Protective oral immunization of chickens against Eimeria tenella with sporozoite surface antigens

Protective Immunity Induced by an Eimeria tenella Whole Sporozoite Vaccine Elicits Specific B-Cell Antigens

Simple Summary

Coccidiosis caused by Eimeria tenella is a dreadful disease with a significant economic impact to the poultry industry. The disease has been controlled by routine medication of feed with synthetic chemicals or ionophore drugs. However, the rising appearance of drug resistance and public demands for reduced drug use in poultry production have driven a dramatic change, replacing anticoccidial drugs with alternative methods, such as vaccination with either virulent or attenuated Eimeria oocysts. Based on preliminary studies, the immune protection evaluating whole-sporozoites of E. tenella vaccine was verified. After this vaccine provided successful protection, the humoral response of a heterologous species like the rabbit was compared with the natural host immune response. Several B-cells antigens from the E. tenella sporozoite suitable for a genetically engineered vaccine were identified. Vaccination with newly identified recombinant antigens offers a feasible alternative for the control of avian coccidiosis into the broiler barns favoring the gradual withdrawal of the anticoccidial drugs.

Abstract

This study investigated protection against Eimeria tenella following the vaccination of chicks with 5.3 × 10⁶E. tenella whole-sporozoites emulsified in the nanoparticle adjuvant IMS 1313 N VG Montanide™ (EtSz-IMS1313). One-day-old specific pathogen-free (SPF) chicks were subcutaneously injected in the neck with EtSz-IMS1313 on the 1st and 10th days of age. Acquired immunity was assayed through a challenge with 3 × 10⁴ homologous sporulated oocysts at 21 days of age. The anticoccidial index (ACI) calculated for every group showed the effectiveness of EtSz-IMS1313 as a vaccine with an ACI of 186; the mock-injected control showed an ACI of 18 and the unimmunized, challenged control showed an ACI of −28. In a comparison assay, antibodies from rabbits and SPF birds immunized with EtSz-IMS1313 recognized almost the same polypeptides in the blotting of E. tenella sporozoites and merozoites. However, rabbit antisera showed the clearest recognition pattern. Polypeptides of 120, 105, 94, 70, 38, and 19 kDa from both E. tenella life cycle stages were the most strongly recognized by both animal species. The E. tenella zoite-specific IgG antibodies from the rabbits demonstrated the feasibility for successful B cell antigen identification.

Vaccines against the avian enteropathogens Eimeria, Cryptosporidium and Salmonella

The worldwide poultry industry provides a substantial proportion of the nutritional requirement of the human population. To keep pace with the increasing demand for the high-quality, low-cost protein source that poultry provides, intensive rearing practices have been developed within the past few decades. For example, chickens are housed routinely in crowded environments under adverse conditions, and genetic strains have been selected for rapid growth, high protein-to-fat content and superior egg-laying characteristics. A major negative consequence of these practices has been an increase in the incidence of diseases. Enteric diseases in particular have emerged as a major problem threatening the future viability of the poultry industry. A variety of methods have been used to combat avian diseases in the commercial setting, including improved farm management practices, the use of antibiotic drugs, the selection of disease-resistant strains of chickens, and the manipulation of the chicken's immune system. In the latter category, the development of vaccines against the major avian diseases has become a priority in the poultry industry. This review will highlight recent progress in vaccine development against three major avian enteric pathogens: Eimeria, Cryptosporidium and Salmonella.

Immune responses in chickens against Eimeria tenella sporozoite antigen

Two-day old broiler chicks were subcutaneously immunized with Eimeria tenella sporozoite antigen (25 microg per chick) with or without adjuvants on 2 and 18 days of age and the effect of induced immunity was determined by challenging the chickens with 10(4) homologous sporulated oocysts at 32 days of age. Chicks immunized with sporozoite antigen emulsified in Freund's Complete Adjuvant (FCA) showed protection in terms of oocyst production, mortality and mean lesion scores. Antigen emulsified in FCA produced significant cell mediated immune responses (as assessed by lymphocyte migration inhibition test) from 12 to 30 days post-immunization. Antibody responses as assessed by enzyme linked immunosorbent assay were significant from 12 days postimmunization when the antigen was administered with or without adjuvants by subcutaneous route.

