FIG. 6.

NA-chIL-2 is incorporated into H1N1 influenza virions. (A) WSN virus harvested from NA-chIL-bearing MDCK or control MDCK was purified by sedimentation through a 14% Optiprep cushion and subjected to heat treatments at 56^°C. Infectivity assays on MDCK cells determined that both heat treatments destroyed viral infectivity. Inactivated virus (300 HAU) was added to cultures of T-cell blasts and uptake of ³H-thymidine was measured. Samples were run in quadruplicate and soluble recombinant IL-2 at 2 × 10⁻⁷ mM served as a positive control. (B) Rabbit antichIL-2 was added to WSN virus preparations an hour prior to addition to T blast cultures and completely neutralized virus-induced ³H-thymidine uptake.