This Competing Continuation Application, focusing on the developing, neonatal, central nervous system (CNS), seeks to determine the molecular basis of AIDS encephalopathy. We hypothesize that soluble HIV proteins indirectly cause neuropathology by activating local expression of certain cytokines that, in turn, are the actual mediators of neurotoxicity. While our original grant was solely an in vitro project that extrapolated the effects of HIV peptides on the immune system to the CNS, the current proposal takes a direct approach and examines both in vivo and in vitro models of HIV neurotoxicity. Our in vivo model consists of the stereotaxic injection of HIV peptides +/- the excitatory amino acid agonist, N-methyl- D-aspartate (NMDA) into rat brains. We reported that a recombinant HIV fusion protein, env-gag, containing sequences from gp4l and p24, when injected into the striatum of neonatal rats acts synergistically with NMDA to produce neuropathology similar to that seen in infants with AIDS encephalopathy. By means of a powerful new method employing reverse transcriptase and the polymerase chain reaction (RT-PCR) in situ in the brain, we shall look for the ability of HIV proteins +/- NMDA to induce the expression of genes for the NMDA receptor, cytokines associated with neurotoxicity, and markers of programmed cell death or apoptosis. In the present proposal we shall compare and contrast these effects in both neonatal and adult animals. Our in vitro model examines the induction of cytokine genes and apoptosis in human peripheral blood mononuclear cells by HIV peptides. Subjects will be stratified on the basis of neonates versus adults and on HIV status. These studies with human immunocytes now will be applied to CNS cells, using primary cultures of rat astrocytes and microglia as an in vitro, animal, model of AIDS encephalopathy. The current project extends our initial observations and examines whether specific HIV proteins can induce cytokine gene expression and apoptosis in cells of both the immune system and the CNS. We shall determine whether it is the HIV proteins themselves or secondary mediators (e.g. cytokines) that are the actual inducers of apoptosis. Our previous data suggest the latter. Thus we propose a logical progression from our original studies correlating interactions between soluble HIV gene products and the immune system and the neonatal CNS to a direct investigation of the molecular mechanisms of HIV induced neuropathology. These latest studies will also include adult samples to determine if the mechanisms of HIV induced neuropathology are similar at both ends of the age spectrum. Based on our preliminary work it appears that significant differences exist at different ages. We propose that certain HIV proteins induce cytokines that then activate apoptosis in cells of both the immune system and the CNS. Our project may lead to an understanding of the fundamental mechanisms underlying the interactions between the immune system and the CNS and perhaps yield new therapies for AIDS encephalopathy, a serious complication of HIV infections in infants and adults.
Showing the most recent 10 out of 23 publications
