Active and Passive Immunization Against Type 2 Diabetes Mellitus
Roesti E., Zabel F., El Turabi A., Vogel M., Bachmann MF.
Amyloid aggregates composed of extracellular fibrils of islet amyloid polypeptide (IAPP, also called amylin) - a peptide synthetized in the pancreatic β-cells and co-secreted with insulin – are found in most type 2 diabetes mellitus (T2DM) patients and has been associated with the progression of the disease. As aggregates are considered to be a key factor in β cell death, we aim at developing a vaccine targeting these pathogenic aggregates to prevent and/or reverse accumulation and enhancing β cell survival. To study this, a transgenic mouse model expressing human IAPP (hIAPP) is used. The vaccines were designed using different amylin peptide sequences chemically cross-linked to virus like particles (VLPs). The induced antibodies response against each peptide, was analyzed by ELISA assay with serum obtained from immunized C57BL/6 mice. The peptides coupled to the VLPs inducing the highest IgG titers against IAPP where then tested in a transgenic mouse model developing spontaneously T2DM. Interestingly, mice immunized with vaccine showed symptoms of T2DM at a later point compared to the control ones, which received only the VLPs. Besides the active immunization, a separate group of mice was immunized with monoclonal antibodies against the same peptide of amylin used in the active immunization. Preliminary results showed that T2DM appeared in the passive immunized mice at a later onset. In addition, based on recent data suggesting that hIAPP interacts with immune cells present in the islets promoting the synthesis of IL-1β via activation of the inflammasome NLRP3; we wanted to assess whether the IgG against IAPP can decrease inflammasome activation and the secretion of IL-1β. For this purpose bone marrow derived dendritic cells (BMDC) were obtained after stimulation with the granulocyte-macrophage colony-stimulating factor (GM-CSF) from C57BL/6 mice; challenged then first with LPS from E. coli to induce the transcription of pro-IL-1β, and later either with hIAPP or rat IAPP (rIAPP) for inflammasome activation and secretion of mature IL-1β. As expected, only hIAPP could induce the activation of the inflammasome after priming; and, as hypothesized, the anti-hIAPP IgG prevented the release of IL-1β in a dose-dependent manner. A mechanistic approach is now under investigation.