FIG. 3.
NA-chIL-2 bioactivity on influenza A/Udorn/72 (H3N2) viral particles is preserved following viral inactivation with UV or heat treatment. Influenza A/Udorn/72 virus harvested from infected MDCK/NA-chIL-2 cells or from vector control MDCK cells was purified by sedimentation through a 14% OptiPrep™ cushion and inactivated by UV treatment for 12 min or heat at 56°C for 20 min. Chicken T blasts were incubated with 30–300 hemagglutinating units (HAU) of inactivated virus for 24 h, the last 6 h in the presence of 3H-thymidine. Proliferation was measured by 3H-thymidine incorporation. Controls included wells with blast cells alone or blast cells with recombinant soluble chIL-2 (2 × 10−7 mM).