Disease prevention with islet autoantigens

Characterization of anti-islet cytotoxic human T-cell clones from patients with type 1 diabetes mellitus

To identify important anti-islet T-cells and their target antigen(s), we have isolated and characterized seventeen human T-cell clones which are reactive to an extract of rat insulinoma (RIN) cells from three children with new onset type 1 diabetes mellitus (T1D). Of these 17 clones, 15 were found tissue specific. Six of eight tested tissue specific clones did not recognize known islet antigens such as GAD, 52 kDa islet protein, insulin, ICA512, and heat shock protein 60 (hsp60), suggesting that these clones recognize an autoantigen not previously identified. All tested clones were phenotypically CD4 and functionally Th0 or Th0/Th1 cells. One RIN extract reactive clone (2E9) recognized hsp60 and was CD4 and TCR alpha/beta positive. This clone also proliferated in response to human and rat islets suggesting that the antigen is conserved between species. This clone and 75% of all the tested RIN reactive clones exhibited anti-islet cytotoxicity by lysing target cells coated with RIN extract. HLA DR determinants may play a role in this cytotoxic activity since preincubation with HLA DR antibody decreased the anti-islet cytoxicity of the two tested clones. In conclusion, we have isolated RIN reactive CD4+T-cell clones from diabetic subjects, six of which appears tissue specific and non-reactive to putative important islet antigens, and in turn may be recognizing yet undiscovered islet antigens. The high frequency anti-islet cytotoxic properties of the islet reactive clones provides evidence for a role of CD4+ cytotoxic T-lymphocytes in the diabetic process. Further, the isolation of hsp60 reactive clone with anti-islet cytotoxic properties suggests that cell mediated immunity against hsp60 may be important in the pathogenesis of diabetes.

Immunological mechanisms associated with long-term remission of human type 1 diabetes

BACKGROUND

Preservation of beta cell function is a central goal in type 1 diabetes (type 1 DM) immune intervention. The characterization of individuals with recovery from established type 1 DM should provide insight into regulatory mechanisms of beta cell autoimmunity.

METHODS

We studied a patient with antibody-positive type 1 DM with complete recovery of beta cell function for an observation period of 60 months. Using a preproinsulin (PPI) peptide library approach and in vitro cytokine profiling, cellular autoimmunity was characterized in peripheral blood mononuclear cells (PBMC) and CD4(+) T-helper cell subsets.

RESULTS

A predominant secretion of interleukin-10 (IL-10) was detected in the patient's PBMC, mostly attributable to naïve and recently primed CD45(+)RA(+) T cells, with limited PPI epitope recognition. In contrast to a cohort of patients with permanent type 1 DM, interferon-gamma secretion was low in PBMC and CD45(+)RA(+), but not in CD45(+)RA(-) insulin-reactive T lymphocytes. Autoantibodies against islet cells, tyrosine phosphatase IA-2, GAD65 and insulin were positive at diabetes onset, but gradually declined during follow-up.

CONCLUSIONS

Our observations support the concept that IL-10-dependent regulatory CD4(+) T-cell pathways are involved in beta cell recovery after the onset of hyperglycemia in autoimmune type 1 DM.

Establishment of native insulin-negative NOD mice and the methodology to distinguish specific insulin knockout genotypes and a B:16 alanine preproinsulin transgene

We hypothesize that NOD mice without native insulin, but with an altered insulin B:9-23 sequence, will be completely protected from diabetes/insulitis if insulin B:9-23 is an essential T cell epitope. To investigate this hypothesis, we have established initial insulin 1- and 2-negative NOD mice with a transgene directing production of preproinsulin with alanine at position B:16 rather than the native tyrosine of both insulin 1 and insulin 2. Sets of primers for PCR-based assays have been created and validated. They are able to distinguish the presence or absence of the insulin gene knockouts and of both native insulin 1 and insulin 2 (and thus distinguish heterozygous versus homozygous knockouts), as well as the presence of the altered insulin transgene, B:16 alanine preproinsulin. Four B:16 alanine transgenic founders were produced directly in NOD mice and, by intercrossing, initial live native insulin-negative B:16 alanine transgenic mice have been generated.

Experimental autoimmune diabetes: a new tool to study mechanisms and consequences of insulin-specific autoimmunity

(Prepro)insulin is considered a central antigenic determinant in diabetic autoimmunity. Insulin has been used to modify diabetes development in NOD mice and prediabetic individuals. We have recently shown that (prepro)insulin can adversely promote diabetes development in murine type 1 diabetes. Based on these findings we have developed experimental autoimmune diabetes (EAD), a new mouse model characterized by (1) CD4(+)/CD8(+) insulitis, induced by (2) (prepro)insulin DNA vaccination, leading to (3) beta cell damage and insulin deficiency in (4) RIP-B7.1 transgenic mice (H-2(b)). EAD develops rapidly in 60-95% of mice after intramuscular, but not intradermal ("gene gun"), vaccination; and DNA plasmids expressing insulin or the insulin analogues glargine, aspart, and lispro are equally potent to induce EAD. Similar to NOD mice, diabetes is adoptively transferred into syngeneic recipients by spleen cell transplantation in a dose-dependent fashion. We have devised a two-stage concept of EAD in which T cell activation and expansion is driven by in vivo autoantigen expression, followed by islet damage that requires beta cell expression of costimulatory B7.1 for disease manifestation. Taken together, EAD is a novel, genetically defined animal model of type 1 diabetes suitable to analyze mechanisms and consequences of insulin-specific T cell autoimmunity.