Vitiligo is a chronic autoimmune depigmenting skin disorder that results from a loss of melanocytes. Multiple combinatorial factors have been involved in disease development, with a prominent role of the immune system, in particular T cells. After repigmentation, vitiligo frequently recurs in the same area, suggesting that vitiligo could involve the presence of resident memory T cells (T). We sought to perform a thorough characterization of the phenotype and function of skin memory T cells in vitiligo. We show that stable and active vitiligo perilesional skin is enriched with a population of CD8 T expressing both CD69 and CD103 compared with psoriasis and control unaffected skin. CD8 T expressing CD103 are mainly localized in the epidermis. Expression of CXCR3 is observed on most CD8 T in vitiligo, including the population of melanocyte-specific CD8 T cells. CD8 T displayed increased production of IFN-γ and tumor necrosis factor-α with moderate cytotoxic activity. Our study highlights the presence of functional CD8 T in both stable and active vitiligo, reinforcing the concept of vitiligo as an immune memory skin disease. The CD8 T that remain in stable disease could play a role during disease flares, emphasizing the interest in targeting this cell subset in vitiligo.

Treatment failure and symptomatic relapse are major concerns in American tegumentary leishmaniasis (TL). Such complications are seen frequently in Leishmania guyanensis infections, in which patients respond variously to first-line antileishmanials and are more prone to develop chronic cutaneous leishmaniasis. The factors underlying this pathology, however, are unknown. Recently, we reported that a double-stranded RNA virus, Leishmania RNA virus 1 (LRV1), nested within L. guyanensis parasites is able to exacerbate experimental murine leishmaniasis by inducing a hyperinflammatory response. This report investigates the prevalence of LRV1 in human L. guyanensis infection and its effect on treatment efficacy, as well as its correlation to symptomatic relapses after the completion of first-line treatment. In our cohort of 75 patients with a diagnosis of primary localized American TL, the prevalence of LRV1-positive L. guyanensis infection was elevated to 58%. All patients infected with LRV1-negative L. guyanensis were cured after 1 dose (22 of 31 [71%]) or 2 doses (31 of 31 [100%]) of pentamidine. In contrast, 12 of 44 LRV1-positive patients (27%) presented with persistent infection and symptomatic relapse that required extended therapy and the use of second-line drugs. Finally, LRV1 presence was associated with a significant increase in levels of intra-lesional inflammatory markers. In conclusion, LRV1 status in L. guyanensis infection is significantly predictive (P = .0009) of first-line treatment failure and symptomatic relapse and has the potential to guide therapeutic choices in American TL.

Immune-mediated responses are consistently observed in progressing vitiligo at the edge of depigmenting patches. Besides the role of the adaptive immune system, the profile of the innate immune response is now at the center of the stage. We report that plasmacytoid dendritic cells (pDC), which are the major interferon (IFN)-alpha-producing cells, are part of the infiltrate of progressive vitiligo with local production of MxA (a protein induced by IFNα). MxA was associated with expression of the type I IFN-inducible ligand CXCL9 and correlated with the recruitment of CXCR3(+) immune cells. Interestingly, strong MxA expression was observed in perilesional skin in close apposition to remaining melanocytes, surrounded by a prominent T-cell infiltrate. In contrast, MxA was not detectable in lesional skin, suggesting that IFN-α production is an early event in the progression of the disease. Our data highlight a new innate immune pathway leading to progression of vitiligo.

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