-associated herpesvirus (KSHV) and is provisionally designated human herpesvirus 8 (HHV-8). Although KSHV does not appear to be present in control tissues from non-acquired immunodeficiency syndrome (AIDS) patients (Chang et al. 1994; Moore and Chang 1995) or in the peripheral blood of normal blood donors (Whitby et al. 1995), it has been detected in two unique and distinctive categories of lymphoid proliferations, namely the primary effusion (body cavity-based) lymphomas (BCBL) (Cesarman et al. 1995a) and multicentric Castleman's disease (Soulier et al. 1995). The BCBLs are a distinct group of B-cell non-Hodgkin lymphomas presenting with a unique spectrum of clinical, morphologic, immunophenotypic, and molecular genetic characteristics that distinguish them from most AIDS-related lymphomas (Knowles et al. 1989; Walts et al. 1990; Green et al. 1995). More specifically, BCBLs tend to present in the pleural, pericardial, and/or abdominal cavities as lymphomatous effusions, usually in the absence of any identifiable tumor mass throughout the clinical course. They have an unusual immunophenotype in that they commonly express CD45 in the absence of other B- or T-cell lineage-restricted antigens. At the molecular level, they are characterized by a B-cell genotype as determined by clonal immunoglobulin (Ig) gene rearrangements, the presence of Epstein-Barr virus (EBV) and the lack of c-myc gene rearrangements (Cesarman et al. 1995a; Knowles et al. 1989; Green et al. 1995; Chadburn et al. 1993).
Sequence analysis of the KS330Bam and KS631Bam fragments of KSHV, as well as of cloned flanking regions (Chang et al. 1994), has shown homology to two viruses in particular: EBV (Baer et al. 1984) and herpesvirus saimiri (HVS) (Albrecht et al. 1992). Both of these viruses are members of the gammaherpesvirinae subfamily of herpesvirus, which members are characterized by their propensity to infect and transform lymphoblastoid cells (Roizman 1990; Liebowitz and Kieff 1993; Fleckenstein and Desrosiers 1982). The degree of homology, with amino acid identities in the range of 30% to 50%, is consistent with these sequences belonging to a novel member of the same family, which is referred to as Kaposi's sarcoma-associated herpesvirus (KSHV) (also referred to as human herpesvirus 8 or HHV-8). It is well known that EBV immortalizes B cells in vitro and is associated with certain malignant lymphomas, including Burkitt's lymphoma, some AIDS-related lymphomas, the post-transplantation lymphoproliferative disorders, and Hodgkin's disease (Liebowitz and Kieff 1993). HVS is a virus of squirrel monkeys (Saimiri sciureus) that can be isolated from peripheral blood mononuclear cells of healthy animals but causes fulminant T-cell lymphomas in New World primates other than its natural hosts (Fleckenstein and Desrosiers 1982). HVS is also capable of transforming human T lymphocytes to continuous growth in vitro (Biesinger et al. 1992). Thus, the two herpesviruses most homologous to KSHV have the ability to latently infect peripheral blood lymphocytes of their natural host, immortalize lymphocytes in vitro, and lead to the development of malignant lymphomas. This finding, in conjunction with the presence of KSHV sequences in all AIDS-BCBLs analyzed thus far, suggests that these sequences may play a pathogenic role in the development of some malignant lymphomas.
A need exists, therefore, to find means to isolate and propagate KSHV so that more can be learned about KSHV.