Advances in neuroimmunology最新文献

The search for an agent that can mediate the symptoms of NeuroAIDS has been directed at gp120, the major envelope protein from HIV. The toxicity associated with gp120 was examined as a model and predictor of the neuropathological and neuropsychiatric manifestations of AIDS. Studies of the neurotoxic effects of purified gp120 on neurons from the rodent CNS cell cultures indicated the following: potent and selective killing of subpopulations of hippocampal neurons; varying potency of gp120s obtained from various HIV isolates; complete and potent protection from gp120 killing action after treatment with peptides related to vasoactive intestinal peptide; and obligatory presence of glia for gp120-related toxicity. Investigations of gp120 treatment of rodents revealed: cortical neurodystrophy with reduced arborizations and swollen processes; delays in developmental behaviors involving motor skills; peptide T prevention or attenuation of the morphological and behavioral deficits/delays produced by administration of gp120; and impairment of learning in the Morris swim maze. In addition, studies of subcutaneously administered, radiolabeled gp120 in neonatal animals demonstrated the presence of toxic fragments of gp120 in the developing brain. With the use of model test systems of non-human derived cell cultures and neonatal rats, we have captured and predicted a number of the morphological and behavioral deficits associated with AIDS. These multi-disciplinary studies of the actions of gp120 and associated fragments in rodents and rodent cells predict that the loss of cognitive and neurological function in patients with AIDS are attributed in part to interference of critical brain functions by the envelope protein, gp120.

AIDS is associated with three major neurological syndromes: dementia (HIVD), vacuolar myelopathy (VM) and plainful sensory neuropathy (PSN). The pathogenesis of these conditions remains unclear although they all demonstrate a marked increase in macrophage number and activation despite systemic immunosuppression. It was therefore of interest to determine the profile of cytokine and HIV expression in brain, spinal cord and peripheral nerves of AIDS patients with AD, VM and PSN, as compared to AIDS patients without neurological disease and seronegative controls.

RNA was extracted from brain, spinal cord and peripheral nerve and RT/PCR for cytokine and HIV mRNA was performed. In situ RT/PCR was performed to determine the number and type of cells expressing cytokine message and this was compared o the number of cells containing HIV DNA detected with in situ PCR.

We found a consistent profile of increased TNFα and decreased IFNγ and IL4 in all three syndromes compared to AIDS patients without neurological disease. IL1 did not increase in parallel with TNFα IL10 was decreased in the VM tissue. HIV transcripts were increased in the AD brains compared to non-demented controls but were detected only occasionally in spinal cord and not at all in peripheral nerve. Preliminary data from in situ RT/PCR suggests that a large number of cells are expressing. TNFα but only a small number are infected with HIV.

The finding of elevated TNFα associated with increased macrophage activation and decreased IL4 suggests that the loss of a subset of T cells expressing macrophage regulatory lymphokines such as IL4 and IL10 may explain the observed macrophage activation seen in the neurological diseases associated with AIDS and play a role in the development of neuronal dysfunction.

The mechanism for AIDS dementia may involve the production of toxic cytokines. Since macrophage/microglia are the infected cells in the brain, we were interested in the production of some of the same cytokines by HIV-infected macrophages from patients with AIDS dementia. HIV-infected macrophages from 11 patients with AIDS dementia were cultured and evaluated for p24, cytomegalovirus (CMV) DNA, and the production of interleukin 6 (IL-6), tumor necrosis factor alpha (TNFα) and other neurotoxic factors. The percentage of HIV macrophage infectivity did not correlate with the severity of dementia nor did the presence of CMV. The production of IL-6 and an unidentified neurotoxin did not correlate with HIV macrophage infectivity suggesting that these soluble factors are strain specific. Production of TNFα by HIV-infected macrophages was relatively low (<1–35 pg/ml) and may not be a significant factor in toxicity.