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PC Esmon, HS Kuo and MA Fournel
Cutter Biological, Miles Inc, Berkeley, CA 94701.
The use of factor VIII prepared genetically engineered cell lines (rFVIII)
may avoid some of the problems inherently associated with administering
plasma-derived factor VIII (pdFVIII) concentrates to hemophilia A patients.
Although rFVIII may represent an improvement over traditional therapeutics,
the chance exists that protein production in cell culture may result in the
presence of novel epitopes that may enhance the formation of inhibitor
antibodies capable of neutralizing either rFVIII or pdFVIII. To assess the
differences between rFVIII and its plasma-derived homologue, a rabbit
immunogenicity model system was developed. Antibodies raised to rFVIII in
rabbits were tested for the presence of antibodies capable of binding
rFVIII but not pdFVIII, the presence of which would suggest that novel
epitope(s) were present. This analysis was performed using a competitive
enzyme-linked immunosorbent assay, as well as immunoadsorption. For either
technique, rFVIII-specific antibodies were not detected, indicating that
differences between rFVIII and pdFVIII were not found. When a rFVIII
B-region deletion mutant was similarly tested, antibodies specific for this
protein were found. These specific antibodies appeared to bind in the
vicinity of the deletion site and their binding was not affected by
carbohydrate removal. These results indicate that the rabbit immunogenicity
model system is sensitive to alterations in the factor VIII molecule and
suggest that full-length rFVIII will not be any more immunogenic in human
patients than pdFVIII.
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| Copyright © 1990 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||