猪繁殖与呼吸综合征病毒GP5基因对猪的DNA免疫

【目的】检测PRRSV GP5 DNA重组质粒在猪体诱导的免疫反应以及细胞因子的佐剂效应。【方法】将表达PRRSV GP5的DNA重组质粒与表达3种细胞因子的重组质粒联合免疫SPF猪，经3次免疫后人工感染PRRSV，检测体液免疫、细胞免疫以及攻毒保护性反应。【结果】重组质粒pCI-GP5可诱导免疫猪产生中和抗体，效价达1:19.2，并可诱导机体产生较强的细胞免疫，攻毒后组织中PRRSV核酸的检出率下降39%，表明表达PRRSV GP5的DNA重组质粒pCI-GP5可诱导一定的免疫效力。pcDNA-IL-4与pCI-GP5共免可将中和抗体效价提高到1:35.5，且可增强细胞免疫反应，与对照组相比，病毒血症的出现频率减少17%，PRRSV阳性组织检出率下降64%；pcDNA-IL-2与pCI-GP5共免也可增强猪的细胞免疫，与对照组相比，病毒血症的出现频率下降50%，PRRSV阳性组织检出率减少59%； pcDNA-IFN- 与pCI-GP5共免对病毒血症的出现及病毒在组织中的分布均没有抑制作用。【结论】动物试验结果表明IL-4及IL-2可作为PRRSV GP5 DNA重组质粒的免疫佐剂。

Immunization in Pigs Vaccined with DNA Encoding PRRSV GP5

【Objective】The aim is to analyze the immune responses and the effects of the cytokines induced by GP5 recombinant plasmids of PRRSV. 【Method】SPF piglets were immunized with DNA recombinant plasmids pCI-GP5 which expresses PRRSV GP5 by co-administration of pcDNA-IFN- , pcDNA-IL-2 and pcDNA-IL-4 for three inoculations. The vaccinated pigs were challenged intranasally with PRRSV BJ-4. 【Result】DNA immunization with pCI-GP5 resulted in the production of both neutralizing antibodies (1:19.2) and cellular immune responses two weeks after the third immunization. The pCI-GP5 showed significantly better protection from the PRRSV challenge compared with the control plasmid. The protection was characterized with a decrease of 39% PRRSV-positive tissues. In addition, the co-administration of pcDNA-IL-4 increased the immune response induced by pCI-GP5. This immune response was characterized by a significant enhancement of a lymphoproliferative response and a higher percentage of CD4-CD8+T cell, showing a higher viral neutralization titer of 1:35.5, a lower percentage of PRRSV-positive tissues and a significantly decreased frequency of viraemia (a drop of 64% and a drop of 17%, respectively, compared with the control group). Delivery of pcDNA-IL-2 paired with pCI-GP5 resulted in enhanced cellular immune responses, remarkably reduced percentage of PRRSV-positive tissues and frequency of viraemia (a drop of 59% and a drop of 50%, respectively, compared with the control group). In contrast, the co-administration of pcDNA-IFN- had no adjuvant effects. 【Conclusion】The results indicated that IL-4 and IL-2 could be used as adjuvant of PRRSV DNA vaccine.