The efficacy of vaccine adjuvants such as Toll-like receptor agonists (TLRa) can be improved through formulation and delivery approaches. Here, we attached small molecule TLR-7/8a to polymer scaffolds (polymer-TLR-7/8a) and evaluated how varying physicochemical properties of the TLR-7/8a and polymer carrier influenced the location, magnitude and duration of innate immune activation in vivo. Particle formation by polymer-TLR-7/8a was critical for restricting adjuvant distribution and prolonging activity in draining lymph nodes. The improved pharmacokinetic profile by particulate polymer-TLR-7/8a was also associated with reduced morbidity and enhanced vaccine immunogenicity for inducing antibodies and T cell immunity. We extended these findings to the development of a modular platform in which protein antigens are site-specifically linked to temperature-responsive polymer-TLR-7/8a adjuvants that self-assemble into immunogenic particles at physiologic temperatures in vivo. Our findings provide a chemical and structural basis for optimizing adjuvant design to elicit broad-based antibody and T cell responses with protein antigens.

Microsporidia comprise a phylum of over 1400 species of obligate intracellular pathogens that can infect almost all animals, but little is known about the host response to these parasites. Here we use the whole-animal host C. elegans to show an in vivo role for ubiquitin-mediated response to the microsporidian species Nematocida parisii, as well to the Orsay virus, another natural intracellular pathogen of C. elegans. We analyze gene expression of C. elegans in response to N. parisii, and find that it is similar to response to viral infection. Notably, we find an upregulation of SCF ubiquitin ligase components, such as the cullin ortholog cul-6, which we show is important for ubiquitin targeting of N. parisii cells in the intestine. We show that ubiquitylation components, the proteasome, and the autophagy pathway are all important for defense against N. parisii infection. We also find that SCF ligase components like cul-6 promote defense against viral infection, where they have a more robust role than against N. parisii infection. This difference may be due to suppression of the host ubiquitylation system by N. parisii: when N. parisii is crippled by anti-microsporidia drugs, the host can more effectively target pathogen cells for ubiquitylation. Intriguingly, inhibition of the ubiquitin-proteasome system (UPS) increases expression of infection-upregulated SCF ligase components, indicating that a trigger for transcriptional response to intracellular infection by N. parisii and virus may be perturbation of the UPS. Altogether, our results demonstrate an in vivo role for ubiquitin-mediated defense against microsporidian and viral infections in C. elegans.

Mammalian barrier surfaces are constitutively colonized by numerous microorganisms. We explored how the microbiota was sensed by the immune system and the defining properties of such responses. Here, we show that a skin commensal can induce T cell responses in a manner that is restricted to non-classical MHC class I molecules. These responses are uncoupled from inflammation and highly distinct from pathogen-induced cells. Commensal-specific T cells express a defined gene signature that is characterized by expression of effector genes together with immunoregulatory and tissue-repair signatures. As such, non-classical MHCI-restricted commensal-specific immune responses not only promoted protection to pathogens, but also accelerated skin wound closure. Thus, the microbiota can induce a highly physiological and pleiotropic form of adaptive immunity that couples antimicrobial function with tissue repair. Our work also reveals that non-classical MHC class I molecules, an evolutionarily ancient arm of the immune system, can promote homeostatic immunity to the microbiota.

Summary Pathogens commonly disrupt host cell processes or cause damage, but the surveillance mechanisms used by animals to monitor these attacks are poorly understood. Upon infection with pathogenic Pseudomonas aeruginosa, the nematode C. elegans upregulates infection response gene irg-1 using the zip-2 bZIP transcription factor. Here we show that P. aeruginosa infection inhibits mRNA translation in the intestine via the endocytosed translation inhibitor Exotoxin A, which leads to an increase in ZIP-2 protein levels. In the absence of infection we find that the zip-2/irg-1 pathway is upregulated following disruption of several core host processes, including inhibition of mRNA translation. ZIP-2 induction is conferred by a conserved upstream open reading frame in zip-2 that could de-repress ZIP-2 translation upon infection. Thus, translational inhibition, a common pathogenic strategy, can trigger activation of an immune surveillance pathway to provide host defense.

White adipose tissue bridges body organs and plays a fundamental role in host metabolism. To what extent adipose tissue also contributes to immune surveillance and long-term protective defense remains largely unknown. Here, we have shown that at steady state, white adipose tissue contained abundant memory lymphocyte populations. After infection, white adipose tissue accumulated large numbers of pathogen-specific memory T cells, including tissue-resident cells. Memory T cells in white adipose tissue expressed a distinct metabolic profile, and white adipose tissue from previously infected mice was sufficient to protect uninfected mice from lethal pathogen challenge. Induction of recall responses within white adipose tissue was associated with the collapse of lipid metabolism in favor of antimicrobial responses. Our results suggest that white adipose tissue represents a memory T cell reservoir that provides potent and rapid effector memory responses, positioning this compartment as a potential major contributor to immunological memory.