title: Molecular imaging with macrophage CRIg-targeting nanobodies for early and preclinical diagnosis in a mouse model of rheumatoid arthritis.
abstract: An accurate and noninvasive tracer able to detect molecular events underlying the development of rheumatoid arthritis (RA) would be useful for RA diagnosis and drug efficacy assessment. A complement receptor of the Ig superfamily (CRIg) is expressed on synovial macrophages of RA patients, making it an interesting target for molecular imaging of RA. We aim to develop a radiotracer for the visualization of CRIg in a mouse model for RA using radiolabeled single-domain variable antibody VHH fragments (Nanobodies).
  
  
  METHODS
  Quantitative polymerase chain reaction was used to locate CRIg expression in mice with collagen-induced arthritis (CIA). A Nanobody, NbV4m119, was generated to specifically target CRIg. Flow cytometry, phosphorimaging, and confocal microscopy were used to confirm NbVm119 binding to CRIg-positive cells. SPECT (SPECT/CT) was used to image arthritic lesions in the inflamed paws of 29 mice using (99m)Tc-NbV4m119 Nanobody.
  
  
  RESULTS
  CRIg is constitutively expressed in the liver and was found to be upregulated in synovial tissues of CIA mice. SPECT/CT imaging revealed that (99m)Tc-NbV4m119 specifically targeted CRIg-positive liver macrophages in naïve wild-type but not in CRIg(-/-) (CRIg knockout) mice. In CIA mice, (99m)Tc-NbV4m119 accumulation in arthritic lesions increased according to the severity of the inflammation. In the knees of mice with CIA, (99m)Tc-NbV4m119 was found to accumulate even before the onset of macroscopic clinical symptoms.
  
  
  CONCLUSIONS
  SPECT/CT imaging with (99m)Tc-NbV4m119 visualizes joint inflammation in CIA. Furthermore, imaging could predict which mice will develop clinical symptoms during CIA. Consequently, imaging of joint inflammation with CRIg-specific Nanobodies offers perspectives for clinical applications in RA patients.
authors.affiliation: Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussel, Brussels, Belgium.
authors.forename: Fang
authors.initials: F
authors.lastname: Zheng
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Put
authors.forename: Luc
authors.initials: L
authors.lastname: Bouwens
authors.forename: Tony
authors.initials: T
authors.lastname: Lahoutte
authors.forename: Patrick
authors.initials: P
authors.lastname: Matthys
authors.forename: Serge
authors.initials: S
authors.lastname: Muyldermans
authors.forename: Patrick
authors.initials: P
authors.lastname: De Baetselier
authors.forename: Nick
authors.initials: N
authors.lastname: Devoogdt
authors.forename: Geert
authors.initials: G
authors.lastname: Raes
authors.forename: Steve
authors.initials: S
authors.lastname: Schoonooghe
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000276:immunology; D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000276:immunology* / Q000378:metabolism; D004195:Disease Models, Animal; D007150:Immunohistochemistry; D007249:Inflammation; D008264:Macrophages / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D057054:Molecular Imaging / Q000379:methods*; D012333:RNA, Messenger / Q000378:metabolism; D019275:Radiopharmaceuticals; D060888:Real-Time Polymerase Chain Reaction; D011951:Receptors, Complement / Q000737:chemistry*; D061905:Single-Domain Antibodies / Q000737:chemistry*; D013583:Synovial Membrane / Q000378:metabolism; D013667:Technetium / Q000737:chemistry; D015899:Tomography, Emission-Computed, Single-Photon; D055114:X-Ray Microtomography
chemical_list: D012333:RNA, Messenger; D019275:Radiopharmaceuticals; D011951:Receptors, Complement; D061905:Single-Domain Antibodies; D013667:Technetium
keywords: Nanobody; SPECT/μCT; collagen-induced arthritis (CIA); complement receptor of the Ig superfamily (CRIg, VSIG4, or Z39Ig); macrophage