Haley Shannon L, Tzvetkov Evgeni P, Lytle Andrew G, Alugupalli Kishore R, Plummer Joseph R, McGettigan James P
Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, PA, United States.
Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, PA, United States; Jefferson Vaccine Center, Thomas Jefferson University, Philadelphia, PA, United States.
Antiviral Res. 2017 Aug;144:130-137. doi: 10.1016/j.antiviral.2017.06.004. Epub 2017 Jun 12.
There is significant need to develop a single-dose rabies vaccine to replace the current multi-dose rabies vaccine regimen and eliminate the requirement for rabies immune globulin in post-exposure settings. To accomplish this goal, rabies virus (RABV)-based vaccines must rapidly activate B cells to secrete antibodies which neutralize pathogenic RABV before it enters the CNS. Increased understanding of how B cells effectively respond to RABV-based vaccines may improve efforts to simplify post-exposure prophylaxis (PEP) regimens. Several studies have successfully employed the TNF family cytokine a proliferation-inducing ligand (APRIL) as a vaccine adjuvant. APRIL binds to the receptors TACI and B cell maturation antigen (BCMA)-expressed by B cells in various stages of maturation-with high affinity. We discovered that RABV-infected primary murine B cells upregulate APRIL ex vivo. Cytokines present at the time of antigen exposure affect the outcome of vaccination by influencing T and B cell activation and GC formation. Therefore, we hypothesized that the presence of APRIL at the time of RABV-based vaccine antigen exposure would support the generation of protective antibodies against RABV glycoprotein (G). In an effort to improve the response to RABV vaccination, we constructed and characterized a live recombinant RABV-based vaccine vector which expresses murine APRIL (rRABV-APRIL). Immunogenicity testing in mice demonstrated that expressing APRIL from the RABV genome does not impact the primary antibody response against RABV G compared to RABV alone. In order to evaluate the necessity of APRIL for the response to rabies vaccination, we compared the responses of APRIL-deficient and wild-type mice to immunization with rRABV. APRIL deficiency does not affect the primary antibody response to vaccination. Furthermore, APRIL expression by the vaccine did not improve the generation of long-lived antibody-secreting plasma cells (PCs) as serum antibody levels were equivalent in response to rRABV-APRIL and the vector eight weeks after immunization. Moreover, APRIL is dispensable for the long-lived antibody-secreting PC response to rRABV vaccination as anti-RABV G IgG levels were similar in APRIL-deficient and wild-type mice six months after vaccination. Mice lacking the APRIL receptor TACI demonstrated primary anti-RABV G antibody responses similar to wild-type mice following immunization with the vaccine vector indicating that this response is independent of TACI-mediated signals. Collectively, our findings demonstrate that APRIL and associated TACI signaling is dispensable for the immune response to RABV-based vaccination.
迫切需要开发一种单剂量狂犬病疫苗，以取代目前的多剂量狂犬病疫苗接种方案，并消除暴露后使用狂犬病免疫球蛋白的需求。为实现这一目标，基于狂犬病病毒（RABV）的疫苗必须迅速激活B细胞以分泌抗体，在致病性RABV进入中枢神经系统之前将其中和。对B细胞如何有效应对基于RABV的疫苗的进一步了解，可能有助于简化暴露后预防（PEP）方案。多项研究已成功将肿瘤坏死因子家族细胞因子增殖诱导配体（APRIL）用作疫苗佐剂。APRIL以高亲和力与成熟各阶段B细胞表达的受体跨膜激活物和钙调亲环素配体相互作用分子（TACI）及B细胞成熟抗原（BCMA）结合。我们发现，RABV感染的原代小鼠B细胞在体外上调APRIL的表达。抗原暴露时存在的细胞因子通过影响T细胞和B细胞激活以及生发中心（GC）形成来影响疫苗接种的结果。因此，我们推测在基于RABV的疫苗抗原暴露时APRIL的存在将有助于产生针对狂犬病病毒糖蛋白（G）的保护性抗体。为了改善对RABV疫苗接种的反应，我们构建并鉴定了一种表达小鼠APRIL的基于RABV的活重组疫苗载体（rRABV-APRIL）。在小鼠中的免疫原性测试表明，与单独的RABV相比，从RABV基因组表达APRIL不会影响针对RABV G的初次抗体反应。为了评估APRIL对狂犬病疫苗接种反应的必要性，我们比较了APRIL缺陷型和野生型小鼠对rRABV免疫的反应。APRIL缺陷不影响疫苗接种的初次抗体反应。此外，疫苗表达APRIL并未改善长寿抗体分泌浆细胞（PC）的产生，因为免疫后八周，对rRABV-APRIL和载体的血清抗体水平相当。此外，APRIL对于rRABV疫苗接种的长寿抗体分泌PC反应是可有可无的，因为接种疫苗六个月后，APRIL缺陷型和野生型小鼠中的抗RABV G IgG水平相似。缺乏APRIL受体TACI的小鼠在用疫苗载体免疫后表现出与野生型小鼠相似的初次抗RABV G抗体反应，表明这种反应独立于TACI介导的信号。总的来说，我们的研究结果表明，APRIL和相关的TACI信号对于基于RABV的疫苗接种的免疫反应是可有可无的。
