Modification of the environment is not the most efficient way to prevent type 1 diabetes

ADA Outstanding Scientific Achievement Lecture 2004. Thirty years of investigating the autoimmune basis for type 1 diabetes: why can't we prevent or reverse this disease?

Thirty years ago, a convergence of investigational observations lead to the now widely accepted notion that type 1 diabetes results from an autoimmune destruction of insulin-producing beta-cells in subjects genetically predisposed to the disease. Improvements in understanding of the natural history of type 1 diabetes, the biochemical identification of autoantigens, the discovery of spontaneous animal models for the disease, the availability of immune-modulating agents, and other important facets, including disease prediction, drove an early sense of optimism that the prevention of type 1 diabetes was possible and, in some research circles, that ability was thought to be within a not-to-distant reach. Unfortunately, those early expectations proved overly optimistic, and despite the aforementioned knowledge gains, the generation of improved investigational tools, the identification of methods to prevent the disease in animal models, and the formation of very large disease prevention trials, a means to prevent type 1 diabetes in humans continues to remain elusive. Believing in the concept of "informative failures" (a.k.a., wise people learn from their mistakes), this lecture reviews the knowledge base collected over this time period and, when combined with an analysis of those research experiences, sets forth a proposal for future investigations that will, hopefully, turn discoveries into a means for the prevention or reversal of type 1 diabetes.

Diabetes acceleration or prevention by a coxsackievirus B4 infection: critical requirements for both interleukin-4 and gamma interferon

Type 1 diabetes acceleration in nonobese diabetic (NOD) mice through coxsackievirus B4 (CVB4) infection requires a preexisting critical mass of autoreactive T cells in pancreatic islets, and in the absence of this insulitic threshold, CVB4 infection leads to long-term disease protection. To understand this acceleration and protection process, we challenged 8- and 12-week-old NOD mice containing a disruption in interleukin-4 (IL-4) or gamma interferon (IFN-gamma) genes (NOD IL-4-/- and NOD IFN-gamma-/-, respectively) with a diabetogenic, pancreatropic Edwards strain of CVB4. The elimination of IL-4 did not alter the rate of insulitis or diabetes development in NOD mice, while the elimination of IFN-gamma delayed these events several weeks. CVB4 infection in 8-week-old mice only significantly accelerated the onset of diabetes in a subset of standard, but not IL-4- or IFN-gamma-deficient, NOD mice. Long-term diabetes protection was established in standard NOD mice as well as in the NOD IFN-gamma-/- mice that did not rapidly develop disease following CVB4 infection at 8 weeks of age. When mice were infected at 12 weeks of age, the onset of diabetes was accelerated in NOD IL-4-/- mice, while neither acceleration nor long-term protection was elicited in NOD IFN-gamma-/- mice. No differences were observed in the kinetics of CVB4 clearance in pancreases from NOD, NOD IL-4-/-, and NOD IFN-gamma-/- mice. Collectively, these results suggest that at the insulitis threshold at which CVB4 infection can first accelerate the onset of diabetes in NOD mice, IL-4 as well as IFN-gamma contributes to this pathogenic process. The protective mechanism against diabetes elicited in NOD mice infected with CVB4 prior to the development of a critical threshold level of insulitis requires neither IL-4 nor IFN-gamma.

Transient insulin autoantibody expression independent of development of diabetes: comparison of NOD and NOR strains

NOD mice spontaneously develop anti-insulin autoantibodies associated with the subsequent development of diabetes. NOD mice that express insulin autoantibodies at 8 weeks of age have a diabetes risk exceeding 90%, while mice that do not express autoantibodies by 16 weeks have a risk of less than 20%. NOD female mice expressed insulin autoantibodies more often than male mice (13/15+ vs. 6/15+). Autoantibodies characteristically developed between 8 and 20 weeks and then for most mice became negative at diabetes onset in NOD mice. In the diabetes-free strain NOR mice, spontaneous expression of insulin autoantibodies was observed in less mice (female 8/15+, male 3/10+) compared to NOD mice. The expression of autoantibodies was transient in NOR mice and followed the same time-course as for NOD mice and they were all negative by 28 weeks (without progression to diabetes). No correlation was found in NOR mice between the levels of autoantibodies and insulitis. The program of insulin autoantibody expression is regulated over approximately 5 months for both NOD and NOR mice with only NOD mice developing diabetes, indicating that depending upon genetic combination, the presence of insulin autoantibodies does not always predict diabetes development. In addition, this data is not consistent with the hypothesis that the time-course of autoantibodies simply reflects the destruction of beta-cells with development of diabetes.