This is what the CAA website has to say about JHK:
Retroviruses
Retroviruses are known to cause uncommon neurological disorders that have a relapsing and remitting pattern similar to CFS. In 1991, a team of researchers led by Dr. Elaine DeFreitas published evidence suggesting that a human T lymphocytic virus type II (HTVL-II)-like retrovirus was present in the lymphocytes of CFS patients and might be the cause of their symptoms.11 Other preliminary evidence of possible retroviral involvement in CFS has been published. Dr. W. John Martin of California reported an association of CFS with a "stealth virus." 12 Dr. Sidney Grossberg of Wisconsin discovered a new virus, called the "JHK" virus, in a CFS patient. Subsequent study by other laboratories failed to reproduce any of these results.13, 14, 15
http://www.cfids.org/about-cfids/viruses.asp?
Here's some info in an article by Cort, written in 2010:
Dr. Sidney Grossberg - An accomplished researcher who had done a stint at the renowned Pasteur Institute in France under the discoverer of the HIV virus, Dr. Luc Montagnier, Dr. Grossberg jumped into the fray in the first quarter of 1992 with a report hed isolated a novel retrovirus from the blood of a CFS patient. Happy to have such a renowned figure involved the CFIDS Association expedited funding for him. Dr. Grossberg went onto to get two grants from the NAIAD, becoming apparently the only researcher to receive federal funding from the NIH to specifically look for a retrovirus in the disease. Interestingly, Dr. Grossberg, too, was unclear whether hed found an endogenous or exogenous retrovirus and like Dr. DeFreitas his virus appeared not to fit in any viral family.
Three years later in 1995 Dr. Grossberg still not published a paper on his virus. In 1998 he published a paper examining the characteristics of a novel retrovirus called JHK but no mention of CFS was made. The CFIDS Association would still be supporting him in 1998 and then again in 2001 but as of 2010, Dr. Grossberg has never published any papers on retroviruses in chronic fatigue syndrome.
His website indicates that the JHK virus and its potential link to leukemia, lymphoma, chronic fatigue syndrome and other immuno-dysfunctional states is still of major interest to him and it refers to four current projects. Dr. Grossberg, has not, however, published a paper on the virus for over 10 years.
Dr. Grossbergs connection to ME/CFS may not, however, end there. In 2003 he co-authored a study announcing the presence of a xenotropic murine leukemia retrovirus in a human B-lymphoblastoid cell line. (XMRV is a a xentropic murine leukemia related virus) Interestingly, Dr. Grossbergs JHK virus first discovered in chronic fatigue syndrome -with was also produced by a B-lymphoblastoid cell line.
http://phoenixrising.me/?p=1232
And from the NATIONAL CFIDS FOUNDATION website:
Is XMRV related to the JHK retrovirus found in CFS patients and discovered by Sidney Grossberg, M.D.?
According to Dr. Grossberg's website, "the JHK virus 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 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. The possible etiological role of the JHK virus in diseases that may involve B-lymphocytes, such as leukemia, lymphoma, chronic fatigue syndrome or immuno-dysfunctional states, remains to be determined [8,9,10]." It would appear that the JHK virus differs from XMRV judging by Grossberg's information.
http://www.ncf-net.org/forum/2010winter2.htm