Non-Invasive Quantification of Vaccine-Mediated Antigen Delivery to

限制对疫苗接种的免疫应答的主要参数是活化的抗原呈递细胞（APC）的数量，所述APC从疫苗位点捕获抗原并迁移到引流淋巴结（LN），T和B细胞引发发生的位点。目前，用于监测体内抗原捕获和递送的定量非侵入性技术正在发展中。细胞磁共振成像（MRI）的使用是一种有前途的方法，用于此目的;然而，细胞成像目前需要离体预标记的细胞与造影剂，然后再引入细胞到受监测的主题。使用小鼠模型，我们开发了一种体内标记方法，该方法依赖于内源性抗原呈递细胞原位捕获疫苗抗原相关的超顺磁性氧化铁（SPIO），以定量AFC向LN的递送。在该系统中，MRI能够监测体内负责诱导肿瘤特异性免疫应答的磁性标记的APC的运输。使用专用软件分析淋巴结MR图像，通过生成像素强度直方图实现信号量化。在体内和离体定量负载疫苗抗原的APC之间观察到极好的相关性，分辨率足以检测由佐剂引起的增加的APC运输。此外，捕获SPIO（和抗原）和交通LN的APC随后可以磁性回收离体，允许影响疫苗诱导免疫的传入臂的上游参数的详细细胞和分子研究。 使用针对肺癌的小鼠疫苗模型，我们现在建议检查通过MRI测量的APC运输程度与下游免疫应答的数量和质量之间的相关性。 该信息将用于评价候选疫苗佐剂增强产生全身免疫的这一关键步骤的能力。我们还将把这项技术扩展到其他疫苗平台，为临床应用奠定基础。

A major parameter limiting immune responses to vaccination is the number of activated antigen presenting cells (APCs) that capture antigen from the vaccine site and migrate to draining lymph nodes (LNs), the site where T and B cell priming occurs. Currently, a quantitative non-invasive technique for monitoring in vivo antigen capture and dehvery is laclting. The use of cellular magnetic resonance imaging (MRI) is a promising approach for this purpose; however, cellular imaging currently requires ex vivo pre-labeling of cells with contrast agents followed by reintroduction of cells into the subject being monitored. Using mouse models, we have developed an in vivo labehng method which relies upon the capture of vaccine antigen-associated superparamagnetic iron oxide (SPIO) by endogenous antigen presenting cells, in situ, in order to quantify AFC delivery to LNs. In this system, MRI is capable of monitoring the trafficking of magnetically labeled APCs in vivo that are responsible for inducing tumor-specific immune responses. Analysis of lymph node MR images using dedicated software enables signal quantification through the generation of pixel intensity histograms. Excellent correlation is observed between in vivo and ex vivo quantification of vaccine antigen-loaded APCs, with resolution sufficient to detect increased APC trafficking elicited by an adjuvant. Furthermore, APCs that capture SPIO (and antigen) and traffic to LN can subsequently be magnetically recovered ex vivo, allowing for detailed cellular and molecular studies of the upstream parameters that influence the afferent arm of vaccine-induced immunity. Using murine vaccine models targeting lung cancer, we now propose to examine the correlation between the extent of APC trafficking as measured by MRI and the quantity and quality of the downstream immune response. This information will be used to evaluate candidate vaccine adjuvants for their ability to augment this critical step In generating systemic immunity. We will also extend this technology to additional vaccine platforms setting the stage for clinical application.