Correlation of Serotype Specificity and Protein Structure of the Five U.S. Serotypes of Bluetongue Virus

Abstract

SUMMARYThe relationship between serotype specificity and protein structure was studied by polyacrylamide gel electrophoresis, peptide mapping and radioimmune precipitation (RIP) of structural and non-structural proteins of the five U.S. serotypes of bluetongue virus (BTV). The surface proteins, VP2 and VP5, showed the most variation in size among the serotypes. Peptide mapping of the proteins showed that VP2 is unique for each of the U.S. serotypes. The nucleocapsid and non-structural proteins showed a high degree of conservation, whereas the other surface protein, VP5, showed intermediate conservation among the serotypes. Monospecific neutralizing antiserum produced in rabbits against each serotype was used in cross-RIP against cytoplasmic extracts prepared from cells infected with each BTV serotype. There were extensive crossreactions among those proteins which showed a high degree of structural conservation, whereas VP2 was immunoprecipitated best in the homologous RIP system. Thus, a correlation between serotype specificity and protein structure was shown among the five U.S. serotypes of BTV.

A Multiplex Real-Time Reverse Transcription Polymerase Chain Reaction Assay for Detection and Differentiation of Bluetongue Virus and Epizootic Hemorrhagic Disease Virus Serogroups

“…19 The outer capsid protein, VP2, is the primary serotype determinant, but the second outer capsid protein VP5 can also influence serotypic epitopes. 21,25,40 The structural genes that are fairly conserved within the virus serogroup encode the inner core proteins VP3 and VP7, 23,42 and this information has been used to develop reverse transcription polymerase chain reaction (RT-PCR) assays. 2 The VP7 protein is commonly used as the antigen for enzyme-linked immunosorbent assays.…”

Evaluation of the Immunogenicity of an Experimental Subunit Vaccine That Allows Differentiation between Infected and Vaccinated Animals against Bluetongue Virus Serotype 8 in Cattle

“…No severe systemic reactions were observed following vaccination with either vaccine. The animals in the SubV group developed higher rectal temperatures than did those in the other groups at 6 h (SubV group: mean, 38 38.4°C]; P Յ 0.01), although mild-to-moderate injection site swelling was observed in animals of both vaccine groups (SubV group: moderate, 4/5 animals; CV group: mild, 4/5 animals; moderate, 1/5 animals) and in 1/5 control animals. No reduction in appetite or change in behavior was observed for any animal throughout the study, and all localized swelling disappeared by 1 week after each vaccination.…”

“…In addition to VP2, proteins such as the nonstructural proteins are suggested to play important roles in inducing cell-mediated immune responses (33,35,36). Furthermore, in the serological and cellmediated immunological assays, NS1 and NS2 have exhibited serotypic cross-reactivity in naturally infected or vaccinated sheep (32,37) and in experimentally infected rabbits (38), respectively. Although it has been proposed that novel assays detecting antibodies to the nonstructural proteins may allow for DIVA compliance (37,39), it is evident that the inclusion of proteins that are conserved across serotypes, such as NS1 and NS2, may facilitate the development of effective polyvalent BT vaccines by inducing cross-serotype cell-mediated immune responses (11).…”

“…Although it has been proposed that novel assays detecting antibodies to the nonstructural proteins may allow for DIVA compliance (37,39), it is evident that the inclusion of proteins that are conserved across serotypes, such as NS1 and NS2, may facilitate the development of effective polyvalent BT vaccines by inducing cross-serotype cell-mediated immune responses (11). The structural protein VP7 is also conserved across BTV serotypes (38) but is considered to induce a serological immune response more than a cell-mediated immune response and is therefore widely used for serological BTV diagnosis (40,41), including monitoring of all serotypes of BTV infections present in Europe. Therefore, exclusion of this protein from a vaccine may enable DIVA compliance when coupled with well-established diagnostic assays.…”

Neutralizing epitopes of the serotypes of bluetongue virus present in the United States

“…An additional serotype, BTV-2, was recently isolated in Florida (Gibbs et al, 1983). Epitopes responsible for the neutralization of BTV have been identified on only the major outer capsid protein VP2 (Huismans & Erasmus, 1981;Appleton & Letchworth, 1983;Letchworth & Appleton, 1983a;Mecham et al, 1986;Huismans et al, 1987;Roy et al, 1990) although the other outer capsid protein, VP5, might be indirectly involved in virus neutralization by its conformational influence on VP2 Mertens et al, 1989;Roy et al, 1990). Multiple neutralizing epitopes exist on BTV (Letchworth & Appleton, 1983 b;Gould & Eaton, 1990;Greider & Schultz, 1990;White & Eaton, 1990), and at least some of these epitopes are intimately associated on VP2 and contribute to a single, larger immunogenic domain (Heidner et al, 1990).…”