title: Monoclonal antibodies to the GP5 of porcine reproductive and respiratory syndrome virus are more effective in virus neutralization than monoclonal antibodies to the GP4.
abstract: The arterivirus porcine reproductive and respiratory syndrome virus (PRRSV) contains six structural proteins the roles of which are not completely understood. In a preceding study, immunization with the dutch isolate I10 of PRRSV had led to the development of MAbs against four structural proteins [Wieczorek-Krohmer, M., 1994. Herstellung und Charakterisierung von monoklonalen Antikörpern gegen das Virus des Porzinen Reproduktiven und Respiratorischen Syndroms (PRRSV). Inaugural-Dissertation, Ludwig-Maximilians-Universität, München] here finally identified by reaction with individual plasmid-expressed PRRSV proteins as products of ORFs 3 (GP3), 4 (GP4), 5 (GP5) and 7 (N). Surprisingly, the MAbs against GP5 revealed the presence of two antigenically distinct virus populations in the isolate I10, the population PRRSV-'PPV', isolated from plaques and the PRRSV-'EPV', gained by end point dilution. MAbs against GP3, GP4 and N reacted with both I10 populations as well as with natural PRRSV isolates. However, the anti-GP5 MAbs exclusively recognized PRRSV-'PPV'. In this study immunization of mice with both separated I10 populations confirmed that solely PRRSV-'PPV' possesses the property to induce an immune response ultimately leading to the establishment of MAbs against GP5. Whereas the 15 anti-GP5 MAbs (derived from four independent fusions) reacted exclusively with PRRSV-'PPV' of the isolate I10, anti-GP4 MAbs detected their target antigen on various isolates of European origin and were able to neutralize them. As indicated by competition assays and selection of neutralization-resistant virus mutants, all GP5 MAbs are directed against a single antigenic site on the ORF 5 protein. Both groups of neutralizing antibodies bound to the surface of purified virions demonstrating that the recognized epitopes represent surface structures of the virion envelope. However, anti-GP5 MAbs mediated the binding of more gold granules than anti-GP4 MAbs. Comparison of the neutralizing effect of anti-GP4 and anti-GP5 MAbs revealed the anti-GP5 MAbs as the more efficient antibodies. For the complete neutralization of about 100 ID50 of PRRSV-'PPV' anti-GP5 culture supernatant was effective up to a dilution of 1:1280 whereas the most effective anti-GP4 antibodies exhibited a comparable effect only up to 1:64. These results indicate that PRRSV GP5 in principle is a major target for neutralizing antibodies, as is found for other arteriviruses, but that in nature 'ORF 5 escape mutants' may develop as easily as in vitro.
authors.affiliation: Federal Research Centre for Virus Diseases of Animals, Tübingen, Germany. emilie.weiland@tue.bfav.de
authors.forename: E
authors.initials: E
authors.lastname: Weiland
authors.forename: M
authors.initials: M
authors.lastname: Wieczorek-Krohmer
authors.forename: D
authors.initials: D
authors.lastname: Kohl
authors.forename: K K
authors.initials: KK
authors.lastname: Conzelmann
authors.forename: F
authors.initials: F
authors.lastname: Weiland
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000914:Antibodies, Viral / Q000276:immunology; D015153:Blotting, Western / Q000662:veterinary; D002460:Cell Line; D004279:DNA, Viral / Q000737:chemistry; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry; D019084:Fluorescent Antibody Technique, Indirect / Q000662:veterinary; D006023:Glycoproteins / Q000235:genetics / Q000276:immunology*; D015186:Hominidae; D016676:Macrophages, Alveolar / Q000166:cytology / Q000276:immunology; D051379:Mice; D016253:Microscopy, Immunoelectron / Q000662:veterinary; D009500:Neutralization Tests / Q000662:veterinary; D016366:Open Reading Frames; D010957:Plasmids / Q000737:chemistry; D019318:Porcine Reproductive and Respiratory Syndrome / Q000276:immunology / Q000821:virology; D019316:Porcine respiratory and reproductive syndrome virus / Q000235:genetics / Q000276:immunology*; D013552:Swine; D014162:Transfection; D015678:Viral Structural Proteins / Q000235:genetics / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D004279:DNA, Viral; D006023:Glycoproteins; D015678:Viral Structural Proteins; D016650:Fluorescein-5-isothiocyanate