CHICAGO — Government scientists reported Thursday that the AIDS virus attacks different types of cells in the brain and central nervous system than in the rest of the body, a finding that may complicate treatment of the deadly infection.
The virus, known as HTLV-3 or HIV, also appears capable of causing some diseases directly rather than by destroying the body's natural immunity to other infections, as is the case in acquired immune deficiency syndrome, researchers at the National Cancer Institute said.
The findings, reported in three articles in the Journal of the American Medical Assn., were hailed as significantly adding to knowledge of how the AIDS virus works.
The presence of the AIDS virus in the brain and central nervous system "is going to make treatment at least somewhat more complicated," said Dr. Robert Joynt, dean of the University of Rochester School of Medicine and Dentistry.
Will Not Work
Drugs and other therapeutic agents cannot pass easily from the bloodstream into the brain and spinal fluid because of the so-called "blood-brain" barrier, and efforts to boost immunity in the body likely will not work in the brain, Joynt said.
"Unfortunately, from an immunological standpoint, the central nervous system acts quite differently from the rest of the body," he said.
But Joynt added that while it is still not known how the AIDS virus gets into the brain and why it behaves differently there, the current research will make finding those answers easier.
"Now that we've localized where the virus attacks the central nervous system, that's really going to increase our whole understanding of this virus," he said.
Using brain tissue from an AIDS patient suffering from dementia, Suzanne Gartner and other National Cancer Institute researchers were able to detect active AIDS virus in monocytes, flat white blood cells that develop into large macrophage "scavenger" cells important in detecting and controlling infection.
A second report by researchers from the University of Rochester found bits of HTLV-3 genetic material in the white matter of the brain, including the macrophages and other related cells.
While the AIDS virus does occasionally infect macrophages in the body, it primarily attacks and destroys the helper T-cell, an important coordinator of the body's immune system. It is the depletion of these cells that leads to AIDS and the less severe AIDS-related complex.
However, when AIDS virus cultured from the brain cells was then injected into helper T cells, the virus failed to thrive, leading the researchers to believe the HTLV-3 in the brain was a slightly mutated form of the one generally found in the body.