FIG. 5.

Western blot analysis of highly purified influenza virus confirms incorporation of membrane-bound NA-chIL-2 into virions. (A) Gradient-purified influenza A/Udorn/72 propagated in MDCK/NA-chIL-2 (AIVAC-chIL-2) or MDCK/Vec (AIVAC) cells was subjected to SDS-12% PAGE and subsequent transfer to PDVF membrane. Blots were incubated with monoclonal anti-chIL-2 (clone G) and goat antineuraminidase antisera (anti-N2), followed by incubation with HRP-conjugated secondary antibodies. Protein bands were visualized by chemiluminescence. ChIL-2 was detectable in as little as 3.4 μg of total viral protein. (B) To quantitate the levels of virion incorporated NA-chIL-2, a standard curve was derived from a Western blot of purified recombinant Thioredoxin-chIL-2 and mean density of NA-chIL-2 in virions was extrapolated to yield 2 ng chIL-2/μg of total viral protein.