title: Human Rh D monoclonal antibodies (BRAD-3 and BRAD-5) cause accelerated clearance of Rh D+ red blood cells and suppression of Rh D immunization in Rh D- volunteers.
abstract: The use of prophylactic anti-D to prevent Rh D immunization in Rh D- women and subsequent hemolytic disease in Rh D+ infants is widespread, but has led to shortages of the anti-D Ig. With the aim of substituting monoclonal anti-D for Rh D prophylaxis, we have compared the abilities of monoclonal and polyclonal anti-D to clear Rh D+ red blood cells (RBCs) infused into Rh D- male volunteers and to suppress Rh D immunization. Two human monoclonal antibodies (MoAbs), BRAD-3 (IgG3) and BRAD-5 (IgG1), produced from stable Epstein-Barr virus-transformed B-lymphoblastoid cell lines, were selected because of their proven in vitro activity in promoting RBC lysis in antibody-dependent cell-mediated cytotoxicity assays. RBC clearance was assessed by intravenous injection of 3 mL of 51chromium-labeled D+ RBCs into 27 volunteers 48 hours after intramuscular injection of monoclonal or polyclonal anti-D. Further 3-mL injections of unlabeled D+ cells were administered at 6 and 9 months to induce immunization. Blood samples were taken throughout the 12-month period of study for the serologic detection of anti-D. The mean half-life (t50%) of RBCs in 7 recipients of 300 micrograms BRAD-5 (5.9 hours) was similar to that in 8 recipients of 500 IU polyclonal anti-D (5.0 hours), whereas D+ cells were cleared more slowly in some of the 8 subjects injected with 300 micrograms BRAD-3 (mean t50% 12.7 hours) and in 1 individual administered 100 micrograms BRAD-3 (t50% 41.0 hours). The rate of RBC clearance in both groups administered 300 micrograms monoclonal anti-D correlated with the amount of antibody bound per cell, determined by flow cytometry. There was no evidence of primary immunization having occurred in any subject after 6 months of follow-up. Five of 24 subjects produced anti-D after one or two further injections of RBCs, confirming that they were responders who had been protected by the monoclonal or polyclonal anti-D administered initially. Four of these responders were recipients of monoclonal anti-D (3 BRAD-3, 1 BRAD-5). One individual who received BRAD-5 produced accelerated clearance of D+ RBCs at the third unprotected RBC challenge but did not seroconvert. This study shows that the human MoAbs BRAD-3 and BRAD-5 can prevent Rh D immunization, and indicates that they may be suitable replacements for the polyclonal anti-D presently used in prophylaxis of Rh D hemolytic disease of the newborn.(ABSTRACT TRUNCATED AT 400 WORDS)
authors.affiliation: International Blood Group Reference Laboratory, Bristol, UK.
authors.forename: B M
authors.initials: BM
authors.lastname: Kumpel
authors.forename: M J
authors.initials: MJ
authors.lastname: Goodrick
authors.forename: D H
authors.initials: DH
authors.lastname: Pamphilon
authors.forename: I D
authors.initials: ID
authors.lastname: Fraser
authors.forename: G D
authors.initials: GD
authors.lastname: Poole
authors.forename: C
authors.initials: C
authors.lastname: Morse
authors.forename: G R
authors.initials: GR
authors.lastname: Standen
authors.forename: G E
authors.initials: GE
authors.lastname: Chapman
authors.forename: D P
authors.initials: DP
authors.lastname: Thomas
authors.forename: D J
authors.initials: DJ
authors.lastname: Anstee
mesh_terms: D000328:Adult; D000906:Antibodies / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000096:biosynthesis / Q000302:isolation & purification / Q000494:pharmacology*; D001402:B-Lymphocytes / Q000276:immunology; D002461:Cell Line, Transformed; D004912:Erythrocytes / Q000276:immunology / Q000502:physiology*; D006461:Hemolysis / Q000276:immunology*; D004854:Herpesvirus 4, Human; D006801:Humans; D007114:Immunization; D007074:Immunoglobulin G / Q000096:biosynthesis / Q000302:isolation & purification / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D012204:Rh-Hr Blood-Group System / Q000276:immunology*
chemical_list: D000906:Antibodies; D000911:Antibodies, Monoclonal; D007074:Immunoglobulin G; D012204:Rh-Hr Blood-Group System