Macrophage chemoattractant protein-1 (MCP-1) may be a key trigger for the i
nflux of macrophages into the brain in human immunodeficiency virus (HIV) e
ncephalitis. In this study, simian immunodeficiency virus-infected macaques
that developed moderate-to-severe encephalitis had significantly higher MC
P-1 levels in cerebrospinal fluid (CSF) than in plasma as early as 28 days
after inoculation, which was before the development of brain lesions. In co
ntrast, CSF:plasma MCP-1 ratios remained constant at preinoculation levels
in macaques that developed minimal or no encephalitis. Abundant MCP-1 prote
in and mRNA were detected in both macrophages and astrocytes in the brain.
Macaques with increased MCP-1 in CSF had significantly greater expression o
f markers of macrophage and microglia activation and infiltration (CD68; P
= .003) and astrocyte activation (glial fibrillary acidic protein; P = .019
and P = .031 and in white and gray matter, respectively). The results sugg
est that the CSF:plasma MCP-1 ratio may be a valuable prognostic marker for
the development of HIV-induced central nervous system disease.