Although the virus has not been identified, the scientists write in today's issue of the British journal Nature that they have found strong indications for the presence of a virus that is related to the human T-cell lymphotrophic viruses, also known as HTLV-I, II and III.
HTLV-I and II have been identified as the causes of two rare forms of leukemia, and HTLV-III is generally believed to be the virus that causes acquired immune deficiency syndrome.
In a telephone interview, Dr. Hilary Kaprowski of the Wistar Institute in Philadelphia emphasized that the viral "footprints" they have observed in white blood cells removed from the spinal fluid of MS patients are not those of the AIDS virus.
"There is no indication of any connection between AIDS and MS," he said.
Multiple sclerosis, or MS, is primarily a disease of young adults that progressively destroys the insulation around nerve fibers, resulting in a variety of neurological impairments. About 250,000 Americans have MS. For reasons not fully understood, the disease is about twice as common in the northern part of the country as in the south.
T-4 Cells Affected
Kaprowski, a virologist and immunologist, is principal author of the report, along with researchers from the University of Lund, Sweden, the University of Miami and the National Cancer Institute in Bethesda, Md.
All three of the known HTLV viruses attack white blood cells known as T-4 cells that are an important element of the body's immune system. The MS study involved eight patients, and the scientists found that T-4 cells obtained from the spinal fluid of five of them showed biochemical and genetic characteristics similar to those seen in T-4 cells that have been attacked by HTLV, particularly by HTLV-I.
Although scientists have long suspected that MS may be a consequence of a viral attack, this is the first time that cells from the spinal fluid of MS patients have been shown to express genetic information indicating they have been invaded by a specific viral agent, the scientists said.
Blood and spinal fluid from patients also contained antibodies related to the HTLV family, they said. In contrast, neither a group of 104 healthy people nor the majority of 17 patients with other types of neurological disease had evidence of the presence of HTLV, they said.
The results do not prove that HTLV is the cause of MS, according to the researchers. One important step toward getting proof will be isolating and identifying the suspected new member of the HTLV family, which they are now trying to do.
'The Same Thing'
"We do not have the virus in hand. All we can say now is that this is as interesting as anything I know that has been published on MS," said Dr. Robert Gallo, the National Cancer Institute scientist in whose laboratory HTLV-I and HTLV-III were first isolated.
Gallo said in an interview that it was several years after he observed the HTLV-I footprints before most other scientists accepted the virus, which he eventually isolated, as being one cause of leukemia.
"We'll go through the same thing with this one," he said.
Gallo and Dr. Mary E. Harper of his laboratory are among the co-authors of the paper. Harper contributed the part of the study showing that the HTLV associated with MS is not the AIDS virus.
The material from the MS patients was obtained from Sweden, where the disease is known to have a high incidence, and from Key West, Fla., which in recent studies has been shown to have an incidence of MS 40 times that for the rest of the state.
Kaprowski and Dr. Elaine C. DeFreitas, a Wistar researcher, said the fact that only about 60% of the MS patients have indications for the presence of HTLV may mean that MS is not a single disease but rather a group of diseases with different causes.
"We used to think that leukemia was a single disease, but now we know there are 10 categories of leukemia. It may be the same with MS," Kaprowski said.
Both HTLV-III, the AIDS virus, and HTLV-I, which causes a kind of leukemia that chiefly affects people living in certain parts of Japan, can be sexually transmitted. But DeFreitas said there is no evidence that MS can be transmitted by intimate contact with a patient.