Astrocytes are a significant CNS reservoir of proviral
HIV-1 DNA and contribute to the pathogenesis of HIV-associated dementia
M. Churchill1,2, P.R. Gorry1,2,3, D. Cowley1, L. Gray1, C. Pardo4, J. McArthur4, B.J. Brew5, S.L. Wesselingh1,2
1Burnet Institute, Centre for Virology, Melbourne, Australia, 2Monash University, Department of Medicine, Melbourne, Australia, 3University of Melbourne, Department of Microbiology and Immunology, Melbourne, Australia, 4Johns Hopkins University School of Medicine, Department of Neurology, Baltimore, United States, 5St. Vincent's Hospital, Department of Neurology and St. Vincent's Centre for Applied Medical Research, Darlinghurst, Australia
Background: HIV-1 penetrates the central nervous system (CNS) frequently
causing encephalitis (HIVE), HIV-associated dementia (HAD) or less severe
neurocognitive impairment. The CNS is also a significant HIV-1 reservoir.
Astrocytes are latently-infected resulting in astrocyte dysfunction. Because
astrocyte infection is considered rare, estimated at 1-3% by early studies[1-3],
astrocytes are thought to be a minor HIV-1 reservoir with a secondary role in
the pathogenesis of HAD. In this study, we re-evaluated the magnitude of
astrocyte infection in vivo and potential role for HIV-1-infected astrocytes HAD
Methods: Autopsied brains of 12 HIV-1+ cases who died with- (n=10) or
without HAD (n=2) were studied. HAD cases consisted of subjects without HIVE
(n=2), with mild (n=1), moderate (n=4) or severe HIVE (n=3). GFAP+ astrocytes
and CD68+ macrophage-lineage cells were identified by immunohistochemistry and
nuclei isolated using Laser-capture microdissection. Integrated HIV-1 DNA was
detected by nested Alu-PCR. Astrocyte infection frequency was determined by multiplexed PCR on
single nuclei to amplify the HIV-1 V3 Env region and cellular GAPDH.
Results: The results of Alu-PCR amplifications confirmed that astrocytes of 5 cases
with severe or moderate HIVE harbored integrated HIV-1 DNA. Single-cell astrocyte
amplifications from all 12 cases showed that astrocyte infection frequency is
extensive, occurring in up to 19% of GFAP+ cells. Astrocyte infection frequency
correlated with severity of HIVE and proximity to macrophages in vivo.
Conclusions: Astrocytes are extensively infected with HIV-1 in subjects
with HAD and harbor integrated proviral DNA. Since astrocytes are terminally
differentiated and essential for brain function, they are an extensive and
permanent reservoir of HIV-1 DNA that complicates virus eradication strategies.
In addition, our results suggest HIV-1-infected astrocytes contribute to the
pathogenesis of HAD.
1. Bagasra et al., AIDS 10:573-585, 1996.
2. Takahashi et al., Ann. Neurol. 39:705-711, 1996.
3. Brack-Werner., AIDS 13:1-22, 1999.
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