SLAMF1 Is Dispensable for Vaccine-Induced T Cell Development but Required for Resistance to Fungal Infection.

Homotypic signaling lymphocyte activation molecule (SLAM) receptor-ligand cell surface interactions between myeloid and lymphoid cells regulate innate and adaptive immune responses. In this article, we report that SLAMF1 is indispensable for host resistance to primary and vaccine-induced protection against fungal infection. Because vaccine immunity is dependent on cell-mediated immunity, we investigated the development of Ag-specific T cells. We studied the T cell-intrinsic and -extrinsic role of SLAMF1. We generated SLAMF1-/- TCR transgenic mice and analyzed the responses of adoptively transferred T cells. We also tracked endogenous Ag-specific T cells by using a tetramer. Intrinsic and extrinsic SLAMF1 signaling was dispensable for the development of antifungal Th1 and Th17 cells, which are requisite for the acquisition of vaccine-induced immunity. Despite intact T cell development, vaccinated SLAMF1-/- mice failed to control fungal infection. Failed accumulation of Ag-specific T cells in the lung on infection of vaccinated mice was due to uncontrolled early infection and inflammation, revealing a role for SLAMF1 in innate host immunity.

Variation in Host Resistance to Blastomyces dermatitidis: Potential Use of Genetic Reference Panels and Advances in Immunophenotyping of Diverse Mouse Strains.

Host genetic determinants that underpin variation in susceptibility to systemic fungal infection are poorly understood. Genes responsible for complex traits can be identified by correlating variation in phenotype with allele in founder strains of wild mice with known genetic variation, assembled in genetic reference panels. In this work, we describe wide natural variation in both primary and acquired resistance to experimental pulmonary blastomycosis in eight founder strains, including 129, A/J, BL/6, CAST, NOD, NZO, PWK, and WSB of the Collaborative Cross collection, and the inbred DBA strain. These differences in susceptibility across strains were accompanied by sharp differences in the accumulation and function of immune cells in the lungs. Immune perturbations were mapped by identifying reagents that phenotypically mark immune cell populations in the distinct strains of mice. In particular, we uncovered marked differences between BL/6 and DBA/2 mouse strains in the development of acquired resistance. Our findings highlight the potential value in using genetic reference panels of mice, and particularly the BXD (recombinant inbred strains of mice from a cross of C57BL/6J and DBA/2J mice) collection harboring a cross between resistant BL/6 and susceptible DBA/2 mice, for unveiling genes linked with host resistance to fungal infection. IMPORTANCE Host genetic variation significantly impacts vulnerability to infectious diseases. While host variation in susceptibility to fungal infection with dimorphic fungi has long been recognized, genes that underpin this variation are poorly understood. We used a collection of seven mouse strains that represent nearly 90% of the genetic variation in mice to identify genetic variability among the strains in resistance to pulmonary infection with the dimorphic fungus Blastomyces dermatitidis. We analyzed differences between the strains in innate resistance by infecting naive mice and in acquired resistance by infecting vaccinated mice. We identified extreme variations in both innate and acquired resistance among the strains. In particular, we found sharp differences between C57BL/6 and DBA/2 strains in the ability to acquire vaccine-induced resistance. We also identified commercial reagents that allowed the phenotyping of immune cells from this strain collection of mice. Because there are additional mice harboring a genetic cross of the C57BL/6 and DBA/2 strains (BXD collection), such mice will permit future investigations to identify the genes that underlie differences in the ability to acquire resistance to infection.

Structural basis of Blastomyces Endoglucanase-2 adjuvancy in anti-fungal and -viral immunity.

The development of safe subunit vaccines requires adjuvants that augment immunogenicity of non-replicating protein-based antigens. Current vaccines against infectious diseases preferentially induce protective antibodies driven by adjuvants such as alum. However, the contribution of antibody to host defense is limited for certain classes of infectious diseases such as fungi, whereas animal studies and clinical observations implicate cellular immunity as an essential component of the resolution of fungal pathogens. Here, we decipher the structural bases of a newly identified glycoprotein ligand of Dectin-2 with potent adjuvancy, Blastomyces endoglucanase-2 (Bl-Eng2). We also pinpoint the developmental steps of antigen-specific CD4+ and CD8+ T responses augmented by Bl-Eng2 including expansion, differentiation and tissue residency. Dectin-2 ligation led to successful systemic and mucosal vaccination against invasive fungal infection and Influenza A infection, respectively. O-linked glycans on Bl-Eng2 applied at the skin and respiratory mucosa greatly augment vaccine subunit- induced protective immunity against lethal influenza and fungal pulmonary challenge.

Antigen discovery unveils resident memory and migratory cell roles in antifungal resistance.

Priming at the site of natural infection typically elicits a protective T cell response against subsequent pathogen encounter. Here, we report the identification of a novel fungal antigen that we harnessed for mucosal vaccination and tetramer generation to test whether we can elicit protective, antigen-specific tissue-resident memory (Trm) CD4+ T cells in the lung parenchyma. In contrast to expectations, CD69+, CXCR3+, CD103- Trm cells failed to protect against a lethal pulmonary fungal infection. Surprisingly, systemic vaccination induced a population of tetramer+ CD4+ T cells enriched within the pulmonary vasculature, and expressing CXCR3 and CX3CR1, that migrated to the lung tissue upon challenge and efficiently protected mice against infection. Mucosal vaccine priming of Trm may not reliably protect against mucosal pathogens.