Targeting Lymph Node Niches Enhances Type 1 Immune Responses to Immunization

Abstract

The generation of a robust CD4+ T helper cell type 1 (Th1) response is an essential component of protective type 1 immunity following infection or vaccination, providing critical support for cytotoxic T cell responses and the production of protective antibodies. This process requires the co-localization and interaction of innate and adaptive immune cells within the reactive lymph node (LN), including the redistribution of CD4+ T cells from the deep paracortex to microenvironments in the peripheral regions of the LN. The mechanisms governing the spatial and temporal coordination of immune cell localization within the LN, and the ability to target aspects of this response through immunization strategies, are incompletely understood. In this work, we examined whether immunization formulation associated with enhanced vaccine efficacy could promote antigen distribution and recruitment of immune cells into LN niches associated with optimal type 1 responses. In contrast to immunization with antigen and toll-like receptor agonist in saline alone, immunization with an identical mixture emulsified in paraffin oil (Incomplete Freund’s Adjuvant) promoted a rapid targeting of antigen to interfollicular regions (IFR) of the LN near B cell areas, which led to increased differentiation of polyfunctional interferon-γ and tumor necrosis factor-α double-producing Th1 cells. Inflammatory monocytes infiltrated the immunized LN, localized toward antigen-rich regions, and highly upregulated CXCL10 in a type I interferon-dependent manner. In turn, CD4+ T cells mobilized out of the T cell zone and into the IFR/B cell regions in a manner not dependent on injection site depot, where they were strategically positioned to encounter IL-12+ inflammatory DCs in an environment rich with CXCR3 ligand-producing cells for Th1 differentiation. Depletion of monocyte-derived cells in MM-DTR mice resulted in a reduction in CD4+ T cell mobilization out of the T cell zone and a loss of enhanced Th1 differentiation in response to emulsified immunization. These data suggest that oil emulsion preferentially targets antigen to LN regions where responding immune cells create an inflammatory niche advantageous for supporting Th1 differentiation. Formulations that can replicate this effect by delivering antigen and adjuvant to distinct LN niches such as IFR may improve vaccine efficacy.