Immunoblot analysis of the antibody response to ovine lentivirus infections.

The antibody response of sheep to maedi-visna virus (MVV) infection was studied, using an immunoblotting technique that identified the four major viral structural proteins: the envelope glycoprotein gp135, and internal proteins p25, p16 and p14. In sequential serum samples of two inoculated sheep, antibodies to p25 appeared first, soon followed by antibodies to p16. In two sheep with natural infections, which were sampled with longer intervals, antibodies to p25 and p16 appeared simultaneously. Antibody response to p14, which was weak and inconsistent in most cases, appeared after the p16 response. Antibodies to gp135 were detected in only one sheep and appeared 7 weeks after those to p25. Antibodies to p25 were particularly persistent. Antibody recognition patterns of 21 necropsied sheep with naturally occurring infections were compared. Sheep with lesions lacked antibodies to p14 and p16 and sometimes even p25, although these antibodies had been present in earlier stages of infection. Since the time of onset of lesions was unknown, we could not determine whether this decline in antibody activity occurred before, together with, or after the onset of lesion development.