Cell-Mediated Antiretroviral Drug Transport in the Lymph Node

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ABSTRACT Recent in vivo studies in humans and primates have demonstrated that the anti-retroviral drugs used to suppress HIV do not distribute uniformly into lymphatic tissues, and drugs that are present in the blood plasma may be completely absent from the lymph nodes of the same patients. The clinical significance of this finding is not well understood, but elevated levels of HIV virus in the lymph nodes of these patients suggest that this may act as a sanctuary site for viral replication. We hypothesize that the selective manner in which drugs and cells are transported into the lymph node from the blood and fluid lymph is the mechanism of exclusion, and that the precise 3D geometry of the lymph node can explain the variation in drug penetration between different lymph nodes, or even between different locations in the same lymph node. In addition to free drug transport patterns, intracellular drug concentration is another crucial factor in the heterogeneous drug distribution observed in the LN. Lymphocytes can act as drug carriers and shuttle drugs through the LN incidentally during trafficking. Cellular transport rates are an order of magnitude slower than free drug transport rates, so cell-mediated trafficking is not a major contributor to drug concentration in well-perfused tissues. In the LN, however, lymphocytes employ active transport mechanisms that allow them to pass the barriers described above, so transport by this pathway can significantly change the overall dynamics of drug concentration. In aim one, we will develop and validate a scalable predictive model of drug transport into lymphoid lobules using 3D reconstructed murine lymph nodes. This model will be equipped with full vascular and sinus geometries and can be used to predict drug distributions in any lobule and determine transport rates. In aim 2, we will investigate the role lymphocytes play in overall drug concentration in the lobule by impeding lymphocyte entry via functional antibody blocking. We propose to integrate experimental design and computational modeling to better understand the mechanisms of drug exclusion from lymph nodes and guide the development of therapeutics that overcome them.