Summary auto-generated
Researchers developed five monoclonal antibodies (MAbs) against infectious pancreatic necrosis virus (IPNV), a birnavirus affecting fish. Using reciprocal blocking ELISA, neutralization assays, and Western immunoblot analysis, they identified at least four distinct epitopes on the virion. One epitope was located on VP2 (51 kDa capsid protein), and another was on VP3 and VP4 (32 and 30 kDa proteins, respectively). Three MAbs recognized epitopes that were masked during protein solubilization. When tested against 14 aquatic birnavirus isolates representing four serotypes, the MAb panel distinguished at least nine antigenically distinct viruses. Two MAbs showed high conservation within the West Buxton (U.S.A.) serotype, while another recognized epitopes present only on some members of this serotype. One MAb identified a more widely distributed epitope found across multiple serotypes. The study demonstrates that antigenic variation exists among isolates within the same serotype and provides standardized reagents for virus identification and characterization.
Key findings
- Five monoclonal antibodies identified at least four structurally and functionally distinct epitopes on IPNV virions
- Different epitopes localized to specific viral proteins: VP2 contained one epitope, while VP3 and VP4 shared another epitope
- The 14 birnavirus isolates tested represented at least nine antigenically distinct viruses despite belonging to only four known serotypes
- Significant antigenic heterogeneity exists among members of the same serotype, particularly within the West Buxton serotype
- Two MAbs showed high conservation and restriction to the West Buxton serotype, while another MAb recognized epitopes distributed across multiple serotypes
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Abstract
A panel of five monoclonal antibodies (MAbs) produced against the West Buxton isolate of infectious pancreatic necrosis virus was used to investigate viral antigens and to compare different aquatic birnavirus isolates antigenically. Reciprocal blocking ELISA and neutralization assays indicated that these MAbs identified four, and possibly five, structurally and/or functionally different epitopes on the virion. Western immunoblot analysis demonstrated that one epitope was present on VP2, the large (51,000 mol. wt., 51K) capsid protein, and another epitope was located on the two smallest structural proteins, VP3 (32K) and VP4 (30K). Three MAbs did not react with any of the solubilized viral proteins; the epitopes recognized by these MAbs may have been altered when the virion was solubilized with SDS. Comparison of reactivity patterns of the five MAbs with various aquatic birnaviruses in ELISA and neutralization tests demonstrated that 14 isolates tested from four serotypes represented a minimum of nine antigenically distinct viruses; i.e., distinct patterns of reactivity were shown among several viruses within the same serotype. Two MAbs identified different epitopes that were highly conserved among, and largely restricted to, members of the West Buxton (U.S.A.) serotype, whereas two other MAbs recognized an epitope(s) present only on some members of this serotype. The other MAb defined an epitope that was more widely distributed among the aquatic birnaviruses and found on all representatives tested from two serotypes.