#05-194

Complete

Date Full Report Received

10/15/2007

Date Abstract Report Received

10/15/2007

Investigation

Institution:
Primary Investigator:
Co-Investigators: Fernando Osorio

In previous studies, we have demonstrated that virus-neutralizing antibodies are important for protective immunity against PRRSV. These neutralizing antibodies constitute a significant correlate for evaluating the efficacy of a vaccine. We also know that the higher and the more cross-reactive is the titer of PRRSV-neutralizing antibodies invoked by a vaccine, the better is its immunogenic potential against infection. Studies conducted by us and others have unambiguously demonstrated that the glycoprotein GP5 is a major inducer of protective neutralizing antibodies. Through genetic manipulation of PRRSV genome, we have recently demonstrated that elimination (through a process called “hypoglycosylation”) of selected sugar moieties present on the surface of GP5 dramatically enhances the ability of a PRRSV strain to invoke a more robust response composed by PRRSV-neutralizing antibodies. As evidence indicates that other glycoproteins that make up the PRRSV may also be involved in the PRRSV-neutralizing response, we had proposed to generate PRRSV containing hypoglycosylated forms of all the remaining glycoproteins (GP2, GP3, and GP4) and assess the cumulative effect of these changes on the ensuing PRRSV-neutralizing antibody response. Mutations in the glycosylation sites of GP2, GP3, and GP4 proteins were introduced individually and mutant PRRSVs were generated from infectious clones containing these mutant glycoproteins. When inoculated into pigs and antibody response in the infected pigs were analyzed, we observed that there was a general down-regulation of neutralizing antibody response in pigs infected with the GP2 and GP4 glycosylation mutants. This result is contrary to our expectation of obtaining higher levels of neutralizing antibody response in these infected pigs. Overall, our results suggest that hypoglycosylation of the minor glycoproteins of PRRSV does not enhance neutralizing antibody response in pigs.

Contact information: Asit K. Pattnaik, Department of Veterinary and Biomedical Sciences, University of Nebraska-Lincoln, E126 Beadle Center, 1901 Vine Street, Lincoln, NE 68588, Phone: 402-472-1067; Fax: 402-472-8722; e-mail: apattnaik2@unl.edu