Immunoprophylaxis to Kell RBC Alloimmunization During Pregnancy

说明(申请人提供)：红细胞同种异体免疫可通过在输血治疗期间或在妊娠或分娩期间胎儿/母亲出血期间暴露于非自身红细胞抗原而发生。从以下角度来看，这些抗体可能是危险的，即接受同种免疫的患者在随后的输血后发生溶血性输血反应的风险增加。它们也可能是危险的；然而，对于红细胞表达同源抗原的胎儿来说。胎儿和新生儿溶血性疾病(HDFN)发生在超过1/600的妊娠，并可能是致命的。虽然自然产生的针对A或B抗原的抗体可能导致轻度HDFN，但严重的HDFN主要是由针对D或Kell等抗原的抗体引起的。唯一能防止孕期同种异体免疫的治疗方法是多克隆抗D抗体，其作用机制(S)尚不清楚。目前还没有预防非D抗原免疫的治疗方法，也没有有针对性的治疗方法来最大限度地减少现有母体同种抗体的危险。这一治疗差距的存在部分是由于人类研究的技术和伦理限制，大多数研究仅限于抗体特异性、效价和胎儿结局之间的观察/相关性研究。在这里，我们提出了一种新的小鼠妊娠(和输血)诱导的抗KEL红细胞同种异体免疫模型，在该模型中，抗KEL穿过胎盘，与KEL阳性的胎儿红细胞结合，似乎对幼鼠不利。与未接种疫苗的未接种母鼠相比，接种者在连续怀孕期间产下的幼崽逐渐变小。中心假设：母体KEL同种抗体通过1)结合和随后清除胎儿红细胞和/或2)抑制胎儿红细胞生成而对KEL阳性幼崽有害。通过肌注多克隆(但不是单克隆)的“KEL”GAM，通过去除KEL阳性的胎儿红细胞和/或通过掩蔽/丢失这些RBC上的KEL抗原，可以防止母体产生抗KEL。具体目标1：通过输血产生的抗KEL抗体与通过妊娠产生的抗KEL抗体的功能特征特定目标2：评估多克隆“KEL”GAM和单抗KEL对胎儿红细胞的作用以及预防孕期母体红细胞同种异体免疫的公共卫生意义/长期目标：这项建议与公共卫生相关，因为它描述了第一个由妊娠诱导的RBC同种异体免疫导致胎儿死亡的动物模型，利用动物模型的优点来探索通过观察性人体研究尚未(和不能)回答的问题。这项工作的最终长期目标是降低母体红细胞在胎儿和新生儿中的异体免疫的发病率/死亡率。 与公共卫生相关：母体抗RBC抗体在输血期间暴露于外来RBC抗原或妊娠期间胎儿/母体出血后可能形成，对表达同源抗原的胎儿可能是致命的。胎儿和新生儿溶血性疾病(HDFN)发生在1/600以上的妊娠中，除了多克隆抗-D(“Rhogam”)外，没有针对性的治疗方法来防止同种异体免疫。这项建议与公共卫生相关，因为它描述了第一个由妊娠诱导的导致胎儿死亡的红细胞同种免疫的动物模型，利用动物模型的优势来探索通过观察性人类研究没有(和不能)回答的问题；这项工作的最终长期目标是减少孕妇红细胞同种免疫在胎儿和新生儿中的发病率/死亡率。

DESCRIPTION (provided by applicant): RBC alloimmunization may occur through exposure to non- self RBC antigens during transfusion therapy or during fetal/maternal bleeds in pregnancy or delivery. These antibodies can be dangerous from the perspective that alloimmunized patients are at increased risk of having hemolytic transfusion reactions following subsequent transfusions. They may also be dangerous; however, to fetuses whose RBCs express cognate antigens. Hemolytic disease of the fetus and newborn (HDFN) occurs in more than 1/600 pregnancies and may be deadly. Although naturally occurring antibodies against A or B antigens may cause mild HDFN, severe HDFN is caused predominantly by antibodies directed against antigens such as D or Kell. The only therapy that exists to prevent alloimmunization during pregnancy is polyclonal anti-D, and its mechanism(s) of action are unclear. There are currently no therapies to prevent immunization to non-D antigens, nor are there targeted therapies to minimize the dangers of existing maternal alloantibodies. This therapeutic gap exists in part due to technical and ethical limitations of human studies, most of which have been limited to observation/correlation studies between antibody specificity, titer, and fetal outcome. Herein, we present a novel murine model of pregnancy (and transfusion) induced anti-KEL RBC alloimmunization, in which anti-KEL crosses the placenta, binds to KEL positive fetal RBCs, and appears detrimental to pups. Progressively smaller litters are produced by immunized mothers in successive pregnancies compared to virgin non-immunized control females. Central Hypothesis: Maternal KEL alloantibodies are detrimental to KEL positive pups through 1) binding and subsequent clearance of fetal RBCs and/or 2) suppression of fetal erythropoiesis. Maternal de novo generation of anti-KEL will be prevented by IM administration of polyclonal (but not monoclonal) "KEL"Gam through removal of KEL positive fetal RBCs and/or through masking/loss of the KEL antigen on these RBCs. Specific Aim 1: Functional Characterization of Anti-KEL Generated Through Transfusion Versus That Generated Through Pregnancy Specific Aim 2: Assessment of the Abilities of Polyclonal "KEL"Gam and Monoclonal Anti-KEL on Fetal RBCs and on the Prevention of Maternal RBC Alloimmunization during Pregnancy Public Health Significance/Long Term Goals: This proposal is relevant to public health in that it describes the first animal model of RBC alloimmunization induced by pregnancy which results in fetal demise, capitalizing on the strengths of an animal model to explore questions that have not (and cannot) be answered through observational human studies. The ultimate long term goal of this work is to diminish the morbidity/mortality of maternal RBC alloimmunization in fetuses and newborns alike. PUBLIC HEALTH RELEVANCE: Maternal anti-RBC antibodies, which may develop following exposure to foreign RBC antigens during transfusion or feto/maternal bleeds during pregnancy, may be deadly to fetuses expressing a cognate antigen. Hemolytic disease of the fetus and newborn (HDFN) occurs in more than 1/600 pregnancies, and with the exception of polyclonal anti-D ("RhoGam") there are no targeted therapies to prevent alloimmunization. This proposal is relevant to public health in that it describes the first animal model of RBC alloimmunization induced by pregnancy which results in fetal demise, capitalizing on the strengths of an animal model to explore questions that have not (and cannot) be answered through observational human studies; the ultimate long term goal of this work is to diminish the morbidity/mortality of maternal RBC alloimmunization in fetuses and newborns alike.