Phage display antibodies to allelic determinants of canine blood cells

Techniques were developed to select useful allele-specific antibodies directed to canine red blood cell alloantigens from a phage display library in which antibody single chain variable fragments (scFv) were expressed on filamentous bacteriophage. First, techniques were developed to detect specific antigens displayed on red blood cells using flow cytometry. Next, techniques permitting the efficient selection of red blood cell binders from a large phage library were developed. Finally, the amplified library was depleted using the red blood cells of one animal and the remainder enriched using cells from a genetically different animal. A high frequency of clones derived from this population bound antigen(s) of the second animal but not the first. Sequence analysis of these clones revealed that at least 11 clonally distinct isolates were present within the selected population. The procedure used to obtain these reagents is simple and inexpensive and the techniques developed should find applications in canine transfusion medicine and parentage assignment.