New Strategies in Oral Immunotherapy for Diabetes Prevention

Activated T lymphocytes from patients with high risk of type I diabetes mellitus have different ability to produce interferon-gamma, interleukin-6 and interleukin-10 and undergo anti-CD95 induced apoptosis after insulin stimulation

Type I Diabetes mellitus (DM1) is the effect of T cell dependent autoimmune destruction of insulin producing beta cells in the pancreas islet. T cells are activated in response to islet dominant autoantigens, the result being the development of DM1. Insulin is one of the islet autoantigens responsible for activation of T lymphocyte functions, inflammatory cytokine production and development of DM1. The experiments reported in this study have shown the spontaneous increase of CD95 molecule expression on lymphocytes of the first-degree relatives of DM1 patients. The autoantigen insulin is responsible for stimulation in vitro of potentially hazardous 'memory' lymphocytes to produce interleukin-6 (IL-6) and interleukin-10 (IL-10) interleukins. Insulin induced stimulation of lymphocytes in vitro was observed in patients at high risk of developing diabetes mellitus (prediabetics). Phytohaemagglutinin (PHA) stimulates lymphocytes of all groups in the same way. Stimulated lymphocytes in second cultures undergo apoptosis induced with anti-Fas specific antibodies. The deletion in vitro of resting peripheral lymphocytes is nonfunctional. Insulin activated T lymphocytes, which undergo apoptosis were not observed in peripheral blood of healthy people and in patients with DM1. This observation suggests that insulin is involved as autoantigen in DM1 progression in patients with high risk of diabetes type I. The autoreactive T lymphocytes may persist in peripheral blood of patients with high risk DM1. Defective elimination of autoreactive T cells may result in autodestructive damage of islets beta cells in the prediabetic stage and disease progression to DM1.

Oral insulin and the induction of tolerance in man: reality or fantasy?

Induction of tolerance to insulin, the only beta-cell-specific antigen in Type 1 diabetes, is under testing for prevention of Type 1 diabetes in the US multicentre trial DPT1. Recently a multicentre double-blind trial with oral insulin in patients with recent onset Type 1 diabetes, conducted by our group, has been completed and showed that oral insulin administration at the dose of 5 mg daily for one year starting at the time of disease onset had no effect on residual beta-cell function as assessed by C-peptide secretion. A similar trial using different doses was carried out at the same time and similarly showed no beneficial effect on the decline of beta-cell function during the first year after diagnosis. In this study oral insulin was administered at the daily doses of 2.5 and 7. 5 mg over a one-year period. Such results challenge the current view that induction of oral tolerance can be established when the immune process is already active.

Prevention of autoimmune diabetes by oral administration of syngeneic pancreatic extract to young NOD mice

Oral administration of relevant autoantigens is being considered as a realistic approach for the prevention of several autoimmune diseases. In this study we administered, orally, to young female NOD/Ak mice (diabetes incidence, 40%) and NOD/LtJ mice (diabetes incidence, 70%) whole pancreatic extract on days 19, 20, 21, 22, 23, 26, and 27 and studied its effects on the development of diabetes until day 250. The cumulative incidence of diabetes in both the colonies after pancreatic extract treatment was compared with the incidence after oral administration of syngeneic liver extract or in untreated mice. In the NOD/Ak mice, the incidence of diabetes in the pancreatic extract group was significantly lower (6%; n = 34, p = 0.004) and was delayed compared with 33% in the liver group (n = 34) and 44% in the untreated group (n = 18). Significant protection from diabetes and a delay in its onset also were observed in the NOD/LtJ mice treated with pancreatic extract (16%; n = 19, p = 0.002) compared with those liver extract treated (72%; n = 18) and in untreated mice (60%; n = 22). Pancreatic histology at day 90 from all the study groups showed that the protection from diabetes in the pancreatic-extract group was not associated with reduced insulitis. We speculate that the marked disease protection observed in this study with orally administered pancreatic extract may be associated with the presence of immunoregulatory cells with a predominant Th2 cytokine bias. Our studies may have implications for the prevention of insulin-dependent diabetes mellitus (IDDM) in humans.

Towards gene therapy of diabetes mellitus

A definitive treatment for diabetes mellitus will be one that maintains a normal blood glucose concentration in the face of fluctuating dietary intake. To accomplish this, there must be mechanisms to sense the amount of blood glucose coupled to rapid release of the right amount of insulin. While mechanical devices to accomplish this are being developed, ultimately the best approach is likely to be based on genetic modification of cells. These could be pancreatic beta-cells, which are the only cells that produce insulin, or other cells that are involved in the pathogenesis of diabetes. Although definitive treatment of diabetes using genetically modified cells is a long-term goal, much progress is being made. This review discusses various approaches to modifying cells genetically, both in vitro and in vivo, for the treatment of diabetes.