Virus and recombinant protein detection in tumor sections. (A) Replicating virus was detected by plaque assay from one to six tumors per group. Data indicate the average viral titer (pfu/g). (B) Representative images of red fluorescence observed in flash-frozen tumor sections. The fluorescence resulted from tandem dimer Tomato red expression during virus infection (200×). (C) Average IL-15 concentration within tumor sections (pg/mg tissue). Error bars represent standard error of the mean. (D) Merged fluorescent images of B16F10 cells infected with MYXV-IL15 24 hpi (100×) or MYXV-Tred 48 hpi (400×).
Notes: Both tandem dimer Tomato red fluorescent protein expression by recombinant MYXVs and fluorescein isothiocyanate-labeled Gr-1+ neutrophils were located in areas of necrosis within the tumors. B16F10 is a murine melanoma cell line.
Abbreviations: dpi, days postinoculation; hpi, hours postinoculation; IL-15, interleukin-15; MYXV, myxoma virus; MYXV-IL15, MYXV coexpressing murine IL-15 and tandem dimer Tomato red fluorescent protein; MYXV-Tred, MYXV expressing tandem dimer Tomato red fluorescent protein; pfu, plaque-forming units.