Infection of microglia by HIV-1 labeled via packaging of fluorescent mRNA probes. HIV-1 packaged with the fluorescently-labeled Tat mRNA probe (red), or no probe, were used to infect primary human microglia in culture, followed by cell fixing and confocal imaging. Representative cells are shown. DAPI (blue) staining indicates cell nuclei. DIC (differential interference contrast) images show cell shape. To demonstrate that the fluorescent signals were located inside cells, three continuous images of a Z-stack series for a single infected cell are presented. Scale bar = 5 μm. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)