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
Recommended Citation
Zhou, Xiaoxin, "Effect of Porcine Reproductive and Respiratory Syndrome Virus Non-structure Protein 2 Epitope Deletion Mutants on the Induction of Host Immune Responses" (2009). Electronic Theses and Dissertations. 1622.
https://openprairie.sdstate.edu/etd2/1622