Iscom is an efficient mucosal delivery system for Mycoplasma mycoides subsp. mycoides (MmmSC) antigens inducing high mucosal and systemic antibody responses

The purpose of this study was to explore the iscom as a mucosal delivery system for Mycoplasma mycoides subsp. mycoides small colony (MmmSC) antigens. BALB/c female mice were immunised intranasally (i.n.) twice, 8 weeks apart with three different doses (3, 10 and 20 microg) or subcutaneously (s.c.) with 3 microg of M. mycoides antigens incorporated into iscoms. Mycoplasma cells were administered s.c. twice, 8 weeks apart at a dose of 3 microg or i.n. at 10 microg as for iscoms. Both i.n. and s.c. modes of immunisation with iscoms induced prominent primary serum antibody responses in a dose-dependent manner, which were efficiently boosted. Compared to whole mycoplasma cells, iscoms enhanced the total Ig and IgG subclass (IgG1, IgG2a and IgG2b) responses in serum and in lungs greatly, and this enhancement was more prominent after i.n. than after s.c. immunisation. By the i.n. mode of immunisation iscoms containing mycoplasma antigens induced a 60-fold higher IgA response in lungs than the whole cell antigen. Iscoms also induced substantially higher total Ig and IgG subclass responses in the lungs. By Western blot a reduced number of bands (7) were detected in lung secretion after both i.n. and s.c. immunisations with iscoms compared to a high number of bands (more than 30) detected by serum antibodies. Interestingly i.n. immunisation with iscoms induced antibodies in lungs as well as in serum to mycoplasma cell antigens which differed from those induced by s.c. immunisation as revealed by the Western blot patterns.

Progress on developing a recombinant coccidiosis vaccine

The past 10 years of research aimed at developing subunit vaccines against a number of apicomplexans, including Eimeria, Plasmodium and Toxoplasma, have, if anything, revealed the complex nature of parasite-host interactions. The Knowledge gained from this research has shown why developing a subunit vaccine based on a single recombinant antigen from one developmental stage of the parasite was an overly optimistic approach. Many apicomplexan parasites have acquired unique strategies to evade host immunity. The variable expression of genes encoding erythrocyte membrane protein 1 of Plasmodium falciparum [1] (Berendt et al. Parasitology 1994;108:S19-S28) exemplifies one such strategy. The particular mechanism for evading immune destruction depends on a number of interrelated factors, not least of which is the parasite life-cycle and the availability of susceptible hosts. The goal of any vaccine, be it an attenuated organism or a recombinant antigen, is to break the cycle of infection. The development of a recombinant vaccine against apicomplexan parasites will depend on identifying those antigens and intracellular processes that are vital to the parasite survival and those which exist merely as a way of evading immunity. The information that follows is a review of both molecular biology/biochemistry of eimerian parasites and factors that influence host immune responses to coccidia.

Oral vaccination against coccidiosis: responses in strains of mice that differ in susceptibility to infection with Eimeria vermiformis

Four strains of mice with different susceptibilities to Eimeria vermiformis were orally dosed with a crude antigen prepared from sporulated oocysts of the parasite, with or without cholera toxin as adjuvant. The effect on subsequent challenge infections depended on the resistance and susceptibility phenotypes of the host: oocyst production was reduced in susceptible C57BL/6 and NIH mice but increased in resistant BALB/c and C3H mice. Despite this contrast, no fundamental differences were detected between the immune responses of BALB/c and C57BL/6 mice, either to vaccination or after superimposed infection, but the suppressing and enhancing effects of vaccination were transmissible to naive recipients via suspensions of mesenteric lymph node cells. The results obtained are compared with those previously reported for parenterally immunized BALB/c and C57BL/6 mice.