Development of a nanoparticle-based vaccine for prevention of acute and recurrent Herpes Simplex Virus infections

人类单纯疱疹病毒（HSV）感染是世界范围内最常见的病毒相关疾病。这种病毒通过直接从一个细胞传播到另一个细胞并建立潜伏期而成功避免被免疫系统清除的能力导致了终身感染。随后，潜伏期的周期性再激活导致原发感染部位的复发性症状感染。尽管已经尝试了许多策略，但迄今为止还没有开发出成功的针对HSV感染的疫苗。控制单纯疱疹病毒感染的主要问题是单纯疱疹病毒用来避免免疫反应的各种机制。特别是，在急性或复发性感染期间，HSV通过细胞间扩散机制直接在相邻细胞之间迁移，而不受细胞或体液免疫化合物的干扰。显然，传统的疫苗方法未能绕过这一障碍。由于迫切需要一种有效的疫苗来预防新的感染和治疗方法，因此本研究应研究一种新的疫苗策略。最近，我们发现高度中和的抗体mAb hu2c能够抑制细胞间扩散机制，在高度免疫低下的NOD/SCID小鼠中介导了完全保护，使其免受致命感染的建立。此外，已经建立的粘膜感染被中和，病毒从周围到大脑的神经元传播可以完全中止。结果表明，能够诱导体液反应的疫苗含有与mAb hu2c具有相同特异性的抗体，应该可以有效地预防新的HSV感染和再激活。基于这些发现，本研究项目的重点是设计和临床前评估一种创新的基于纳米颗粒的疫苗，该疫苗旨在诱导能够预防HSV感染的高度中和抗体，并通过抑制病毒的细胞间传播来限制再激活的频率。因此，对mAb hu2c具有高亲和力的肽将被选择用于生成衣壳样颗粒（CLPs）或磷酸钙纳米颗粒（CaPs）。随后，将在小鼠中研究这些纳米颗粒在介导保护性体液反应中的功效，这些保护性体液反应含有高度中和和细胞间扩散抑制抗体。诱导最高水平的中和和细胞间扩散抑制抗体的候选药物将被考虑用于随后的动物挑战实验。小鼠实验将用于研究疫苗对新的单纯疱疹病毒感染的影响，而豚鼠实验将用于检查疫苗对单纯疱疹病毒再激活的功效。计划的实验应对研制有效的HSV预防和治疗疫苗作出重要贡献。

Human Herpes Simplex Virus (HSV) infections belong to the most frequently occurring virus-associated diseases worldwide. The ability of the virus to successfully avoid clearance by the immune system by spreading directly from cell to cell and establishing latency leads to lifelong infection. Subsequently, periodic reactivations from latency result in recurrent symptomatic infections at the site of primary infection. Although many strategies have been tried, no successful vaccine against HSV infections was developed so far. The major problem of controling HSV-infections are the various mechanisms HSV uses to avoid the immune response. Particularly, HSV migrates directly between adjacent cells over the the cell-to-cell spread mechanism during acute or recurrent infections without beeing disturbed by cellular or humoral immune compounds. Obviously, conventional vaccine approaches failed to circumvent this obstacle. Because of the urgent need of an effective vaccine for the prevention of new infections and for therapeutic approaches, a novel vaccine strategy should be investigated in the present study. Recently, we showed that the presence of the highly neutralizing antibody mAb hu2c, which is capable of inhibiting the cell-to-cell spread mechanism, mediated complete protection from the establishment of an otherwise lethal infection in highly immunocompromized NOD/SCID mice. Moreover, an already established mucosal infection was neutralized and the neuronal spread of the virus from the periphery to the brain could be completely aborted. The results indicate that a vaccine capable of inducing a humoral response containing antibodies with equal specificities as mAb hu2c should be effective in preventing new HSV infections and reactivations. Based on these findings, the focus of this research project is the design and pre-clinical evaluation of an innovative mimotope-based nanoparticle vaccine designed to induce highly neutralizing antibodies capable of preventing HSV infections and limiting the frequency of reactivations by inhibiting the cell-to-cell transmission of the virus. Therefore, peptides exhibiting high avidity to mAb hu2c will be selected for the generation of capsid-like particles (CLPs) or calcium-phosphate nanoparticles (CaPs. Subsequently, the efficacy of these nanoparticles in mediating protective humoral responses containing highly neutralizing and cell-to-cell spread inhibiting antibodies will be investigated in mice. Candidates inducing the highest levels of neutralizing as well as cell-to-cell spread inhibiting antibodies will then be considered for subsequent challenge experiments in animals. Mouse experiments will be performed to investigate the impact of the vaccine on a new HSV infection, whereas guinea pigs will serve for examination of the efficacy of the vaccine on HSV reactivations. The planned experiments shall make an important contribution to the development of an effective prophylactic and therapeutic HSV vaccine.