本研究的目的是評估以glycine-proline-glycine-proline (GPGP)作為連接子,同時表現豬生殖與呼吸道綜合症病毒(PRRSV)的封套醣蛋白(GP5)和膜蛋白(M)之DNA疫苗免疫小鼠時,是否能促進小鼠的免疫反應,共設計三組不同的DNA構築;分別為(1)不具GPGP連接子的pcDNA-56;(2)具有GPGP連接子的pcDNA-5L6;(3)具有GPGP連接子的pcDNA-6L5。將上述三組構築載入真核表現系統之載體(pcDNA3.1/V5-His TOPO)內,作為DNA疫苗使用,再將此三組疫苗以肌肉注射的方式免疫小鼠四次,每次間隔兩週,藉以評估其誘發之免疫反應,於實驗期間收集小鼠之血清作為PRRSV特異性抗體檢測之用,並於小鼠犧牲時收集其脾臟細胞作為淋巴細胞增殖反應檢測之用。結果顯示小鼠免疫pcDNA-5L6或pcDNA-6L5組所誘發的PRRSV特異性血清IgG抗體、中和抗體、和淋巴細胞增殖反應都比pcDNA-56組為佳。此結果證實以GPGP連接子同時表現GP5和M蛋白時,具有還原GP5/M蛋白自然結構的功能,進而促進該蛋白對小鼠的免疫原性。
The objective of the study was to evaluate whether co-expressing porcine reproductive and respiratory syndrome virus (PRRSV) envelop glycoprotein 5 (GP5) and matrix (M) protein linked by glycine-proline-glycine-proline (GPGP) could enhance its immunogenicity in mice. Three DNA constructs expressing GP5/M without GPGP linker (pcDNA-56), GP5/M conjugated by GPGP linker (pcDNA-5L6), and M/GP5 conjugated by GPGP linker (pcDNA-6L5) were included. These constructs were then inserted into an eukaryotic expression vector, pcDNA3.1/V5-His TOPO, as DNA vaccines to inject mice intramuscularly for four times at a 2-week interval. Serum samples were collected at various designated time points for the measurement of PRRSV-specific antibodies and splenocytes were isolated at time of sacrifice for lymphocyte blastogenesis assay. The results showed that pcDNA-5L6- and pcDNA-6L5-inoculated mice displayed higher PRRSV-specific neutralizing antibody (NA) titers, serum IgG responses, and lymphocyte proliferative responses than did the pcDNA-56-inoculated mice. The data indicated that co-expressing GP5/M with GPGP can indeed improve the immunogenicity of the heterodimeric complex.