Ostrowski M, Galeota J A, Jar A M, Platt K B, Osorio F A, Lopez O J
Wolf Biotech, Lincoln, Nebraska, USA.
J Virol. 2002 May;76(9):4241-50. doi: 10.1128/jvi.76.9.4241-4250.2002.
After infection of swine with porcine reproductive and respiratory syndrome virus (PRRSV), there is a rapid rise of PRRSV-specific nonneutralizing antibodies (NNA), while neutralizing antibodies (NA) are detectable not sooner than 3 weeks later. To characterize neutralizing epitopes, we selected phages from a 12-mer phage display library using anti-PRRSV neutralizing monoclonal antibody (MAb) ISU25-C1. In addition, phages carrying peptides recognized by swine antibodies with high seroneutralizing titer were isolated after subtracting from the library those clones binding to swine anti-PRRSV serum with no neutralizing activity. Two epitopes located in the ectodomain of PRRSV GP5 were identified. One of these epitopes, which we named epitope B, was recognized both by neutralizing MAb ISU25-C1 and swine neutralizing serum (NS) but not by swine nonneutralizing serum (NNS), indicating that it is a neutralizing epitope. Epitope B is sequential, conserved among isolates, and not immunodominant. Antibodies directed against it are detected in serum late after infection. In contrast, the other epitope, which we named epitope A, is hypervariable and immunodominant. Antibodies against it appear early after infection with PRRSV. This epitope is recognized by swine NNA but is not recognized by either neutralizing MAb ISU25-C1 or swine NA, indicating that it is not involved in PRRSV neutralization. During infection with PRRSV, epitope A may act as a decoy, eliciting most of the antibodies directed to GP5 and delaying the induction of NA against epitope B for at least 3 weeks. These results are relevant to the design of vaccines against PRRSV.
猪感染猪繁殖与呼吸综合征病毒（PRRSV）后，PRRSV特异性非中和抗体（NNA）迅速上升，而中和抗体（NA）最早在3周后才能检测到。为了表征中和表位，我们使用抗PRRSV中和单克隆抗体（MAb）ISU25-C1从一个12肽噬菌体展示文库中筛选噬菌体。此外，在从文库中减去那些与无中和活性的猪抗PRRSV血清结合的克隆后，分离出携带被高血清中和滴度的猪抗体识别的肽的噬菌体。鉴定出位于PRRSV GP5胞外域的两个表位。其中一个表位，我们命名为表位B，被中和单克隆抗体ISU25-C1和猪中和血清（NS）识别，但不被猪非中和血清（NNS）识别，表明它是一个中和表位。表位B是连续的，在分离株中保守，且不具有免疫显性。感染后期血清中可检测到针对它的抗体。相比之下，另一个表位，我们命名为表位A，是高变且具有免疫显性的。感染PRRSV后早期出现针对它的抗体。这个表位被猪NNA识别，但不被中和单克隆抗体ISU25-C1或猪NA识别，表明它不参与PRRSV中和。在PRRSV感染期间，表位A可能起到诱饵的作用，引发大多数针对GP5的抗体，并将针对表位B的NA的诱导至少延迟3周。这些结果与抗PRRSV疫苗的设计相关。
