This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. BACKGROUND AND PURPOSE: In vivo 1H MR spectroscopy (MRS) demonstrates elevation in Cho/Cr and MI/Cr) in many neurological diseases, which has been ascribed to gliosis. Using a nonhuman primate model of neuroAIDS, we tested the hypotheses that in vivo levels of Cho/Cr and/or MI/Cr correlate with GFAP immunostaining, and that water soluble metabolites account for in vivo changes in Cho/Cr and MI/Cr. METHODS: Post mortem evaluations by 1H MRS and GFAP immunohistochemistry of brains from 7 acutely infected SIV rhesus macaques and 4 control macaques were performed, and compared to a previously reported in vivo MRS study. Changes in neuropathological and MRS markers after infection, and relationships between plasma viral load, GFAP immunostaining, ex vivo, and in vivo MRS measures were statistically evaluated. RESULTS: GFAP immunostaining and in vivo MRS Cho/Cr and MI/Cr attained their highest levels near the time of peak plasma viral loads at 11 days post infection (dpi). Subsequently, GFAP immunostaining returned to baseline by 14 dpi, while Cho/Cr and MI/Cr had different time courses with the former dropping below baseline and the latter remaining elevated. A significant correlation was found between viral load and GFAP immunostaining. No correlation was found between ex vivo Cho/Cr and MI/Cr and viral load, or between in vivo and ex vivo MRS metabolite ratios. CONCLUSIONS: In acute SIV infection, plasma viral load significantly correlates with brain GFAP immunostaining and in vivo 1H MRS Cho/Cr. In vivo changes in Cho/Cr and MI/Cr are principally due to contributions other than low molecular weight, water soluble metabolites.
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