Background: Peanut allergy is a severe and increasingly frequent disease with high medical, psychosocial, and economic burden for affected patients and wider society. A causal, safe, and effective therapy is not yet available. Objective: We sought to develop an immunogenic, protective, and nonreactogenic vaccine candidate against peanut allergy based on virus-like particles (VLPs) coupled to single peanut allergens. Methods: To generate vaccine candidates, extracts of roasted peanut (Ara R) or the single allergens Ara h 1 or Ara h 2 were coupled to immunologically optimized Cucumber Mosaic Virus-derived VLPs (CuMVtt). BALB/c mice were sensitized intraperitoneally with peanut extract absorbed to alum. Immunotherapy consisted of a single subcutaneous injection of CuMVtt coupled to Ara R, Ara h 1, or Ara h 2. Results: The vaccines CuMVtt-Ara R, CuMVtt-Ara h 1, and CuMVtt-Ara h 2 protected peanut-sensitized mice against anaphylaxis after intravenous challenge with the whole peanut extract. Vaccines did not cause allergic reactions in sensitized mice. CuMVtt-Ara h 1 was able to induce specific IgG antibodies, diminished local reactions after skin prick tests, and reduced the infiltration of the gastrointestinal tract by eosinophils and mast cells after oral challenge with peanut. The ability of CuMVtt-Ara h 1 to protect against challenge with the whole extract was mediated by IgG, as shown via passive IgG transfer. FcgRIIb was required for protection, indicating that immune complexes with single allergens were able to block the allergic response against the whole extract, consisting of a complex allergen mixture. Conclusions: Our data suggest that vaccination using single peanut allergens displayed on CuMVtt may represent a novel therapy against peanut allergy with a favorable safety profile. (J

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The gastrointestinal (GI) tract constitutes an essential barrier against ingested microbes, including potential pathogens. Although immune reactions are well studied in the lower GI tract, it remains unclear how adaptive immune responses are initiated during microbial challenge of the oral mucosa (OM), the primary site of microbial encounter in the upper GI tract. Here, we identify mandibular lymph nodes (mandLNs) as sentinel lymphoid organs that intercept ingested Listeria monocytogenes (Lm). Oral Lm uptake led to local activation and release of antigen-specific CD8 + T cells that constituted most of the early circulating effector T cell (T EFF ) pool. MandLN-primed T EFF disseminated to lymphoid organs, lung, and OM and contributed substantially to rapid elimination of target cells. In contrast to CD8 + T EFF generated in mesenteric LN (MLN) during intragastric infection, mandLN-primed T EFF lacked a gut-seeking phenotype, which correlated with low expression of enzymes required for gut-homing imprinting by mandLN stromal and dendritic cells. Accordingly, mandLN-primed T EFF decreased Lm burden in spleen but not MLN after intestinal infection. Our findings extend the concept of regional specialization of immune responses along the length of the GI tract, with CD8 + T EFF generated in the upper GI tract displaying homing profiles that differ from those imprinted by lymphoid tissue of the lower GI tract.

The gastrointestinal (GI) tract constitutes an essential barrier against ingested pathogens. While immune reactions are well-studied in the lower GI tract, it remains unclear how adaptive immune responses are initiated during microbial challenge of the oral mucosa, the primary site of pathogen encounter in the upper GI tract. Here, we identify mandibular lymph nodes (mandLN) as sentinel lymphoid organs that collect orally administered Listeria monocytogenes (Lm), leading to local CD8+ T cell activation. In contrast to CD8+ T effector cells (TEFF) generated in mesenteric lymph nodes, mandLN CD8+ TEFF lacked a gut-seeking phenotype but contributed to systemic host protection. Accordingly, mandLN stromal and dendritic cells expressed low levels of enzymes required for gut homing imprinting. Our findings extend the concept of regional specialization of immune responses along the length of the GI tract, with mandLN acting as oral lymph-draining counterparts of intestinal lymph-draining LN of the lower GI tract.SummaryListeria monocytogenes ingestion leads to priming of cytotoxic T cells in oral mucosa draining mandibular lymph nodes, which contribute to systemic host protection.

Members of the Regulator of G-protein signaling (Rgs) family regulate the extent and timing of G protein signaling by increasing the GTPase activity of Gα protein subunits. The Rgs family member Rgs1 is one of the most up-regulated genes in tissue-resident memory (TRM) T cells when compared to their circulating T cell counterparts. Functionally, Rgs1 preferentially deactivates Gαq, and Gαi protein subunits and can therefore also attenuate chemokine receptor-mediated immune cell trafficking. The impact of Rgs1 expression on tissue-resident T cell generation, their maintenance, and the immunosurveillance of barrier tissues, however, is only incompletely understood. Here we report that Rgs1 expression is readily induced in naïve OT-I T cells in vivo following intestinal infection with Listeria monocytogenes-OVA. In bone marrow chimeras, Rgs1-/- and Rgs1+/+ T cells were generally present in comparable frequencies in distinct T cell subsets of the intestinal mucosa, mesenteric lymph nodes, and spleen. After intestinal infection with Listeria monocytogenes-OVA, however, OT-I Rgs1+/+ T cells outnumbered the co-transferred OT-I Rgs1-/- T cells in the small intestinal mucosa already early after infection. The underrepresentation of the OT-I Rgs1-/- T cells persisted to become even more pronounced during the memory phase (d30 post-infection). Remarkably, upon intestinal reinfection, mice with intestinal OT-I Rgs1+/+ TRM cells were able to prevent the systemic dissemination of the pathogen more efficiently than those with OT-I Rgs1-/- TRM cells. While the underlying mechanisms are not fully elucidated yet, these data thus identify Rgs1 as a critical regulator for the generation and maintenance of tissue-resident CD8+ T cells as a prerequisite for efficient local immunosurveillance in barrier tissues in case of reinfections with potential pathogens.