The signal transducer and activator of transcription 6 gene (STAT6) increases the propensity of patients with atopic dermatitis toward disseminated viral skin infections

Abstract

Background: Atopic dermatitis (AD) is a chronic inflammatory skin disease associated with increased susceptibility to recurrent skin infections.

Objective: We sought to determine why a subset of patients with AD have an increased risk of disseminated viral skin infections.

Methods: Human subjects with AD with a history of eczema herpeticum (EH) and various control groups were enrolled. Vaccinia virus (VV) expression was measured by means of PCR and immunofluorescent staining in skin biopsy specimens from each study group after incubation with VV. Transgenic mice with a constitutively active signal transducer and activator of transcription 6 gene (STAT6) were characterized for response to VV skin inoculation. Genotyping for 10 STAT6 single nucleotide polymorphisms (SNPs) was performed in a white patient sample (n = 444).

Results: VV gene and protein expression were significantly increased in the skin of patients with EH compared with other subject groups after incubation with VV in vitro. Antibody neutralization of IL-4 and IL-13 resulted in lower VV replication in patients with a history of EH. Mice that expressed a constitutively active STAT6 gene compared with wild-type mice had increased mortality and satellite lesion formation after VV skin inoculation. Significant associations were observed between STAT6 SNPs and EH (rs3024975, rs841718, rs167769, and rs703817) and IFN-γ production. The strongest association was observed for a 2-SNP haplotype (patients with AD with a history of EH vs patients with AD without a history of EH, 24.9% vs 9.2%; P = 5.17 × 10(-6)).

Conclusion: The STAT6 gene increases viral replication in the skin of patients with AD with a history of EH. Further genetic association studies and functional investigations are warranted.

Copyright © 2011 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.

Figures

Figure 1

ADEH+ skin supports significantly greater VV replication. A) DNA was isolated from media or VV stimulated non-lesional skin and analyzed for VV gene expression by real-time RT-PCR. B) Immunofluorescent staining for A27L. C) The MFI for VV expression in the basal keratinocytes of each biopsy. *, ** and *** indicate significant differences of P <0.05, P <0.01 and P <0.001, respectively.

Figure 1

ADEH+ skin supports significantly greater VV replication. A) DNA was isolated from media or VV stimulated non-lesional skin and analyzed for VV gene expression by real-time RT-PCR. B) Immunofluorescent staining for A27L. C) The MFI for VV expression in the basal keratinocytes of each biopsy. *, ** and *** indicate significant differences of P <0.05, P <0.01 and P <0.001, respectively.

Figure 1

ADEH+ skin supports significantly greater VV replication. A) DNA was isolated from media or VV stimulated non-lesional skin and analyzed for VV gene expression by real-time RT-PCR. B) Immunofluorescent staining for A27L. C) The MFI for VV expression in the basal keratinocytes of each biopsy. *, ** and *** indicate significant differences of P <0.05, P <0.01 and P <0.001, respectively.

Figure 2

IL-4 and IL-13 modulate VV replication. VV expression in non-lesional skin from ADEH− (panel A; n=17) and ADEH+ (panel B; n=6) subjects infected with VV following pre-treatment with/without neutralizing antibodies to IL-4 and IL-13. * indicates significant difference of P <0.05.

Figure 2

IL-4 and IL-13 modulate VV replication. VV expression in non-lesional skin from ADEH− (panel A; n=17) and ADEH+ (panel B; n=6) subjects infected with VV following pre-treatment with/without neutralizing antibodies to IL-4 and IL-13. * indicates significant difference of P <0.05.

Figure 3

Constitutive STAT6 expression predisposes mice to disseminated VV infection. A) Satellite lesions, B) Mortality rate, C) VV gene expression, and D) VV protein staining in wild type and STAT-6VT mice following infection with 5×106 pfu of VV. VV replication was visualized by staining for the surface protein A27L (red) and wheat germ agglutinin (green) to visualize the epidermis. *, ** and *** indicate significant differences of P <0.05, P <0.01 and P <0.001, respectively.

Figure 3

Constitutive STAT6 expression predisposes mice to disseminated VV infection. A) Satellite lesions, B) Mortality rate, C) VV gene expression, and D) VV protein staining in wild type and STAT-6VT mice following infection with 5×106 pfu of VV. VV replication was visualized by staining for the surface protein A27L (red) and wheat germ agglutinin (green) to visualize the epidermis. *, ** and *** indicate significant differences of P <0.05, P <0.01 and P <0.001, respectively.

Figure 3

Constitutive STAT6 expression predisposes mice to disseminated VV infection. A) Satellite lesions, B) Mortality rate, C) VV gene expression, and D) VV protein staining in wild type and STAT-6VT mice following infection with 5×106 pfu of VV. VV replication was visualized by staining for the surface protein A27L (red) and wheat germ agglutinin (green) to visualize the epidermis. *, ** and *** indicate significant differences of P <0.05, P <0.01 and P <0.001, respectively.

Figure 3

Constitutive STAT6 expression predisposes mice to disseminated VV infection. A) Satellite lesions, B) Mortality rate, C) VV gene expression, and D) VV protein staining in wild type and STAT-6VT mice following infection with 5×106 pfu of VV. VV replication was visualized by staining for the surface protein A27L (red) and wheat germ agglutinin (green) to visualize the epidermis. *, ** and *** indicate significant differences of P <0.05, P <0.01 and P <0.001, respectively.

Figure 4

Analysis of STAT6 polymorphisms in European American samples. A) STAT6 gene structure and distribution of the genotyped SNPs across the gene (22.6 kb) on chromosome 12q13 Haplotype block structure of STAT6 SNPs in European American healthy controls (n = 166) was presented. The intensity of shading represents D' (a measure of LD) generated using HAPLOVIEW software, with red (100) to green reflecting higher to lower D’ values. Both rs3024951 and rs3024955 were excluded in LD plot because of their low allele frequencies, B) Haplotype results showing Omnibus P-values constructed across sliding windows of sizes 2–5 for eight common SNPs and ADEH+. Black vertical lines represent all individual SNP tests, and colored horizontal lines represent 2-, 3, 4, 5, haplotype tests. *see detailed data in Table IV.

Figure 4

Analysis of STAT6 polymorphisms in European American samples. A) STAT6 gene structure and distribution of the genotyped SNPs across the gene (22.6 kb) on chromosome 12q13 Haplotype block structure of STAT6 SNPs in European American healthy controls (n = 166) was presented. The intensity of shading represents D' (a measure of LD) generated using HAPLOVIEW software, with red (100) to green reflecting higher to lower D’ values. Both rs3024951 and rs3024955 were excluded in LD plot because of their low allele frequencies, B) Haplotype results showing Omnibus P-values constructed across sliding windows of sizes 2–5 for eight common SNPs and ADEH+. Black vertical lines represent all individual SNP tests, and colored horizontal lines represent 2-, 3, 4, 5, haplotype tests. *see detailed data in Table IV.

Figure 5

Association of STAT6 SNPs with IFNγ production in HSV-stimulated PBMCs from AD patients (n=44) as determined by the log10-transformed mean SFC/106 cells. A) The association was observed for SNP rs3024951 (TC [n=7] vs CC [n=32)] P = 0.008), B) the association was observed for SNP rs324013 (CC [n=13] vs CT [n=18] +TT [n = 8], P = 0.025). N.S.: not significant.