Immunologic Characterization of Soluble Antigen Derived From Cell Culture of Babesia Bovis

Abstract

Soluble cell culture derived antigens of Babesia bovis were studied for their biophysical and chemical properties. The fraction found to be antigenically active by in vitro test and immunogenically potent by inoculation of susceptible animals was thermostable, sensitive to 2-mercaptoethanol, and subject to a partial and a complete destruction by papain and alpha-amlase, respectively. Accordingly, soluble B. bovis antigen appears to be a polysacharide-protein entity or more specifically a relatively heat stable glycoprotein.

Inoculation of cattle with a mixture of soluble B. bovis antigen and saponin adjuvant resulted in a prompt production of blood serum antibodies detectable by an indirect fluorescent antibody (IFA) test. These antibodies persisted at detectable levels for 3 to 4 months. Re-vaccination at 7 months following first inoculation resulted in an anamnestic immune response indicating a recognition and persistence of immunologic memory to primary sensitization.

Thirty 2-year old Hereford cattle which were inoculated with saponin fortified soluble B. bovis antigen, and 20 non-vaccinated similar animals experienced a natural outbreak of babesiosis upon introduction from a tick-free region into a babesiosis endemic area. All animals of the control groups developed signs of the disease and 8 of them died. Among vaccinated animals there was febrile response, hematologic abnormalities and parasitemia, however, all animals remained grossly clinically free of signs and continued to make adequate weight progress.