Even after the introduction of combination antiretroviral therapies, HIV infection persists in the central nervous system (CNS). The chronic presence of virus and the associated inflammation supports an increasing prevalence of CNS disease as the HIV-infected population ages. In vitro studies have shown that neuronal dysfunction is triggered by a destabilization of neuronal calcium followed by the appearance of damage in the form of dendritic beading, pruning of processes and synapse loss. We have demonstrated that the novel p75 neurotrophin receptor ligand, LM11A-31, prevents the neural dysfunction and damage, in feline neural cultures infected with feline immunodeficiency virus (FIV) or rat neural cultures exposed to HIV virions, gp120 or toxic macrophage conditioned medium. As seen in many disease models, neuronal p75 increases in response to HIV, thereby providing a therapeutic target that is upregulated by the disease process. The protective effect was seen at nanomolar concentrations and was due, in part, to a restoration of calcium homeostasis, thereby preventing the initial dysfunction that leads to neuronal damage. Separate studies demonstrated that the compound crossed the blood-brain barrier, accumulated in the brain compartment and was free of adverse effects at high concentrations in vitro and in vivo in both mice and cats. Tests for adverse effects included physiological (body weight, CBC, urinalysis, blood chemistry, organ weights and histology) and behavioral measures (thermal sensitivity, gait analysis, veterinary examination). Neuroprotective efficacy has also been reported in animal models of aging, Alzheimer disease, Huntington disease, spinal cord injury and traumatic brain injury. Based in part on the above studies, LM11A-31 has been approved for Phase I studies for development as a treatment for Alzheimer disease. Our in vitro results and preliminary in vivo studies indicate that LM11A-31 will also be an effective intervention to protect the nervous system against HIV-associated damage. The proposed studies will test this assumption using the FIV model of HIV-associated neuropathogenesis while also addressing issues important for the proposed therapeutic use of the compound in the context of HIV infection. This natural infectious model has been optimized for therapeutic testing and recapitulates features of infection and CNS disease important for translation to humans. A major endpoint will be the reversal of FIV-induced cognitive deficits. Additional endpoints will include demonstration of reduced inflammation in the brain, assessment of toxicity/adverse effects with long-term treatment and evaluation of effects on virus titers and disease progression. These studies will establish initial in vivo efficacy and safety of LM11A-31 in preparation for subsequent studies designed to establish LM11A-31 as a treatment for HIV-associated neural dysfunction.
The proposed studies are designed to test the therapeutic efficacy of the novel neurotrophin ligand, LM11A-31, in an in vivo infectious animal model of HIV-associated neurological disease. The infection paradigm and tests of disease progression have been developed to evaluate effects of the compound on viral burden, pathogenesis and cognitive decline with an emphasis on issues of importance for translation to humans. These complementary endpoints will provide valid and sensitive indices for the evaluation of both efficacy and safety and will provide needed data to progress to studies in HIV-infected patients.