The present study dissected the role of a Th2 bias in pathogenesis of Cryptococcus neoformans H99 infection by comparing inhalational H99 infections in wild-type BALB/c and IL-4/IL-13 double knockout mice. H99-infected wild-type mice showed all major hallmarks of Th2 but not Th1/Th17 immunity in the lungs and lung-associated lymph nodes. In contrast, the IL-4/13 ؊/؊ mice developed robust hallmarks of Th1 and Th17 but not Th2 polarization. The IL-4/IL-13 deletion prevented pulmonary eosinophilia, goblet cell metaplasia in the airways and resulted in elevated serum IgE, and a switch from alternative to classical activation of macrophages. The development of a robust Th1/Th17 response and classical activation of macrophages resulted in significant containment of H99 in the lungs of IL-4/13 ؊/؊ mice compared with unopposed growth of H99 in the lungs of wild-type mice. However, IL-4/13 ؊/؊ mice showed only 1-week longer survival compared with wild-type mice. The comparison of brain and spleen cryptococcal loads at weeks 2, 3, and 4 postinfection revealed that the systemic dissemination in IL-4/13 ؊/؊ mice occurred with an approximate 1-week delay but subsequently progressed with similar rate as in the wild-type mice. Furthermore, wild-type and IL-4/13 ؊/؊ mice developed equivalently severe meningitis/encephalitis at the time of death. These data indicate that the Th2 immune bias is a crucial mechanism for pulmonary virulence of H99, whereas other mechanisms are largely responsible for its central nervous system tropism and systemic dissemination.

Changes in airway dynamics have been reported in the rat model of pulmonary cryptococcosis. However, it is not known if Cryptococcus neoformans-induced changes in lung functions are related to the immunophenotype that develops in response to cryptococcal infection in the lungs. In this study we performed a parallel analysis of the immunophenotype and airway resistance (standard resistance of the airways [SRAW]) in BALB/c mice infected with highly virulent C. neoformans strain H99 and moderately virulent strain 52D. H99 infection evoked a Th2 response and was associated with increased SRAW, while the SRAW for 52D infection, which resulted in a predominantly Th1-skewed response, did not differ from the SRAW for uninfected mice. We found that an altered SRAW in mice did not positively or negatively correlate with the pulmonary fungal burden, the magnitude of inflammatory response, the numbers of T cells, eosinophils or eosinophil subsets, neutrophils, or monocytes/macrophages, or the levels of cytokines (interleukin-4 [IL-4], IL-10, gamma interferon, or IL-13) produced by lung leukocytes. However, the level of a systemic Th2 marker, serum immunoglobulin E (IgE), correlated significantly with SRAW, indicating that the changes in lung functions were proportional to the level of Th2 skewing in this model. These data also imply that IgE may contribute to the altered SRAW observed in H99-infected mice. Lung histological analysis revealed severe allergic bronchopulmonary mycosis pathology in H99-infected mice and evidence of protective responses in 52D-infected mice with well-marginalized lesions. Taken together, the data show that C. neoformans can significantly affect airflow physiology, particularly in the context of a Th2 immune response with possible involvement of IgE as an important factor.Cryptococcus neoformans is an encapsulated yeast and is one of the leading fungal opportunistic pathogens worldwide, with increasing potential to affect both immunocompromised and noncompromised individuals (22,35). The primary site of C. neoformans infection is the respiratory tract, where the infection is either cleared (predominantly by Th1 immune responses) or persists in the absence of protective responses. Th1 immune responses in C. neoformans infection models are characterized by recruitment of CD4 ϩ and CD8 ϩ lymphocytes, production of Th1 cytokines (tumor necrosis factor alpha [TNF-␣], gamma interferon [IFN-␥], and interleukin-12 [IL-12]), and formation of tight granulomas containing classically activated macrophages, followed by clearance of the infection and resolution (4,7,26,39). In contrast, Th2 immune responses are nonprotective. These responses are characterized by production of Th2 cytokines (IL-4, IL-5, and IL-13), pulmonary eosinophilia, alternative activation of macrophages (YM crystal formation), elevation of serum immunoglobulin E (IgE) levels, and chronic infection with severe lung pathology (3,8,17,33,34,40).The Th2-driven pulmonary diseases are allergic diseases and include asthma, hypersensitivity pneum...

Background: Kidney organ transplant recipients are at increased risk of severe outcomes during COVID-19. Antibodies directed against the virus are thought to offer protection, but a thorough characterization of anti-SARS-CoV-2 immune globulin isotypes in kidney transplant recipients following SARS-CoV-2 infection has not been reported. Methods: We performed a cross-sectional study of 49 kidney transplant recipients and 42 immunocompetent controls at early (≤14 days) or late (>14 days) time points after documented SARS-CoV-2 infection. Using a validated semi-quantitative Luminex-based multiplex assay, we determined IgM, IgG, IgG1-4 and IgA antibodies against 5 distinct viral epitopes. Results: Kidney transplant recipients showed lower levels of total IgG anti-trimeric spike (S), S1, S2, and receptor-binding domain (RBD), but not nucleocapsid (NC) at early versus late time points after SARS-CoV-2 infection. Early levels of IgG anti-spike protein epitopes were also lower than in immunocompetent controls. Anti-SARS-CoV-2 antibodies were predominantly IgG1 and IgG3 with modest class switching to IgG2 or IgG4 in either cohort. Later levels of IgG anti-Spike, S1, S2, RBD and NC were not significantly different between cohorts. There was no significant difference in the kinetics of either IgM or IgA anti-Spike, S1, RBD or S2 based on timing after diagnosis or transplant status. Conclusions: Kidney transplant recipients mount early anti-SARS-CoV-2 IgA and IgM responses while IgG responses are delayed compared to immunocompetent individuals. These findings might explain the poor outcomes in transplant recipients with COVID-19.