Immune response in pigs vaccinated with plasmid DNA encoding ORF5 of porcine reproductive and respiratory syndrome virus.

Abstract

The ORF5-encoded major envelope glycoprotein (GP 5 ) of porcine reproductive and respiratory syndrome virus (PRRSV) is one of the three major structural proteins of this virus. While some porcine convalescent sera and monoclonal antibodies directed against GP 4 and GP 5 have the capacity to neutralize the virus in vitro, the protein specificity of porcine neutralizing sera has not yet been established. DNA immunization with a plasmid encoding GP 5 of PRRSV, under the control of a human cytomegalovirus promoter, induced anti-GP 5 -specific neutralizing antibodies in pigs and BALB/c mice. The GP 5 protein specificity of neutralizing sera was confirmed by immunoblotting and ELISA. Peripheral blood mononuclear cells obtained from DNA-vaccinated pigs underwent blastogenic trans-

Evolution of Porcine Reproductive and Respiratory Syndrome Virus during Sequential Passages in Pigs

“…Many ORF 5 variants had amino acid substitutions at residue 33 (asparagine to arginine) or 34 (aspartic acid to asparagine or arginine). Since amino acids at positions 33 and 34 are known to be part of the ectodomain of GP5, any change in this region may affect the N-linked glycosylation or the conformation of GP5, which is important for interactions with the M protein (19,24,29,30,32,45,44,46,53). Theoretically, such a change could result in the loss of an epitope or an alteration in the immune response, but no such changes were found in this study.…”

Identification of Neutralizing and Nonneutralizing Epitopes in the Porcine Reproductive and Respiratory Syndrome Virus GP5 Ectodomain

“…Likewise, antibodies passively transferred to pigs (final titer, 8) cleared PRRSV viremia effectively (41). In addition, young pigs immunized with a DNA vaccine comprising the ORF 5 gene developed PRRSV-specific NAs and protective immunity (29).…”

Alternative codon usage of PRRS virus ORF5 gene increases eucaryotic expression of GP5 glycoprotein and improves immune response in challenged pigs

“…Immunization of mice with Escherichia coli-expressed GST-ORF5 recombinant fusion protein, as well as with purified PRRSV, induced specific anti-GP5 neutralizing monoclonal antibodies [7]. Furthermore, genetic immunization of pigs with plasmidic DNA expressing the ORF5 gene triggered the production of transient and low titers of neutralizing antibodies to PRRSV and conferred protection against development of clinical disease and lung lesions but were not sufficient to inhibit virus persistence and shedding in the respiratory tract of PRRSV challenged pigs [8]. On the other hand, when the E. coli-expressed GST-ORF5 recombinant fusion protein was used as immunogen prior to challenge with pathogenic virus, the disease was more severe, despite the development of high titers of non-neutralizing antibodies to GP5 thus suggesting the involvement of a possible antibodydependent enhancement phenomenon [8].…”

“…Furthermore, genetic immunization of pigs with plasmidic DNA expressing the ORF5 gene triggered the production of transient and low titers of neutralizing antibodies to PRRSV and conferred protection against development of clinical disease and lung lesions but were not sufficient to inhibit virus persistence and shedding in the respiratory tract of PRRSV challenged pigs [8]. On the other hand, when the E. coli-expressed GST-ORF5 recombinant fusion protein was used as immunogen prior to challenge with pathogenic virus, the disease was more severe, despite the development of high titers of non-neutralizing antibodies to GP5 thus suggesting the involvement of a possible antibodydependent enhancement phenomenon [8]. These findings suggest also that the amounts of GP5 synthesized in the infected cells, as well as conformation of the protein which may be influenced by the type of oligosaccharide side chains present on the molecule, are apparently crucial to trigger an effective humoral immune response to PRRSV.…”