The goal of this proposal is to develop and validate a diagnostic assay for the quantitation of Human Immunodeficiency Virus (HIV)-infected cells using peripheral blood specimens and a highly automated digital microscopy system. (ACISTM, ChromaVision Medical Systems) with unique capability for the detection and enumeration of rare cellular populations. Current methods for assessing plasma HIV viral load are indirect (i.e. not directed toward the site of viral application), expensive, and technically demanding. Studies focusing on chronically infected individuals have further shown that a reservoir of infected cells persist even when virus cannot be detected in plasma following highly active anti-retroviral therapy (HAART). We propose here to develop and optimize a large automated cell-based assay using immunocytochemical (anti-p24) staining and ACIS-assisted digital microscopy. Initial studies will utilize a p24+ cell model system. Following independent validation by PCR and PACS, a two-parameter assay for CD4-and p24-positive cells will be devised.. We anticipate that this novel assay will enable more effective monitoring and clinical management of HIV infected persons. Satisfactory completion of this phase I proposal will lay the foundation of a multi-center clinical trial designed to facilitate FDA approval for this assay, and ultimately its commercialization in the diagnostic laboratory setting. PROPOSED COMMERCIAL APPLICATIONS: A commercially viable test for cellular HIV load is the goal of this project. This assay would be used to more effectively evaluate the total cellular viral reservoir in HIV-infected persons. The potential clinical marker for such a test is large and could bring considerable long-term economic benefit to the company, and would be of great benefit to the HIV-infected patient.