Vaccination is currently the most effective strategy to control porcine reproductive and respiratory syndrome (PRRS). New-generation PRRS vaccines are required to be safe and broadly cross-protective. We have recently created the chimeric PRRS virus K418DM which proved to be a good vaccine candidate under field conditions. In the present study, we designed safety and efficacy tests under experimental and field conditions for further evaluation of K418DM1.1, a plaque-purified K418DM. In the homologous challenge study, K418DM1.1 induced high serum virus neutralization (SVN) antibody titers (i.e., 4.2 log₂ ± 1.7) at 21 days post-challenge (dpc) and provided protection as demonstrated by the significantly lower levels of viremia at 3 and 7 dpc and significantly lower microscopic lung lesion scores compared to the unvaccinated group. K418DM1.1 was also protective in the heterologous challenge study, with vaccinated pigs showing significantly lower levels of viremia at 14 dpc compared to the unvaccinated pigs. A field study was performed to evaluate the efficacy of K418DM1.1 against heterologous exposure and vaccinated pigs presented significantly lower viremia than unvaccinated pigs. According to the safety test for the examination of virulence reversion, no infectivity was observed in tissue homogenate filtrate both in the vaccinated and comingled groups. Thus, the risk of virulence, as well as transmission, appeared negligible. These overall results indicate that K418DM1.1 is a good vaccine candidate based on its safety and protective efficacy.

疫苗接种是目前控制猪繁殖与呼吸综合征（PRRS）的最有效策略。新一代PRRS疫苗需要安全且具有广泛的交叉保护作用。我们最近创建了嵌合PRRS病毒K418DM，该病毒在野外条件下被证明是很好的候选疫苗。在本研究中，我们设计了在实验和现场条件下的安全性和有效性测试，以进一步评估斑块纯化的K418DM1.1。在同源攻击研究中，K418DM1.1诱导了高血清病毒中和（SVN）抗体滴度（即4.2 log ₂ 攻击后（dpc）第21天（±1.7）并提供保护，如未接种疫苗的组在3 dpc和7 dpc时的病毒血症水平显着降低，并且微观肺损伤评分显着降低。K418DM1.1在异源攻击研究中也具有保护作用，接种疫苗的猪在14 dpc时的病毒血症水平明显低于未接种疫苗的猪。进行了一项现场研究以评估K418DM1.1对异源暴露的功效，接种疫苗的猪的病毒血症明显低于未接种疫苗的猪。根据用于检查毒力回复的安全性测试，在接种组和骆驼科中，组织匀浆中均未观察到感染性。因此，毒力以及传播的风险似乎可以忽略不计。