Bovine hemoglobin (glutamer-250, Hemopure)-specific immunoglobulin G antibody cross-reacts with human hemoglobin but does not lyse red blood cells in vitro.
BACKGROUND
Bovine hemoglobin (Hb)-based oxygen carrier (HbOC-201; Hb glutamer-250, Hemopure, Biopure Corp.) is a blood replacement and augmentation drug that increases oxygen-carrying capacity of circulating blood in patients with anemia and acute blood loss. The objective of this study was to assess the biologic significance (cross-reactivity, hemolysis) of humoral immune responses in humans receiving repetitive HbOC-201 administrations.


METHODS
Serum samples containing immunoglobulin G (IgG) anti-HbOC-201 (n = 146) or no antibody (n = 16) were collected from subjects receiving HbOC-201 in clinical studies. IgG anti-HbOC-201 levels were quantified and the extent of cross-reactivity to human hemoglobin (HuHb) was assessed in direct-binding and competitive-inhibition immunoassays. Serum samples containing the highest levels of IgG anti-HbOC-201 were studied in a complement-mediated hemolysis assay for their ability to lyse human red cells (RBCs).


RESULTS
The IgG anti-HbOC-201 levels in the antibody-positive serum samples ranged from 0.7 to 86.8 mug per mL. Of the 146 IgG anti-HbOC-201-positive serum samples, 88.4 percent contained IgG antibodies whose binding to solid-phase HbOC-201 was competitively inhibited by incubation with soluble HuHb (11.6% [<20% inhibition]; 63% [20%-80% inhibition]; and 25.4% [>81% inhibition]). Direct-binding analysis to solid-phase HuHb confirmed that 74 percent contained IgG antibodies reactive with HuHb. Dichotomous competitive inhibition and direct-binding IgG anti-HuHb data correlated significantly (r(2) = 0.77, p < 0.001). Serum samples with the highest levels of IgG anti-HuHb, as identified from clinical studies, did not lyse human RBCs in the presence of exogenous complement or induce the direct sensitization of RBCs with human IgG or complement.


CONCLUSIONS
These analyses indicate that HbOC-201 administration elicits IgG antibodies in humans that react with bovine and HuHb, but do not cause hemolysis in vitro.
Hamilton
Robert G
RG
Division of Allergy and Clinical Immunology and Hematology, Departments of Medicine and Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21224, USA. Rhamilto@jhmi.edu
Kickler
Thomas S
TS
D000818:Animals; D000906:Antibodies / Q000097:blood / Q000276:immunology*; D002417:Cattle; D003429:Cross Reactions / Q000276:immunology; D004912:Erythrocytes / Q000166:cytology / Q000276:immunology*; D006454:Hemoglobins / Q000276:immunology*; D006461:Hemolysis / Q000276:immunology; D006801:Humans; D007118:Immunoassay; D007074:Immunoglobulin G / Q000276:immunology*
D000906:Antibodies; D006454:Hemoglobins; D007074:Immunoglobulin G; C096798:HBOC 201