Evolution of the HIV-1 transgenic rat: utility in assessing the progression of HIV-1-associated neurocognitive disorders

Understanding the progression of HIV-1-associated neurocognitive disorders (HAND) is a critical need as the prevalence of HIV-1 in older individuals (> 50 years) is markedly increasing due to the great success of combination antiretroviral therapy (cART). Longitudinal experimental designs, in comparison to cross-sectional studies, provide an opportunity to establish age-related disease progression in HAND. The HIV-1 transgenic (Tg) rat, which has been promoted for investigating the effect of long-term HIV-1 viral protein exposure, was used to examine two interrelated goals. First, to establish the integrity of sensory and motor systems through the majority of the animal's functional lifespan. Strong evidence for intact sensory and motor system function through advancing age in HIV-1 Tg and control animals was observed in cross-modal prepulse inhibition (PPI) and locomotor activity. The integrity of sensory and motor system function suggested the utility of the HIV-1 Tg rat in investigating the progression of HAND. Second, to assess the progression of neurocognitive impairment, including temporal processing and long-term episodic memory, in the HIV-1 Tg rat; the factor of biological sex was integral to the experimental design. Cross-modal PPI revealed significant alterations in the development of temporal processing in HIV-1 Tg animals relative to controls; alterations which were more pronounced in female HIV-1 Tg rats relative to male HIV-1 Tg rats. Locomotor activity revealed deficits in intrasession habituation, suggestive of a disruption in long-term episodic memory, in HIV-1 Tg animals. Understanding the progression of HAND heralds an opportunity for the development of an advantageous model of progressive neurocognitive deficits in HIV-1 and establishes fundamental groundwork for the development of neurorestorative treatments.