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Application of reverse genetics to porcine reproductive and respiratory syndrome virus vaccinology
Porcine reproductive and respiratory syndrome virus (PRRSV) is endemic in most swine-producing countries, causing significant economic loss to swine producers. Current PRRSV vaccines are not adequately effective for control and eradication of the disease. The vaccines fail to elicit a robust neutralizing antibody (NAb) response in vaccinated pigs although NAbs can fully protect pigs from PRRSV infection. In addition, the vaccines do not allow serologically Differentiating Infected from Vaccinated Animals, a feature known as DIVA. A DIVA system is crucial for control and eradication of several important viral diseases in livestock. The objectives of this dissertation were: (i) to identify the mechanisms that PRRSV employs to evade NAb response and (ii) to develop a DIVA system for PRRSV. I indentified a PRRSV isolate called PRRSV-01 that elicited an unusually robust NAb response in infected pigs. Sequence analysis revealed that PRRSV-01 lacked two N-glycosylation sites in its envelope glycoproteins: one in GP3 and the other in GP5, both of which are consistently present in other PRRSV isolates. Through the gain-of-function studies, I found that the N-glycosylation sites in both GP3 and GP5 of PRRSV-01 were involved in subversion of NAb response. I also report here different approaches to develop a DIVA system for PRRSV. Through the use of reverse genetics, two mutant viruses were generated, both of which carried mutations in a conserved and immunodominant epitope (designated as epitope-201) located in the membrane protein. When experimentally inoculated into pigs, one of the mutant viruses was no longer able to elicit antibodies to the epitope-201. Consequently, the animals infected with this epitope-201 mutant virus were serologically differentiated from those infected with wt-PRRSV through the use of a blocking ELISA. Collectively, the results presented in this dissertation provide novel information for the development of more effective PRRSV vaccines.
Vu, Hiep Lai Xuan, "Application of reverse genetics to porcine reproductive and respiratory syndrome virus vaccinology" (2013). ETD collection for University of Nebraska - Lincoln. AAI3558016.