Fatal iatrogenic cerebral β-amyloid-related arteritis in a woman treated with lecanemab for Alzheimer’s disease.

Inclusion and ethics statement

We confirm that our research complies with all pertinent ethical regulations, including CARE guidelines and the Declaration of Helsinki principles. The patient’s surrogates provided informed consent to participate in this case report. Vanderbilt University Medical Center’s Institutional Review Board provided ethical oversight as part of our ongoing Observational Study of CAA and Related Disorders (OSCAAR), protocol number 180287.

Post-mortem MR imaging

Coronal tissue slabs were sliced coronally and embedded in 1% agarose under degassing conditions, with care to avoid air bubbles.

Post-mortem susceptibility weighted imaging

(SWI) and T2-weighted FLuid Attenuated Inversion Recovery (FLAIR) MRI were obtained on both 3.0 T (Philips Ingenia) and 7.0 T (Philips Achieva) human clinical scanners using 32-channel phased array reception.

T

SWI (technique = 3D gradient echo, number of echoes = 4, first echo = 7.2 ms, echo spacing = 6.2 ms, repetition time = 31 ms, spatial resolution = 0.6 × 0.6 × 2 mm), 3.0 T FLAIR (technique = 3D turbo-inversion-recovery, echo time = 271 ms, repetition time = 4800 ms, inversion time =1650 ms, spatial resolution = 1.0 × 1.0 × 1.0 mm), 7.0 T SWI (technique = 3D gradient echo, number of echoes = 9, first echo = 8.0 ms, echo spacing = 4 ms, repetition time = 64.3 ms, spatial resolution = 0.65 × 0.65 × 0.9 mm, and 7.0 T FLAIR (technique = 3D turbo-inversion-recovery, echo time = 280 ms, repetition time = 3952 ms, inversion time = 1375 ms, spatial resolution = 0.80 × 0.80 × 0.80 mm) were performed on the same day with sequence parameters chosen to parallel in vivo protocols.

Immunohistochemistry

Immunostaining of brain sections for the autopsy was conducted according to Clinical Laboratory Improvement Amendments (CLIA) standards using approved antibodies. For exploratory analysis, floating sections were prepared on a Leica 1200 S vibratome with a thickness of 50 μm or 100 μm depending on the application. Meningeal tissue was gently removed from the surface of the brain, stained, and mounted as a whole-mount preparation. Aggregated tau and β-amyloid were detected using thiazine red (1 µM, Chemsaves) or methoxy-X04 (1 µM, Tocris, Minneapolis, MN), lectin (dilution 1:250, Lycopersicon esculentum (Vector Laboratories, Tomato) labeled, Fluorescein (FL-1171-1)) was used as a vascular marker. The primary antibodies we used were anti-PLD3 rabbit polyclonal antibody (3 μg/mL, HPA012800; Sigma-Aldrich, St. Louis, MO), anti-ATP6V 0 A 1 rabbit polyclonal antibody (10 μg/mL, NBP1-89342, Novus Biologicals), anti-CD11b chicken polyclonal antibody (10 μg/mL, MAC, AvesLabs) and anti-IBA1 mouse monoclonal antibody (5 μg/mL, Cat# 66827-1-Ig, CloneNo. 1C6A10, Proteintech, Rosemont, IL). The antibodies used in autopsy are the following: β-amyloid- ready to use prediluted 7 mL from BioSB, REF BSB 3442, clone RBT-A4, antibody incubation time 15 min, anti-Tau-1:15,000 from Invitrogen (Thermo Fisher Scientific), REF MN1020, clone AT8, antibody incubation 30 min; anti-CD68- ready to use from Roche, REF 790–2931, clone KP-1, antibody incubation 16 min, anti-CD4- ready to use from Leica, REF PA0427, clone 4B12, antibody incubation for 15 min, anti-CD8- ready to use from Leica, REF PA0183, clone 4B11, antibody incubation for 15 min with ER1 for 15 min. For the β-amyloid, Tau, CD4, CD8 antibodies, the following detection kit was used: Leica Bond III IHC stains- BOND Polymer Refine Detection- REF DS9800. For CD68 antibody, Ventana Roche Ultra Benchmark IHC stain- ultraView Universal DAB Detection Kit- REF 760-500 was used. Confocal images were acquired through the Vanderbilt Cell Imaging Shared Resource (CISR) using a Zeiss LSM 710 confocal laser-scanning microscope (Carl Zeiss AG, Germany) with a 20× air/dry or 63× oil-immersion objective with a minimum resolution of 2000 × 2000 pixels.

CLARITY and light-sheet microscopy

For three-dimensional, light-sheet microscopy tissue blocks were incubated for 3 days in 4% paraformaldehyde (PFA) and embedded in CLARITY acrylamide hydrogel (4% Acrylamide, 0.05% Bis-Acrylamide, 0.25% temperature-triggering initiator VA-044 in 0.1 M phosphate-buffered saline in water- PBS) for 4-5 weeks. The tissue was then placed in a 37 °C water bath to initiate hydrogel polymerization. The blocks were passively clarified in 200 mM boric acid, 4% w/v SDS, pH 8.5 at 37 °C until translucent, then pigmentation was photo-cleared with exposure to an LED microarray. The blocks were stained with Lectin ( Lycopersicon esculentum (Tomato) labeled, dilution 1:200, FL-1171-1, Vector Laboratories) and thiazine red (1 µM, Chemsaves #2150336) in PBS- Triton 0.1%. After overnight incubation in 68% thiodiethanol (TDE) and achieving a refractive index of 1.33, the blocks were imaged using a Light-Sheet microscope. Image processing was done with Imaris Microscopy Image Analysis Software (Oxford Instruments).

Statistics and reproducibility

The nature of this case report suggests a detailed analysis of one patient’s data. Thus, no statistical method was used to predetermine sample size. Due to the descriptive nature of the case report, no data was excluded, the experiments were not randomized, and the experimenters were not blinded to allocation during the experiment and outcome assessment. For the light microscopy from the patient’s autopsy, histological and immunohistological findings are representative of an examination of the sixteen tissue blocks shown in Supplementary Fig. 7 . For fluorescence microscopy, each marker was assessed on a minimum of five tissue sections. Three meningeal specimens were prepared. Reporting summary Further information on research design is available in the Nature Portfolio Reporting Summary linked to this article.

Supplementary information Supplementary Information Peer Review File Description of Additional Supplementary Files Supplementary Movie 1 Supplementary Movie 2 Reporting Summary