title: Noninvasive imaging of immune responses.
abstract: At their margins, tumors often contain neutrophils, dendritic cells, and activated macrophages, which express class II MHC and CD11b products. The interplay between stromal cells, tumor cells, and migratory cells such as lymphocytes creates opportunities for noninvasive imaging of immune responses. We developed alpaca-derived antibody fragments specific for mouse class II MHC and CD11b products, expressed on the surface of a variety of myeloid cells. We validated these reagents by flow cytometry and two-photon microscopy to obtain images at cellular resolution. To enable noninvasive imaging of the targeted cell populations, we developed a method to site-specifically label VHHs [the variable domain (VH) of a camelid heavy-chain only antibody] with (18)F or (64)Cu. Radiolabeled VHHs rapidly cleared the circulation (t1/2 ≈ 20 min) and clearly visualized lymphoid organs. We used VHHs to explore the possibility of imaging inflammation in both xenogeneic and syngeneic tumor models, which resulted in detection of tumors with remarkable specificity. We also imaged the infiltration of myeloid cells upon injection of complete Freund's adjuvant. Both anti-class II MHC and anti-CD11b VHHs detected inflammation with excellent specificity. Given the ease of manufacture and labeling of VHHs, we believe that this method could transform the manner in which antitumor responses and/or infectious events may be tracked.
authors.affiliation: Whitehead Institute for Biomedical Research, Cambridge, MA 02142; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142;
authors.forename: Mohammad
authors.initials: M
authors.lastname: Rashidian
authors.affiliation: Center for Systems Biology, Massachusetts General Hospital, Boston, MA 02114; Department of Radiology, Massachusetts General Hospital, Boston, MA 02114;
authors.forename: Edmund J
authors.initials: EJ
authors.lastname: Keliher
authors.affiliation: Whitehead Institute for Biomedical Research, Cambridge, MA 02142;
authors.forename: Angelina M
authors.initials: AM
authors.lastname: Bilate
authors.affiliation: Whitehead Institute for Biomedical Research, Cambridge, MA 02142;
authors.forename: Joao N
authors.initials: JN
authors.lastname: Duarte
authors.affiliation: Center for Systems Biology, Massachusetts General Hospital, Boston, MA 02114;
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Wojtkiewicz
authors.affiliation: Whitehead Institute for Biomedical Research, Cambridge, MA 02142; Center for Immune Regulation, Oslo University Hospital, University of Oslo, N-0372 Oslo, Norway;
authors.forename: Johanne Tracey
authors.initials: JT
authors.lastname: Jacobsen
authors.affiliation: Whitehead Institute for Biomedical Research, Cambridge, MA 02142;
authors.forename: Juanjo
authors.initials: J
authors.lastname: Cragnolini
authors.affiliation: Whitehead Institute for Biomedical Research, Cambridge, MA 02142;
authors.forename: Lee Kim
authors.initials: LK
authors.lastname: Swee
authors.affiliation: Whitehead Institute for Biomedical Research, Cambridge, MA 02142;
authors.forename: Gabriel D
authors.initials: GD
authors.lastname: Victora
authors.affiliation: Center for Systems Biology, Massachusetts General Hospital, Boston, MA 02114; Department of Radiology, Massachusetts General Hospital, Boston, MA 02114; and Department of Systems Biology, Harvard Medical School, Boston, MA 02115.
authors.forename: Ralph
authors.initials: R
authors.lastname: Weissleder
authors.affiliation: Whitehead Institute for Biomedical Research, Cambridge, MA 02142; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142; ploegh@wi.mit.edu.
authors.forename: Hidde L
authors.initials: HL
authors.lastname: Ploegh
mesh_terms: D019881:Aminoacyltransferases / Q000502:physiology; D000818:Animals; D000906:Antibodies / Q000276:immunology; D000970:Antineoplastic Agents / Q000627:therapeutic use; D001426:Bacterial Proteins / Q000502:physiology; D001854:Bone Marrow Cells / Q000378:metabolism; D003301:Copper Radioisotopes / Q000737:chemistry; D003546:Cysteine Endopeptidases / Q000502:physiology; D005434:Flow Cytometry; D005462:Fluorine Radioisotopes / Q000737:chemistry; D005620:Freund's Adjuvant; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D006801:Humans; D007107:Immune System / Q000502:physiology*; D007143:Immunoglobulin Heavy Chains / Q000276:immunology; D007249:Inflammation; D051379:Mice; D008810:Mice, Inbred C57BL; D022423:Myeloid Cells / Q000473:pathology; D009368:Neoplasm Transplantation; D009369:Neoplasms / Q000276:immunology* / Q000628:therapy; D049268:Positron-Emission Tomography
chemical_list: D000906:Antibodies; D000970:Antineoplastic Agents; D001426:Bacterial Proteins; D003301:Copper Radioisotopes; D005462:Fluorine Radioisotopes; D000949:Histocompatibility Antigens Class II; D007143:Immunoglobulin Heavy Chains; D005620:Freund's Adjuvant; D019881:Aminoacyltransferases; C120542:sortase A; D003546:Cysteine Endopeptidases
keywords: PET imaging; camelid single domain antibodies; cancer; inflammation; non-invasive imaging