The Correlation of Protective Effects and Antibody Production in Immunized Chickens with Recombinant R7 Vaccine against Leucocytozoon caulleryi.

Abstract

ABSTRACT. Protective effects of recombinant R7 (rR7) vaccine against Leucocytozoon caulleryi in chickens were studied. After injection of oil-adjuvanted rR7 vaccine into chickens, antibody titers against second-generation schizonts (2GS) antigen of L. caulleryi (anti-2GS antibody) rapidly rose in all the immunized chickens, reached to a peak value 2 weeks after injection, and the titers persisted through 4 or 5 months after injection. Chickens having high levels of the anti-2GS antibody titers (≥ 102,400 ) at pre-challenge completely protected against sporozoites challenge of L. caulleryi. After the challenge inoculation, relatively high parasitemia of L. caulleryi was observed in all the inadequately immunized chickens having low levels of the antibody titers (≤ 3,200 ) at pre-challenge, although some of them seemed to be clinically normal. Correlation of protective effects in the immunized chickens was observed between both prevention of appearance of clinical signs and parasitemia after parasites challenge and anti-2GS antibody titers of the chickens at pre-challenge. The present study shows that chicken leucocytozoonosis can be prevented by vaccination, and humoral immunity may play an important role in the control of chicken leucocytozoonosis. KEY WORDS: humoral immunity, Leucocytozoon caulleryi, recombinant vaccine, second-generation schizont.

Field Efficacy of Recombinant R7 Vaccine against Chicken Leucocytozoonosis

“…Injection of oil-adjuvanted rR7 vaccine into chickens: Oil-adjuvanted rR7 (O-rR7) vaccine that was prepared in the exactly same way with one made in previous experiment [8] . The vaccine was injected into leg muscle of the chickens with the amount of 0.25 ml/dose (10,000 antigen unit/ dose as antigen titer) [8] , at 91 days of age.…”

“…The vaccine was injected into leg muscle of the chickens with the amount of 0.25 ml/dose (10,000 antigen unit/ dose as antigen titer) [8] , at 91 days of age. This vaccination was done on June 30th, 1998, about one and a half months before the mid-August, in which the outbreak of leucocytozoonosis is observed every year in this farm.…”

“…Similarly, serum samples of 60 same chickens in control group were obtained to confirm L. caulleryi infection. Enzyme-linked immunosorbent assay (ELISA) was used to detect serum anti-2GS antibody titers [4,8]. Samples from vaccinated group that showed positive response at the 1,600 or higher anti-2GS antibody titers were considered as positive to protective antibody [8].…”

“…Enzyme-linked immunosorbent assay (ELISA) was used to detect serum anti-2GS antibody titers [4,8]. Samples from vaccinated group that showed positive response at the 1,600 or higher anti-2GS antibody titers were considered as positive to protective antibody [8]. On the other hand, samples from control group that showed positive response at the 100 or higher anti-2GS antibody titers were considered as positive to infectious antibody.…”

“…Gotanda et al established monoclonal antibody that recognize immunogenic antigen of 2GS [3]. Recently, the gene encoding an immunogenical protein of 2GS, named gene R7, has been cloned and vaccine with recombinant R7 protein (rR7) have protective effects strongly against sporozoite of L. caulleryi challenge [8] . The present study was to evaluate the effects of the vaccine used rR7 against L. caulleryi on clinical and parasitic parameters under field condition in a typical Japan poultry.…”