Mercury exposure in protein A immunoadsorption.
BACKGROUND
Immunoadsorption is increasingly used to treat antibody-mediated autoimmune diseases. To prevent microbial growth during storage, reusable protein A-Sepharose gel columns are primed with ethyl mercury thiosalicylate (thiomersal, 0.1% solution) and rinsed with phosphate buffer before use. In this study, we tested the hypothesis of systemic mercury exposure in protein A immunoadsorption.


METHODS
Whole blood mercury levels were measured by atomic absorption spectroscopy before and after protein A immunoadsorption (11 patients, 26 treatments), anti-IgG immunoadsorption (eight patients, 13 treatments) and LDL apheresis (DALI and Therasorb systems; nine patients, 14 treatments).


RESULTS
Patients treated with protein A immunoadsorption had significantly elevated baseline mercury levels compared with the other groups, which were not different from healthy controls. Following protein A immunoadsorption, mercury levels increased from 5.9+/-1.4 microg/l (mean+/-SEM, normal, <5 microg/l) to 32.3+/-5.7 microg/l, P<0.001). In one intensively treated patient, acute neurological toxicity developed at a mercury level of 107 microg/l. Symptoms abated slowly and did not recur after switching to a thiomersal-free system and chelation therapy. No mercury release to patients occurred in anti-IgG immunoadsorption or LDL apheresis treatments.


CONCLUSIONS
This preliminary report suggests that protein A immunoadsorption columns primed with thiomersal during storage may cause a sustained increase of systemic mercury concentrations, which exceed current safety recommendations in a proportion of patients. Considering the potential for mercury-induced toxicity, every effort should be undertaken to reduce systemic mercury exposure, either by adding chelators to the rinsing solution or ideally by replacement of thiomersal.
Kramer
Ludwig
L
Department of Medicine IV, University of Vienna Medical School, Vienna, Austria. ludwig.kramer@akh-wien.ac.at
Bauer
Edith
E
Jansen
Martin
M
Reiter
Daniela
D
Derfler
Kurt
K
Schaffer
Andreas
A
D000328:Adult; D000888:Antibodies, Anti-Idiotypic / Q000378:metabolism; D001781:Blood Component Removal / Q000009:adverse effects / Q000379:methods; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006084:Graft Rejection / Q000517:prevention & control*; D006801:Humans; D007163:Immunosorbent Techniques / Q000009:adverse effects*; D007676:Kidney Failure, Chronic / Q000601:surgery; D016030:Kidney Transplantation / Q000009:adverse effects* / Q000276:immunology; D008077:Lipoproteins, LDL / Q000378:metabolism; D008297:Male; D008628:Mercury / Q000097:blood* / Q000378:metabolism; D008875:Middle Aged; D011336:Probability; D018570:Risk Assessment; D013205:Staphylococcal Protein A / Q000378:metabolism
D000888:Antibodies, Anti-Idiotypic; D008077:Lipoproteins, LDL; D013205:Staphylococcal Protein A; C048844:anti-IgG; D008628:Mercury