T Cell Receptor Genotype and Ubash3a Determine Susceptibility to Rat Autoimmune Diabetes.

Genetic analyses of human type 1 diabetes (T1D) have yet to reveal a complete pathophysiologic mechanism. Inbred rats with a high-risk class II major histocompatibility complex (MHC) haplotype (RT1B/Du) can illuminate such mechanisms. Using T1D-susceptible LEW.1WR1 rats that express RT1B/Du and a susceptible allele of the Ubd promoter, we demonstrate that germline knockout of Tcrb-V13S1A1, which encodes the Vß13a T cell receptor ß chain, completely prevents diabetes. Using the RT1B/Du-identical LEW.1W rat, which does not develop T1D despite also having the same Tcrb-V13S1A1 ß chain gene but a different allele at the Ubd locus, we show that knockout of the Ubash3a regulatory gene renders these resistant rats relatively susceptible to diabetes. In silico structural modeling of the susceptible allele of the Vß13a TCR and its class II RT1u ligand suggests a mechanism by which a germline TCR ß chain gene could promote susceptibility to T1D in the absence of downstream immunoregulation like that provided by UBASH3A. Together these data demonstrate the critical contribution of the Vß13a TCR to the autoimmune synapse in T1D and the regulation of the response by UBASH3A. These experiments dissect the mechanisms by which MHC class II heterodimers, TCR and regulatory element interact to induce autoimmunity.

PEGylation enables subcutaneously administered nanoparticles to induce antigen-specific immune tolerance.

The development of nanomaterials to induce antigen-specific immune tolerance has shown promise for treating autoimmune diseases. While PEGylation has been widely used to reduce host immune responses to nanomaterials, its tolerogenic potential has not been reported. Here, we report for the first time that a subcutaneous injection of PEGylated poly(lactide-co-glycolide) (PLGA) nanoparticles containing auto-antigen peptide MOG35-55 without any tolerogenic drugs is sufficient to dramatically ameliorate symptoms after disease onset in an antigen-specific manner in a mouse model of multiple sclerosis. Neither free MOG35-55 nor particles without PEG exhibit this efficacy. Interestingly, mechanistic studies indicate that PEGylation of nanoparticles does not reduce dendritic cell activation through direct nanoparticle-cell interactions. Instead, PEGylated nanoparticles induce lower complement activation, neutrophil recruitment, and co-stimulatory molecule expression on dendritic cells around the injection sitecompared to non-PEGylated PLGA nanoparticles, creating a more tolerogenic microenvironment in vivo. We further demonstrate that the locally recruited dendritic cells traffic to lymphoid organs to induce T cell tolerance. These results highlight the critical role of surface properties of nanomaterials in inducing immune tolerance via subcutaneous administration.

Analysis of the rat Iddm14 diabetes susceptibility locus in multiple rat strains: identification of a susceptibility haplotype in the Tcrb-V locus.

Iddm14 (formerly Iddm4) is a non-MHC-linked genetic locus associated with autoimmune diabetes. Its effects have been well-documented in BB-derived rats in which diabetes is either induced by immunologic perturbation or occurs spontaneously. The role of Iddm14 in non-BB rat strains is unknown. Our goal was to extend the analysis of Iddm14 in new diabetes-susceptible strains and to identify candidate genes in the rat Iddm14 diabetes susceptibility locus that are common to these multiple diabetic strains. To determine if Iddm14 is important in strains other than BB, we first genotyped a (LEW.1WR1 x WF)F2 cohort in which diabetes was induced by perturbation with polyinosinic:polycytidylic acid. We found that Iddm14 is a major determinant of diabetes susceptibility in LEW.1WR1 rats. We then used nucleotide sequencing to establish a strain distribution pattern of polymorphisms (insertions, deletions, and single nucleotide polymorphisms [SNPs]) that predicts susceptibility to diabetes in a panel of inbred and congenic rats. Using the positional information from the congenic strains and the new linkage data, we identified a susceptibility haplotype in the T-cell receptor Vbeta chain (Tcrb-V) locus. This haplotype includes Tcrb-V13, which is identical in five susceptible strains but different in resistant WF and F344 rats. We conclude that Iddm14 is a powerful determinant of both spontaneous and induced autoimmune diabetes in multiple rat strains, and that Tcrb-V13 SNPs constitute a haplotype of gene elements that may be critical for autoimmune diabetes in rats.

