704 Innate and Adaptive Immune Responses in Murine Model of HIV-1 Encephaltis: Regulation of Viral Infection and Neurodegeneration L. Poluektova*, J. Faraci, K. Birusingh, S. Gorantla, H. Gendelman Univ of Nebraska Med Ctr, Omaha
Background: The relative roles of the innate and adaptive immune responses to affect neural injury during HIV encephalitis (HIVE) have not been resolved. In attempts to address the complex issues of immune regulation of viral replication and neurodegeneration in HIVE, we reconstituted NOD/SCID mice with human peripheral blood lymphocytes (PBL) then induced a focal encephalitis by intracranial injection of HIV-1ADA-infected human monocyte-derived macrophages (MDM).
Methods: Leukocytes from healthy donors were used in 6 independent experiments. Human PBL were placed intra-peritoneally and a wk later MDM (infected or uninfected) were injected stereotactically into the basal ganglia. Mice were sacrificed on days 7, 14, 21, and 26. Brains were prepared for immunohistochemistry, quantitative immunoblots, and real time PCR (viral load, expression of mouse and human cytokines [TNF, IL-1, IL-4, IL-6, IL-10], and neurotrophic factors [BDNF, NT-3]). Evaluation of glial (microglial and astrocyte) activation, neuronal damage (MAP-2, neurofilament, and NeuN expression) was done by computer-based quantitation of immunostained areas on the affected and contralateral hemisphere. CTL responses were assessed by tetramer staining, egress of granzyme B/CD8 lymphocytes, and IFNgamma ELISpot.
Results: HIV-1-infected MDM triggered lymphocyte brain migration, the generation of CTL, attraction of immunoglobulin producing B-cells and elimination of infected MDM at days 14-26 in 80% of reconstituted animals. Severe neuronal damage was associated with a 3-5 fold increase in glial activation in areas where infected MDM and PBL were found when compared to non-reconstituted animals. However, increased MAP-2 and NeuN antigens and restoration of neuronal morphology occurred in all animal groups (from days 14-26) despite high levels of glial activation in the reconstituted mice. This coincided with increased BDNF expression and proliferation of murine neural cells.
Conclusions: Adaptive immune responses to HIV-1 in brain contribute to multifaceted pathways for viral control, neurodegeneration, and repair during HIVE.
