The severe combined immunodeficient (SCID) mouse model of human immunodeficiency virus encephalitis: deficits in cognitive function.

The severe combined immunodeficient (SCID) mouse model of human immunodeficiency virus (HIV) encephalitis exhibits many of the histopathological and pathophysiological features of human HIV-associated dementia (HAD). Although deficits that may resemble HAD in humans have been reported for HIV-infected SCID mice, the cognitive deficit aspect of the model has very limited empirical support. Here, the authors report that HIV-infected SCID mice display cognitive deficits on a task requiring the animal to learn and remember the spatial relationship of cues in its environment in order to locate a submerged platform in a Morris water maze. The cognitive deficits manifest as longer latencies to locate the platform on the last day of the maze acquisition period and during a retention test 8 days later. Control experiments indicated that the poor performance by HIV-infected mice in comparison to controls was not due to impaired motor function or swimming ability, impaired visual acuity, or increased susceptibility to fatigue. Thus, the increased times required for HIV-infected mice to locate the submerged platform during the acquisition and memory tests likely reflect a cognitive deficit, rather than sensorimotor or emotional abnormalities. These behavioral deficits are associated with significant increases in astrogliosis and microgliosis in the HIV-infected mice. The results of this study strengthen the SCID mouse model of HIV encephalitis by definitively establishing cognitive deficits for the model in addition to its previously reported neuropathological features.