Herpetic whitlow during isotretinoin therapy

Retinoid X receptor α attenuates host antiviral response by suppressing type I interferon

The retinoid X receptor α (RXRα), a key nuclear receptor in metabolic processes, is downregulated during host antiviral response. However, the roles of RXRα in host antiviral response are unknown. Here we show that RXRα overexpression or ligand activation increases host susceptibility to viral infections in vitro and in vivo, while Rxra-/- or antagonist treatment reduces infection by the same viruses. Consistent with these functional studies, ligand activation of RXR inhibits the expression of antiviral genes including type I interferon (IFN) and Rxra-/- macrophages produce more IFNβ than WT macrophages in response to polyI:C stimulation. Further results indicate that ligand activation of RXR suppresses the nuclear translocation of β-catenin, a co-activator of IFNβ enhanceosome. Thus, our studies have uncovered a novel RXR-dependent innate immune regulatory pathway, suggesting that the downregulation of RXR expression or RXR antagonist treatment benefits host antiviral response, whereas RXR agonist treatment may increase the risk of viral infections.

Recurrent herpes labialis during isotretinoin therapy: is there a role for photosensitivity?

Isotretinoin (13-cis-retinoic acid) is one of the synthetic retinoids derived from vitamin A. Vitamin A derivatives demonstrate virucidal activity, both in vivo and in vitro. Isotretinoin has been used for the treatment of recurrent herpes simplex with encouraging results. However, we present a case with frequent attacks of herpes labialis during isotretinoin therapy for acne, who had a marked decrease in frequency of recurrences following strict use of sunscreens.