title: Expression of chicken parvovirus VP2 in chicken embryo fibroblasts requires codon optimization for production of naked DNA and vectored meleagrid herpesvirus type 1 vaccines.
abstract: Meleagrid herpesvirus type 1 (MeHV-1) is an ideal vector for the expression of antigens from pathogenic avian organisms in order to generate vaccines. Chicken parvovirus (ChPV) is a widespread infectious virus that causes serious disease in chickens. It is one of the etiological agents largely suspected in causing Runting Stunting Syndrome (RSS) in chickens. Initial attempts to express the wild-type gene encoding the capsid protein VP2 of ChPV by insertion into the thymidine kinase gene of MeHV-1 were unsuccessful. However, transient expression of a codon-optimized synthetic VP2 gene cloned into the bicistronic vector pIRES2-Ds-Red2, could be demonstrated by immunocytochemical staining of transfected chicken embryo fibroblasts (CEFs). Red fluorescence could also be detected in these transfected cells since the red fluorescent protein gene is downstream from the internal ribosome entry site (IRES). Strikingly, fluorescence could not be demonstrated in cells transiently transfected with the bicistronic vector containing the wild-type or non-codon-optimized VP2 gene. Immunocytochemical staining of these cells also failed to demonstrate expression of wild-type VP2, indicating that the lack of expression was at the RNA level and the VP2 protein was not toxic to CEFs. Chickens vaccinated with a DNA vaccine consisting of the bicistronic vector containing the codon-optimized VP2 elicited a humoral immune response as measured by a VP2-specific ELISA. This VP2 codon-optimized bicistronic cassette was rescued into the MeHV-1 genome generating a vectored vaccine against ChPV disease.
authors.affiliation: Southeast Poultry Research Laboratory, Agricultural Research Service, United States Department of Agriculture, 934 College Station Rd, Athens, GA, 30605, USA, Stephen.Spatz@ars.usda.gov.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Spatz
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Volkening
authors.forename: Robert
authors.initials: R
authors.lastname: Mullis
authors.forename: Fenglan
authors.initials: F
authors.lastname: Li
authors.forename: John
authors.initials: J
authors.lastname: Mercado
authors.forename: Laszlo
authors.initials: L
authors.lastname: Zsak
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D036022:Capsid Proteins / Q000235:genetics* / Q000276:immunology; D002642:Chick Embryo; D002645:Chickens; D003062:Codon; D004797:Enzyme-Linked Immunosorbent Assay; D005347:Fibroblasts / Q000821:virology; D005453:Fluorescence; D015870:Gene Expression; D017930:Genes, Reporter; D005822:Genetic Vectors; D026002:Herpesvirus 1, Meleagrid / Q000235:genetics; D007150:Immunohistochemistry; D017992:Parvovirus / Q000235:genetics* / Q000276:immunology; D019444:Vaccines, DNA / Q000235:genetics* / Q000276:immunology; D014765:Viral Vaccines / Q000235:genetics* / Q000276:immunology
chemical_list: D000914:Antibodies, Viral; D036022:Capsid Proteins; D003062:Codon; D019444:Vaccines, DNA; D014765:Viral Vaccines