The Tissue Analysis Core (TAC) within the AIDS and Cancer Virus Program will process, embed, and perform microtomy on fixed tissue samples presented in ethanol. CD4 (DAB) and CD68/CD163 (FastRed) double immunohistochemistry will be performed, allowing for the specific identification of both CD4+ T cell and myeloid/macrophage populations (a component of a TAC approved and available TSA service). A high-resolution digital image of each stained sample will be generated using the Aperio ScanScope CS System. Under the guidance of a subject matter expert, the TAC will annotate tissue regions of interest and specific cell populations (i.e., CD4+ T cells or CD68+/CD163+ macrophages) to highlight the specific anatomical tissue compartments and specify the cell populations to be captured by laser capture microdissection (LCM). LCM will be performed on an ArcturusXT Laser Capture Microdissection System. Up to 3,000 individual CD4+ T cells or macrophages will be captured, treated using the Arcturus PicoPure DNA Extraction kit, and quantitative PCR performed for HIV/SIV vDNA (Gag) and the cellular gene CCR5 for cell equivalent enumeration (modification of an Quantitative Molecular Diagnostic Core-approved TSA). The fraction of captured CD4+ T cells or macrophages harboring HIV/SIV vDNA will be calculated, relevant data will be provided electronically, and a report with interpretation/conclusions will be supplied. Sufficient basic consultation with a subject matter expert is included with the service.