INSERTIONS, DUPLICATIONS AND SUBSTITUTIONS IN RESTRICTED GP90 REGIONSOF EQUINE INFECTIOUS-ANEMIA VIRUS DURING FEBRILE EPISODES IN AN EXPERIMENTALLY INFECTED HORSE

We have studied a horse which exhibited typical clinical signs of dise ase when experimentally infected with a non-adapted virulent strain of equine infectious anaemia virus (EIAV), designated V70. Five viruses (F1V, F2V, F3V, F4V and F5V) were recovered during periodic febrile ep isodes, Cross-neutralization tests revealed that all of these variants and the parental V70 were antigenically distinct, Sequencing of their full-length env gp90 genes and gp45 5' sequences revealed novel mutat ions at a limited number of nucleotide positions, consisting of insert ions and duplications in the gp90 principal neutralizing domain (PND) in F1V, F3V and F5V, Parts or all of small units (6, 9 and 12 nucleoti des) located just before the insertion site were used for the duplicat ions, Furthermore, amino acid substitutions in the env PND and hyperva riable region were also observed in all five viruses, These mutations may contribute to the generation of serial variants. Consequently, the full-length gp90 sequences showed close relationships between V70, F2 V and F4V, and between F1V, F3V and F5V. In addition to the two domain s (PND and hypervariable region), a comparison of these viruses with t he reported env gp90 sequences revealed four additional variable domai ns, although these four domains were highly conserved among the five v ariants.