Neuropathology of NFHgp160 transgenic mice expressing HIV-1 env protein in neurons

The physiopathology of HIV-1 dementia remains largely hypothetical. Although several sets of evidence point towards an indirect multicellular inflammatory pathway, gp120, one of the HIV-1 env products, was shown to be very cytotoxic for neurons in vitro. To explore a direct pathway in the physiopathology of dementia in AIDS, we developed transgenic mouse models carrying the HIV-1 env proteins gp 120 and gp 41 (gp 160) under the control of the human light neurofilament and murine heavy neurofilament promoters. To date, this is the first mouse model in which the HIV-1 env protein can be detected in neurons by immunohistochemistry. The expression is found in several brainstem and spinal cord gray structures and in the cerebellum in one of the mouse lines bearing the NFHgp160 transgene. The morphological findings at 3 months are subtle and are dominated by a watery, dendritic degeneration and a reactive gliosis. At 12 months, the evidence of neuronal degeneration and loss is present along with various degenerative phenomena involving synapses, dendrites and axons, including axonal swellings. Cytoskeletal abnormalities were found by immunohistochemistry. Chronic inflammation was also observed in the leptomeninges of the spinal cord and brainstem and in the cerebellar white matter. These models thus offer an exciting sequence of morphological findings initiated by the neuronal expression of the HIV-1 env proteins and offer a different tool to explore the neuronal dysfunction in AIDS.