Commentary from the CDC HIV/STD/TB Prevention News Update:
Intravenous drug users may be more susceptible to HIV's effects on the brain and spinal cord, and they appear to be at greater risk of encephalitis and other complications, according to the results of a study presented recently at a meeting of the Society for General Microbiology in Warwick, England. Professor Jeanne Bell of Edinburgh University and colleagues conducted 250 postmortem examinations of gay men and intravenous drug users (IVDU's) with late-stage HIV infection, in an ongoing study launched in 1990 and continued after the widespread introduction of highly active antiretroviral therapy (HAART) in 1996. "We found that HIV encephalitis was much more common in IVDU's compared with gay men," Bell told Reuters Health. Her team also observed much higher levels of mental impairment and dementia in drug users.
"Because some drug users sadly die before the onset of dementia, we were also able to get a picture of events in the brain before the onset of AIDS and dementia by studying postmortem brains," she said. Her team observed two types of subtle damage in the presymptomatic phase of AIDS. The first was low-grade inflammation due to the presence of a small amount of virus; the second was background damage as the result of intravenous drug use. In the presence of heroin, methadone and, in some cases, amphetamines, the team observed activation of immune system microglial cells in the brain. Bell explained that microglial cells are the only cells with CD4 receptors, which targets them for infection with HIV. Activation of these cells in IVDUs may make HIV infection of the central nervous system more likely.
"HAART effectively arrests individuals in the presymptomatic stages of HIV/AIDS, but does not eradicate HIV from the body," she stressed. "Despite the effectiveness of HAART, our studies suggest that we may not have seen the last of the brain complications of AIDS, particularly IVDU's." Bell noted that the results of brain-imaging studies suggest that activation of microglial cells may also contribute to the disease process of Alzheimer's. "There is also some observational evidence that long-term anti-inflammatory drug treatment may afford protection against Alzheimer's. Further studies are needed to determine whether inflammation is still occurring in the brains of HAART-treated HIV/AIDS patients and perhaps whether anti-inflammatory drugs would then be helpful," she added.
(Commentary from the CDC HIV/STD/TB Prevention News Update)
