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Eimeria species, of the Phylum Apicomplexa, cause the disease coccidiosis in poultry, resulting in severe economic losses every year. Transmission of the disease is via the faecal-oral route, and is facilitated by intensive rearing conditions in the poultry industry. Additionally, Eimeria has developed drug resistance against most anticoccidials used today, which, along with the public demand for chemical free meat, has lead to the requirement for an effective vaccine strategy. This review focuses on the history and current status of anticoccidial vaccines, and our work in developing the transmission-blocking vaccine, CoxAbic (Netanya, Israel). The vaccine is composed of affinity-purified antigens from the wall-forming bodies of macrogametocytes of Eimeria maxima, which are proteolytically processed and cross-linked via tyrosine residues to form the environmentally resistant oocyst wall. The vaccine is delivered via maternal immunization, where vaccination of laying hens leads to protection of broiler offspring. It has been extensively tested for efficacy and safety in field trials conducted in five countries and involving over 60 million offspring chickens from immunized hens and is currently the only subunit vaccine against any protozoan parasite to reach the marketplace.

The oocyst wall of apicomplexan parasites protects them from the harsh external environment, preserving their survival prior to transmission to the next host. If oocyst wall formation could be disrupted, then logically, the cycle of disease transmission could be stopped, and strategies to control infection by several organisms of medical and veterinary importance such as Eimeria, Plasmodium, Toxoplasma, Cyclospora, and Neospora could be developed. Here, we show that two tyrosine-rich precursor glycoproteins, gam56 and gam82, found in specialized organelles (wall-forming bodies) in the sexual stage (macrogamete) of Eimeria maxima are proteolytically processed into smaller glycoproteins, which are then incorporated into the developing oocyst wall. The identification of high concentrations of dityrosine and 3,4-dihydroxyphenylalanine (DOPA) in oocyst extracts by high-pressure liquid chromatography, together with the detection of a UV autofluorescence in intact oocysts, implicates dityrosine-and possibly DOPA-protein cross-links in oocyst wall hardening. In addition, the identification of peroxidase activity in the wall-forming bodies of macrogametes supports the hypothesis that dityrosine-and DOPA-mediated cross-linking might be an enzyme-catalyzed event. As such, the mechanism of oocyst wall formation in Eimeria, is analogous to the underlying mechanisms involved in the stabilization of extracellular matrices in a number of organisms, widely distributed in nature, including insect resilin, nematode cuticles, yeast cell walls, mussel byssal threads, and sea urchin fertilization membranes.Eimeria maxima is an intestinal parasite of chickens and is one of the causative agents of coccidiosis, contributing to costs on the order of billions of dollars per year to the poultry meat industry (34, 37). The life cycle of Eimeria includes asexual and sexual stages of development that lead to the formation of the infective form of the parasite, the oocyst (23). Prior to excretion, the oocyst is encapsulated by a hard barrier, the oocyst wall, which protects the parasite from the harsh external environment. Once excreted from the host, the oocyst develops further (sporulation) and is passed onto the next host via the fecal-oral route.The oocyst wall is a structure that is vital to the parasite and ensures the organism's survival and transmission to the next host. It is bilayered, composed of a 10-nm-thick lipid outer layer and a 90-nm-thick glycoprotein inner layer arising from the contents of specialized organelles called wall-forming bodies, which are found exclusively in the sexual stage (macrogamete or macrogametocyte) of the parasite (13,26,31). Progress towards understanding the mechanism of oocyst wall formation in Eimeria has been difficult due to the lack of a good culture system for studying the sexual stages of Eimeria and problems associated with isolating large quantities of parasites. However, with the advent of new technologies in proteomics and molecular biology, together with improved methods for the increased ...

Antiviral, antibacterial, and antiparasitic drugs and vaccines are essential to maintaining the health of humans and animals. Yet, their production can be slow and expensive, and efficacy lost once pathogens mount resistance. Chicken immunoglobulin Y (IgY) is a highly conserved homolog of human immunoglobulin G (IgG) that has shown benefits and a favorable safety profile, primarily in animal models of human infectious diseases. IgY is fast-acting, easy to produce, and low cost. IgY antibodies can readily be generated in large quantities with minimal environmental harm or infrastructure investment by using egg-laying hens. We summarize a variety of IgY uses, focusing on their potential for the detection, prevention, and treatment of human and animal infections.