Endogenous Retroviruses and the Immune Response to Pathogens

描述(申请人提供)：大约8%的人类基因组由逆转录病毒DNA的整合拷贝组成。至少有一些内源性逆转录病毒被转录并翻译成蛋白质，但其功能后果尚不清楚。然而，内源性逆转录病毒与外源性逆转录病毒编码许多相同的基因，众所周知，外源性逆转录病毒操纵免疫系统，允许慢性感染和疾病。例如，与BetaretroVirus小鼠乳腺肿瘤病毒(MMTV)相关的内源性前病毒(又名MTV)已知通过表达超抗原(SAG)影响小鼠的T细胞库。一种与BALB/c小鼠同源但缺乏内源性MTV前病毒的新小鼠品系BALB/MTV-Null已被培育出来。我们已经证明，与亲本BALB/c株相比，MTV缺失的小鼠对特定的病毒和细菌病原体更具抵抗力，包括外源MMTV、Friend鼠白血病病毒和革兰氏阴性菌霍乱弧菌。尽管每种病原体的耐药机制可能不同，但初步数据表明，与BALB/c小鼠相比，MTV基因缺失的小鼠拥有更多的成熟不变自然杀伤T细胞(INKT)。有趣的是，单个MTV前病毒位于不同的小鼠染色体上，具有不同数量的基因，对iNKT表型或对病原体感染的抵抗力的贡献并不相等。霍乱弧菌对霍乱弧菌的敏感性由三种内源性MTV中的任何一种重组，其中一种仅编码SAG。然而，仅有SAG的MTV前病毒只部分重建了对MMTV诱导的乳腺肿瘤的易感性，并且不会增加对Friend病毒疾病的易感性。另一方面，一个完整的前病毒Mtw9重建了对MMTV和Friend病毒的易感性。完整的MMTV前病毒编码Rem，一种与人类内源性病毒K(Herv-K)Rec蛋白相关的Rev样蛋白。REC与转录因子PLZF相互作用，PLZF控制iNKT细胞的功能和成熟。我们认为，由特定的小鼠和人类逆转录病毒编码的REV样蛋白通过PLZF和iNKT细胞控制对病原体的免疫反应。在第一个特定目标中，将发展表达rem或rec的转基因小鼠，并研究它们对iNKT细胞成熟和对外源性逆转录病毒的敏感性的影响。在第二个特定目标中，将表达rem或rec的逆转录病毒转导原代胸腺细胞，以确定它们对细胞表型和PLZF功能的影响。这些实验将增加我们对T细胞选择和分化以及对病原体的免疫反应的理解。这项提议的长期目标是开发治疗传染病的新方法。

DESCRIPTION (provided by applicant): Approximately 8% of the human genome is composed of integrated copies of retroviral DNA. At least some of the endogenous retroviruses are transcribed and translated into proteins, but the functional consequences are unclear. Nevertheless, endogenous retroviruses encode many of the same genes as exogenous retroviruses, which are known to manipulate the immune system to allow chronic infections and disease. For example, endogenous proviruses related to the betaretrovirus mouse mammary tumor virus (MMTV) (aka Mtvs) are known to affect the T-cell repertoire of mice through expression of superantigen (Sag). A novel mouse strain, BALB/Mtv-null, has been developed that is congenic to BALB/c mice, but lacks endogenous Mtv proviruses. We have shown that the Mtv-null mice are more resistant to specific viral and bacterial pathogens, including exogenous MMTV, Friend murine leukemia virus, and the gram- negative bacterium, Vibrio cholerae, compared to the parental BALB/c strain. Although the mechanism of resistance may not be the same for each pathogen, preliminary data indicate that Mtv-null mice have increased numbers of mature invariant natural killer T (iNKT) cells compared to those of BALB/c mice. Interestingly, individual Mtv proviruses, which are located on different mouse chromosomes and have different numbers of genes, do not contribute equally to iNKT phenotype or resistance to pathogen infection. Susceptibility to V. cholerae is reconstituted by any one of three endogenous Mtvs, including one that encodes only Sag. Nevertheless, the Sag-only Mtv provirus only partially reconstitutes susceptibility to MMTV-induced mammary tumors, and does not increase susceptibility to Friend virus disease. On the other hand, a complete provirus, Mtv9, reconstitutes susceptibility to both MMTV and Friend virus. Complete MMTV proviruses encode Rem, a Rev-like protein related to the human endogenous virus type K (HERV-K) Rec protein. Rec has been shown to interact with the transcription factor, PLZF, which controls the function and maturation of iNKT cells. We propose that Rev-like proteins encoded by specific murine and human retroviruses control the immune response to pathogens through PLZF and iNKT cells. In the first specific aim, transgenic mice expressing either rem or rec will be developed and characterized for their effects on the maturation of iNKT cells and susceptibility to exogenous retroviruses. In the second specific aim, primary thymocytes will be transduced with retroviruses expressing either rem or rec to determine their effects on cellular phenotype and PLZF function. These experiments will increase our understanding of T- cell selection and differentiation as well as the immune response to pathogens. The long-term goal of this proposal is the development of new approaches for treatment of infectious disease.