Potential of a recombinant antigen as a prophylactic vaccine for day-old broiler chickens against Eimeria acervulina and Eimeria tenella infections

A genetically engineered Eimeria tenella antigen (GX3262), produced as a fusion protein with beta-galactosidase and identified with a monoclonal antibody, induced partial but significant protection in young broiler chickens against experimental E. tenella and Eimeria acervulina infections. The antigen appears to share a T-helper cell epitope with the parasite as evidenced by (a) booster inoculation with either the recombinant antigen or with a small number of live oocysts enhanced the protective immunity in GX3262 primed chickens, and (b) ability of the antigen to induce in vitro stimulation of T-cells from chickens immunized with antigen or parasite. These observations suggest the feasibility of a single vaccination of 1 or 2-day-old broilers with GX3262 to induce an acceptable degree of protective immunity. The implications of the observations reported here are far reaching in terms of a practical coccidiosis vaccine for poultry, and show for the first time that 1-day-old broiler chickens can be efficiently vaccinated with a recombinant antigen against one or more species of Eimeria.

Characterization and vaccine potential of a novel recombinant coccidial antigen

A cDNA clone derived from sporulated oocysts of Eimeria tenella and encoding the expression product GX3262 was identified using a monoclonal antibody raised against Eimeria acervulina sporozoites. The cDNA fragment containing the coccidial antigen gene was cloned in bacteriophage lambda gt11, transferred to a plasmid, and introduced into Escherichia coli for analysis of the gene products. The strain carrying the plasmid produced GX3262 as part of a fusion protein consisting of the first 1,006 amino acids of E. coli beta-galactosidase and 112 amino acids of the E. tenella protein of approximately 12 kilodaltons. Partially purified antigen, heat-killed recombinant bacterin, and live E. coli containing the recombinant coccidial antigen were used to immunize 1-week-old or newly hatched broiler chicks. Several immunization protocols were utilized, including boosts with partially purified beta-galactosidase-GX3262, bacterin, or small numbers of live E. tenella oocysts. After challenge with an experimental E. tenella infection, the birds were evaluated by scoring cecal lesions to determine the level of protection. The greatest degree of protection was seen after only a single immunization of 2-day-old birds with a live recombinant E. coli preparation. The results presented here identify GX3262 as a potential candidate coccidial vaccine antigen and provide evidence for the first time that newly hatched chickens can be successfully vaccinated with a recombinant antigen.

Production of monoclonal antibodies to salinomycin

Protein conjugates of salinomycin were prepared and utilized to produce murine monoclonal antibodies (MAbs) in the BALB/c-P3X63.Ag 8.653 fusion system. Several antibodies were cloned, stabilized, and evaluated for cross-reactivity to other ionophorous antibiotics. Selected antibodies were used to develop quantitative assays for salinomycin by means of an enzyme-linked immunosorbent assay (ELISA). These assays were sensitive to 50 ng of salinomycin.

Effect of elicitation on peritoneal macrophage subpopulations: size distributions, ectoenzyme phenotypes and antitumor activity

Resident (R), Brewer's thioglycollate broth (TG) and C. parvum (CP)-elicited murine peritoneal cell populations were separated into subpopulations by centrifugation on discontinuous Ficoll gradients consisting of layers of 4, 6, 8 and 10% Ficoll. The resulting subpopulations were shown to be distinct on the basis of cell size, ectoenzyme phenotypes and antitumor activity. The cell size distributions were analyzed by means of a Coulter channelyzer and software developed for a computer. The 4-6% Ficoll interface fraction comprised the smallest macrophages, with most cells in this subpopulation appearing to range in cell volume from 150-275 microns 3. The largest sized macrophages were found in the 10%-pellet fraction, with most cells appearing to range in cell volume from 300-600 microns 3. The ectoenzyme phenotypes of the R, TG and CP unseparated macrophage populations were significantly different. Moreover, the ectoenzyme phenotypes of the smallest, (4-6% Ficoll interface) subpopulation in the R and CP macrophages differed from the other subpopulations. Reduction in alkaline phosphodiesterase 1 (APD-1) ectoenzyme activity (as compared with unseparated R macrophages) appeared to be a marker for acquisition of antitumor activity. The small CP macrophages (4-6% Ficoll interface) showed no antitumor activity while the unseparated CP macrophages and all other CP macrophages subpopulations exhibited antitumor activity. The CP macrophage unseparated population and the subpopulations with antitumor activity expressed reduced ADP-1 activity. Conversely, the R or TG macrophage unseparated populations and their subpopulations, along with the CP macrophage 4-6% subpopulation, lacked antitumor activity and failed to show a change in ADP-1 ectoenzyme activity.