Coordinate genomic association of transcription factors controlled by an imported quorum sensing peptide in Cryptococcus neoformans.

Qsp1 is a secreted quorum sensing peptide required for virulence of the fungal meningitis pathogen Cryptococcus neoformans. Qsp1 functions to control cell wall integrity in vegetatively growing cells and also functions in mating. Rather than acting on a cell surface receptor, Qsp1 is imported to act intracellularly via the predicted oligopeptide transporter Opt1. Here, we identify a transcription factor network as a target of Qsp1. Using whole-genome chromatin immunoprecipitation, we find Qsp1 controls the genomic associations of three transcription factors to genes whose outputs are regulated by Qsp1. One of these transcription factors, Cqs2, is also required for the action of Qsp1 during mating, indicating that it might be a shared proximal target of Qsp1. Consistent with this hypothesis, deletion of CQS2 impacts the binding of other network transcription factors specifically to Qsp1-regulated genes. These genetic and genomic studies illuminate mechanisms by which an imported peptide acts to modulate eukaryotic gene expression.

Chronic Candida albicans Meningitis in a 4-Year-Old Girl with a Homozygous Mutation in the CARD9 Gene (Q295X).

A 4-year-old Turkish girl of consanguineous parents was hospitalized for the evaluation of headaches and recurrent febrile episodes of unknown origin. Her medical history was unremarkable except for a few episodes of uncomplicated oral thrush. Meningitis was diagnosed, and Candida albicans was the only pathogen identified by polymerase chain reaction and culture. Despite systemic antifungal multidrug therapy, a prolonged course of 16 months of therapy was necessary to clear C. albicans from the cerebrospinal fluid. Molecular genetic analysis revealed a homozygous caspase recruitment domain 9 (CARD9) mutation (Q295X), which was reported to predispose to chronic mucocutaneous candidiasis. Immunologic workup excluded predisposing B-cell and T-cell defects. In addition, T cells producing interleukin-17 were repeatedly measured within the normal range. Analyses of neutrophils demonstrated normal nicotinamide adenine dinucleotide phosphate oxidase activity in response to various stimuli including Staphylococcus aureus and C. albicans. Additional neutrophilic functional testing, however, showed a decreased cytotoxicity to nonopsonized C. albicans, indicating an impaired killing mechanism against Candida spp. independent from the production of reactive oxygen species by the nicotinamide adenine dinucleotide phosphate oxidase system. Because this defect was only demonstrated in the absence of opsonins, it might especially predispose to chronic C. albicans infections in the central nervous system where opsonin concentrations are usually low. We, therefore, suggest that due to an additional neutrophil dependent defect CARD9 deficiency predisposes not only to chronic mucocutaneous candidiasis, but also to invasive chronic Candida infections, especially of the central nervous system.

A homozygous CARD9 mutation in a family with susceptibility to fungal infections.

BACKGROUND: Chronic mucocutaneous candidiasis may be manifested as a primary immunodeficiency characterized by persistent or recurrent infections of the mucosa or the skin with candida species. Most cases are sporadic, but both autosomal dominant inheritance and autosomal recessive inheritance have been described. METHODS: We performed genetic studies in 36 members of a large, consanguineous five-generation family, in which 4 members had recurrent fungal infections and an additional 3 members died during adolescence, 2 after invasive infection of the brain with candida species. All 36 family members were enrolled in the study, and 22 had blood samples taken for DNA analysis. Homozygosity mapping was used to locate the mutated gene. In the 4 affected family members (patients) and the 18 unaffected members we sequenced CARD9, the gene encoding the caspase recruitment domain-containing protein 9, carried out T-cell phenotyping, and performed functional studies, with the use of either leukocytes from the patients or a reconstituted murine model of the genetic defect. RESULTS: We found linkage (lod score, 3.6) to a genomic interval on chromosome 9q, including CARD9. All four patients had a homozygous point mutation in CARD9, resulting in a premature termination codon (Q295X). Healthy family members had wild-type expression of the CARD9 protein; the four patients lacked wild-type expression, which was associated with low numbers of Th17 cells (helper T cells producing interleukin-17). Functional studies based on genetic reconstitution of myeloid cells from Card9(-/-) mice showed that the Q295X mutation impairs innate signaling from the antifungal pattern-recognition receptor dectin-1. CONCLUSIONS: An autosomal recessive form of susceptibility to chronic mucocutaneous candidiasis is associated with homozygous mutations in CARD9.

Mannose-binding lectin serum levels are low in persons with clinically active coccidioidomycosis.

BACKGROUND: Mannose-binding lectin (MBL) is a circulating collectin that is part of the innate immune response. We explored the serum levels of MBL in persons with different forms of coccidioidomycosis. METHODS: Serum MBL was measured by ELISA from samples obtained from healthy donors with immunity to Coccidioides, and those with various forms of active coccidioidomycosis. Blood cell specimens from a subgroup of subjects with active coccidioidomycosis were examined for single nucleotide polymorphisms of the MBL gene and promoter regions. RESULTS: The control group comprised 29 healthy immune subjects. Patient groups with active coccidioidomycosis consisted of 20 patients with symptomatic primary pulmonary coccidioidomycosis, 26 with non-meningeal disseminated coccidioidomycosis, and nine with coccidioidal meningitis. The group with active coccidioidomycosis was significantly older and more likely to be male than the control group (for both, P < 0.001). The mean +/- SEM level of serum MBL in the healthy controls was 169.4 +/- 28.6 ng/ml, significantly higher than the 79.2 +/- 10.9 ng/ml for all active groups (P < 0.001). Moreover, the active coccidioidomycosis group was significantly more likely to have serum MBL level

Investigation of the basis of virulence in serotype A strains of Cryptococcus neoformans from apparently immunocompetent individuals.

Cryptococcus neoformans serotype A strains commonly infect immunocompromised patients to cause fungal meningitis. To understand the basis of serotype A cryptococcal infections in apparently immunocompetent patients, we tested two hypotheses: the strains were naturally occurring hypervirulent pkr1 (PKA regulatory subunit) mutants, or the strains were hybrids with C. neoformans var. gattii strains that normally infect immunocompetent individuals. Analysis of clinical isolates obtained from apparently immunocompetent individuals from three continents revealed that none were pkr1 mutants, but several exhibited phenotypes consistent with perturbations in cAMP signaling. Additionally, none of the strains were unusual hybrids with gattii strains. Except for one strain that was an AD hybrid, all others were serotype A (var. grubii) isolates. Taken together, our findings indicate that the ability of these clinical isolates to infect apparently normal individuals may be attributable to mutations other than pkr1 and/or underlying immune system impairment in patients.

Case report: familial chronic mucocutaneous candidiasis complicated by deep candida infection.

Chronic mucocutaneous candidiasis (CMC) is usually characterized by onset in childhood and is almost never complicated by deep fungal infection. The authors report two cases of fatal candida meningitis in patients who suffered from mild, adult-onset CMC. The pedigrees suggest an autosomal recessive disorder. In the index cases and in a symptomatic sibling, the immunologic work-up showed a specific cellular deficit as opposed to Candida albicans, as is typical of other forms of CMC. Both families were of French Canadian descent and originated from eastern Quebec. Three other cases of primary candida meningitis in patients of the same ethnic origin are also reported and reviewed. It is suggested that these cases may represent a variant of familial adult-onset CMC, in which there is a striking predisposition to deep infection.