Early or Late IL-10 Blockade Enhances Th1 and Th17 Effector Responses and Promotes Fungal Clearance in Mice with Cryptococcal Lung Infection

Abstract

The potent immunoregulatory properties of Interleukin-10 (IL-10) can counteract protective immune responses and thereby promote persistent infections as evidenced by prior studies of cryptococcal lung infection in IL-10 deficient mice. To further investigate how IL-10 impairs fungal clearance the current study utilized an established murine model of C57BL/6 mice infected with C. neoformans strain 52D. Our results demonstrate that fungal persistence is associated with an early and sustained expression of IL-10 by lung leukocytes. To examine whether IL-10-mediated immune modulation occurs during the early or late phase of infection, assessments of fungal burden and immunophenotyping were performed on mice treated with anti-IL-10 receptor blocking antibody at 3, 6, and 9 days post-infection (dpi) (early phase) or at 15, 18, and 21 dpi (late phase). We found that both early and late IL-10 blockade significantly improved fungal clearance within the lung when assessed 35 dpi compared to isotype control treatment. Immunophenotyping identified that IL-10 blockade enhanced several critical effector mechanisms including: a) increased accumulation of CD4+ T cells and B cells, but not CD8+ T cells, b) specific increases in the total numbers of Th1 and Th17 cells, and c) increased accumulation and activation of CD11b+ dendritic cells and exudate macrophages. Importantly, IL-10 blockade effectively abrogated dissemination of C. neoformans to the brain. Collectively, this study identifies early and late cellular and molecular mechanisms through which IL-10 impairs fungal clearance and highlights the therapeutic potential of IL-10 blockade in the treatment of fungal lung infections.

Local GM-CSF–Dependent Differentiation and Activation of Pulmonary Dendritic Cells and Macrophages Protect against Progressive Cryptococcal Lung Infection in Mice

“…We used established gating strategies (references (23, 27), the Materials and Methods section, and Figure 3A) to identify and enumerate CD11b+ lung DC by FCA at baseline and throughout the infection (Figures 3A and B). We found similar numbers of CD11b+ DC in the lungs of uninfected GM +/+ and GM −/− mice (day 0).…”

“…We also evaluated the expression of MHC Class II and costimulatory molecules CD40, CD80, and CD86 by CD11b+ DC in GM +/+ and GM −/− mice as prior studies have demonstrated a positive association between their expression and clearance or containment of cryptococcal lung infection (27, 29–32). No differences in the expression of these molecules were observed on CD11b+ DC in the lungs of uninfected GM +/+ and GM −/− mice (data not shown).…”

“…The objective of the current study was to further investigate the in vivo effects of GM-CSF on pulmonary DC and macrophages in mice infected by the intratracheal route with a moderately-virulent strain of C. neoformans (strain 52D). Our studies were performed using GM +/+ mice (C57BL/6J mice) which develop persistent cryptococcal lung infection (17, 26, 27) and GM −/− mice (C57BL/6J genetic background) which develop progressive lung infection (17). Our results show that GM-CSF promotes the differentiation, accumulation, activation, and alveolar localization of lung DC and macrophages.…”

CD4 + T Cells Orchestrate Lethal Immune Pathology despite Fungal Clearance during Cryptococcus neoformans Meningoencephalitis

“…Data generated by multiple labs, using multiple strains of mice and of C. neoformans, uniformly support the idea that Th1 responses are protective, promoting fungal clearance and recovery, while Th2 responses allow for fungal persistence and drive immune pathology in the infected lungs. In particular, C57BL/6 mice develop a mixed Th2/Th1/Th17 response to pulmonary infection with C. neoformans 52D, resulting in immunological stalemate and persistent infection, but outcomes can be improved by provoking a greater Th1 bias (12,58,59) or worsened when stronger Th2 bias is induced (44,60,61). Our data significantly differ from this balanced Th polarization paradigm, in that we did not observe any hallmarks of Th2 or Th17 response within the infected CNS of C57BL/6 mice at any time point.…”

Two-spotted cricket as an animal infection model of human pathogenic fungi

“…Mammals such as mice and rabbits have been used to evaluate fungal virulence properties in various organs, including the skin (8), lung (9), stomach (10), oral cavity (11), urethral tube (12), and vagina (13). Mammals are homeothermic animals, however, and cannot be used to evaluate fungal virulence at low temperatures.…”