[Mechanism of neuronal damage in AIDS]

Neurologic problems in AIDS are usually caused by opportunistic infections or secondary malignancy of the central nervous system (CNS), but brain damage occurs primarily as the result of HIV infection in CNS. In one of the typical opportunistic virus infections of CNS, progressive multifocal leukoencephalopathy (PML), oligodendroglial cells which maintain and support myelin sheaths are specifically attacked by JC virus. As the consequence, demyelination occurred, which could well explain the neuronal deficits. In contrast, in HIV the viral target cells are not neuronal cells, but infiltrating macrophages in CNS. Thus, the indirect injury such as HIV-related neurotoxic substances and macrophage-released cytokines would be augmented to induce diffuse neuronal damage in HIV infected brains. Recent discovery of co-receptor, chemokine receptor (CCR5) which is expressed in macrophages, may give a clue to understand the mechanism of HIV encephalopathy more precisely.