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Clinical Trial
. 2014 Sep 11;124(11):1715-26.
doi: 10.1182/blood-2014-02-558296. Epub 2014 Jul 18.

Dynamics of complement activation in aHUS and how to monitor eculizumab therapy

Marina Noris  1 , Miriam Galbusera  1 , Sara Gastoldi  1 , Paolo Macor  2 , Federica Banterla  1 , Elena Bresin  1 , Claudio Tripodo  3 , Serena Bettoni  1 , Roberta Donadelli  1 , Elisabetta Valoti  1 , Francesco Tedesco  4 , Alessandro Amore  5 , Rosanna Coppo  5 , Piero Ruggenenti  6 , Eliana Gotti  6 , Giuseppe Remuzzi  7
Affiliations
Clinical Trial

Dynamics of complement activation in aHUS and how to monitor eculizumab therapy

Marina Noris et al. Blood. .

Abstract

Atypical hemolytic-uremic syndrome (aHUS) is associated with genetic complement abnormalities/anti-complement factor H antibodies, which paved the way to treatment with eculizumab. We studied 44 aHUS patients and their relatives to (1) test new assays of complement activation, (2) verify whether such abnormality occurs also in unaffected mutation carriers, and (3) search for a tool for eculizumab titration. An abnormal circulating complement profile (low C3, high C5a, or SC5b-9) was found in 47% to 64% of patients, irrespective of disease phase. Acute aHUS serum, but not serum from remission, caused wider C3 and C5b-9 deposits than control serum on unstimulated human microvascular endothelial cells (HMEC-1). In adenosine 5'-diphosphate-activated HMEC-1, also sera from 84% and 100% of patients in remission, and from all unaffected mutation carriers, induced excessive C3 and C5b-9 deposits. At variance, in most patients with C3 glomerulopathies/immune complex-associated membranoproliferative glomerulonephritis, serum-induced endothelial C5b-9 deposits were normal. In 8 eculizumab-treated aHUS patients, C3/SC5b-9 circulating levels did not change posteculizumab, whereas serum-induced endothelial C5b-9 deposits normalized after treatment, paralleled or even preceded remission, and guided drug dosing and timing. These results point to efficient complement inhibition on endothelium for aHUS treatment. C5b-9 endothelial deposits might help monitor eculizumab effectiveness, avoid drug overexposure, and save money considering the extremely high cost of the drug.

