Submitted to: Molecular and Biochemical Parasitology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/6/2006
Publication Date: 2/13/2007
Citation: Miska, K.B., Fetterer, R.H., Lillehoj, H.S., Jenkins, M.C., Allen, P.C., Harper, S. 2007. The first characterization of macrophage migration inhibitory factor (mif) molecules from apicomplexan parasites belonging to genus Eimeria, the causative agents of chicken coccidiosis. Molecular and Biochemical Parasitology. 151:173-183. Interpretive Summary: Eimeria are single celled parasites that infect chickens and cause an intestinal infection called coccidiosis that leads to economic losses sustained by the poultry industry. Through molecular characterization of Eimeria parasites, a novel molecule has been discovered in these species which is related to a mammalian cytokine (molecules which regulate immune responses) named Macrophage Migration Inhibitory Factor (MIF). It is very interesting why a single celled organism contains such molecules, especially since Eimeria are not capable of complex immune responses. It is however, possible that Eimeria uses MIF to evade host recognition. In order to begin characterization of MIF in Eimeria, the gene encoding this protein was cloned, sequenced, and a protein was expressed using recombinant methods. Our findings suggest that MIF is only present during the intracellular parts of the life cycle. This protein is also secreted out of the parasite. Both these findings support the possibility that MIF may be an immuno-regulatory protein in Eimeria. Future studies will be carried out which will specifically address the role of MIF in Eimeria since its basic characterization has now been achieved.
Technical Abstract: Macrophage Migration Inhibitory Factor (MIF) was the first cytokine to be identified almost forty years ago. Homologues of MIF have been recently isolated from invertebrates, making it an interesting molecule from an evolutionary as well as functional perspective. The present study represents the first report of MIF homologues in apicomplexan parasites, belonging to the genus Eimeria. A single full-length clone was isolated from Eimeria acervulina that shared between 35-38% amino acid identity with the MIFs of vertebrates. A MIF cDNA from E. tenella shared 64% amino acid identity with E. acervulina MIF. The mRNA expression was highest in merozoites, with developing oocysts and sporozoites expressing low to undetectable levels. Protein expression patterns were nearly identical to that observed by RT-PCR. Immuno-fluorescence staining of E. acervulina merozoites indicated that MIF is distributed throughout the cytosol, and appears to be concentrated in the apical end of the parasite. Presence of MIF was detected in ES products collected from E. acervulina merozoites, and isoelectric focusing indicated that 3 MIF isoforms are present in this stage. Phylogenetic analysis revealed that apicomplexan MIF sequences form a sister relationship to MIF-like molecules from Arabidopsis thaliana.