Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 8, 2004
Publication Date: July 7, 2004
Citation: Fetterer, R.H., Miska, K.B., Jenkins, M.C., Barfield, R.C. 2004. A conserved 19 kda Eimeria tenella antigen is a profilin-like protein. Journal of Parasitology. 90:1321-1328.
Interpretive Summary: Coccidiosis has significant economic compact on the poultry industry causing world-wide losses estimated to be over 800 million annually. Losses are due to reduced weight gains and feed efficiency caused by infection of birds. Current control strategies are based on prophylactic chemical treatment of birds with medicated feed. Alternative controls using vaccines show promise to control coccidiosis and reduce the need for use of drug-containing feeds. These vaccines consist of one or more defined proteins that stimulate immunity to cocccidia infection in vaccinated birds and thus reduce the impact of the disease on the infected birds. Development of vaccines have been hampered by lack of knowledge of biological function of proteins that may be useful antigenic components of a vaccine. In the current research we investigated the function of a previously described antigen, SZ-1, that stimulates immunity to coccidia infections. This protein was shown to be expressed in the developmental stages of the important coccidia species and was distributed in the parasites cytoplasm. Analysis of the gene for the protein indicated it had molecular properties similar to profilins which are proteins which regulate motility. Biochemical studies confirm that SZ-1 has functional properties related to profilins. The results are the first report of profilin in avian coccidiosis and demonstrated the function of a potentially important vaccine component.
A wide range of recombinant proteins from Eimeria species have been reported to offer some degree of protection against infection and disease, but specific biological function of these proteins is largely unknown. Previous studies have demonstrated a 19 k Da protein of unknown function designated SZ1 in sporozoites and merozoites of Eimeria acervulina that can be used to confer at least partial protection against coccidiosis. RT-PCR indicated that the gene for SZ-1 is expressed by all the asexual stages of E. tenella. Rabbit antisera to recombinant SZ1 recognized an approximately 19 k Da protein from extracts of Eimeria tenella sporozoites, merozoites, sporulated oocysts and oocysts in various stages of sporulation. Immuno fluorescence antibody staining indicated specific staining of E.tenella, sporozoites, and merozoites. Staining was most intense in the cytoplasm of the posterior end of the parasite. The structure of the gene for E. tenella SZ-1 deduced from the E. tenella genome indicated a conserved domain for the actin-binding protein profilin. A conserved binding site for poly-l-proline (PLP), characteristic of profilin was also observed. SZ-1 was separated from soluble extract of E. tenella proteins by affinity chromatography using a PLP ligand confirming the ability of SZ-1 to bind PLP. SZ-1 also partially inhibited the polymerization of actin. The current results taken together, suggest a hypothesis that SZ-1 is related to profilin.