Antigenic analysis of isolated polypeptides from Visna virus.

The antigenic activity of 10 Visna polypeptides separated by gel filtration in the presence of 6 M guanidine hydrochloride (GuHCl) was examined with rabbit antisera made specific for Visna virus. The results showed that the first (GuHCl 1) and the ninth (GuHCl 9) polypeptide peak reacted with the antisera when examined in immunodiffusion, passive hemagglutination, and complement fixation tests. Whole virus, GuHCl 1, and GuHCl 9, when tested with the antisera, appeared to be immunologically identical in the immunodiffusion test. However, GuHCl 1 reacted weakly with the antisera by all three techniques as compared with GuHCl 9 and whole virus. GuHCl 9, when subjected to polyacrylamide gel electrophoresis containing 0.1% sodium lauryl sulfate, revealed the presence of one polypeptide with a molecular weight of 25,000. By the same method, GuHCl 1 was found to contain an aggregate of four different polypeptides, the major one having a molecular weight of 25,000. The results indicate that the antigenic activity of both GuHCl 1 and GuHCl 9 was associated with a single polypeptide having a molecular weight of 25,000.