"Effect of Porcine Reproductive and Respiratory Syndrome Virus Non-stru" by Xiaoxin Zhou

Author

Xiaoxin Zhou

Document Type

Thesis - University Access Only

Award Date

2009

Degree Name

Master of Science (MS)

Department / School

Veterinary and Biomedical Sciences

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most important diseases in the swine industry all over the world. One of the main reasons for failure to control PRRSV infection is the lack of effective vaccines. Most current experimental vaccines and immune studies have focused on PRRS viral GP5 and M proteins. Our studies have highlighted the potential importance of the non-structural proteins (nsp), particularly nsp2. The nsp2 is the largest viral protein of PRRSV. Besides its crucial role in viral replication, recent studies have shown that it is also involved in modulation of host immunity. In this study, we investigated the effect of nsp2 epitope deletion (~ES) mutants on the innate and cellular immunity. Using a Type 1 PRRSV cDNA infectious clone, each of the six identified B-cell epitopes (ES2 through ES7) was deleted. Deletion of ES3, ES4, or ES7 allowed the generation of viable virus. In comparison with the parental virus, the ~ES3 mutant showed increased cytolytic activity and more vigorous growth kinetics, while ~ES4 and ~ES7 mutants displayed decreased cytolytic activity and slower growth kinetics in MARC-145 cells. The expression ofIL-1~ and TNF-a from the parental or mutant viruses infected macrophages was measured by swine cytokine ELISAs. Results showed that the IL-1 ~ and TNF-a expression levels were higher in cells infected with the ~ES7 mutant than with the parental virus, while much lower with the ~ES3 mutant. The results from the animal study were also consistent with the in vitro study. We confirmed our findings by real-time RT-PCR quantification of innate and T helper 1 (Th 1) immune marker genes induced by these mutant viruses. Our result suggests that certain regions in nsp2 are non-essential for PRRSV replication but play an important role in modulation of host immunity in vivo. By modifying certain nsp2 regions, virus-specific host immunity could be enhanced.

Library of Congress Subject Headings

Porcine reproductive and respiratory syndrome

Viral proteins

Immune response

Vaccines

Format

application/pdf

Number of Pages

108

Publisher

South Dakota State University

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