T-cell reactivity to the P2C nonstructural protein of a diabetogenic strain of coxsackievirus B4

Enteroviruses are proposed as initiating factors in the etiology of Type I diabetes mellitus (Type 1 DM). Molecular mimicry between the autoantigen gl utamic acid decarboxylase 65 (GAD65) and the coxsackievirus B4 (CVBLF) nons tructural protein P2C is frequently cited as a mechanism by which this viru s triggers the disease, but little is known about the immunogenicity of thi s viral protein in humans, mainly due to the problem of obtaining highly pu re preparations of P2C. We generated large amounts of highly pure, soluble P2C protein, coupled to the fusion partner maltose binding protein (MBP-P2C ) using the PMAL-c2 bacterial expression plasmid and a two-step purificatio n system comprising amylose resin and ion exchange. Using purified viral pr otein we show that specific T-cell responses against P2C are detected in th e blood of healthy donors and Type 1 DM patients. Proliferation responses t o P2C were detected only in subjects also demonstrating T-cell proliferatio n to CVB4 Vero cell lysates. However, in additional cases T-cell responses to P2C were detectable through the release of interieron-gamma or interleuk in-4 in individuals who did not make proliferative responses. Taken togethe r, our data show that the P2C nonstructural protein of CVB4 is targeted by T cells during the antiviral immune response and may trigger the production of T helper 1 and T helper 2 cytokines. The availability of pure, immunoge nic P2C should allow the putative role of antiviral responses in the develo pment of autoimmune diabetes to be investigated. (C) 2000 Academic Press.