Abstract:Eimeria tenella is the causative agent of coccidiosis in poultry. Infection of the chicken intestine begins with ingestion of sporulated oocysts releasing sporocysts, which in turn release invasive sporozoites. The monoclonal antibody E2E5 recognizes wall-forming body type II (WFBII) in gametocytes and the WFBII-derived inner wall of oocysts. Here we describe that this antibody also binds to the stieda body of sporocysts and significantly impairs in vitro excystation of sporozoites. Using affinity chromatograp… Show more
“…We have recently obtained similar results with both E. tenella and E. acervulina, demonstrating the conservation of these proteins and the process of wall formation (SI Belli et al, unpublished observations). Recently, Krücken et al (2008) have confirmed the presence of two E. tenella homologues of EmGam56 and, additionally, reported the discovery of a 22 kDa antigen in the macrogametocytes of E. tenella. Like the other proteins so far characterized, antibodies to this protein react with WFB2 and the inner layer of the oocyst wall.…”
Section: Proteins Of the Oocyst Wallmentioning
confidence: 86%
“…It is notable for another reason, namely that its gene is present in extremely high copy number (in contrast to the single copies of the genes for, for example, EmGam56 and EmGam82), indicating that it may be important in oocyst wall formation via a mechanism distinct from that of the tyrosine-rich proteins. As yet, no information is available about whether this 22 kDa protein is processed into smaller polypeptides nor how it is incorporated into the oocyst wall, though its involvement in stabilizing the oocyst wall via cross-links between histidine and catechols, as seen in insect cuticles (Christensen et al 1991, Xu et al 1997, Kerwin et al 1999, is a distinct possibility (Krücken et al 2008). …”
“…We have recently obtained similar results with both E. tenella and E. acervulina, demonstrating the conservation of these proteins and the process of wall formation (SI Belli et al, unpublished observations). Recently, Krücken et al (2008) have confirmed the presence of two E. tenella homologues of EmGam56 and, additionally, reported the discovery of a 22 kDa antigen in the macrogametocytes of E. tenella. Like the other proteins so far characterized, antibodies to this protein react with WFB2 and the inner layer of the oocyst wall.…”
Section: Proteins Of the Oocyst Wallmentioning
confidence: 86%
“…It is notable for another reason, namely that its gene is present in extremely high copy number (in contrast to the single copies of the genes for, for example, EmGam56 and EmGam82), indicating that it may be important in oocyst wall formation via a mechanism distinct from that of the tyrosine-rich proteins. As yet, no information is available about whether this 22 kDa protein is processed into smaller polypeptides nor how it is incorporated into the oocyst wall, though its involvement in stabilizing the oocyst wall via cross-links between histidine and catechols, as seen in insect cuticles (Christensen et al 1991, Xu et al 1997, Kerwin et al 1999, is a distinct possibility (Krücken et al 2008). …”
“…7), and this may have a direct link with the stockpiling and eventual cross-linking of the oocyst wall glycoproteins Gam56 and Gam82 (6,7). It is possible that O glycosylation is required for trafficking of these proteins to the oocyst wall, a hypothesis supported by the conservation of an O glycosylation motif in both EmGam56 and EtGam56 and an additional oocyst wall protein of E. tenella, EtGam22 (19).…”
Section: Discussionmentioning
confidence: 99%
“…EmGam56 and EmGam82 are processed into smaller peptides prior to incorporation into the oocyst wall, where proposed cross-linking occurs to ensure the formation of a stable extracellular matrix (5,6). EtGam56, an E. tenella homologue of EmGam56, appears to undergo a similar process of truncation prior to oocyst wall formation (19,25), implying that this mechanism is strongly conserved within the Eimeria genus.…”
mentioning
confidence: 99%
“…It is unclear why these wallforming proteins require glycosylation; however, the strong conservation of O-glycosylation motifs in both EmGam56 and EtGam56 (19) implies that it is an important process. N-Acetylgalactosamine (GalNAc) has also been implicated as the likely glycan moiety of glycoproteins present in the oocyst wall of the related apicomplexan, Cryptosporidium parvum, with a proposed role in host cell attachment (20,35).…”
Sexual-stage glycoproteins of Eimeria are important components of the oocyst wall, a structure that ensures the efficient transmission of these and related parasites. In this study, the primary enzyme in the glycosylation pathway of Eimeria tenella, glucosamine:fructose-6-phosphate aminotransferase (EtGFAT), has been characterized as a macrogamete-specific protein. Although the transcription of EtGFAT was observed early in macrogamete development, protein expression was restricted to mature macrogametes, prior to their conversion into unsporulated oocysts. Genes coding for three other enzymes required for N-acetylgalactosamine (GalNAc) synthesis were also transcribed during E. tenella macrogamete development. Gene transcription of the enzyme responsible for the O-linked transfer of GalNAc to proteins, EtGalNAc-T, was upregulated primarily in unsporulated oocyst stages, and accordingly, a significant increase in GalNAc levels was observed in E. tenella gametocytes and oocysts. Gam56 and Gam82, two well-characterized glycoproteins of Eimeria macrogametes and the oocyst wall, contain high levels of GalNAc and represent probable targets of GalNAc O linkage. It appears that the glycosylation pathway, specifically relating to the formation of GalNAc O links, is dramatically upregulated in E. tenella sexual stages and may play a role in directing a number of macrogamete proteins to the developing oocyst wall.
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