Diversity of the T-Cell Response to PulmonaryCryptococcus neoformansInfection

Abstract

Cell-mediated immunity plays an important role in immunity to the pathogenic fungus Cryptococcus neoformans. However, the antigen specificity of the T-cell response to C. neoformans remains largely unknown. In this study, we used two approaches to determine the antigen specificity of the T-cell response to C. neoformans. We report here that a diverse T-cell receptor (TCR) V␤ repertoire was maintained throughout the primary response to pulmonary C. neoformans infection in immunocompetent mice. CD4؉ T-cell deficiency resulted in relative expansion of all CD8 ؉ T-cell subsets. During a secondary immune response, preferential usage of a TCR V␤ subset in CD4؉ T cells occurred in single individuals, but the preferences were "private" and not shared between individuals. Both CD4 ؉ and CD8 ؉ T cells from the secondary lymphoid tissues of immunized mice proliferated in response to a variety of C. neoformans antigens, including heat-killed whole C. neoformans, culture filtrate antigen, C. neoformans lysate, and purified cryptococcal mannoprotein. CD4؉ and CD8 ؉ T cells from the secondary lymphoid tissues of mice undergoing a primary response to C. neoformans proliferated in response to C. neoformans lysate. In response to stimulation with C. neoformans lysate, lung CD4؉ and CD8 ؉ T cells produced the effector cytokines tumor necrosis factor alpha and gamma interferon. These results demonstrate that a diverse T-cell response is generated in response to pulmonary C. neoformans infection.The fungal pathogen Cryptococcus neoformans can infect immunocompetent individuals, but this organism causes disease primarily in individuals with defects in cellular immunity (5). T-cell-mediated immunity plays a critical role in clearance of pulmonary C. neoformans infection in mice, but the antigen specificity of the responding CD4 ϩ and CD8 ϩ T cells remains largely unknown. In this study, we used two approaches to determine the antigen specificity of the T-cell response to C. neoformans.In ␣␤ T cells, which comprise the majority of T cells, the T-cell receptor (TCR) is expressed as a heterodimeric protein composed of ␣ and ␤ subunits. Somatic recombination of diversity and joining regions in V␣ and somatic recombination of variable, diversity, and joining regions in V␤ result in the diversity of the TCR repertoire (3). A number of studies, including studies of the pathogenic fungus Histoplasma capsulatum, have demonstrated that there are V␤ preferences during T-cell responses, which correlate to T-cell function or antigen specificity (7-11). Similar to control of C. neoformans infection, control of H. capsulatum infection is primarily dependent on CD4 ϩ T cells. Based on these results, we studied the V␤ TCR expression by CD8 ϩ and CD4 ϩ T cells during pulmonary C. neoformans infection.Our first objective in this study was to characterize the V␤ TCR usage by CD4 ϩ and CD8 ϩ T cells during primary and secondary responses to pulmonary C. neoformans infection. Our goals were to determine (i) whether preferential expansion of specific V␤ sub...

Cryptococcal Urease Promotes the Accumulation of Immature Dendritic Cells and a Non-Protective T2 Immune Response within the Lung

“…24,26,29,31 The phenotype observed in mice infected with urease-deficient C. neoformans is similar to that identified in IL-4 knockout mice infected with ureaseproducing C. neoformans (ie, improved cryptococcal clearance, reduced lung eosinophilia, and a reduced IL-4:IFN-␥ ratio). 25 Thus, the data suggest that cryptococcal urease promotes T cell polarization toward nonprotective T2 phenotype.…”

“…This time point coincides with the development of T cell polarization in this model system. 25,41,43 Thus, we have defined cryptococcal urease as a virulence factor that exerts a strong effect at the later stages of the host response against the organism specifically within the lung (the primary site of infection).…”

“…[22][23][24] Both CD4 ϩ and CD8ϩ T cells are required for this protective response. 25 In contrast, the development of a T2 response in the lungs is nonprotective and associated with persistence of C. neoformans. 26 -29 Experimentally altering the T1 versus T2 balance profoundly affects pulmonary clearance of the organism.…”

Robust Th1 and Th17 Immunity Supports Pulmonary Clearance but Cannot Prevent Systemic Dissemination of Highly Virulent Cryptococcus neoformans H99

“…The wild-type mice demonstrated rapid unopposed growth of H99 at all time points in contrast with gradual decrease in C. neoformans load in IL-4/13 Ϫ/Ϫ mice from weeks 2 to 4 postinfection, timing consistent with the efferent adaptive immune response. 26,29,40,45,46 This improved containment of H99 resulted in a 1500-fold difference in pulmonary load of H99 between the wild-type and IL-4/13 Ϫ/Ϫ mice at week 4. Interestingly, the marked improvement of pulmonary control of H99 in IL-4/13 Ϫ/Ϫ did not provide longterm survival benefit.…”

PI3K signaling of autophagy is required for starvation tolerance and virulenceof Cryptococcus neoformans

“…TNF-α is induced during human and murine cryptococcosis (20) and is normally present 3-7 days after pulmonary inoculation with intact fungal cells (21). In as little as 5 hours, TNF-α production was significantly induced after inoculation with the vps34Δ mutant (Supplemental Figure 2), most likely a result of host exposure to liberated fungal proteins from rapidly dying mutant cells, which has been shown previously to induce this cytokine (22). These data show the importance of the VPS34 locus during murine cryptococcosis.…”