Comparison of antibody production to human interleukin-6 (IL-6) by sheep and chickens

Chicken antibodies have been reported to provide an excellent alternative to their mammalian counterparts for immunodiagnostics, but detailed studies, particularly regarding their avidity, are limited. Prior to the development of an immunoassay for measuring human interleukin-6 (hIL-6) we compared the serum antibody responses of sheep and chickens to immunization with recombinant human IL-6 (rhIL-6) and studied the transfer of chicken serum antibodies to the egg yolk. Both chickens and sheep produced high avidity antisera (average avidity constants being 1.3 x 10(10) l/mol and 3.1 x 10(10) l/mol respectively after four immunizations) with chickens producing an unusually high avidity response after a single immunization. Although both antisera showed extremely high specificity for their ligand, both demonstrated a high degree of recognition for Chinese hamster ovary cell-derived IL-6 (CHO-IL-6), a glycosylated form of recombinant human interleukin-6 (rhIL-6) more akin to natural hIL-6. A delay of 3-4 days was found between the appearance of serum anti-IL-6 antibodies and their detection in the egg yolk; specific antibody in the latter was concentrated by a factor of 1.23 +/- 0.07 relative to serum. The binding characteristics of paired serum and yolk antibodies with respect to both rhIL-6 and CHO-IL-6 were identical. These studies demonstrate the suitability of both chickens and sheep as hosts for the production of large quantities of high quality antiserum to human IL-6.