NeuroAIDS, current understanding and future directions

Morphological correlates of neurological dysfunction in macaques infected with neurovirulent simian immunodeficiency virus

The pattern of neurological disease caused by human immunodeficiency virus (HIV) infection of the central nervous system (CNS) was investigated using a macaque model of acquired immune defiency syndrome (AIDS). Seven of nine macaques inoculated with neurovirulent simian imunodeficiency virus (SIVmac ) developed AIDS within 3 months. Four of these had clinically obvious neurological disease and extensive conduction defects in the form of latency increases in evoked potential (EP) responses. Neuropathologically, all four animals had disseminated white matter disease in the form of multifocal, perivascular and nodular parenchymal mononuclear cell infiltrates, along with extensive involvement of the cortical grey matter, leptomeninges and intracranial portions of cranial nerves. A brisk multinucleated giant cell (MGC) response was a frequent accompaniment in the affected areas. Three of the animals in this group also showed spongiform vacuolation in the occipital grey matter, a lesion described only rarely in HIV encephalitis. In the remaining three animals, there was only minimal evidence of overt neurological impairment or conduction defects. These animals had only mild to moderate neuropathological changes and lesions were virtually confined to the white matter regions of the brain. MGC responses were rare or absent in the CNS of these animals. Neuropathological findings in this SIVmac model have therefore shown good correlation with the severity of clinical and neurophysiological changes, and are reminiscent of HIV-1 encephalitis. More importantly, white matter involvement was a consistent finding in the affected macaques, regardless of the duration and severity of disease, or type of virus inoculated, suggesting an unusual susceptibility for lentiviral infection in these regions of the macaque CNS.

HIV-1 proviral DNA load across neuroanatomic regions of individuals with evidence for HIV-1-associated dementia

A definitive relation between HIV-1 load and the clinical diagnosis of HIV-1-associated dementia (HAD) has not yet been established. Knowledge of the neuroanatomic distribution of HIV-1 load in the brain of individuals with HAD and HIV-1 encephalitis may facilitate elucidation of this relation. Nine individuals with AIDS were analyzed postmortem by three independent methods with each assessment performed blinded to the others: 1) a neuropsychiatric review of clinical records for evidence of possible HAD, 2) HIV-1 DNA load determination by quantitative polymerase chain reaction (PCR) across several neuroanatomic regions, and 3) a pathologic examination for diagnosis of HIV-1 encephalitis by immunohistochemical techniques. Of eight AIDS cases with clinical records sufficient for neuropsychiatric review, seven were shown to have evidence for HAD. HIV-1 DNA was detected and quantified in specimens from all of the medial temporal lobe regions analyzed but was not detectable in the frontal lobe at the same level of sensitivity in two of these cases (<1 per 1000 cellular genomes). HIV-1 DNA load in the medial temporal lobe region was significantly larger than that in the frontal lobe. Only four of seven cases with evidence for HAD were also diagnosed with HIV-1 encephalitis.