Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Four isolates of equine infectious anemia virus (EIAV) recovered weeks apart from a single experimentally infected Shetland pony (Orrego, 1983) were examined in both antigenic and structural analyses to investigate variation occurring during persistent infection. These four isolates were shown to be antigenically distinct in both serum neutralization assays and in immunoblot analysis with either a polyclonal equine reference antiserum or a panel of virus-specific monoclonal antibodies. Two-dimensional mapping of tryptic peptides of viral components from these isolates revealed that both gp90 and gp45 undergo structural variation during virus replication in a single animal, but that no such structural variation occurs in the internal proteins p26, p15, or p9. A panel of nine EIAV isolates recovered from two Shetland ponies infected in parallel with the same EIAV inoculum were examined by the same antigenic and structural analyses to investigate the extent of variation possible. No pattern of evolution of variation was evident by comparison of the nine isolates from the two parallel infections, indicating that a relatively large number of distinct EIAV variants may be possible. Hydropathic character and general conformation of the gp90 and gp45 polypeptides were accomplished by computer analysis of the amino acid sequence of the envelope polyprotein, as predicted from the nucleic acid sequence of the proviral env gene (Rushlow et al., 1986). The results predict that gp90 is a relatively hydrophilic, globular protein with 13 potential glycosylation sites evenly distributed throughout the molecule. The gp45 polypeptide is relatively hydrophobic with four of five possible glycosylation sites localized to the N-terminal region, and contains four possible transmembrane regions. It appears from the conformational analysis that an extensive region of (beta)-sheet may exist at the C-terminus of gp90 and the N-terminus of gp45, thus forming an area of interchain hydrogen bonding responsible for the close association of these two molecules in the mature virion. By combining all predicted structural features, it was possible to construct a model of the gp90/gp45 complex. This model may serve as a reference for the production of effective vaccination protocols against this economically important virus. (Abstract shortened with permission of author.).