Research Article

Chronic Mucocutaneous Candidiasis in Humans with Inborn Errors of Interleukin-17 Immunity

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Science  01 Apr 2011:
Vol. 332, Issue 6025, pp. 65-68
DOI: 10.1126/science.1200439


Chronic mucocutaneous candidiasis disease (CMCD) is characterized by recurrent or persistent infections of the skin, nails, and oral and genital mucosae caused by Candida albicans and, to a lesser extent, Staphylococcus aureus, in patients with no other infectious or autoimmune manifestations. We report two genetic etiologies of CMCD: autosomal recessive deficiency in the cytokine receptor, interleukin-17 receptor A (IL-17RA), and autosomal dominant deficiency of the cytokine interleukin-17F (IL-17F). IL-17RA deficiency is complete, abolishing cellular responses to IL-17A and IL-17F homo- and heterodimers. By contrast, IL-17F deficiency is partial, with mutant IL-17F–containing homo- and heterodimers displaying impaired, but not abolished, activity. These experiments of nature indicate that human IL-17A and IL-17F are essential for mucocutaneous immunity against C. albicans, but otherwise largely redundant.

Chronic mucocutaneous candidiasis (CMC) is characterized by infections of the skin, nails, and oral and genital mucosae with Candida albicans, which is commensal in healthy individuals (1). In patients with inherited or acquired T cell immunodeficiencies, CMC is associated with various infectious diseases (1). In patients with STAT3 deficiency and a lack of interleukin-17A (IL-17A)– and IL-22–producing T cells (25), CMC is associated with severe cutaneous and pulmonary staphylococcal infections (1). In some patients with IL-12p40 or interleukin-12 receptor β1 (IL-12Rβ1) deficiency and mycobacterial disease (2) and in a family with caspase recruitment domain 9 (CARD9) deficiency with systemic candidiasis and peripheral dermatophytosis (6), CMC and low proportions of IL-17A–producing T cells were also documented. Finally, CMC is the only infection of patients with autoimmune regulator (AIRE) deficiency, who have neutralizing autoantibodies against IL-17A, IL-17F, and/or IL-22 (7, 8). These data suggest that human IL-17A, IL-17F, and/or IL-22 are involved in mucocutaneous immunity to C. albicans (1). CMC disease (CMCD), the molecular and cellular basis of which is unknown, consists of CMC in the absence of other overt infectious or autoimmune signs (1). CMCD was initially thought to be benign, until squamous cell carcinoma (9) and cerebral aneurysms (10) were reported. First described in 1967 in sporadic cases (11), familial CMC segregating as autosomal dominant (AD) (12) and autosomal recessive (AR) traits (13) was soon reported. We thus searched for the genetic basis of CMCD, testing the hypothesis that CMCD may be caused by inborn errors of IL-17A, IL-17F, or IL-22 immunity (1, 14).

Autosomal recessive IL-17RA deficiency. We first investigated a French child born to first-cousin parents of Moroccan descent (Fig. 1A) [report S1 (15)]. He presented with C. albicans dermatitis during the neonatal period and displayed Staphylococcus aureus dermatitis at 5 months of age. Known causes of CMC were excluded clinically and genetically, and the lack of any phenotype other than CMC led to a diagnosis of AR CMCD. We sequenced the candidate genes encoding IL-22, IL-22RA1, IL-10RB, IL-17A, IL-17F, IL-17RA, and IL-17RC (1618). IL-22 binds as a monomer to its receptor, composed of IL-22RA1 and IL-10RB, whereas IL-17A and IL-17F can form homo- or heterodimers that signal via a receptor comprising IL-17RA and IL-17RC chains. The child was found to be homozygous for the c.850C>T nonsense mutation (c.850C>T/c.850C>T), which replaces the glutamine codon in position 284 with a stop codon (Q284X/Q284X) in the IL17RA gene (19) (Fig. 1B). This premature stop codon is located in the part of the gene encoding the extracellular domain of IL-17RA, upstream from the transmembrane domain sequence (Fig. 1C). No mutations were found elsewhere in IL17RA or in any of the other six genes sequenced. The parents and siblings of this child are healthy and heterozygous for the mutant allele, consistent with AR inheritance for this trait. The mutant allele was not found in 1065 healthy controls from 52 ethnic groups from the Centre d'Etude du Polymorphisme Humain–Human Genome Diversity Cell Line Panel CEPH-HGDP, 100 French controls, and 70 Moroccan controls of Berber descent, which ruled out an irrelevant polymorphism and suggested that the mutation may define a rare AR CMCD-causing allele.

