085 Autoantigen screening in C3H/HeJ mouse model of alopecia areata revealed high antigenicity of melanocyte-associated antigen epitopes

Abstract

Alopecia areata (AA) is an autoimmune form of hair loss involving infiltration of CD8+ T cells in the hair follicles (HFs) in conjunction with the upregulated antigen presentation processes. The growing (anagen) HFs are preferentially attacked in AA, leading to the hypothesis that epitopes derived from anagen-specific proteins are targeted by the T cells. Melanogenesis is a highly active process during anagen and clinical observations reported preferential loss of pigmented hairs during the initial onset of AA and regrowth of unpigmented hair during recovery. However, whether melanogenesis antigens are an inciting factor for AA has not been determined. We utilized a computer-assisted epitope prediction algorithm to design a panel of candidate CD8 T cell-specific epitope sequences in the C3H/HeJ mouse model, which we derived from several sources including our previous GWAS studies, published data, and known melanogenesis proteins. In addition, we isolated protein homogenates from the skin of AA-affected and normal-haired C3H/HeJ mice at either anagen or telogen stages of hair cycle. The epitope peptides and protein homogenates were used to stimulate skin-draining lymph node cells (LNCs) of C3H/HeJ mice with chronic AA or normal-haired mice and assessed the number of activated IFNg-producing CD8 T cells via ELISpot assays. We found that anagen stage protein homogenates induced a higher level of CD8 T cell activation, especially those with higher molecular weight, supporting the hypothesis that AA is an anagen-specific disease. Interestingly, epitopes derived from melanosomal membrane glycoprotein OA1 and transport protein SLC24A5 and SLC45A2 induced significantly higher frequency of CD8 T cell activation. Some of the antigens that showed higher antigenicity were suggested in previous studies to display molecular mimicry with peptides from the HBV vaccine. Further finemapping of epitopes will help define AA-associated antigens and the development of potential antigen-specific tolerogenic therapies. DNA immunization has theoretical and practical advantages over conventional protein-based immunization strategies. Though studies in animal models demonstrate the promise of nonviral DNA vaccines, clinical translation has thus far been disappointing. Here we develop a unique approach to increase the immunogenicity of non-viral DNA vaccines by combining "skin targeting" with a novel keratinocyte targeted approach to create a pro-immunogenic cutaneous microenvironment. Specifically, we co-delivered antigen with the transcription factor x-box binding protein 1 (XBP1) to the skin. XBP1 is an endoplasmic reticulum (ER) stress-associated factor that regulates ER function, promotes the production and secretion of proteins, regulates survival and function of antigen presenting cells, and has been shown to induce innate immunity under some conditions. In mouse models, we find that compared to delivery of antigen encoding plasmid alone, co-delivery with K14 promoter driven XBP1 plasmid DNA results in improved antigen-specific humor...

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“…GOLGA8M, which encodes Golgin A8 family member M, contributes to the development of HBV-related HCC (Jiang et al 2020 ). The researchers have shown that the transport protein SLC24A5 induces a significantly higher frequency of CD8 T cell activation in an autoimmune disease like Alopecia areata (Wang et al 2019 ).…”