Inhibition Of S100a11 Gene Expression Impairs Keratinocyte Response Against Vaccinia Virus: Implications For Eczema Vaccinatum

RATIONALE: We have previously demonstrated that S100A11 gene expression is down-regulated in atopic dermatitis (AD) skin. S100A11 is a calcium-sensing protein that may play a role in keratinocyte differentiation. AD patients are predisposed to disseminated vaccinia viral (VV) skin infection after smallpox vaccination. Therefore, we investigated whether inhibiting expression of S100A11 increased the replication of VV in human keratinocytes and the role of HBD-3 in this process.METHODS: Small interfering RNA sequences were used to reduce gene expression of S100A11 and HBD3 in the HaCaT keratinocyte cell line. VV replication was evaluated by real-time RT-PCR and viral plaque assay under low and high calcium conditions. Cytopathic effects were observed under phase microscopy and quantified after crystal violet staining. S100A11 and HBD3 were assessed by real-time PCR and western blot.RESULTS: Transfection of HaCaT cells with S100A11 siRNA resulted in a 90% reduction of S100A11 protein expression by western blot. VV gene expression was significantly increased in S100A11 knocked-down HaCaT cells (mean: 4.22 ± 0.07 ng VV/ng GAPDH compared with control (mean: 1.36 ± 0.03; p < 0.05). The significantly increased VV replication in S100A11 knocked-down cells was confirmed by VV plaque assay. Inhibition of S100A11 led to a significant reduction in HBD3 (p < 0.01). Reduction of HBD3 gene expression by RNA interference also increased VV replication in keratinocytes (p < 0.05).CONCLUSIONS: Inhibition of S100A11 gene expression impairs the ability of keratinocytes to control VV replication. This anti-viral effect is mediated, in part, through regulation of HBD-3 expression. Reduced S100A11 expression in AD skin may increase propensity towards disseminated VV infection. RATIONALE: We have previously demonstrated that S100A11 gene expression is down-regulated in atopic dermatitis (AD) skin. S100A11 is a calcium-sensing protein that may play a role in keratinocyte differentiation. AD patients are predisposed to disseminated vaccinia viral (VV) skin infection after smallpox vaccination. Therefore, we investigated whether inhibiting expression of S100A11 increased the replication of VV in human keratinocytes and the role of HBD-3 in this process. METHODS: Small interfering RNA sequences were used to reduce gene expression of S100A11 and HBD3 in the HaCaT keratinocyte cell line. VV replication was evaluated by real-time RT-PCR and viral plaque assay under low and high calcium conditions. Cytopathic effects were observed under phase microscopy and quantified after crystal violet staining. S100A11 and HBD3 were assessed by real-time PCR and western blot. RESULTS: Transfection of HaCaT cells with S100A11 siRNA resulted in a 90% reduction of S100A11 protein expression by western blot. VV gene expression was significantly increased in S100A11 knocked-down HaCaT cells (mean: 4.22 ± 0.07 ng VV/ng GAPDH compared with control (mean: 1.36 ± 0.03; p < 0.05). The significantly increased VV replication in S100A11 knocked-down cells was confirmed by VV plaque assay. Inhibition of S100A11 led to a significant reduction in HBD3 (p < 0.01). Reduction of HBD3 gene expression by RNA interference also increased VV replication in keratinocytes (p < 0.05). CONCLUSIONS: Inhibition of S100A11 gene expression impairs the ability of keratinocytes to control VV replication. This anti-viral effect is mediated, in part, through regulation of HBD-3 expression. Reduced S100A11 expression in AD skin may increase propensity towards disseminated VV infection.