Kininogen Cleavage Assay: Diagnostic Assistance for Kinin-Mediated Angioedema Conditions

PLoS One. 2016 Sep 29;11(9):e0163958. doi: 10.1371/journal.pone.0163958. eCollection 2016.

Abstract

Background: Angioedema without wheals (AE) is a symptom characterised by localised episodes of oedema presumably caused by kinin release from kininogen cleavage. It can result from a hereditary deficiency in C1 Inhibitor (C1Inh), but it can present with normal level of C1Inh. These forms are typically difficult to diagnose although enhanced kinin production is suspected or demonstrated in some cases.

Objectives: We wanted to investigate bradykinin overproduction in all AE condition with normal C1Inh, excluding cases with enhanced kinin catabolism, and to propose this parameter as a disease biomarker.

Methods: We retrospectively investigated high molecular weight kininogen (HK) cleavage pattern, using gel electrophoresis and immunorevelation. Plasma samples were drawn using the same standardised procedure from blood donors or AE patients with normal C1Inh conditions, normal kinin catabolism, and without prophylaxis.

Results: Circulating native HK plasma concentrations were similar in the healthy men (interquartile range: 98-175μg/mL, n = 51) and in healthy women (90-176μg/mL, n = 74), while HK cleavage was lower (p<0.001) in men (0-5%) than women (3-9%). Patients exhibited lower native HK concentration (p<10-4; 21-117μg/mL, n = 31 for men; 0-84μg/mL, n = 41 for women) and higher HK cleavage (p<10-4; 10-30% and 14-89%, respectively) than healthy donors. Pathological thresholds were set at: <72μg/mL native HK, >14.4% HK cleavage for men; <38μg/mL; native HK, >33.0% HK cleavage for women, with >98% specificity achieved for all parameters. In plasma from patients undergoing recovery two months after oestrogen/progestin combination withdrawal (n = 13) or two weeks after AE attack (n = 2), HK cleavage was not fully restored, suggesting its use as a post-attack assay.

Conclusion: As a diagnostic tool, HK cleavage can offer physicians supportive arguments for kinin production in suspected AE cases and improve patient follow-up in clinical trials or prophylactic management.

Grant support

This work was funded by a research program conducted within European framework 7 (acronym HAEIII; CD), a National grant for TRALI (APR2011; CD) from the Etablissement Français du Sang, and by the national rare disease program from the French Ministry of Health (CREAK; CD). KininX provided support in the form of salaries for PS and AG, Salaam-Antibody to MH, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.