Using this approach, we have now identified 4 immunogenic peptides out of 573 HLA-DR-presented peptides (0

Using this approach, we have now identified 4 immunogenic peptides out of 573 HLA-DR-presented peptides (0.07%) identified from the synovial tissue of 5 patients with antibiotic-refractory Lyme arthritis. the initial skin lesion of the infection. Months later, after priming of the immune response to MMP-10 in early infection, a subset of patients with antibiotic-responsive or antibiotic-refractory arthritis had MMP-10 autoantibodies, but only patients with antibiotic-refractory arthritis had both T and B cell responses to the protein, providing evidence for a second autoimmune hit. Further support for a biologically relevant autoimmune event was observed by the positive correlation of anti-MMP-10 autoantibodies with distinct synovial pathology. This experience demonstrates the power of new, discovery-based methods to identify relevant autoimmune responses in chronic inflammatory forms of arthritis. occurs in temperate regions on North America, Europe, and Asia [1C3]. According to estimates from the Centers for Disease Control and Prevention, approximately 300, 000 new cases of the infection occur yearly in the United States, primarily in the northeastern U.S. [4,5]. The disease usually begins with an expanding skin lesion, erythema migrans (EM), which occurs at the site of the tick bite [1]. Months to several years later, untreated patients in the northeastern U.S. often develop Lyme arthritis (LA). Although it is no longer possible to study the natural history of the disease in the same patient longitudinally because of antibiotic therapy for early infection, many patients, who often lack signs or symptoms of early disease, still develop LA months to several years after the initial tick bite and exposure to can establish persistent infections in multiple immunocompetent animal models [10C13]. In C3H/HeN mice, in which the goal was to assess the long-term fate of persisting non-cultivable spirochetes, a dosage regimen of ceftriaxone for 25 days, a regimen that does not to mimic human treatment, was utilized to analyze this population of bacteria [14,15]. In this model, the mice remained infected following TMI-1 antibiotic treatment, and persistent, non-cultivatable spirochetes re-emerged, as shown by PCR, histology, xenodiagnosis, and cytokine analysis [15]. Although patients with refractory arthritis might have persistent infection in a protected site, such as tendons [16], culture and PCR results for from synovial tissue during the post-antibiotic period have been uniformly negative [17], and reactivation of infection has not been observed even during treatment with immunosuppressive DMARDs after antibiotic therapy [6]. Regarding the retained spirochetal antigen hypothesis, animal models show that highly cationic outer-surface proteins of may bind to cartilage [18]. Moreover, in a myeloid differentiation factor 88-deficit (MyD88?/?) mouse model, which have high pathogen loads, antigens are retained near cartilage surfaces after antibiotic therapy, and patellae homogenates from these mice induce macrophages to secrete TNF- [19]. However, in human LA, in which patients with antibiotic-responsive or antibiotic-refractory arthritis have low pathogen loads [17], it is not yet clear whether retained spirochetal antigens may be a factor in persistent synovitis after antibiotic treatment. The first observation suggesting that autoimmunity may contribute to the pathogenesis of antibiotic-refractory LA was that specific HLA-DR alleles, such as the DRB1*0401 allele, were increased in frequency in these patients [20] and these DRB1 molecules bound an immunodominant PRPH2 epitope of outer-surface protein A (OspA) [21]. In an initial search for molecular mimicry between spirochetal and host proteins, partial sequence homology was found between this epitope of OspA and an epitope of human LFA-1 [22] or MAWD-BP [23], but these self-proteins TMI-1 stimulated only low-level T cell responses and did not induce autoantibody responses. Later, human cytokeratin-10 was identified as having a cross-reactive target ligand recognized by anti-OspA antibodies in a small group of patients with antibiotic-refractory arthritis, but T cell reactivity was not explored [24]. Finally, several nonprotein antigens and neural proteins have been reported to induce T or B cell responses in patients with neuroborreliosis [25C29] or post-Lyme disease syndrome [30]. However, it was unclear whether any of these human self-antigens were the targets of pathogenic autoantibody responses in patients with antibiotic-refractory arthritis. In general, TMI-1 studies of autoimmune diseases have been hindered by difficulty in identifying relevant autoantigens. However, new discovery-based methods offer innovative approaches. Microarrays that express most human proteins or sequencing of plasmablast receptors may give a broad view of autoantibody specificities [31C34], but it is often difficult to assess and validate.