Surface envelope glycoprotein is B-lymphocyte immunodominant in sheep naturally infected with ovine progressive pneumonia virus

The B-lymphocyte-immunodominant antigen involved in naturally ovine progressive pneumonia virus (OPPV)-infected mature sheep remains unknown. Therefore, the amount of antibody in sera from 10 naturally OPPV-infected sheep was evaluated by immunoprecipitation (IP) of the major viral proteins in [S-35] methionine/cysteine-labeled OPPV (whole virus) lysate. Using an excess of OPPV proteins in whole-virus lysate, 8 out of 10 sheep had the highest serum antibody IP endpoint titers to the gp135 surface envelope glycoprotein (SU). Also, 2 out of 10 sheep had equivalent serum antibody IP endpoint titers to the transmembrane glycoprotein oligomer (TM90) and SU. Since these data indicate that SU is the immunodominant protein in most mature sheep persistently infected with OPPV, SU-specific diagnostic serological assays can be utilized for OPPV diagnosis.