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173 Generation of Cytotoxic T-Cell Responses against HIV-1-Infected Brain Macrophages
L. Poluektova*, Y. Persidsky, and H. Gendelman
Univ. of Nebraska Med. Ctr., Omaha, USA
Background: We investigated whether HIV-1-infected brain macrophages generate de novo cytotoxic T-cell responses resulting in the selective destruction of virus-infected cells in the CNS. Such T-cell responses are necessary for the development of an effective vaccine against HIV-1.
Methods: HIV-1 encephalitis (HIVE) was created in NOD/SCID mice by stereotactic injection of virus-infected (HIV-1ADA) human monocyte-derived macrophages (MDM) into the caudate and putamen; areas most damaged in human disease. Syngeneic peripheral blood lymphocytes (PBL) from HLA-A2-positive donors served to reconstitute the murine immune system generating NOD/SCID (HIVE/hu-PBL) mice (n = 13). Control mice received HIV-1-infected MDM without reconstitution (n = 12). Animals were sacrificed at days 7, 14, and 21 for pathological and immune studies. Levels of specific anti-viral CTL responses were determined by tetramer staining and FACS of splenocytes and PHA/IL-2-activated human PBL (lymphoblasts).
Results: HIV-1-specific human CTLs were detected by FACS in spleen tissue reconstituted by human cells. Splenocyte expansion studies performed at days 7, 14, and 21 of HIVE/hu-PBL mouse sacrifice showed 1.04 ± 0.32%, 3.91 ± 0.70%, and 1.24 ± 0.27% of HIV-1gag and 0.39 ± 0.17%, 1.45 ± 0.29%, and 1.08 ± 0.58% of HIV-1pol-specific CD8+ cells, respectively. HIVE/hu-PBL mice showed serum HIV-1 p24 antigens with marked reductions in the numbers of CD4+ T cells at day 21. Immunohistochemistry showed CD8, granzyme B, and CD45R0 antigen-reactive T cells in areas with human HIV-1-infected MDM. Productively infected MDM were either eliminated or reduced significantly (>85%) in HIVE/hu-PBL mice as compared with HIVE controls. Numbers of NK, CD8+, and HIV-1-specific CTL inversely correlated with numbers of brain macrophages. Elimination of CD4+ cells was accompanied by a decline of HIV-1gag and HIV-1pol-specific CD8+ cells and marked reduction of lymphocyte migration to affected brain tissue.
Conclusions: HIV-1-infected brain macrophages serve as a powerful antigen-presenting cell for generation of anti-viral cellular immune responses. This HIVE/hu-PBL model should be valuable to study acquired immune responses against HIV-1 in the CNS.
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