Figure 3.

GM-CSF mobilizes CD11b⁺ cells into tumorsin vivoleading to enhanced reovirus delivery to tumors. (a) C57Bl/6 mice were vaccinated i.p. with reovirus (2 × 10⁷ TCID₅₀). After 14 days, mice were seeded with s.c. B16 tumors. Mice bearing 10-day established s.c. B16 tumors were given three daily injections of PBS or GM-CSF; after 48 hours, tumors were harvested, dissociated, and analyzed for CD45⁺/CD11b⁺ infiltrating cells by FACS. Reovirus-vaccinated, tumor-bearing mice as in a were given three daily injections of PBS or GM-CSF followed by two daily injections of PBS or reovirus i.v. After 72 hours, tumors (b) were harvested and reovirus titer determined. The third PBS/Reo-treated mouse had no detectable virus in the explanted tumor, which may have been due to technical reasons with virus injection and/or the low levels of virus which reached the tumor in this animal in the absence of GM-CSF conditioning. FACS, fluorescence-activated cell sorting.