Serologic marker candidates identified among B-cell linear epitopes of Nsp2 and structural proteins of a North American strain of porcine reproductive and respiratory syndrome virus

Abstract

We describe B-cell linear epitopes detected by Pepscan in the Nsp2 and all of the structural proteins of a US PRRSV strain, using sera of 15 experimentally infected pigs. The Nsp2 was found to contain the highest frequency of immunodominant epitopes (n = 18) when compared to structural proteins. Ten of these 18 Nsp2 peptides were reactive with 80 to 100% of the examined sera. In the structural proteins, epitopes consistently recognized by immune sera were located at gp2 (n = 2), gp3 (n = 4), gp5 (n = 3), M (n = 2) and N (n = 2). Overall, the highest degree of immunogenicity and conservation was exhibited by two epitopes identified in the C-terminal end of the M protein (ORF6). The antibodies recognizing the immunodominant epitopes of each protein were detected as early as days 7 to 15 pi and remained detectable until the end of the experiment (day 90 pi). These findings have direct implications for PRRSV differential diagnostics and eventual eradication as the identified epitopes may represent serologic marker candidates for differential (DIVA) PRRSV vaccines, derived from infectious cDNA clones.

Antibody Response to Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Nonstructural Proteins and Implications for Diagnostic Detection and Differentiation of PRRSV Types I and II

“…Previous studies of the humoral immune response to PRRSV focused mainly on detection of antibodies to viral structural proteins, especially N (9,22,26,29). Several studies showed that certain nsps, such as nsp1 and nsp2, are highly immunogenic (4,7,13,24,25). Antibody responses to linear epitopes in nsp2 have been reported to appear within 1 to 4 weeks of infection in type I and type II PRRSV strains (4,24,25).…”

“…Several studies showed that certain nsps, such as nsp1 and nsp2, are highly immunogenic (4,7,13,24,25). Antibody responses to linear epitopes in nsp2 have been reported to appear within 1 to 4 weeks of infection in type I and type II PRRSV strains (4,24,25). Johnson et al (13) observed robust and rapid cross-reactive antibody responses induced by nsp1 and nsp2 to vaccine and field isolates and substantially higher levels of immunoreactivity related to conformational epitopes.…”

“…Our previous studies showed that the PRRSV nsp2 region is highly variable within and between genotypes, with 70.6% to 91.6% amino acid identity within type I PRRSV and 74.9% to 95.6% amino acid identity within type II PRRSV, but only 33.8% identity between type I and type II genotypes (7,8,23,28). The central region of nsp2 contains hypervariable domains with insertions and deletions (10,12,27,30,33), and most identified B-cell epitopes are located in these regions (4,24). In contrast, nsp7 is relatively conserved within each genotype and is divergent between genotypes.…”

Comparative Measurement of Cell-Mediated Immune Responses of Swine to the M and N Proteins of Porcine Reproductive and Respiratory Syndrome Virus

“…Our laboratory results also confirmed that the N-specific antibody had no neutralizing effect (data not shown). It is known that two major B-cell epitopes are located at the C-terminal region of the PRRSV-M protein (7). In this study, we utilized the plasmid DNA encompassing the B-cell epitope region of the PRRSV-M gene to immunize the experimental pigs.…”

Characterization of Equine Humoral Antibody Response to the Nonstructural Proteins of Equine Arteritis Virus

“…As in PRRSV, there is significant variation in EAV nsp2 (5, 62). However, unlike the PRRSV nsp2, until now, no B-cell or T-cell epitopes have been identified in this protein in the case of EAV (20,41,60).…”