Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 23, 2013
Publication Date: October 1, 2013
Citation: Fetterer, R.H., Schwarz, R., Miska, K.B., Jenkins, M.C., Barfield, R.C., Murphy, C. 2013. Characterization and localization of an Eimeria-specific protein in Eimeria maxima. Journal of Parasitology. 112(10):3401-3408. Interpretive Summary: Poultry coccidiosis, which is an intestinal disease caused by protozoal parasites, costs the US poultry industry millions of dollars annually. The primary control for the disease is through application of medications in the feed as birds are raised in confinement housing. Such medications are becoming both less effective because of increased resistance to the drugs and less desirable due to concerns about drug residues possibly remaining in the meat and environment. New control methods are needed. Coccidian parasites possess a precise and unique method to invade host cells which requires specialized paired organelles (rhobtries)for cellular invasion. Using antibody staining techniques we characterized a unique protein and determined that this protein is expressed during intra-cellular development. This protein, which is found in all the important species of this parasite, may play a role in regulating cellular invasion. Since the present results identify a novel target for developing new control strategies they are valuable to the poultry industry, parasitologist and poultry scientist and ultimately will benefit the consumer by reducing cost and improving quality of poultry products.
Technical Abstract: A recently completed analysis of Eimeria maxima transcriptome indentified a gene with homology to sequences expressed by E. tenella and E. acervulina but lacking homology with other organisms including other apicomplexans. This gene designated ESP codes for a protein with predicted molecular weight of 18.8 kDa. The ESP gene was cloned and the recombinant protein expressed in bacteria, purified for preparation of specific antisera. Quantitative RT-PCR indicated that relative expression of ESP is low in the unsporulated oocysts and after 24 hr of sporulation. However, relative expression nearly doubled after 48 hrs of sporlation and reached its highest expression levels in sporozoites (SZ) and merozoites (MZ). The protein is detectable by Western blot in both sporulated oocysts and in MZ but the relative molecular weight Mr) of the ESP is somewhat lower (17.5kDA) in these stages than observed in SZ (25.5 kDa). Immuno-localization by both light and electron microscopy indicated that the ESP is located in the MZ rhoptries but no specific staining of any SZ structures by ESP was detected. In addition, localization studies on intestinal sections recovered from birds 120 hr post-infection indicates that undeveloped oocysts do not stain with antiESP but staining of microgametocytes was observed. The results strongly indicate that ESP is a component of the rhoptry in E. maxima MZ but is unclear if the protein is stage specific or has a function in other developmental stages.