Background: Most methods for cellular analysis require labeling with specific antibodies or dyes and are often destructive. We have developed a technology called Optophoresis™, which measures cell physiology based on the cell's motion in a near-infrared optical gradient. This technique does not require labels, is nondestructive, and involves minimal sample processing. Methods: We have used Optophoresis to interrogate nonproductive and productive adenovirus-infected cell lines. Using an adenoviral vector containing green fluorescent protein (GFP) as a secondary assay, we show that viral infection can be monitored with Optophoresis. Results: In HeLa cells, adenovirus infection after 24 h caused a 12% to 17% increase in optophoretic motility of the cells. In 293 cells, adenovirus infection resulted in a

A novel membrane-bound form of GM-CSF (mbGM-CSF) was expressed on the surface of the mouse mastocytoma cell line P815 to target tumor cell-associated Ags to epidermal Langerhans cells. Transfected clones stimulated the proliferation of syngeneic bone marrow cells, indicating that mbGM-CSF is biologically active. We evaluated the in vivo effects of mbGM-CSF by comparing the growth of mbGM-CSF cells (termed 1D6.1E5) to that of wild-type P815 cells in DBA/2 mice. The growth rates of tumors initiated by P815 and 1D6.1E5 were similar until day 12, after which P815 tumors grew to large sizes while 1D6.1E5 tumors were rejected. In contrast, the growth of both tumors was unimpeded when injected into nude mice, suggesting that a T cell-dependent antitumor response was induced by 1D6.1E5 in normal mice. Lymphocytes from 1D6.1E5-vaccinated mice were able to kill 51Cr-labeled P815 cells in a dose-dependent fashion that was inhibited by anti-CD8 Abs, suggesting that the antitumor response involved CD8+ CTL. We then tested whether vaccination with these cells would elicit a protective antitumor response by injecting mice with either irradiated 1D6.1E5 or P815 cells and challenging them with nonirradiated P815 cells. 1D6.1E5-treated mice grew small tumors that soon disappeared in all animals. In contrast, the majority of animals receiving the irradiated wild-type tumor vaccine grew large tumors, and 50% died. These data demonstrate that mbGM-CSF expressed on the surface of tumor cells is biologically active and elicits protective antitumor immunity.