Fig. 1

A kindred with autosomal recessive IL-17RA deficiency. (A) Pedigree of the family established by IL-17RA genotyping. The proband is indicated by an arrow. E? indicates individuals whose genetic status could not be evaluated. (B) IL17RA DNA sequence electrophoregrams for a control and the patient. (C) Schematic diagram of the IL-17RA protein with the signal sequence (SS), extracellular (EC), transmembrane (TM), intracellular (IC), and SEFIR (expression similar to fibroblast growth factor–IL-17R) domains and the position within the extracellular domain affected by the mutation.

The IL-17RA protein was not detected on the surface of fibroblasts, peripheral blood mononuclear cells (PBMCs), or, more specifically, CD4+ T cells, CD8+ T cells, and monocytes from the patient, as shown by flow cytometry with two specific antibodies against the extracellular domain (Fig. 2A and fig. S1). The absence of IL-17RA had no impact on the expression of IL-17RC, which was normal on the patient’s monocytes (the only leukocyte subset expressing IL-17RC in controls) and fibroblasts (figs. S1 and S2). Likewise, IL-22RA1 was normally expressed on the patient’s fibroblasts (fig. S2). The patient also had a normal proportion of circulating IL-17A– and IL-22–producing T cells (fig. S3). We investigated whether the lack of IL-17RA expression had any functional consequences for the response to IL-17 cytokines, by testing the responses of the patient’s fibroblasts to various concentrations of recombinant IL-17A and IL-17F homodimers and to IL-17A–IL-17F heterodimers (17, 18). Like nuclear factor-κB essential modulator (NEMO)–deficient fibroblasts, which have impaired NF-κB activity, and unlike fibroblasts from a healthy control, the patient’s fibroblasts did not respond to any of the three IL-17 cytokines, in terms of IL-6 and growth-regulated oncogene-α (GRO-α) induction (20), as assessed by enzyme-linked immunosorbent assay (ELISA) on supernatants (Fig. 2, B and C). Moreover, the patient’s PBMCs did not respond above baseline to IL-17A or IL-17F for any of the cytokines tested (fig. S4A). Transfection of the patient’s fibroblasts with wild-type (WT) IL17RA, but not with a mock vector, restored IL-17RA expression and the response to IL-17 cytokines (Fig. 2, D to F). By contrast, IL-6 production by NEMO-deficient cells was not rescued by transfection with IL17RA (fig. S4B). Thus, the patient with CMCD that we studied displayed AR, complete IL-17RA deficiency, and a lack of cellular responses to at least three IL-17 cytokine dimers—IL-17A, IL-17F, and IL-17A–IL-17F—in fibroblasts and leukocytes.

Fig. 2

Production and function of the mutant IL-17RA chain. (A) IL-17RA expression in SV40-immortalized fibroblasts (top) and nonadherent PBMCs (bottom) from a control and the patient, as detected by flow cytometry. Isotype control, black; IL-17RA antibody, gray. (B) IL-6 and (C) GRO-α production by SV40-immortalized fibroblasts from a control, the patient, and NEMO-deficient cells after 24 hours of stimulation with IL-17A, IL-17F, and IL-17A–IL-17F. Means ± SD (error bars) of three independent experiments, as detected by ELISA. UD, undetectable. (D) IL-17RA expression in SV40-immortalized fibroblasts from the patient, transfected with the empty pORF9mcs plasmid (left) or the pORF9-hIL-17RA plasmid (right), as detected by flow cytometry. Isotype control, black; IL17RA antibody, gray. (E) IL-6 and (F) GRO-α production by SV40-immortalized fibroblasts from the patient, transfected with the empty pORF9mcs plasmid (white) or the pORF9-hIL17RA plasmid (gray), after 24 hours of stimulation with IL-17A, IL-17F, and IL-17A–IL-17F. Means ± SD (error bars) of three independent experiments, as detected by ELISA.

