Isolation of an in vitro-produced soluble Anaplasma-albumin complex

A soluble Anaplasma-albumin complex was isolated from supernatants of A marginale cultures by affinity chromatography. Holstein calves inoculated with this fraction produced anti-A marginale antibodies detected in the indirect fluorescent antibody test at titers similar to those found in cattle immunized with unfractionated culture supernatant. Titers of both groups peaked slightly above 1:2,000 on postinoculation day 46.