Refinement of the Iddm4 diabetes susceptibility locus reveals TCRVbeta4 as a candidate gene.

Iddm4 is a dominant non-major histocompatibility complex (MHC) determinant of diabetes susceptibility in BBDR rats treated with poly I:C, plus depletion of regulatory T cells. In congenic MHC-identical normal WF rats, Iddm4(d) sensitively and specifically predicts induced diabetes. We report a new diabetes-susceptible subcongenic line that carries Iddm4 in a < 2.6 megabase interval. Candidate genes include the T cell receptor beta chain variable (TCRVbeta) family. We found that TCRVbeta4 in WF rats contains a stop codon, whereas 5/5 diabetes-susceptible rat strains express TCRVbeta4. We conclude that Iddm4-mediated diabetes resistance in rats may be due to a recessive protective mutation in TCRVbeta4.

Secreted phospholipase A2 activity in experimental autoimmune encephalomyelitis and multiple sclerosis.

BACKGROUND: There is increased interest in the contribution of the innate immune system to multiple sclerosis (MS), including the activity of acute inflammatory mediators. The purpose of this study was to test the involvement of systemic secreted phospholipase A2 (sPLA2) enzymes in experimental autoimmune encephalomyelitis (EAE), an MS model, and to determine if enzyme activity is elevated in MS patients. METHODS: A non-invasive urinary assay was developed in order to monitor enzymatically active sPLA2 levels in Dark Agouti rats after induction of EAE. Some Rats were treated with nonapeptide CHEC-9, an uncompetitive sPLA2 enzyme inhibitor, during the initial rise in urinary enzyme levels. Body weight and clinical EAE score were measured for 18 days post immunization (PI), after which the rats were sacrificed for H&E and myelin staining, and for ED-1 immunocytochemistry, the latter to quantify macrophages and activated microglia. The urinary sPLA2 assay was also applied to un-timed samples collected from a cross section of 44 MS patients and 14 healthy controls. RESULTS: Mean levels of enzymatically active sPLA2 in the urine increased following immunization and peaked between days 8-10 PI which was just prior to the onset of EAE symptoms. At this time, a transient attenuation of activity was detected in the urine of CHEC-9 treated rats consistent with the activity-dependent properties of the inhibitor. The peptide also reduced or abolished EAE symptoms compared to vehicle-injected controls. Histopathological changes in the spinal cords of the EAE rats correlated generally with clinical score including a significant reduction in ED-1+ cells after peptide treatment. Multiple Sclerosis patients also showed elevations in sPLA2 enzyme activity. Mean levels of sPLA2 were increased 6-fold in the urine of patients with active disease and 4-fold for patients in remission, regardless of immunomodulating therapy. CONCLUSION: The results suggest that sPLA2 enzymes, traditionally thought to be part the acute phase inflammatory response, are therapeutic targets for MS.

Autoantigen-induced focusing of Vß13+ T cells precedes onset of autoimmune diabetes in the LEW.1WR1 rat.