Autosomal dominant IL-17F deficiency. We then investigated a multiplex family from Argentina, with AD inheritance of CMCD (Fig. 3A) [report S2 (15)]. The IL22, IL22RA, IL10RB, IL17RA, IL17RC, and IL17A genes contained no mutations, but a heterozygous missense mutation was found in the IL17F gene of the index case. This mutation, c.284C>T, replaced the serine residue in position 65 of the mature protein with a leucine residue (S65L) (Fig. 3, B and C). The Ser65 residue is conserved across mammalian species (fig. S5). Moreover, the sequencing of 1074 control individuals from the CEPH-HGD panel ruled out the possibility that this mutation was an irrelevant polymorphism. Computational analysis showed that Ser65 lies in the cavity of the protein, which is thought to be involved in cytokine-to-receptor binding (Fig. 3C) (21). No other IL17F variations were found in the index case, including the IL17F g.7488T>C (rs763780) polymorphism, in which an arginine residue replaced a histidine in position 161 of the protein (H161R), a mutation previously thought to be loss-of-function (22). By contrast, we found that the H161R allele encoded an IL-17F protein able to stimulate murine lung epithelial cells (MLEs) (fig. S6). Heterozygosity for the S65L allele was found in all tested members of the kindred with CMCD; we were unable to genotype the fifth patient (III.1 in Fig. 3A), who died at 6 years of age from complications of the disease. The mutant allele was found in only two apparently healthy family members, aged 9 months (III.3 in Fig. 3A) and 21 years (II.8 in Fig. 3A), which suggested incomplete clinical penetrance. We did not detect IL-17F–expressing T cells in controls by flow cytometry, but the patients tested displayed normal proportions of IL-17A– and IL-22–expressing T cells, and their PBMCs secreted normal amounts of cytokines, as measured by Bioplex (fig. S7, A and B).

Fig. 3

A kindred with autosomal dominant IL-17F deficiency. (A) Family pedigree, with allele segregation. The patients, shown in black, are all heterozygous for the mutation, as is II.8, who is asymptomatic. The proband is indicated by an arrow. E? indicates individuals whose genetic status could not be evaluated. III.3 is a 9-month-old baby, also heterozygous for the mutation and currently asymptomatic. All other family members are healthy and WT for IL17F and are shown in white. (B) Heterozygous c.284C>T mutation in the patients. IL17F DNA sequence electrophoregrams of a control and the patient III.2. (C) Ribbon trace of the IL-17F dimer. Beta strands are labeled. Sulfur atoms are shown in yellow. The position of the cavity that binds to the receptor is indicated by a black circle.

We investigated the possible deleterious effects of the S65L mutation by producing the mutant IL-17F protein in human embryonic kidney (HEK) 293 cells. The mutation did not seem to affect production of the monomeric protein or the formation of IL-17F homodimers (mutant-mutant and wild-type–mutant) or heterodimers with IL-17A (fig. S8). The mutant-containing dimers seemed to bind normally to homodimeric IL-17 receptors (IL-17RA and IL-17RC), as shown by surface plasmon resonance (table S1 and fig. S9). However, the mutant proteins did not bind IL-17RA on fibroblasts, as shown by flow cytometry, with IL-17RA–deficient cells as controls (confirming that their lack of IL-17RA expression prevented cytokine binding) (figs. S10 and S11). Accordingly, when control fibroblasts (Fig. 4, A and B) and keratinocytes (fig. S12, A and B) were stimulated with mutant S65L IL-17F homodimers, they displayed much weaker IL-6 and GRO-α induction than observed with WT IL-17F homodimers (IL-17WT), IL-17A homodimers, or IL-17A–IL-17FWT heterodimers (20). Moreover, control PBMCs showed impaired induction of several cytokines when stimulated with S65L IL-17F homodimers compared with WT IL-17F homodimers (fig. S12C). These data suggest that the IL17F S65L allele is severely hypomorphic (Fig. 4, A and B, and fig. S12, A and B). Furthermore, when the S65L mutant IL-17F formed a heterodimer with either IL-17FWT or IL-17A, the induction of IL-6 and GRO-α was severely impaired in control fibroblasts (Fig. 4, A and B) and keratinocytes (fig. S12, A and B), which indicated a dominant-negative effect of this allele. Finally, as predicted by the lack of binding of mutant cytokine dimers to their receptor (fig. S11), these dimers did not compete with WT dimers (fig. S13, A to D). Thus, the AD CMCD in this kindred results from a hypomorphic, dominant-negative IL17F allele, which impairs the receptor binding and bioactivity of both IL-17F homodimers and IL-17A–IL-17F heterodimers.

