Serum YFP specific antibody titers in chickens and rabbits immunized with T. gondii YFP and/or rYFP protein. Chickens and rabbits were primed s.c. with 5 × 106 and 1 × 107 T. gondii YFP tachyzoites, respectively. The primed chickens were boosted i.m. 20 days later with 160 μg of rYFP emulsified in Freund complete adjuvant, and the primed rabbits were boosted i.m. 35 days later with 500 μg of recombinant YFP emulsified in Freund complete adjuvant. Serum YFP specific IgG titers were measured 10 days after the booster immunization.