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Figures

Figure 1
Figure 1
Immunohistochemical analysis of C3 and C9 (C5b-9) staining in kidney biopsy specimens from aHUS patients. Representative results are shown. (A) C3 deposits with main endothelial localization in a glomerulus from a patient with a CFI mutation and normal SC5b-9 plasma levels. (B) C9 staining restricted to hilar area in a glomerulus from a patient with a C3 mutation. (C) Diffuse C9 deposits in 2 glomeruli with marked ischemic injury from a patient with CFH mutation and increased SC5b-9 levels. (D) C9 deposits in glomeruli from a patient without mutations/anti-CFH antibodies. (E-F) endothelial C3 staining in arterioles from patients with CFH (E) and CFI (F) mutations. (G) Subendothelial localization of C9 staining in an arteriole from a patient with a CFH mutation and normal SC5b-9 level. (H) Control section (healthy portion of nephrectomy for cancer, C9 staining). Original magnification ×400, counterstaining with hematoxylin.
Figure 2
Figure 2
aHUS serum induces C3 and C5b-9 deposition on microvascular endothelial cells (HMEC-1). (A-B) Endothelial surface area covered by C3 (A) or C5b-9 (B) staining after incubation of unstimulated (resting) or ADP-activated HMEC-1 for 4 hr with serum (diluted 1:2 in test medium) from healthy subjects (Ctr; n = 4) or from aHUS patients (C3: n = 3, 1 with CFH mutation, 1 with anti-CFH antibodies, and 1 without identified mutations/anti-CFH antibodies; C5b-9: n = 7, 3 with CFH mutation, 1 with anti-CFH antibodies, and 3 without identified mutations/anti-CFH antibodies) studied both during the acute phase of the disease (Acute) and at remission (Rem) or from 7 aHUS patients studied in the acute phase only (panel B, C5b-9, acute only, all without identified mutations/anti-CFH antibodies). Data are mean ± standard error (SE). ^P < .01 vs control resting; °°P < .01, °°°P < .05 vs control ADP-activated; &P < .001, &&P < .01, &&&P < .05 vs remission resting. (C,E) Endothelial surface area covered by C3 (C) or C5b-9 (E) staining after incubation of ADP-activated HMEC-1 for 4 hr with serum from aHUS patients studied in remission (C3: n = 25, CFH mutations: n = 10; CFI mutations: n = 4; C3 mutations: n = 3; CFB mutation: n = 1; anti-CFH antibodies: n = 2; without identified mutations/anti-CFH antibodies: n = 5 ; C5b-9: n = 29, CFH mutations or CFHR1/CFH hybrid gene: n = 12; anti-CFH antibodies: n = 2; CFI mutations: n = 4; C3 mutations: n = 3; CFB mutation: n = 1; without identified mutations/anti-CFH antibodies: n = 7), in the presence or not of the complement inhibitor sCR1 (150 μg/mL). Range of deposits induced by control serum (mean ± SE): dotted horizontal areas. (D,F) Representative confocal microscopy images of C3 (D, in green) or C5b-9 (F, in green) staining of ADP-activated HMEC-1 exposed to serum from an healthy subject (Ctr) or an aHUS patient in remission (aHUS) (original magnification ×400). Additional images are shown in supplemental Figure 11. Data are mean ± SE. °P < .001, °°°P < .05 vs control serum; *P < .001, **P < .01 vs aHUS serum without sCR1. Both C3 and C5b-9 deposits were prevented by addition of sCR1 (an inhibitor of all the 3 complement pathways) to patient serum, indicating that the staining was specifically related to complement activation products. mut, mutation.
Figure 3
Figure 3
Effect of complement inhibitors on aHUS serum-induced C3 and C5b-9 deposition on ADP-activated HMEC-1. (A-B) Effect of selective inhibitors of the alternative pathway of complement, an anti-CFB antibody (anti-CFB, 150 μg/mL), the CR2-FH fusion protein (CR2-FH, 150 μg/mL and 300 μg/mL), and a CFH concentrate from human plasma (CFH conc, at levels comparable to those of normal human serum, 230 μg/mL) on C3 deposition induced on ADP-activated HMEC-1 by serum from 3 patients with aHUS and CFH mutations studied in remission in 3 independent experiments. (C) Effect of terminal complement pathway inhibitors, an anti-C5 minibody (anti-C5, 135 μg/mL), or an anti-C7 goat polyclonal antibody (anti-C7, 350 μg/mL) or eculizumab (Ecu, 150 μg/ml) on C5b-9 deposition induced on ADP-activated HMEC-1 by serum of patients with aHUS studied in remission. Data are from 3 different experiments in 3 patients (CFH mutations, n = 2; C3 mutation, n = 1) and 3 controls. (D) Effect of 3 doses of eculizumab (Ecu; 100, 50, or 25 μg/mL) on C5b-9 deposition on ADP-activated HMEC-1 induced by serum of patients with aHUS studied in the acute phase before any treatment. Data are from 3 different experiments in 3 patients (without mutations or anti-CFH antibodies) and 3 controls. Data are mean ± SE. °P < .001, °°P < .01, °°°P < .05 vs control serum; *P < .001, **P < .01, ***P < .05 vs aHUS serum untreated. Control range: dotted horizontal areas. ctr, control.
