Antigenic analysis of equine infectious anemia virus (EIAV) variants by using monoclonal antibodies: epitopes of glycoprotein gp90 of EIAV stimulate neutralizing antibodies

Abstract

Monoclonal antibodies produced against the prototype cell-adapted Wyoming strain of equine infectious anemia virus (EIAV), a lentivirus, were studied for reactivity with the homologous prototype and 16 heterologous isolates. Eighteen hybridomas producing monoclonal antibodies (MAbs) were isolated. Western blot (immunoblot) analyses indicated that 10 were specific for the major envelope glycoprotein (gp9O) and 8 for the transmembrane glycoprotein (gp45). Four MAbs specific to epitopes of gp9O neutralized prototype EIAV infectivity. These neutralizing MAbs apparently reacted with variable regions of the envelope gp9O, as evidenced by their unique reactivity with the panel of isolates, suggesting recognition of at least three different neutralization epitopes. The conformation of these epitopes appears to be continuous, as they resisted treatment with sodium dodecyl sulfate and reducing reagents. Monoclonal antibodies that reacted with conserved epitopes on gp9O or gp45 failed to neutralize EIAV. Our data also demonstrated that there was a large spectrum of possible EIAV serotypes and confirmed that antigenic variation occurs with high frequency in EIAV. Moreover, the data showed that variation is a rapid and random process, as no pattern of variant evolution was evident by comparison of 13 isolates from parallel infections. These results represent the first production of neutralizing MAbs specific for a lentivirus glycoprotein and document alterations in one or more neutralization epitopes of the major surface glycoprotein among sequential isolates of EIAV recovered during persistent infection. * Corresponding author. t Approved for publication by the Director of the Louisiana Agricultural Experiment Station as Manuscript Number 87-64-1351. undoubtedly pose serious problems for vaccine development.

The immunopathogenesis of equine infectious anemia virus

“…In contrast, no variation is observed in the viral core proteins (Salinovich et al, 1986). Comparisons of peptide and genomic maps of virus isolates recovered from sequential febrile episodes reveal each isolate to be structurally unique, with variation occurring in a random, non-cumulative process (Payne et al, 1987b;Hussain et al, 1987). Rapid epitope alterations in gp90 and gp45 have been documented using neutralizing monoclonal antibodies against the virion surface glycoproteins (Hussain et al, 1987).…”

“…Comparisons of peptide and genomic maps of virus isolates recovered from sequential febrile episodes reveal each isolate to be structurally unique, with variation occurring in a random, non-cumulative process (Payne et al, 1987b;Hussain et al, 1987). Rapid epitope alterations in gp90 and gp45 have been documented using neutralizing monoclonal antibodies against the virion surface glycoproteins (Hussain et al, 1987). Selective immune pressure has been hypothesized as the driving force behind the antigenic variation seen in clinical cases of EIA Salinovich et al, 1986;Kono et al, 1973a,b).…”

“…This selective, type-specific neutralization is due to the rapid variation in neutralization epitopes on the viral envelope glycoproteins. Monoclonal antibodies that react with variable epitopes on gp90 or gp45 effectively neutralize the virus (Hussain et al, 1987;Payne et al, 1989). Non-neutralizing antibodies react primarily with variable epitopes of gp90 and gp45 (Hussain et al, 1987;Payne et al, 1989).…”

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

“…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).…”

“…Sequence analysis showed that much of the genetic variation in gp90 was clustered in a single area termed the variable region (30). Ball et al (3) localized a principal neutralizing domain (PND) to the gp90 variable region, which accounts for the variable reactivity of different virus isolates to PND-specific, neutralizing monoclonal antibodies (14). Additional studies on EIAV sequence diversity have yielded similar results and have identi-fied a second highly variable segment of the genome within the U3 region of the long terminal repeat (LTR) (1,6,30,31,34).…”