The use of goat model to test human Brucella vaccines in Argentina

描述(由申请人提供)：我们建议的研究目标是开发安全有效的布鲁氏菌感染疫苗。我们的总体方法侧重于使用减毒活疫苗(LAV)。使用活的减毒生物通常被认为是布鲁氏菌等胞内细菌的首选疫苗。这一策略利用了生物体的自然属性，包括细胞侵袭和组织趋向性，同时提供了完整的免疫原，并得到了成功历史的支持。然而，目前可用的疫苗在人类身上使用是不安全的。我们试图确定在人类身上安全使用的改进的活的减毒疫苗候选疫苗。潜在布鲁氏菌疫苗的常规测试利用小鼠模型来评估毒力和免疫保护。然而，小鼠没有表现出感染布鲁氏菌的外在迹象。因此，候选疫苗评估的下一步是 目标物种。对于人类疫苗的开发，这可能建议在评估阶段使用非人类灵长类动物。然而，疫苗的评估可以在绵羊或山羊等小型反刍动物模型中进行，以消除产生与包括流产在内的疾病相关症状的候选疫苗，从而提供最终的安全性评估。虽然胎盘组织趋向性在反刍动物中仍然是一个有充分证据的现象，但布鲁氏菌并不被认为是人类流产的重要原因。然而，最近的证据显示，在流行地区，暴露与高堕胎率之间存在很强的相关性。此外，有强有力的证据支持羊布鲁氏菌在人滋养层细胞中的生长。综上所述，这些数据为我们的LAV的继续发展提供了强有力的支持，因为我们显然需要改进保护战略，以减少人类疾病的可能性。在山羊身上的实验有望为在非人类灵长类动物中测试这些候选动物的实验提供支持，最终目标是开发一种安全有效的人类使用的布鲁氏菌疫苗。概述的努力利用了我们最近开发的平台(封装)来延长免疫系统刺激，而不延长疫苗株的存活时间。使用这一创新方法，我们通过多层次的调查取得了进展，以证明LAV的有效性和安全性，为实现发展提供了强有力的理由。这个 提出的竞争优势和方法创新包括：(1)在成熟、稳定的遗传背景下对高度衰减的、安全的、基因敲除进行评估；(2)在尽可能严格的条件下进行安全性评估；(3)支持开发非人类灵长类动物模型；(4)降低生物遏制水平和对制造的支持(GMP)的可能性；以及临床试验、生产和分销的未来进展。

DESCRIPTION (provided by applicant): The goal of our proposed research is the development of vaccines against Brucella infection that are safe and efficacious. Our general approach has focused on the use of live attenuated vaccines (LAV). The use of live attenuated organisms are generally considered to be the vaccine of choice for intracellular bacteria such as Brucella spp. This strategy take advantage of the natural properties of the organism, including cell invasion and tissue tropism while presenting a full complement of immunogens, and is supported by a history of success. However, currently available vaccines are unsafe for use in humans. We have sought to identify improved live, attenuated vaccine candidates that are safe for use in humans. Routine testing of potential Brucella vaccines utilizes the mouse model to evaluate virulence and immune protection. However, mice fail to exhibit the outward signs of "Brucella" infection. As a result the next step in evaluation of vaccine candidates has been in the target species. For human vaccine development this might suggest the use of nonhuman primates at this stage of evaluation. However, evaluation of vaccines may be performed in a small ruminant model such as sheep or goats to eliminate candidates that produce symptoms associated with disease including abortion, providing an ultimate evaluation of safety. Although placental tissue tropism remains a well-documented phenomenon in ruminants, Brucella has not been considered to be a significant cause of human abortion. However, recent evidence revealed a strong correlation between exposure and elevated rates of abortion in endemic regions. Furthermore, there is strong evidence supporting growth of Brucella melitensis in human trophoblasts. Taken together, these data provide strong support for continued development of our LAV based on the obvious need for improved protection strategies to reduce the potential for human disease. Experiments in goats are expected to provide the support for experimentation to test these candidates in nonhuman primates with the ultimate goal of developing a Brucella vaccine that is safe and efficacious for human use. The efforts outlined have taken advantage of our recently developed platform (encapsulation) to prolong immune system stimulation without prolonging the survival of the vaccine strain. Using this innovative approach we have progressed through multiple levels of investigation to demonstrate efficacy and safety of the LAV providing strong justification to bring development to fruition. The competitive advantages and innovations of approach presented include: (1) evaluation of highly attenuated, safe, gene knockouts in well-established, stable genetic background; (2) safety evaluation under the most stringent conditions possible, (3) support for development of a nonhuman primate model; (4) potential to reduce biocontainment level and support for manufacturing (GMP) and future progress for clinical trials, production and distribution.