GFAP and Gliosis: In simian immunodeficiency virus (SIV), Cr correlated neither with the astrocyte marker glial fibrillary acidic protein (GFAP) nor with the microglial marker ionized calcium binding adaptor molecule 1 (although Cr did correlate modestly with gliosis and NAA/Cr did correlate negatively with inflammatory elements such as perivascular histiocytic infiltrates, multinucleated giant cells, and CD14 + CD16+ monocytes in the brain).