title: The immunogenicity of DNA constructs co-expressing GP5 and M proteins of porcine reproductive and respiratory syndrome virus conjugated by GPGP linker in pigs.
abstract: The heterodimer of glycoprotein 5 (GP5) and non-glycosylated matrix protein (M) is the leading target for the development of new generation of vaccines against porcine reproductive and respiratory syndrome virus (PRRSV) infection. It has been demonstrated that DNA vaccine co-expressing GP5 and M proteins as a fusion protein aroused better immunogenicity than that expressing GP5 or M alone, but it was no better than the DNA vaccine co-expressing GP5 and M proteins with two different promoters. Altered natural conformation of the co-expressed GP5 and M fusion protein was considered as the major cause. Glycine-proline-glycine-proline (GPGP) linker can minimize the conformational changes in tertiary structure and provide flexibility of the peptide chain. The objective of this study was to evaluate whether the immunogenicity of DNA constructs co-expressing GP5 and M proteins linked by GPGP could be enhanced in pigs. Three recombinant DNA constructs expressing GP5/M fusion protein without GPGP linker (pcDNA-56), GP5/M fusion protein conjugated by GPGP linker (pcDNA-5L6), and M/GP5 fusion protein conjugated by GPGP linker (pcDNA-6L5) were established. Sixteen PRRSV-free pigs were randomly assigned to four groups and inoculated intramuscularly with 3 consecutive doses of 500 μg of empty vector pcDNA3.1, pcDNA-56, pcDNA-5L6 or pcDNA-6L5 each at a 2-week interval followed by challenge with 5 × 10(5) TCID(50) PRRSV at 3 weeks after the final inoculation. All pcDNA-56-, pcDNA-5L6-, and pcDNA-6L5- but not pcDNA-3.1-inoculated pigs developed neutralizing antibodies (NAs) 3 weeks after the final inoculation and a gradual increase in NA titers after PRRSV challenge, indicating that pigs inoculated with these DNA constructs could establish a sufficient immune memory. The pcDNA-5L6- and pcDNA-6L5-inoculated pigs displayed lower level and shorter period of viremia and lower tissue viral load following PRRSV challenge than did the pcDNA-56-inoculated pigs. The strategy of co-expressing GPGP-linked GP5 and M fusion protein may be a promising approach for future PRRSV vaccine development, possibly via the improvement of natural conformation of the target fusion protein.
authors.affiliation: Graduate Institute of Veterinary Medicine, School of Veterinary Medicine, Taipei 106, Taiwan, ROC.
authors.forename: Min-Yuan
authors.initials: MY
authors.lastname: Chia
authors.forename: Shih-Hsuan
authors.initials: SH
authors.lastname: Hsiao
authors.forename: Hui-Ting
authors.initials: HT
authors.lastname: Chan
authors.forename: Yi-Yin
authors.initials: YY
authors.lastname: Do
authors.forename: Pung-Ling
authors.initials: PL
authors.lastname: Huang
authors.forename: Hui-Wen
authors.initials: HW
authors.lastname: Chang
authors.forename: Yi-Chieh
authors.initials: YC
authors.lastname: Tsai
authors.forename: Chun-Ming
authors.initials: CM
authors.lastname: Lin
authors.forename: Victor Fei
authors.initials: VF
authors.lastname: Pang
authors.forename: Chian-Ren
authors.initials: CR
authors.lastname: Jeng
mesh_terms: D000818:Animals; D057134:Antibodies, Neutralizing / Q000097:blood; D000914:Antibodies, Viral / Q000097:blood; D006157:Guanosine Monophosphate / Q000031:analogs & derivatives* / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D019318:Porcine Reproductive and Respiratory Syndrome / Q000276:immunology; D019316:Porcine respiratory and reproductive syndrome virus / Q000235:genetics / Q000276:immunology*; D013552:Swine; D019444:Vaccines, DNA / Q000235:genetics / Q000276:immunology; D014759:Viral Envelope Proteins / Q000235:genetics* / Q000276:immunology*; D019562:Viral Load; D014763:Viral Matrix Proteins / Q000235:genetics* / Q000276:immunology*; D014765:Viral Vaccines / Q000235:genetics / Q000276:immunology*; D014766:Viremia / Q000276:immunology
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; C525999:M protein, porcine reproductive and respiratory syndrome virus; D019444:Vaccines, DNA; D014759:Viral Envelope Proteins; D014763:Viral Matrix Proteins; D014765:Viral Vaccines; C114789:glycoprotein 5, PRRSV; C024662:GpGp; D006157:Guanosine Monophosphate