Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, TX 77555-1019, USA.
Vaccine. 2013 Jan 7;31(3):559-65. doi: 10.1016/j.vaccine.2012.10.118. Epub 2012 Nov 12.
The safety and immunogenicity of two authentic recombinant (ar) Rift Valley fever (RVF) viruses, one with a deletion in the NSs region of the S RNA segment (arMP-12ΔNSs16/198) and the other with a large deletion of the NSm gene in the pre Gn region of the M RNA segment (arMP-12ΔNSm21/384) of the RVF MP-12 vaccine virus were tested in crossbred ewes at 30-50 days of gestation. First, we evaluated the neutralizing antibody response, measured by plaque reduction neutralization (PRNT(80)), and clinical response of the two viruses in groups of four ewes each. The virus dose was 1×10(5)plaque forming units (PFU). Control groups of four ewes each were also inoculated with a similar dose of RVF MP-12 or the parent recombinant virus (arMP-12). Neutralizing antibody was first detected in 3 of 4 animals inoculated with arMP-12ΔNSm21/384 on Day 5 post inoculation and all four animals had PRNT(80) titers of ≥1:20 on Day 6. Neutralizing antibody was first detected in 2 of 4 ewes inoculated with arMP-12ΔNSs16/198 on Day 7 and all had PRNT(80) titers of ≥1:20 on Day 10. We found the mean PRNT(80) response to arMP-12ΔNSs16/198 to be 16- to 25-fold lower than that of ewes inoculated with arMP-12ΔNSm21/384, arMP-12 or RVF MP-12. No abortions occurred though a single fetal death in each of the arMP-12 and RVF MP-12 groups was found at necropsy. The poor PRNT(80) response to arMP-12ΔNSs16/198 caused us to discontinue further testing of this candidate and focus on arMP-12ΔNSm21/384. A dose escalation study of arMP-12ΔNSm21/384 showed that 1×10(3)plaque forming units (PFU) stimulate a PRNT(80) response comparable to doses of up to 1×10(5)PFU of this virus. With further study, the arMP-12ΔNSm21/384 virus may prove to be a safe and efficacious candidate for a livestock vaccine. The large deletion in the NSm gene may also provide a negative marker that will allow serologic differentiation of naturally infected animals from vaccinated animals.
在妊娠 30-50 天的杂交母羊中，对两种真正的重组（ar）裂谷热（RVF）病毒的安全性和免疫原性进行了测试，一种是在 S RNA 片段的 NSs 区有缺失（arMP-12ΔNSs16/198），另一种是在 M RNA 片段的前 Gn 区有 NSm 基因的大片段缺失（arMP-12ΔNSm21/384）。RVF MP-12 疫苗病毒。首先，我们通过蚀斑减少中和试验（PRNT（80））评估了两种病毒在每组 4 只母羊中的中和抗体反应和临床反应。病毒剂量为 1×10（5）蚀斑形成单位（PFU）。每组 4 只母羊的对照组也接种了类似剂量的 RVF MP-12 或亲本重组病毒（arMP-12）。在接种 arMP-12ΔNSm21/384 的 4 只动物中，有 3 只在接种后第 5 天首次检测到中和抗体，第 6 天所有 4 只动物的 PRNT（80）滴度均≥1:20。在接种 arMP-12ΔNSs16/198 的 4 只母羊中，有 2 只在第 7 天首次检测到中和抗体，第 10 天所有母羊的 PRNT（80）滴度均≥1:20。我们发现，与接种 arMP-12ΔNSm21/384、arMP-12 或 RVF MP-12 的母羊相比，接种 arMP-12ΔNSs16/198 的母羊的平均 PRNT（80）反应低 16-25 倍。虽然在剖检时发现 arMP-12 和 RVF MP-12 组各有一只胎儿死亡，但未发生流产。arMP-12ΔNSs16/198 引起的 PRNT（80）反应不佳，导致我们停止了对该候选物的进一步测试，并将重点转移到 arMP-12ΔNSm21/384 上。arMP-12ΔNSm21/384 的剂量递增研究表明，1×10（3）蚀斑形成单位（PFU）可刺激与该病毒高达 1×10（5）PFU 的剂量相当的 PRNT（80）反应。经过进一步研究，arMP-12ΔNSm21/384 病毒可能被证明是一种安全有效的牲畜疫苗候选物。NSm 基因的大片段缺失也可能提供一个负标记，允许对自然感染动物和接种动物进行血清学区分。
