Coordinated regulation of SIV replication and immune responses in the CNS.
Central nervous system (CNS) invasion during acute-stage HIV-infection has been demonstrated in a small number of individuals, but there is no evidence of neurological impairment at this stage and virus infection in brain appears to be controlled until late-stage disease. Using our reproducible SIV macaque model to examine the earliest stages of infection in the CNS, we identified immune responses that differentially regulate inflammation and virus replication in the brain compared to the peripheral blood and lymphoid tissues. SIV replication in brain macrophages and in brain of SIV-infected macaques was detected at 4 days post-inoculation (p.i.). This was accompanied by upregulation of innate immune responses, including IFNbeta, IFNbeta-induced gene MxA mRNA, and TNFalpha. Additionally, IL-10, the chemokine CCL2, and activation markers in macrophages, endothelial cells, and astrocytes were all increased in the brain at four days p.i. We observed synchronous control of virus replication, cytokine mRNA levels and inflammatory markers (MHC Class II, CD68 and GFAP) by 14 days p.i.; however, control failure was followed by development of CNS lesions in the brain. SIV infection was accompanied by induction of the dominant-negative isoform of C/EBPbeta, which regulates SIV, CCL2, and IL6 transcription, as well as inflammatory responses in macrophages and astrocytes. This synchronous response in the CNS is in part due to the effect of the C/EBPbeta on virus replication and cytokine expression in macrophage-lineage cells in contrast to CD4+ lymphocytes in peripheral blood and lymphoid tissues. Thus, we have identified a crucial period in the brain when virus replication and inflammation are controlled. As in HIV-infected individuals, though, this control is not sustained in the brain. Our results suggest that intervention with antiretroviral drugs or anti-inflammatory therapeutics with CNS penetration would sustain early control. These studies further suggest that interventions should target HIV-infected individuals with increased CCL2 levels or HIV RNA in the CNS.
Witwer
Kenneth W
KW
Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
Gama
Lucio
L
Li
Ming
M
Bartizal
Christopher M
CM
Queen
Suzanne E
SE
Varrone
John J
JJ
Brice
Angela K
AK
Graham
David R
DR
Tarwater
Patrick M
PM
Mankowski
Joseph L
JL
Zink
M Christine
MC
Clements
Janice E
JE
D000208:Acute Disease; D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D001921:Brain / Q000276:immunology / Q000821:virology; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism; D002490:Central Nervous System / Q000276:immunology* / Q000473:pathology / Q000821:virology*; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism; D005786:Gene Expression Regulation; D007109:Immunity / Q000276:immunology*; D007113:Immunity, Innate / Q000235:genetics; D007249:Inflammation / Q000378:metabolism; D008251:Macaca / Q000276:immunology* / Q000821:virology*; D008264:Macrophages / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012367:RNA, Viral / Q000097:blood; D016097:Simian Acquired Immunodeficiency Syndrome / Q000097:blood / Q000276:immunology / Q000821:virology; D015302:Simian Immunodeficiency Virus / Q000502:physiology*; D013997:Time Factors; D014771:Virion / Q000378:metabolism; D014779:Virus Replication / Q000502:physiology*
D022782:CCAAT-Enhancer-Binding Protein-beta; D016207:Cytokines; D012333:RNA, Messenger; D012367:RNA, Viral