Figure 4
Figure 4
Serum from healthy carriers of complement gene mutations induces C3 and C5b-9 deposition on ADP-activated microvascular endothelial cells (HMEC-1). (A-B) Endothelial surface area covered by C3 (A) or C5b-9 (B) staining after incubation of ADP-activated HMEC-1 for 4 hr with serum (diluted 1:2 in test medium) from aHUS patients (C3 deposits: n = 6, 4 with CFH mutations, 1 with C3 mutation, and 1 with CFI mutation; C5b-9 deposits: n = 7, 4 with CFH mutations, 1 with C3 mutation, 1 with CFI mutation, and 1 with CFHR1/CFH hybrid gene) or from their healthy relatives carrying the same mutations (C3 deposits: n = 5, 3 with CFH mutation, 1 with C3 mutation, and 1 with CFI mutation; C5b-9 deposits: n = 6, 3 with CFH mutation, 1 with C3 mutation, 1 with CFI mutation, and 1 with CFHR1/CFH hybrid gene) in the presence or not of the complement inhibitor sCR1 (150 μg/mL) or from 7 healthy relatives without mutations (C5b-9 deposits). Control serum range: dotted horizontal areas. Data are mean ± SE. °P < .001, °°P < .01, vs control serum; *P < .001, **P < .01 vs aHUS patients without sCR1; §P < .001 vs mutation carriers without sCR1; #P < .01 vs carrier; &P < .001, &&P < .01 vs no carrier. (C) Data of plasma SC5b-9 levels and serum-induced C3 and C5b-9 deposition on ADP-activated HMEC-1 in unaffected relatives carrying complement gene mutations (healthy mutation carrier, n = 7) and unaffected relatives without mutations (only C5b-9, healthy no carrier, n = 7). °Limits of normal ranges (as defined in supplemental “Methods”). *P < .05 vs control serum (statistical comparisons were made for each relative by comparing deposits in pixel2 recorded in 15 fields analyzed for the relative and for the corresponding control run in parallel, as detailed in supplemental “Methods”). £: Serum-induced C3 or C5b-9 deposits on ADP-activated HMEC-1. mut, mutation; n.a., not available; n.d., not done.
Figure 5
Figure 5
Effect of eculizumab on clinical and complement parameters in case 5. Treatments, platelet count, plasma SC5b-9 levels, and serum-induced complement deposition on ADP-activated HMEC-1 (by calculating HMEC-1 area covered by C5b-9 staining in pixel2) after incubation (4 hr) with serum (diluted 1:2 with test medium) from case 5 taken immediately pretransplant before eculizumab treatment (pre-Ecu), at 15 months posttransplant after eculizumab treatment (post-Ecu, 300 or 600 mg), and 21 months posttransplant after eculizumab treatment (post-Ecu, 600 mg). Green arrow indicates eculizumab prophylaxis for kidney transplant. Black arrow indicates the time of kidney transplant. Red arrows indicate times of sampling for plasma SC5b-9 and serum-induced ex vivo complement deposits. Data are mean ± SE of 15 fields examined for each sample. The horizontal rectangle shows range of endothelial C5b-9 deposits with control sera (mean ± SE). °P < .001, °°°P < .05 vs control serum; #P < .01 vs case 5 pre-Ecu; xxxP < .05 vs case 5, 8 days post-Ecu 300 mg.
Figure 6
Figure 6
Effect of eculizumab on clinical and complement parameters in case 7. Treatments, platelet count, plasma SC5b-9 levels, and complement deposition on ADP-activated HMEC-1 (by calculating HMEC-1 area covered by C5b-9 staining in pixel2) after 4-hr incubation with serum (diluted 1:2 in test medium) from case 7 taken during the acute phase before start of eculizumab treatment (pre-Ecu) and in full remission (normal renal and hematologic parameters) after eculizumab (at the adult dose of 1200 mg every 2 and 3 weeks; post-Ecu). Red arrows indicate times of sampling for plasma SC5b-9 and serum-induced ex vivo complement deposits. Green arrow: from this time, the patient was treated with eculizumab every 3 weeks. Data are mean ± SE of 15 fields examined for each sample. The horizontal rectangle shows range of endothelial C5b-9 deposits with control sera (mean ± SE). °P < .001 vs control serum; $P < .001 vs case 7 pre-Ecu.
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Comment in

  • COMPLEMENTing the diagnosis of aHUS.
    Afshar-Kharghan V. Afshar-Kharghan V. Blood. 2014 Sep 11;124(11):1699-700. doi: 10.1182/blood-2014-07-590356. Blood. 2014. PMID: 25214194 Free PMC article.

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