The earliest events leading to autoimmune type 1 diabetes (T1D) are not known in any species. A T-cell receptor (TCR)-variable region, TCR-Vß13, is required for susceptibility to autoimmune diabetes in rats, and selective depletion of Vß13(+) T cells with an allele-specific monoclonal antibody prevents disease in multiple rat strains. To investigate the role of Vß13 early in diabetes, we examined islet T-cell transcripts in susceptible (LEW.1WR1) and resistant (LEW.1W and Wistar Furth) strains induced with polyinosinic:polycytidylic acid. Vß13(+) T cells displayed antigenic focusing in LEW.1WR1 islets 5 days postinduction and were characterized by a substantial decrease in complementarity determining region 3 diversity. This occurred prior to significant islet T-cell accumulation (day 7) or frank diabetes (days 10-14). Vß13(+) transcripts increased in LEW.1WR1 islets during diabetes progression, but not in resistant rats. We also analyzed transcript clonality of rat TCR-Vα5, an ortholog of the dominant TCR-Vα chain found on insulin B:9-23-reactive T cells in nonobese diabetic rat islets. We observed clonal expansion of Vα5(+) transcripts in prediabetic LEW.1WR1 islets, suggesting that rat Vα5 is also an important component of islet autoantigen recognition. These data provide additional evidence that genome-encoded TCR sequences are important determinants of genetic susceptibility to T1D.

Prevention of type 1 diabetes in the rat with an allele-specific anti-T-cell receptor antibody: Vß13 as a therapeutic target and biomarker.

In earlier studies of the Iddm14 diabetes susceptibility locus in the rat, we identified an allele of the T-cell receptor (TCR) ß-chain, Tcrb-V13S1A1, as a candidate gene. To establish its importance, we treated susceptible rats with a depleting anti-rat Vß13 monoclonal antibody and then exposed them to either polyinosinic:polycytidylic acid or a diabetogenic virus to induce diabetes. The overall frequency of diabetes in the controls was 74% (n = 50), compared with 17% (n = 30) in the anti-Vß13-treated animals, with minimal islet pathology in nondiabetic treated animals. T cells isolated from islets on day 5 after starting induction showed a greater proportion of Vß13(+) T cells than did peripheral lymph node T cells. Vß13 transcripts recovered from day 5 islets revealed focused Jß usage and less CDR3 diversity than did transcripts from peripheral Vß13(+) T cells. CDR3 usage was not skewed in control Vß16 CDR3 transcripts. Anti-rat Vß13 antibody also prevented spontaneous diabetes in BBDP rats. The Iddm14 gene is likely to be Tcrb-V13, indicating that TCR ß-chain usage is a determinant of susceptibility to autoimmune diabetes in rats. It may be possible to prevent autoimmune diabetes by targeting a limited element of the T-cell repertoire.

Virus-induced autoimmune diabetes in the LEW.1WR1 rat requires Iddm14 and a genetic locus proximal to the major histocompatibility complex.

OBJECTIVE: To identify genes that confer susceptibility to autoimmune diabetes following viral infection in the LEW.1WR1 rat. RESEARCH DESIGN AND METHODS: About 2% of LEW.1WR1 rats develop spontaneous autoimmune diabetes. Immunological perturbants including viral infection increase both the frequency and tempo of diabetes onset. To identify diabetes susceptibility genes (LEW.1WR1 x WF), F2 rats were infected with Kilham rat virus following brief pretreatment with polyinosinic:polycytidylic acid. This treatment induces diabetes in 100% of parental LEW.1WR1 rats and 0% of parental WF rats. Linkage to diabetes was analyzed by genome-wide scanning. RESULTS: Among 182 F2 rats, 57 (31%) developed autoimmune diabetes after a mean latency of 16 days. All diabetic animals and approximately 20% of nondiabetic animals exhibited pancreatic insulitis. Genome-wide scanning revealed a requirement for the Iddm14 locus, long known to be required for diabetes in the BB rat. In addition, a new locus near the RT1 major histocompatibility complex (MHC) was found to be a major determinant of disease susceptibility. Interestingly, one gene linked to autoimmune diabetes in mouse and human, UBD, lies within this region. CONCLUSIONS: The Iddm14 diabetes locus in the rat is a powerful determinant of disease penetrance in the LEW.1WR1 rat following viral infection. In addition, a locus near the MHC (Iddm37) conditions diabetes susceptibility in these animals. Other, as-yet-unidentified genes are required to convert latent susceptibility to overt diabetes. These data provide insight into the polygenic nature of autoimmune diabetes in the rat and the interplay of genetic and environmental factors underlying disease expression.