Parenteral vaccination strategies target protective immunity to the small and large intestine mucosa

Abstract

Abstract Prophylactic vaccines are most commonly given by a parenteral route. However, this strategy often confers poor protection against GI pathogens because antigens are primarily presented in peripheral lymph nodes, which do not provide the prerequisite ‘tissue imprinting signals’ to target memory T and B cells to the gut. Here, we describe a platform that enables parenteral vaccines to target protection to the GI tract. This was achieved by subcutaneous (s.c.) delivery of compounds known to imprint gut tropism onto lymphocytes. Am80, a retinoic acid receptor agonist, targeted immunity to the small intestine through up-regulation of gut-homing receptors α4β7 and CCR9, and promotion of IgA class-switching. S.c. injection of OVA + CpG combined with repeated injections of Am80 generated significantly higher and durable fecal anti-OVA IgA titers, compared to OVA + CpG without Am80. Vaccination with Am80 also increased antigen-specific CD4 and CD8 T cell trafficking to the small intestine and generated tissue resident memory T (Trm) cells. To overcome the need for multiple doses of Am80, which can cause tissue toxicity at the injection site and hinder clinical translation, we developed a polymeric nanocarrier that showed equivalent imprinting efficacy upon a single injection, lowering the cumulative dose to one-third. Furthermore, we also developed a modified vaccination strategy that could augment effector and memory T cell responses not only in the small intestine, but also in the cecum, colon and rectum, conferring protection to the entire intestinal tract. We conclude that supplementation with mucosal imprinting signals is a promising approach to enhance parenteral vaccines by generating mucosal protection against GI infections. Supported by the Bill & Melinda Gates Foundation