Our current research deals with the molecular, immunological, and biological characterization of a new human RNA virus that replicates in human B-lymphoblastoid cells. The virus, designated JHKV, is an enveloped, relatively fragile particle containing RNA, reverse transcriptase, and prominent, knobbed glycoprotein projections. Although the JHK virus resembles a retrovirus (but 35% smaller than most other retroviruses), it is clearly not like any of the known human retroviruses (human immunodeficiency virus or human T-lymphotropic virus), as determined either by polymerase chain reactions or electron microscopy. The JHK-3 B-lymphoblastoid cell line that constitutively produces the JHK virus (and the Epstein-Barr virus as well) has the antigenic markers of immature B-lymphocytes by flow cytometry. cDNA libraries produced by reverse transcription of JHK viral RNA have been constructed and are being analyzed; the sequences determined of the many clones produced have so far revealed no significant homology with known viruses. Polyclonal antibodies and certain monoclonal antibodies we have produced react with JHKV by enzyme-linked immunosorbent assay, Western immunoblot, and immunogold binding, like sera from certain patients. The possible etiological role of the JHK virus in diseases that may involve B-lymphocytes, such as leukemia, lymphoma, chronic fatigue syndrome or immune dysfunction states, remains to be determined. The goals of current experimental studies are to (i) clone, sequence, and map the viral genome; (ii) characterize monoclonal antibodies to the virus; (iii) identify viral antigens; and (iv) develop methods to detect JHKV infection, using nucleic acid probes for hybridization and primers for the polymerase chain reaction.