Fig. 4

Function of the mutant IL-17F protein. (A) Production of IL-6 and (B) GRO-α by control SV40 fibroblasts in response to increasing doses (ng/ml) of IL-17A, IL-17FWT, mutant IL-17F (IL-17FS65L), IL-17FWT–IL-17FS65L homodimers and of IL-17A–IL-17FWT and IL-17A–IL-17FS65L heterodimers for 24 hours. Means ± SD (error bars) of three independent experiments, as detected by ELISA.

Concluding remarks. IL-17RA and IL-17F deficiencies underlying mucocutaneous disease caused by C. albicans and, to a lesser extent, S. aureus are consistent with the mouse model (23). IL-17RA– and IL-17RC–deficient mice were more susceptible to oropharyngeal candidiasis (24, 25) and IL-17RA–deficient mice to cutaneous staphylococcal disease (26). IL-17A–deficient mice also display impaired clearance of C. albicans skin infection (27). IL-17F–deficient mice have not yet been tested, but IL-23–deficient mice with impaired expression of IL-17A and IL-17F are also vulnerable (27). IL-17A or IL-17F alone are not required for peripheral immunity to S. aureus, but mice deficient for both IL-17A and IL-17F display an impaired peripheral immunity to S. aureus (28). Somewhat at odds with our observations, IL-17A is also required for systemic immunity to C. albicans (29) and S. aureus (30). Moreover, mice with IL-17RA, IL-17RC, IL-17A, or IL-17F deficiency are vulnerable to multiple infections at various anatomical sites (17, 23). Overall, our report indicates that human IL-17A and IL-17F are essential for protective immunity to C. albicans and, to a lesser extent, S. aureus in the nails, skin, and oral and genital mucosae, but otherwise redundant. We cannot exclude the possibility that other infections may occur in patients with inborn errors of IL-17 immunity. In any event, in natura, inborn errors of IL-17 immunity clearly impair mucocutaneous immunity to C. albicans (14, 31). Patients receiving IL-17–blocking agents should be carefully monitored, at least for mucocutaneous infections (32).

Supporting Online Material

Materials and Methods

Figs. S1 to S13

Table S1


  • * These authors contributed equally to this work.

  • These authors contributed equally to this work.

References and Notes

  1. Materials and methods are available as supporting material on Science Online.
  2. Single-letter abbreviations for the amino acid residues are as follows: A, Ala; C, Cys; D, Asp; E, Glu; F, Phe; G, Gly; H, His; I, Ile; K, Lys; L, Leu; M, Met; N, Asn; P, Pro; Q, Gln; R, Arg; S, Ser; T, Thr; V, Val; W, Trp; Y, Tyr; and X, stop.
  3. We thank the patients, their families, and their clinicians. We also thank all members of the laboratory for helpful discussions and T. Kochetkov for keratinocyte culture. This work was supported by institutional funding from INSERM, University Paris Descartes, the Rockefeller University, the Rockefeller University CTSA grant number 5UL1RR024143-04, the St. Giles Foundation, and the Candidoser association awarded to J.-L.C. Genomic DNA sequences of the mutations IL-17RA (JF305973) and IL-17F (JF305974) can be found in GenBank. The following reagents are available under a Materials Transfer Agreement: human IL-17A homodimer (– mutation) purified protein, human IL-17F homodimer (+/− mutation) purified protein, human IL-17A–IL-17F heterodimer (+/− mutation) purified protein, and antibody against human IL-17F.

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