HLA and autoantibodies define scleroderma subtypes and risk in African and European Americans and suggest a role for molecular mimicry.

Systemic sclerosis (SSc) is a clinically heterogeneous autoimmune disease characterized by mutually exclusive autoantibodies directed against distinct nuclear antigens. We examined HLA associations in SSc and its autoantibody subsets in a large, newly recruited African American (AA) cohort and among European Americans (EA). In the AA population, the African ancestry-predominant HLA-DRB1*08:04 and HLA-DRB1*11:02 alleles were associated with overall SSc risk, and the HLA-DRB1*08:04 allele was strongly associated with the severe antifibrillarin (AFA) antibody subset of SSc (odds ratio = 7.4). These African ancestry-predominant alleles may help explain the increased frequency and severity of SSc among the AA population. In the EA population, the HLA-DPB1*13:01 and HLA-DRB1*07:01 alleles were more strongly associated with antitopoisomerase (ATA) and anticentromere antibody-positive subsets of SSc, respectively, than with overall SSc risk, emphasizing the importance of HLA in defining autoantibody subtypes. The association of the HLA-DPB1*13:01 allele with the ATA+ subset of SSc in both AA and EA patients demonstrated a transancestry effect. A direct correlation between SSc prevalence and HLA-DPB1*13:01 allele frequency in multiple populations was observed (r = 0.98, P = 3 × 10-6). Conditional analysis in the autoantibody subsets of SSc revealed several associated amino acid residues, mostly in the peptide-binding groove of the class II HLA molecules. Using HLA α/ß allelic heterodimers, we bioinformatically predicted immunodominant peptides of topoisomerase 1, fibrillarin, and centromere protein A and discovered that they are homologous to viral protein sequences from the Mimiviridae and Phycodnaviridae families. Taken together, these data suggest a possible link between HLA alleles, autoantibodies, and environmental triggers in the pathogenesis of SSc.

Brief Report: Whole-Exome Sequencing to Identify Rare Variants and Gene Networks That Increase Susceptibility to Scleroderma in African Americans.

OBJECTIVE: Whole-exome sequencing (WES) studies in systemic sclerosis (SSc) patients of European American (EA) ancestry have identified variants in the ATP8B4 gene and enrichment of variants in genes in the extracellular matrix (ECM)-related pathway that increase SSc susceptibility. This study was undertaken to evaluate the association of the ATP8B4 gene and the ECM-related pathway with SSc in a cohort of African American (AA) patients. METHODS: SSc patients of AA ancestry were enrolled from 23 academic centers across the US under the Genome Research in African American Scleroderma Patients consortium. Unrelated AA individuals without serologic evidence of autoimmunity who were enrolled in the Howard University Family Study were used as unaffected controls. Functional variants in genes reported in the 2 WES studies in EA patients with SSc were selected for gene association testing using the optimized sequence kernel association test (SKAT-O) and pathway analysis by Ingenuity Pathway Analysis in 379 patients and 411 controls. RESULTS: Principal components analysis demonstrated that the patients and controls had similar ancestral backgrounds, with roughly equal proportions of mean European admixture. Using SKAT-O, we examined the association of individual genes that were previously reported in EA patients and none remained significant, including ATP8B4 (P = 0.98). However, we confirmed the previously reported association of the ECM-related pathway with enrichment of variants within the COL13A1, COL18A1, COL22A1, COL4A3, COL4A4, COL5A2, PROK1, and SERPINE1 genes (corrected P = 1.95 × 10-4 ). CONCLUSION: In the largest genetic study in AA patients with SSc to date, our findings corroborate the role of functional variants that aggregate in a fibrotic pathway and increase SSc susceptibility.

Retinopathy in monkeys with spontaneous type 2 diabetes.

PURPOSE: Type 2 diabetes occurs spontaneously in rhesus monkeys and shows an extraordinary similarity to human diabetes in clinical features and relative time course. The purpose of this study was to investigate clinically and histopathologically the ocular changes in these monkeys. METHODS: Ophthalmoscopic examinations were performed on aged normal and diabetic monkeys. Retinas from 16 diabetic monkeys and 6 nondiabetic monkeys were incubated postmortem for adenosine diphosphatase (ADPase) activity (labels viable retinal blood vessels) and flat-embedded in JB-4. Tissue sections were cut through areas of interest. RESULTS: Cotton-wool spots, intraretinal hemorrhages, and hard exudates in the macula were observed by ophthalmoscopy in some diabetic monkeys. Dot/blot hemorrhages, cotton-wool spots, and small nonperfused areas were the earliest histologically documented changes in the retinas. Large nonperfused areas extending from optic disc to midfovea were observed in four diabetic monkeys. Formation of small intraretinal microvascular abnormalities (IRMAs) and microaneurysms were associated with the areas of nonperfusion. There were apparent fluid-filled spaces in the outer plexiform layer in three of these maculas, suggesting macular edema. There was a significant correlation between the occurrence of retinopathy and hypertension (P = 0.037 for systolic pressure; P = 0.019 for diastolic pressure). In elastase-digested retinas, the ratio of pericytes to endothelial cells was 0.66:1 in diabetic and 0.64:1 in nondiabetic (P = 0.75) retinas. CONCLUSIONS: This is the first detailed analysis of retinopathy in a colony of spontaneous type 2 diabetic monkeys. Monkeys with type 2 diabetes have many of the angiopathic changes associated with human diabetic retinopathy. Hypertension correlates with the severity of the diabetic retinopathy.

Minimally invasive surgery via laparoscopy for intra-abdominal biopsy in obese rhesus macaques (Macaca mulatta).

PURPOSE: To determine the safety and effectiveness of laparoscopy for repeated intra-abdominal biopsy of liver and omental adipose tissue (AT) in obese rhesus monkeys (Macaca mulatta). METHODS: Nine obese rhesus monkeys were studied by use of 18 laparoscopic procedures (two procedures each, approx. six weeks apart). Time-sensitive liver and omental AT specimens were obtained from monkeys under general anesthesia, using a three-port approach with a roticulating endoscopic stapler/divider and a monopolar electrosurgery for hemostasis. RESULTS: All subjects tolerated the initial and repeat laparoscopic procedures well. Liver specimens weighed a mean +/- SEM of 3.8 +/- 0.5 g, and omental AT specimens weighed 16.6 +/- 0.8 g. Compared with previous studies of conventional laparotomy with liver wedge resection, the monkeys experienced faster postoperative recovery via laparoscopy, with rapid return to normal food intake and activity. Minimal to no adhesions were observed by use of the repeat procedure in all monkeys, with no major complications. CONCLUSIONS: Laparoscopy in obese rhesus monkey (ranging from young to older-aged), with repeated intra-abdominal liver and omental AT biopsy, was an excellent minimally invasive surgical method. In contrast to laparotomy with wedge resection, this approach greatly decreases operative time and stress, provides generous tissue specimens in a time-efficient manner, and facilitates rapid and full recovery of the nonhuman primate.