BIOMEDICINE: Only Skin Deep

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Science  14 Apr 2006:
Vol. 312, Issue 5771, pp. 161d-163d
DOI: 10.1126/science.312.5771.161d

Although smallpox was declared eradicated by the World Health Organization in 1980, the threat of bioterrorism means that future vaccination against this virus is being considered. However, for sufferers of atopic dermatitis, vaccination itself poses a problem because these individuals are prone to developing the condition eczema vaccinatum: an exacerbated skin infection that follows inoculation with the vaccinia virus used in smallpox vaccination.

In looking at why atopic dermatits patients might be more susceptible, Howell et al. conclude that the effective control of vaccinia virus may hinge on an antimicrobial peptide called cathelicidin LL-37, which has been shown to have direct antiviral properties in vitro. In explant studies, patient skin had reduced LL-37 expression and allowed higher levels of viral replication than skin from normal individuals. Further experiments showed that the T helper cell type 2 cytokines interleukin-4 (IL-4) and IL-13 elevated viral replication and decreased LL-37 in normal skin, with the opposite effect seen after blocking the cytokines in skin from atopic dermatitis subjects. Mice lacking a homolog of LL-37 also showed poor control of vaccinia replication. These results suggest that as well as modulating adaptive immune responses to poxviruses, the cytokine environment of the skin substantially influences early innate immune protection. — SJS

Immunity 24, 341 (2006).

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