Evidence for the viral aetiology of IDDM

Vaccine therapies for the prevention of type 1 diabetes mellitus

Type 1 diabetes mellitus results from immune-mediated destruction of pancreatic beta-cells, leading to loss of insulin production. Strategies to prevent or reverse diabetes development include beta-cell protection, regeneration, or replacement. Recent advances in our understanding of the autoimmune process leading to diabetes has generated interest in the potential use of immunomodulatory agents that may collectively be termed vaccines, to prevent type 1 diabetes. Vaccines may work in various ways, including changing the immune response from a destructive (e.g. Th1) to a more benign (e.g. Th2) response, inducing antigen-specific regulatory T cells, deleting autoreactive T cells, or preventing immune cell interaction. To date, most diabetes vaccine development has been in animal models, with relatively few human trials having been completed. A major finding of animal models such as the non-obese diabetic (NOD) mouse is that they are extremely sensitive to diabetes protection, such that many interventions that protect mice are not successful in humans. This is particularly evident for human insulin tolerance studies, including the Diabetes Prevention Trial-1, where no human protection was seen from insulin despite positive NOD results. Further challenges are posed by the need to translate protective vaccine doses in mice to effective human doses. Despite such problems, some promising human vaccine data are beginning to emerge. Recent pilot studies have suggested a beneficial effect in recent-onset human type 1 diabetes from administration of nondepleting anti-CD3 antibodies or a peptide from heat shock protein 60. Given past experience, however, large multicenter, double-blind, controlled confirmatory studies are clearly required and longer term toxicity issues of drugs such as anti-CD3 need to be addressed.Diabetes vaccine development would benefit greatly from the development of reliable surrogate markers of immunoregulation. These would allow faster and more efficient screening of vaccine candidates, and would also assist in the translation of vaccine doses from animal to human studies. Unfortunately, research funding bodies desperate to find a cure are embarking on expensive clinical trials without first addressing important underlying issues such as animal-human dose translation and possible mechanisms of action. No doubt this is due to pressure from their constituency to rapidly find a cure, but unfortunately this approach may slow rather than speed the development of an effective vaccine cure. However, despite the significant hurdles that remain, vaccines remain one of the most promising strategies to prevent type 1 diabetes, with major advantages including convenience, safety, and long-lasting protection.

Prospects for the prevention and reversal of type 1 diabetes mellitus

Type 1 (insulin-dependent) diabetes mellitus results from selective immune-mediated destruction of pancreatic islet beta cells. Strategies to prevent or reverse the development of diabetes can be divided into three groups, depending on whether they focus on beta-cell protection, regeneration or replacement. Prevention of immune beta-cell destruction involves either halting the immune attack directed against beta cells or making beta cells better able to withstand immune attack, for example, by making them resistant to free radical damage. The recent identification of beta-cell growth factors and development of stem cell technologies provides an alternative route to the reversal of diabetes, namely beta-cell regeneration. Interestingly, stem cell-derived islets appear to be less sensitive to recurrent immune destruction that is normally seen in response to islet transplantation. The last alternative is beta-cell replacement or substitution. This covers a wide range of interventions including human whole pancreas transplantation, xenotransplantation, genetically modified beta cells, mechanical insulin sensing and delivery devices, and the artificial pancreas. This review describes recent advances in each of these research areas and aims to provide clinicians with an idea of where and when an effective strategy to prevent or reverse diabetes development will become available.

Echovirus 4 and type 1 diabetes mellitus

AIMS/HYPOTHESIS

To determine the association between exposure to enteroviruses and Type 1 diabetes.

METHODS

We measured neutralizing antibodies to the following enteroviruses: Coxsackievirus CA9, CB1, CB2, CB3, CB4, CB5, CB6, and Echovirus E4, E6, E9, E11 in the sera of (1) Type 1 diabetic patients at diagnosis (n = 33), (2) healthy offspring of parents with Type 1 diabetes without islet cell antibodies (ICA) (n = 43) and (3) normal controls (n = 57). All subjects were less than 20 years old. We performed the neutralization test determining the cytopathogenic effect on Vero cells. HLA DR serotyping was also performed in Group 2.

RESULTS

Type 1 diabetic patients showed a higher frequency (21.2%, p < 0.01) of neutralizing antibodies to E4 in relation to controls (1.8%), although there were no differences comparing with offspring of Type 1 diabetic patients (20.9%). Healthy offspring carrying Type 1 diabetes HLA DR susceptibility genes were also exposed to E4 (15.0%). High frequencies of neutralizing antibodies to most enteroviruses were found in the control group.

CONCLUSION

This study shows the association between Type 1 diabetes and the presence of neutralizing antibodies to Echovirus 4, suggesting the possible participation of this virus as an environmental trigger of this autoimmune disease. Interestingly, our population displays high frequencies of exposure to enterovirus (including CB4) although the incidence for Type 1 diabetes is low (2.9 per 100,000 inhabitants).