Analysis of the long terminal repeat from a cytopathic strain of equine infectious anemia virus.

Sequential passage of the tissue culture-adapted prototype strain of EIAV in fetal donkey dermal (FDD) cell cultures generated a virus stock which exhibits cytopathic effects in FDD cell cultures. In this study, the effects of the long terminal repeat (LTR) region on virus replication and cytopathogenicity were examined. The FDD-adapted virus LTR was found to contain a number of base pair mutations and a large insertion within the U3 region in comparison with the previously characterized LTR, lambda12. Transient gene expression studies showed that basal promoter activity, in FDD cell cultures, of the FDD-adapted virus LTR was more than seven times greater than that of lambda12. Analysis of an infectious EIAV molecular clone in which the LTR region was replaced with the corresponding region of FDD-adapted virus showed that the LTR increased replication capacity but did not influence cytopathogenicity.