Researchers suggested that tryptophan immunoadsorption (IA) therapy improved neurological function and visual acuity in patients with neuromyelitis optica spectrum disorder (NMOSD), as published in the Journal of Clinical Apheresis.

IA therapy effectively lowered the serum concentration of the antibody against the astrocytic aquaporin-4 immunoglobulin G (AQP4-IgG) water channel protein, with an acceptable safety profile.

Patients subjected to tryptophan IA therapy showed lower Expanded Disability Status Scale scores after their last treatment session when compared to baseline values (4.64±2.29 vs 5.71±2.04, P =.006). The scores were maintained at a 60-day follow-up.

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In addition, the visual acuity of 3 patients admitted due to visual dysfunction improved after therapy completion. The levels of AQP4-IgG decreased from 80.00 U/mL to 9.72 U/mL (P =.018) after therapy. Two patients who had >80 U/mL AQP4-IgG at baseline had their values decreasing to 55.57 U/mL and 19.29 U/mL after therapy.

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The levels of immunoglobulin G, immunoglobulin A, and complement components C3 and C4 also decreased after therapy. The largest decrease was observed for IgG (12.32±2.95 g/L to 5.44±0.72 g/L, P =.003), although a decrease was also noticed for immunoglobulin M, it did not reach statistical significance.

Regarding side effects, only 1 patient experienced transient hypotension during IA therapy, which was successfully managed with rehydration therapy. No bleeding complications were reported. The study enrolled 7 females diagnosed with NMOSD (average age, 41.00±11.62 years, age range, 27 to 64 years), and IA was performed once every other day for a total of 5 treatments.

“Based on the electrostatic and hydrophobic interactions between proteins and amino acids in the adsorption column, tryptophan IA can adsorb and remove pathogenic agents more specifically, and no allogeneic plasma or albumin is required,” the authors said.

IA is a method of blood purification that has been used for treating autoimmune disorders. To the authors’ knowledge, this is the first prospective study assessing the efficacy and safety of tryptophan IA in NMOSD.


Liu J, Zhou R, Gong Y, et al. A prospective study on tryptophan immunoadsorption in AQP4 antibody‐positive neuromyelitis optica spectrum disorders. J Clin Apher. 2022;1-8. doi:10.1002/jca.21965