Mulder W A, De Jong M C, Priem J, Bouma A, Pol J M, Kimman T G
Institute for Animal Science and Health, Department of Porcine and Exotic Viral Diseases, AJ Lelystad, The Netherlands.
Vaccine. 1995 Dec;13(18):1763-9. doi: 10.1016/0264-410x(95)00156-u.
There is concern that live pseudorabies virus (PRV) vaccine or PRV vector vaccine strains may spread from vaccinated to unvaccinated pigs. Moreover, it is feared that recombining PRV vaccine strains with related vaccine or wild-type strains may lead to spread and survival of recombinant PRV. To learn more about to what extent different PRV vaccine strains could spread we used a previously described experimental model to study the transmission of intranasally inoculated PRV mutant strains under experimental conditions. We used PRV strains that lacked glycoprotein E (gE) or thymidine kinase (TK), and a PRV vector vaccine (gE-, TK-, gG-) that expresses the glycoprotein E1 (E1) of hog cholera virus. In addition, we investigated whether intranasally co-inoculated gE-negative and gE-positive PRV strains competed in transmission among pigs. The extent of transmission was estimated using the reproduction ratio R. This ratio has a threshold property; when R1, the infection can spread; when R < 1, the infection will disappear. We found that R for a gE-negative strain was 10.1, and R for a TK-negative strain was 5. Furthermore, the R for the vector vaccine (gE-, TK-, gG-) expressing E1 was 0.18, and did not differ significantly from the R for the control strain without E1. The R of gE-negative strain was significantly 1 (P = 0.0005). Co-inoculation with a gE-positive field strain did not prevent the transmission of a gE-negative strain. This study shows that a small-scale experiment can be used to estimate the transmission of genetically engineered organisms in their host species. The results of this study indicate that the deletion of gE alone or TK alone is not enough to prevent spread of PRV among susceptible pigs, and that transmission of gE-negative PRV is not firmly limited by co-presence of a gE-positive strain.
人们担心伪狂犬病病毒（PRV）活疫苗或PRV载体疫苗株可能从接种疫苗的猪传播到未接种疫苗的猪。此外，还担心PRV疫苗株与相关疫苗或野生型毒株重组可能导致重组PRV的传播和存活。为了更多地了解不同PRV疫苗株的传播程度，我们使用了先前描述的实验模型来研究在实验条件下经鼻接种的PRV突变株的传播情况。我们使用了缺乏糖蛋白E（gE）或胸苷激酶（TK）的PRV株，以及一种表达猪霍乱病毒糖蛋白E1（E1）的PRV载体疫苗（gE-、TK-、gG-）。此外，我们研究了经鼻共同接种的gE阴性和gE阳性PRV株在猪之间的传播是否存在竞争。传播程度用繁殖率R来估计。这个比率具有阈值特性；当R>1时，感染可以传播；当R<1时，感染将消失。我们发现gE阴性株的R为10.1，TK阴性株的R为5。此外，表达E1的载体疫苗（gE-、TK-、gG-）的R为0.18，与不含E1的对照株的R没有显著差异。gE阴性株的R显著大于1（P = 0.0005）。与gE阳性田间毒株共同接种并不能阻止gE阴性株的传播。这项研究表明，小规模实验可用于估计基因工程生物体在其宿主物种中的传播情况。本研究结果表明，单独缺失gE或TK不足以防止PRV在易感猪之间传播，并且gE阴性PRV的传播不受gE阳性株共存的严格限制。
