Herpesvirus Connection in the Expression of Autoimmune Vitiligo in Smyth Line Chickens

Abstract

The Smyth line (SL) chicken is an animal model for human vitiligo, a common acquired depigmentary disorder affecting about 1-2% of people worldwide. The vitiligo-like depigmentation in SL chickens typically develops when the birds are between 6 and 14 weeks of age and may affect 70-95% of hatch mates. The development of SL vitiligo is considered to depend on two interacting components, namely an inherent melanocyte defect and an autoimmune reaction to melanocytes. Recently, a role for an environmental factor in the expression of vitiligo was suggested by the observation that only 10% of SL chicks imported from the University of Massachusetts (UM) and reared in isolation at biosecurity level 2 (BSL 2) at the University of Arkansas (UA) exhibited vitiligo. Following further assessment of environmental differences between UA and UM SL chickens, three environmental factors that may have influenced the expression of SL vitiligo were identified. Included were housing condition, status of Mycoplasma synoviae infection, and turkey herpesvirus (HVT) vaccination status. Studies were subsequently conducted at UA and UM to assess the role of these environmental factors in the expression of SL vitiligo. M. synoviae infection was not found necessary for vitiligo expression in SL chickens. However, HVT emerged as a strong candidate for an important environmental factor in SL vitiligo. The connection between HVT and SL vitiligo was confirmed for both BSL 2 and conventional housing. Therefore, the observations reported here suggest a strong causative link between HVT infection and SL vitiligo.

Physiopathology and genetics of vitiligo

“…Recent data strongly suggest that the mechanism involved in the death of melanocytes in Smyth line vitiligo is an apoptosis induced by infiltrating cytotoxic T lymphocytes [17]. Interestingly, a strong causative link between herpes virus and Smyth line vitiligo has been reported, supporting the role of environmental factors in the expression of vitiligo in these chickens [18]. Although the pathogenesis of human vitiligo could be different from this animal model, the genetic background, the effect of immunity cells and the environmental role, all observed in Smyth line vitiligo, strongly recall data reported in human vitiligo.…”

Characterization and experimental reproduction of peripheral neuropathy in White Leghorn chickens

“…Alternatively, the basic nature and aetiology of IP and PN may differ in ways, presently not understood, that would influence the efficacy of experimental transfer. Interestingly, HVT has recently been shown to influence the expression of autoimmune vitiligo in genetically susceptible Smyth-line chickens (Erf et al, 2001).…”

Marek’s disease virus and skin interactions

“…Among three important differences, vaccination of the birds against MD using the heterologous HVT appeared to be the most important factor. Indeed, it has been shown that 20 week-old birds vaccinated with HVT had an incidence of vitiligo 4 times higher than non-vaccinated birds [72]. This puzzling result raises various hypotheses regarding the impact of HVT vaccination on the development of vitiligo, knowing that the HVT vaccine also penetrates and replicates in feather follicles [51,59].…”