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dc.contributor.authorGillespie, Jennifer Annen_US
dc.date.accessioned2014-03-14T20:32:39Z
dc.date.available2014-03-14T20:32:39Z
dc.date.issued2009-03-05en_US
dc.identifier.otheretd-03142009-140813en_US
dc.identifier.urihttp://hdl.handle.net/10919/31475
dc.description.abstractPorcine circovirus type 2 (PCV2) is the primary causative agent of porcine circovirus associated disease (PCVAD), an economically important swine disease that causes wasting in pigs 5-18 weeks of age. There exist two different types of porcine circoviruses: porcine circovirus type 1 (PCV1) was discovered as a contaminant of porcine kidney (PK-15) cells and was determined to be nonpathogenic in swine; whereas porcine circovirus type 2 (PCV2) is pathogenic. A recently released vaccine for PCVAD was generated by inserting the gene encoding the immunogenic capsid protein of PCV2 into the genetic backbone of the non-pathogenic PCV1. This chimeric PCV vaccine, called PCV1-2, was shown to induce protective immunity against PCV2 infection in pigs. The vaccine is currently on the market in a killed form. In order to develop a live version of the vaccine, the genetic stability of the chimeric PCV1-2 vaccine virus was investigated by in vitro and in vivo passaging of the vaccine virus. In vitro passaging of the PCV1-2 vaccine virus was done in a porcine kidney PK-15 cell line. Cells were infected with the PCV1-2 vaccine virus and then serially passaged 11 times. The passaged vaccine viruses recovered from passages 5 and 11 were sequenced, and the sequences were compared to that of the original PCV1-2 vaccine virus. The in vitro serial passage result showed that no mutation occurred during the 11 in vitro passages. The in vivo passaging was done using specific-pathogen-free (SPF) pigs. In in vivo â passage 1â , nine piglets were divided into 3 groups of 3 each: group 1 each inoculated with 200ug of PCV1-2 plasmid, group 2 each with 1Ã 103 TCID50 live PCV1-2 vaccine virus, and group 3 each with 3ml phosphate buffered saline (PBS) buffer as a control. One pig from each group was necropsied at 14, 21, and 28 days post-inoculation (DPI), respectively. A panel of tissue samples including lymph nodes and thymus were collected from each pig. Tissue homogenates from DPI 28 that were positive by PCR for PCV1-2 DNA were used to inoculate new piglets in the in vivo passage 2 experiment. Viruses recovered from passage 2 pigs were subsequently used for inoculation in the in vivo passage 3 experiment. The PCV1-2 vaccine virus DNA from pigs in each passage was amplified and sequenced. The results of the in vivo serial passage experiment showed that, after 3 passages of the PCV1-2 vaccine virus in pigs, there were no new mutations in the viruses recovered from pigs. The PCV1-2 vaccine contained an introduced marker mutation at amino acid position number 79, which is in the capsid region. During the in vivo passaging of the vaccine virus in pigs, this marker mutation quickly reverted back to its original nucleotide. This marker back mutation occurred between DPI 21 and DPI 28 of passage 1 in the PCV1-2 live vaccine virus group, and between DPI 28 of passage 1 and DPI 14 of passage 2 in the PCV1-2 vaccine plasmid group, and remained stable throughout the reminder of the in vivo study. Based upon the results from this study, we conclude that the PCV1-2 chimeric vaccine virus is genetically stable in vitro and in pigs, and thus should serve as a good candidate for a live vaccine against PCV2.en_US
dc.publisherVirginia Techen_US
dc.relation.haspartJGillespiethesis2.pdfen_US
dc.rightsI hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Virginia Tech or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.en_US
dc.subjectPostweaning Multisystemic Wasting Syndromeen_US
dc.subjectvaccineen_US
dc.subjectswineen_US
dc.subjectPorcine Circovirusen_US
dc.subjectPCV2en_US
dc.titleGenetic Stability of a Genetically-Engineered Chimeric Porcine Circovirus (PCV) Vaccine, PCV1-2en_US
dc.typeThesisen_US
dc.contributor.departmentVeterinary Medical Sciencesen_US
thesis.degree.nameMaster of Scienceen_US
thesis.degree.levelmastersen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
dc.contributor.committeechairMeng, Xiang-Jinen_US
dc.contributor.committeememberPierson, Frank Williamen_US
dc.contributor.committeememberBoyle, Stephen M.en_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-03142009-140813/en_US
dc.date.sdate2009-03-14en_US
dc.date.rdate2012-06-22
dc.date.adate2009-06-04en_US


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