In vitro and in vivo efficacy of a recombinant immunotoxin against folate receptor beta on the activation and proliferation of rheumatoid arthritis synovial cells.
OBJECTIVE
To investigate the effects of the recombinant immunotoxin dsFv anti-FRbeta-PE38, which consists of the disulfide-stabilized Fv fragment (dsFv) of the anti-folate receptor beta (anti-FRbeta) antibody and the 38-kd portion of Pseudomonas exotoxin A (PE38), on the activation and proliferation of cells that function in inflammatory and degradative processes in rheumatoid arthritis (RA) synovial tissue.


METHODS
The Ig VH-PE38 fusion protein and the Ig VL protein were produced in Escherichia coli, and then joined with a disulfide bond by engineering cysteine residues in the framework regions of these proteins. The effects of dsFv anti-FRbeta-PE38 on the activation and proliferation of cells in RA synovial tissue were investigated by immunohistochemistry; the numbers of cells expressing CD68, vascular cell adhesion molecule 1, angiopoietin 1, CD34, proliferating cell nuclear antigen, and interleukin-6 and the numbers of apoptotic cells were counted in RA synovial tissue engrafted into SCID mice treated or not treated with dsFv anti-FRbeta-PE38. The effects of dsFv anti-FRbeta-PE38 on the generation of osteoclasts from RA adherent synovial mononuclear cells in vitro was investigated by counting the number of resorption pits on dentin slices treated or not treated with dsFv anti-FRbeta-PE38.


RESULTS
Administration of dsFv anti-FRbeta-PE38 reduced the numbers of macrophages, activated fibroblast-like cells, endothelial cells, and proliferating cells and increased the numbers of apoptotic cells in RA synovial tissue engrafted into SCID mice. In vitro, the generation of osteoclasts from RA adherent synovial mononuclear cells was largely suppressed by treatment with dsFv anti-FRbeta-PE38.


CONCLUSIONS
Our findings show that dsFv anti-FRbeta-PE38 immunotoxin would be a promising tool for the treatment of RA synovitis, especially when administered intraarticularly.
Nagai
Taku
T
Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan.
Tanaka
Masashi
M
Tsuneyoshi
Yasuhiro
Y
Matsushita
Kakushi
K
Sunahara
Nobuhiko
N
Matsuda
Takemasa
T
Yoshida
Hiroki
H
Komiya
Setsuro
S
Onda
Masanori
M
Matsuyama
Takami
T
D036002:ADP Ribose Transferases / Q000276:immunology*; D000818:Animals; D000906:Antibodies / Q000276:immunology; D017209:Apoptosis / Q000187:drug effects; D001172:Arthritis, Rheumatoid / Q000188:drug therapy / Q000276:immunology / Q000473:pathology*; D001427:Bacterial Toxins / Q000276:immunology*; D002352:Carrier Proteins / Q000276:immunology*; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D004220:Disulfides; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli; D005098:Exotoxins / Q000276:immunology*; D058973:Folate Receptors, GPI-Anchored; D006801:Humans; D000922:Immunotoxins / Q000276:immunology / Q000494:pharmacology* / Q000627:therapeutic use; D008099:Liver / Q000187:drug effects; D008297:Male; D051379:Mice; D016513:Mice, SCID; D010010:Osteoclasts / Q000187:drug effects / Q000473:pathology; D011956:Receptors, Cell Surface / Q000276:immunology*; D011994:Recombinant Proteins / Q000276:immunology / Q000494:pharmacology* / Q000627:therapeutic use; D013583:Synovial Membrane / Q000187:drug effects* / Q000473:pathology*; D014162:Transfection; D037521:Virulence Factors / Q000276:immunology*; D000097668:Pseudomonas aeruginosa Exotoxin A
D036002:ADP Ribose Transferases; D000906:Antibodies; D001427:Bacterial Toxins; D002352:Carrier Proteins; D004220:Disulfides; D005098:Exotoxins; D058973:Folate Receptors, GPI-Anchored; D000922:Immunotoxins; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A