RAC1 and encephalitis: However, we do not believe that these tissue damages could have impacted our results on cells expressing activated Rac1, because analysis of brain tissues from HIV seronegative controls, HIV+ cases without encephalitis, and HIVE patients showed that activated Rac1 (S71) were mostly expressed in brain macrophages and blood vessels, and none of the sample analyzed showed expression of phosphorylated Rac1 (S71) in neurons or astrocytes.