Application of ex vivo lymph node slices and traditional in vivo models to study lymph node responses to vaccine adjuvants

Vaccines remain one of the most powerful tools in the arsenal of human medicine, responsible for saving countless number of lives and billions of dollars in associated economic costs. Yet, there is a critical need for the development of novel vaccine adjuvants that can be used in vaccines to combat intracellular pathogens such as HIV and diseases such as cancer. Vaccine adjuvants often target the lymph node, a tissue that has evolved to have a complex structure and dynamically regulated chemokine system that drives cell-cell interactions required for the development of adaptive immunity. Although the spatial organization of the lymph node is critical in understanding how the immune response develops, it remains poorly understood how different adjuvants shape and impact the structure of the tissue.
Traditional in vitro and in vivo models of studying immunity have provided great insight in the dynamic events; however, both approaches have their drawbacks in studying spatially resolved events in the lymph node. The emergence of ex vivo lymph node slice platform to study spatially resolved immune activation presents a perfect complement to in vitro and in vivo models in answering questions on how different adjuvants shape the spatial organization of the lymph node.
Part 1 of thesis focuses on validating ex vivo lymph node slices as a model to study immune activation to adjuvants ex vivo. Chapter 2 specifically characterizes the response of slices to adjuvants ex vivo; as well as slice responses to an antigen-rechallenge after in vivo vaccination. Chapter 3 details a method to improve the collection of slices from mice vaccinated in vivo. Here, as the lymph node expands after vaccination, the tissue expands into the surrounding adipose tissue, coating it in molecular layer of fat. The use of detergent wash removes this layer enabling slicing of the tissue.
Chapter 4 focuses on testing a novel hypothesis on how different adjuvants influence chemokine expression around B cell follicles. Here, the signaling pathway that drives CXCL9 expression in the interfollicular zone after poly I:C vaccination is detailed. CXCL9 expression was correlated with IgG2c polarization; however, the expression of the ligand’s receptor, CXCR3, was not required for this response.
Part 3 consists of Chapter 5 and 6, and in this section, work is focused on future applications of lymph node slices. Specifically, Chapter 5 focuses on understanding basic slice biology in the hopes of culturing the tissue long-term to study the complete development of the immune response. Chapter 6 details a unique collaboration between a microfluidic expert with an immunologist to develop a 3D printed multi-organ chip to study how adjuvant drainage impacts the initial events that facilitate immune activation in the lymph node. In summary, the work in this thesis focuses on analyzing adjuvant impacts on the lymph node and using new methods and techniques to answer these questions.