Evaluation of LASV Protective Immunity in Mice Using Reassortant Virus ML29

描述（由申请人提供）：拉沙病毒（LASV）是拉沙热（LF）的病原体，拉沙热是西非流行的人畜共患病毒性出血热，造成广泛传播的疾病和显著的发病率和死亡率。目前还没有针对LF的疫苗，而对这种疫苗的需求却在不断增加。利巴韦林是唯一已知的在感染后早期有效治疗LF的药物，在流行地区很难获得，而在大范围流行地区，啮齿动物储存库控制是一种不可行的策略。此外，由于LASV被列为a类优先剂，对疫苗开发研究的需求甚至更高。然而，LASV是一种需要最高水平的生物控制才能进行研究的病原体，因此开发这种疫苗既困难又昂贵。随着重组病毒ML29的产生，有可能建立小鼠模型，用于在生物安全4级（BSL-4）环境外评估LF候选疫苗。ML29是一种重组病毒，含有LASV的遗传亲缘关系——非致病性mopea病毒（MOPV）的复制机制，并编码LASV主要抗原、糖蛋白前体（GPC）和核蛋白（NP）。与野生型LASV相比，它在体外和体内均表现出减弱的表型。此外，与以往使用假型病毒呈现LASV抗原的努力不同，该重组病毒是一种表达野生型LASV免疫原GPC和NP的复制能力强的完全沙粒病毒，使ML29成为研究LASV样攻击免疫生物学保护的理想候选病毒。小鼠模型为脾细胞过继性转移模型。近亲繁殖的CBA/J小鼠已被证明易受ML29致死性脑内（i.c）攻击，但对腹腔（i.p）免疫没有反应，类似于密切相关的原型沙粒病毒淋巴细胞性脉络丛脑膜炎病毒（LCMV）。通过追踪非特异性和特异性细胞介导的免疫反应，ML29免疫小鼠被用来进一步表征重组病毒引发的免疫反应。众所周知，抗体应答在病毒清除中作用不大，而细胞介导的GPC和NP应答似乎是对抗LCMV和LASV的主要保护手段。一旦建立，该模型将为研究lasv样免疫提供一个极好的工具，并为评估潜在的LF候选疫苗提供一个适当的平台。ML29是一种介于Mopeia病毒和拉沙病毒之间的重组病毒，它将允许研究拉沙样沙粒病毒在小鼠中引起的免疫反应。所提出的小鼠模型将允许评估对拉沙样感染的免疫原性和拉沙热候选疫苗的评估。

DESCRIPTION (provided by applicant): Lassa virus (LASV) is the causative agent of Lassa Fever (LF), a zoonotic viral hemorrhagic fever endemic in West Africa responsible for wide spread disease and significant morbidity and mortality. There currently exists no vaccine against LF, while the need for such a vaccine is ever increasing. Ribavirin, the only known treatment to be effective against LF early on after infection, is hard to come by in endemic areas while rodent reservoir control is an unfeasible strategy over the wide ranging areas of endemicity. Furthermore, with the classification of LASV as a Category A Priority agent the need for vaccine development research is even higher. However, LASV is a pathogen that requires the highest level of biocontainment for study and as such vaccine development is both difficult and costly. With the generation of a reassortant virus ML29 there exists the potential to develop a mouse model for the purpose of evaluating the LF vaccine candidates outside of a biosafety level 4 (BSL-4) environment. ML29 is a reassortant virus containing the replication machinery of the nonpathogenic Mopeia virus (MOPV), a genetic relative of LASV, and encodes the LASV major antigens, glycoprotein precursor (GPC) and the nucleoprotein (NP). It displays an attenuated phenotype both in vitro and in vivo as compared to wild type LASV. Furthermore, unlike past efforts to present LASV antigens using pseudotyped viruses, this reassortant virus is a replication competent complete arenavirus expressing wild type LASV immunogens GPC and NP making ML29 the ideal candidate to study the immunobiology involved in the protection against a LASV-like challenge. The proposed mouse model is a splenocyte adoptive transfer model. Inbred CBA/J mice have been shown to be susceptible to a lethal intracerebral (i.c.) challenge with ML29, but display no disease in response to an intraperitoneal (i.p.) immunization, similar to the closely related prototype arenavirus lymphocytic choriomeningitis virus (LCMV). ML29 immunized mice have been used to further characterize the immune response elicited by the reassortant virus by tracking non-specific and specific cell mediated immune responses. It is known that antibody responses play little role in viral clearance, while cell mediated responses to GPC and to NP seem to be the primary means of protection against LCMV and LASV. Once established, the model will provide an excellent tool for the study of a LASV-like immunity as well as an appropriate platform for the evaluation of potential LF vaccine candidates. ML29, a reassortant virus between Mopeia virus and Lassa virus will allow the study of the immune response elicited by a Lassa-like arenavirus in mice. The proposed mouse model will allow the evaluation of immunogenicity to a Lassa like-infection and the evaluation of Lassa fever vaccine candidates.