Impact of immunosuppressive therapy on therapy-neutralizing antibodies in transplanted patients with Fabry disease.

BACKGROUND: Inhibitory antibodies towards enzyme replacement therapy (ERT) are associated with disease progression and poor outcome in affected male patients with lysosomal disorders such as Fabry disease (FD). However, little is known about the impact of immunosuppressive therapy on ERT inhibition in these patients with FD. METHODS: In this retrospective study, we investigated the effect of long-term immunosuppression on ERT inhibition in male patients with FD (n = 26) receiving immunosuppressive therapy due to kidney (n = 24) or heart (n = 2) transplantation. RESULTS: No ERT-naïve transplanted patient (n = 8) developed antibodies within follow-up (80 ±72 months) after ERT initiation. Seven (26.9%) patients were tested ERT inhibition positive prior to transplantation. No de novo ERT inhibition was observed after transplantation (n = 18). In patients treated with high dosages of immunosuppressive medication such as prednisolone, tacrolimus and mycophenolate-mofetil/mycophenolate acid, ERT inhibition decreased after transplantation (n = 12; P = 0.0160). Tapering of immunosuppression (especially prednisolone) seemed to re-increase ERT inhibition (n = 4, median [range]: 16.6 [6.9; 36.9] %; P = 0.0972) over time. One ERT inhibition-positive patient required interventions with steroid therapy and increased doses of tacrolimus, which also lowered ERT inhibition. CONCLUSION: We conclude that the immunosuppressive maintenance therapy after transplantations seems to be sufficient to prevent de novo ERT inhibition in ERT-naïve patients. Intensified high dosages of immunosuppressive drugs are associated with decreased antibody titres and decreased ERT inhibition in affected patients, but did not result in long-term protection. Future studies are needed to establish ERT inhibition-specific immunosuppressive protocols with long-term modulating properties to warrant an improved disease course in ERT inhibition-positive males.

Physical Exercise in Patients with Fabry Disease - a Pilot Study.

The aim of this study was to assess the extent of exercise intolerance in Fabry disease (FD) patients and to report individual effects of physical exercise. Exercise capacity and strength of 14 patients (mean age 46 years, 6 females) were determined using cycle ergometry and isokinetic measurements. Patients performed a strength/circuit exercise training protocol for 12 months. The mean relative maximum performance of the group was low at baseline and increased by 12.1% (baseline: 1.9 [0.9-3.4] W·kg-1vs. re-test: 2.1 [1.1-3.8] W·kg-1; p=0.035) during the study. Patients' mean baseline maximum performance blood lactate of 5.4 [1.3-9.9] mmol·L-1 increased to a mean of 7.2 (2.4-10.2) mmol·L-1 (p=0.038). Mean strength of the lower limbs (left/right extensors and flexors, total work of 5 sets) changed from 2269 (1017-2913) kg·m2·s - 2 to 2325 (1359-3107) kg·m2·s-2 (not significant). Patients reported increased well-being, daily activity and reduced fatigue during the study. Our results indicate that exercise intolerance in FD patients often results from physical inactivity. FD patients may perform exercise training to improve exercise capacity and muscle strength. Future studies will address the clinical benefits of exercise in FD.

Common exonic missense variants in the C2 domain of the human KIBRA protein modify lipid binding and cognitive performance.

The human KIBRA gene has been linked to human cognition through a lead intronic single-nucleotide polymorphism (SNP; rs17070145) that is associated with episodic memory performance and the risk to develop Alzheimer's disease. However, it remains unknown how this relates to the function of the KIBRA protein. Here, we identified two common missense SNPs (rs3822660G/T [M734I], rs3822659T/G [S735A]) in exon 15 of the human KIBRA gene to affect cognitive performance, and to be in almost complete linkage disequilibrium with rs17070145. The identified SNPs encode variants of the KIBRA C2 domain with distinct Ca(2+) dependent binding preferences for monophosphorylated phosphatidylinositols likely due to differences in the dynamics and folding of the lipid-binding pocket. Our results further implicate the KIBRA protein in higher brain function and provide direction to the cellular pathways involved.