C. neoformans is a leading cause of fatal mycosis linked to CNS dissemination.
Laccase, encoded by the LAC1 gene, is an important
virulence factor implicated in brain dissemination yet little is known about the mechanism(s) accounting for this observation. Here, we investigated whether the presence or absence of
laccase altered the local immune response in the lungs by comparing
infections with the highly virulent strain, H99 (which expresses
laccase) and mutant strain of H99 deficient in
laccase (lac1Δ) in a mouse model of pulmonary
infection. We found that LAC1 gene deletion decreased the pulmonary fungal burden and abolished CNS dissemination at weeks 2 and 3. Furthermore, LAC1 deletion lead to: 1) diminished
pulmonary eosinophilia; 2) increased accumulation of CD4+ and CD8+ T cells; 3) increased Th1 and Th17
cytokines yet decreased Th2
cytokines; and 4) lung macrophage shifting of the lung macrophage phenotype from M2- towards M1-type activation. Next, we used adoptively transferred CD4+ T cells isolated from pulmonary lymph nodes of mice infected with either lac1Δ or H99 to evaluate the role of
laccase-induced
immunomodulation on CNS dissemination. We found that in comparison to PBS treated mice, adoptively transferred CD4+ T cells isolated from lac1Δ-infected mice decreased CNS dissemination, while those isolated from H99-infected mice increased CNS dissemination. Collectively, our findings reveal that immune modulation away from Th1/Th17 responses and towards Th2 responses represents a novel mechanism through which
laccase can contribute to cryptococcal virulence. Furthermore, our data support the hypothesis that
laccase-induced changes in polarization of CD4+ T cells contribute to CNS dissemination.