A mutant of fowl plague virus (influenza A) with an enhanced electrophoretic mobility of RNA segment 8.

A temperature-sensitive mutant (ts 1/9) obtained by undiluted passage of fowl plague virus (FPV) at 33 degrees C carried a strong ts defect in RNA segment 6 [neuraminidase (NA) gene] and a weak ts defect in RNA segment 8 [non-structural (NS) protein Although the viral proteins have normal migration rates, the NS gene migrated during polyacrylamide gel electrophoresis (PAGE) significantly faster than the NS gene of wild-type FPV, even after denaturation by glyoxal. Despite this observation, the NS gene of ts 1/9 did not carry a deletion as shown by sequence determination. There were only five base replacements which resulted in three changes in amino acids. Three of the base replacements led to a more compact secondary structure of RNA segment 8, which seems to be responsible for the faster migration rate during PAGE and which seems to resist, at least partially, the treatment with glyoxal.