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Session 18 Oral Abstract Presentations Viral Neuropathogenesis Session Day and Time: Wednesday 10 am - 12:30 pm Presentation Time: 12:15 Room: Ballroom C

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Vacuolar Myelopathy In Transgenic Mice Expressing HIV-1 Nef in Oligodendrocytes With Alteration of Oligodendrocyte Phenotype In Vitro
D. G. Kay*¹, F. Radja¹, S. Albrecht², P. Jolicoeur^1,3,4
1Clin Res Inst of Montréal, Canada; ²Jewish Gen Hosp, Montréal, Canada; ³McGill Univ Hlth Ctr, Montréal, Canada; and ⁴Univ de Montréal, Canada

Background: We previously reported that Transgenic (Tg) mice expressing the entire HIV-1 genome, under the control of the myelin basic protein promoter (MBP/HIV^Wt), developed a vacuolar myelopathy (VM), closely resembling the human disease.
Methods: Generation of Tg mice, Southern, Northern and Western blotting, cell culture, in situ hybridization and immunocytochemistry.
Results: Here we report that the expression of Nef alone (MBP/HIV^Nef) causes a VM in Tg mice, which is histologically indistinguishable from that observed in the MBP/HIV^Wt mice. Transgene RNA and protein expression was restricted to cells exhibiting an oligodendrocyte-like morphology. Surprisingly, few of the transgene expressing cells co-expressed the oligodendrocyte specific marker CNPase, suggesting an altered state of differentiation of Tg oligodendrocytes. Additionally, some cells in spinal cord white matter tracts contained elevated levels of phosphotyrosine. In vitro, we observed more complex networks of cell processes in oligodendrocyte-enriched primary cultures derived from Tg relative to non-Tg mice, suggesting a more mature morphology for Tg oligodendrocytes. IHC to detect the galactolipids galactocerebroside and sulphatide indicated a substantially decreased intensity of immunostaining in Tg oligodendrocytes, whereas the percentage of anti-lipid immunostained cells did not differ statistically between Tg and non-Tg oligodendrocyte cultures. IHC to detect the proteins CNPase and MBP demonstrated a statistically significant decrease in the percentage of immunostained cells in the Tg derived cultures, while the intensity of the immunostaining was unchanged, relative to non-Tg oligodendrocytes. Interestingly, these changes in morphology and immunophenotype were observed even in a founder line expressing very low levels of Nef. The morphologically more mature appearance of Tg oligodendrocytes is discordant with the less mature biochemical phenotype.
Conclusions: Thus, Nef expression alone in oligodendrocytes leads to a dysregulation of their state of differentiation, affects signal transduction, and is sufficient to elicit VM in mice. (FR and DGK contributed equally to this work.)

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