A rapid label-free method for quantitation of human immunodeficiency virus type-1 particles by nanospectroscopy

Infection of cells with human immunodeficiency virus type-1 (HIV-1) results in the production of both infectious and non-infectious virions. At present, several assays are available for the quantitation of virus particles based on the presence of either viral capsid protein or nucleic acid. However, the ability to detect the total number of virus particles, both infectious and non-infectious, has been an elusive goal that would advance the study of virus assembly and egress. A rapid optical detection scheme for real-time label-free quantitation of HIV-1 virus particles was developed. Virions produced in cell cultures transfected transiently were evaluated with a nanospectroscopic assay. Quantitation with the optical detection scheme correlated with routine conventional assays. Nanospectroscopy can be used for the detection of both infectious and non-infectious, wild type and mutant strains of HIV-1 in solution at concentrations as low as 7×10(10)particles/ml, requiring volumes as small as 2 microl per assay, and in significantly less time than standard techniques. This assay provides a rapid, reliable system for quantifying virus particles in solution and could be applied to the study of viral particle production in cell culture.