Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)

First Advisor

Ding Shih


Equine infectious anemia virus (EIAV) is the causative agent of a persistent disease in horses. The long terminal repeat (LTR) region of EIAV contains the enhancer and promoter elements necessary for transcription of the proviral genome. The LTR is also prone to a high degree of sequence variability between different virus isolates. Sequence alignments of LTR variants from both tissue culture-adapted strains of the virus as well as sequential horse isolates showed a high degree of sequence variability between variants. Sequence variability was further localized to a hypervariable region approximately 60 bp upstream of the TATA box. This region contained insertions resulting in the duplication of flanking sequences and the putative cis-elements they contain. Transient gene expression analysis of the LTR variants in three different cell lines showed that the promoter activities of the LTR variants were different and that these differences were cell line dependent. Further analysis using deletion mutants indicated that the hypervariable and flanking regions contained several cis-elements important for promoter activity and that duplication of these elements increased activity under basal conditions. Analysis of infected horse tissue DNA using competitive PCR analysis did not indicate a high degree of sequence divergence localized to the LTR. Therefore, LTR heterogeneity may not be required for the onset of acute disease. To assess the impact of LTR variability on viral replication kinetics and cytopathogenicity, an infectious EIAV molecular clone was created in which the cognate LTR region was replaced with the corresponding region of a virus stock which demonstrates accelerated cytopathogenic effects. The study showed that the LTR increased replication capacity but did not influence cytopathogenicity.