Course and extent of variation of equine infectious anemia virus during parallel persistent infections

Abstract

Comparisons of peptide and oligonucleotide maps of glycoproteins and RNA from nine isolates of equine infectious anemia virus (EIAV) that were generated during parallel infections of two Shetland ponies revealed that each isolate was structurally unique. Each EIAV isolate contained a unique subset of variant peptides, oligonucleotides, or both, indicating that structural variation in EIAV is a random and noncumulative process and that a large spectrum of possible EIAV variants can be generated in infected animals.

Genomic quasispecies associated with the initiation of infection and disease in ponies experimentally infected with equine infectious anemia virus

“…3]). These results are not surprising since differences in the tryptic glycopeptide maps among various EIAV isolates have been noted previously (33,38), and sequence analysis of EIAV and other lentiviruses has yielded similar changes in potential N-glycosylation sites (4,5,22,28,30). The addition of a potential N-glycosylation site within the PND of EIAV PV could account, in part, for its altered neutralization properties as described previously (37).…”

“…Sequence diversity in the env gene of the EIAV PV stock was low and was only slightly higher in the ponies infected with EIAV PV . While the former result is likely due to the fact that EIAV PV is a biological clone (37), the latter finding was somewhat surprising since previous studies have demonstrated rapid variations in the antigenic (14,33,38) and pathogenic (27) properties of EIAV during persistent infections in Shetland ponies. In fact, the predominant virus isolates from successive disease episodes separated by as few as 14 days have been shown to contain different gp90 and gp45 peptide maps (27,33).…”

“…It has been demonstrated that serum from an EIAVinfected animal can neutralize virus isolates recovered from prior but not subsequent disease episodes and that each disease episode is associated with a novel predominant antigenic variant (16,25). Biochemical (25,33,36,38) and immunological (14,32) studies of the predominant virus isolate recovered during disease episodes indicate that the two glycoproteins, gp90 (SU protein) and gp45 (TM protein), vary extensively. In addition, the predominant viruses isolated from sequential febrile episodes in a single pony were shown to be different at the genetic level by RNase mapping experiments (29,33) and by sequence analysis of the envelope (env) gene (30).…”

“…Biochemical (25,33,36,38) and immunological (14,32) studies of the predominant virus isolate recovered during disease episodes indicate that the two glycoproteins, gp90 (SU protein) and gp45 (TM protein), vary extensively. In addition, the predominant viruses isolated from sequential febrile episodes in a single pony were shown to be different at the genetic level by RNase mapping experiments (29,33) and by sequence analysis of the envelope (env) gene (30). Sequence analysis showed that much of the genetic variation in gp90 was clustered in a single area termed the variable region (30).…”

“…Experiments in which an attenuated strain of EIAV was serially passaged in Shetland ponies resulted in a rapid evolution in the pathogenic properties of the virus (27). Furthermore, when antigenic variation in gp90 and gp45 was probed by immunoreactivity to monoclonal antibodies (14) or by peptide mapping (33,38), it took as few as 14 to 28 days for variation to be seen in sequential disease episodes from a single animal. Finally, sequence analysis early after infection of a horse with the Wyoming strain of EIAV showed that portions of the env gene exhibited significant heterogeneity during the first disease episode (1).…”