Coccidiosis is a ubiquitous intestinal protozoan infection of poultry seriously impairing the growth and feed utilization of infected animals. Conventional disease control strategies have relied on prophylactic medication. Due to the continual emergence of drug resistant parasites in the field and increasing incidence of broiler condemnations due to coccidia, novel approaches are urgently needed to reduce economic losses. Understanding the basic biology of host-parasite interactions and protective intestinal immune mechanisms, as well as characterization of host and parasite genes and proteins involved in eliciting protective host responses are crucial for the development of new control strategy. This review will highlight recent developments in coccidiosis research with special emphasis on the utilization of cutting edge techniques in molecular/cell biology, immunology, and functional genomics in coccidia vaccine development. The information will enhance our understanding of host-parasite biology, mucosal immunology, and host and parasite genomics in the development of a practical and effective control strategy against Eimeria and design of nutritional interventions to maximize growth under the stress caused by vaccination or infection. Furthermore, successful identification of quantitative economic traits associated with disease resistance to coccidiosis will provide poultry breeders with a novel selection strategy for development of genetically stable, coccidiosis-resistant chickens, thereby increasing the production efficiency.
Animals ; Biotechnology/methods ; Chickens ; Coccidiosis/prevention&control/*veterinary ; Eimeria/*immunology ; Poultry Diseases/parasitology/*prevention&control ; *Protozoan Vaccines

Protective efficacy of vaccination with Neospora caninum multiple recombinant antigens against N. caninum infection was evaluated in vitro and in vivo. Two major immunodominant surface antigens (NcSAG1 and NcSRS2) and two dense granule proteins (NcDG1 and NcDG2) of N. caninum tachyzoites were expressed in E. coli, respectively. An in vitro neutralization assay using polyclonal antisera raised against each recombinant antigen showed inhibitory effects on the invasion of N. caninum tachyzoites into host cells. Separate groups of gerbils were immunized with the purified recombinant proteins singly or in combinations and animals were then challenged with N. caninum. Following these experimental challenges, the protective efficacy of each vaccination was determined by assessing animal survival rate. All experimental groups showed protective effects of different degrees against experimental infection. The highest protection efficacy was observed for combined vaccination with NcSRS2 and NcDG1. Our results indicate that combined vaccination with the N. caninum recombinant antigens, NcSRS2 and NcDG1, induces the highest protective effect against N. caninum infection in vitro and in vivo.
Animals ; Antibodies, Protozoan/immunology ; Antigens, Protozoan/immunology ; Cercopithecus aethiops ; Coccidiosis/prevention & control ; Dose-Response Relationship, Immunologic ; Gene Expression ; Gerbillinae ; Neospora/*immunology ; Protozoan Vaccines/*immunology ; Research Support, Non-U.S. Gov't ; Vaccines, Synthetic/immunology ; Vero Cells

To control coccidiosis without using prophylactic medications, a DNA vaccine targeting the gametophyte antigen Gam56 from Eimeria maxima in chickens was constructed, and the immunogenicity and protective effects were evaluated. The ORF of Gam56 gene was cloned into an eukaryotic expression vector pcDNA3.1(zeo)+. Expression of Gam56 protein in COS-7 cells transfected with recombinant plasmid pcDNA-Gam56 was confirmed by indirect immunofluorescence assay. The DNA vaccine was injected intramuscularly to yellow feathered broilers of 1-week old at 3 dosages (25, 50, and 100 microg/chick). Injection was repeated once 1 week later. One week after the second injection, birds were challenged orally with 5x10(4) sporulated oocysts of E. maxima, then weighed and killed at day 8 post challenge. Blood samples were collected and examined for specific peripheral blood lymphocyte proliferation activity and serum antibody levels. Compared with control groups, the administration of pcDNA-Gam56 vaccine markedly increased the lymphocyte proliferation activity (P<0.05) at day 7 and 14 after the first immunization. The level of lymphocyte proliferation started to decrease on day 21 after the first immunization. A similar trend was seen in specific antibody levels. Among the 3 pcDNA-Gam56 immunized groups, the median dosage group displayed the highest lymphocyte proliferation and antibody levels (P<0.05). The median dosage group had the greatest relative body weight gain (89.7%), and the greatest oocyst shedding reduction (53.7%). These results indicate that median dosage of DNA vaccine had good immunogenicity and immune protection effects, and may be used in field applications for coccidiosis control.
Animals ; Antibodies, Protozoan/blood ; Antigens, Protozoan/genetics/*immunology ; Cell Proliferation ; Chickens ; Coccidiosis/immunology/pathology/*prevention & control ; Disease Models, Animal ; Eimeria/genetics/*immunology ; Injections, Intramuscular ; Lymphocytes/immunology ; Protozoan Vaccines/administration & dosage/genetics/*immunology ; Vaccination/methods ; Vaccines, DNA/administration & dosage/genetics/*immunology

A novel recombinant Bacille Calmette-Guerin (rBCG) vaccine co-expressed Eimeria tenella rhomboid and cytokine chicken IL-2 (chIL-2) was constructed, and its efficacy against E. tenella challenge was observed. The rhomboid gene of E. tenella and chIL-2 gene were subcloned into integrative expression vector pMV361, producing vaccines rBCG pMV361-rho and pMV361-rho-IL2. Animal experiment via intranasal and subcutaneous route in chickens was carried out to evaluate the immune efficacy of the vaccines. The results indicated that these rBCG vaccines could obviously alleviate cacal lesions and oocyst output. Intranasal immunization with pMV361-rho and pMV361-rho-IL2 elicited better protective immunity against E. tenella than subcutaneous immunization. Splenocytes from chickens immunized with either rBCG pMV361-rho and pMV361-rho-IL2 had increased CD4+ and CD8+ cell production. Our data indicate recombinant BCG is able to impart partial protection against E. tenella challenge and co-expression of cytokine with antigen was an effective strategy to improve vaccine immunity.
Adjuvants, Immunologic/genetics/*metabolism ; Administration, Intranasal ; Animals ; Antigens, Protozoan/genetics/*immunology ; BCG Vaccine/administration & dosage/*genetics ; CD4-Positive T-Lymphocytes/immunology ; CD8-Positive T-Lymphocytes/immunology ; Chickens ; Coccidiosis/*prevention & control ; Disease Models, Animal ; Drug Carriers/administration & dosage ; Eimeria tenella/genetics/*immunology ; Genetic Vectors ; Injections, Subcutaneous ; Interleukin-2/genetics/*metabolism ; Protozoan Vaccines/administration & dosage/genetics/*immunology ; Spleen/immunology ; Vaccines, Synthetic/administration & dosage/genetics/immunology