Control of chicken coccidiosis

Effects of encapsulated cinnamaldehyde and citral on the performance and cecal microbiota of broilers vaccinated or not vaccinated against coccidiosis

This study investigated the effects of encapsulated cinnamaldehyde (CIN) and citral (CIT) alone or in combination (CIN + CIT) on the growth performance and cecal microbiota of nonvaccinated broilers and broilers vaccinated against coccidiosis. Vaccinated (1,600) and nonvaccinated (1,600) 0-day-old male Cobb500 broilers were randomly allocated to 5 treatments: basal diet (control) and basal diet supplemented with bacitracin (BAC, 55 ppm), CIN (100 ppm), CIT (100 ppm), and CIN (100 ppm) + CIT (100 ppm). In general, body weight (BW) and feed conversion ratio were significantly improved in birds treated with BAC, CIN, CIT, and CIN + CIT (P < 0.05) but were all decreased in vaccinated birds compared with nonvaccinated birds (P < 0.05). Significant interactions (P < 0.05) between vaccination and treatments for average daily gain during the periods of starter (day 0–9) and BW on day 10 were noted. Broilers receiving vaccines (P < 0.01) or feed supplemented with BAC, CIN, CIT, or CIN + CIT (P < 0.01) showed reductions in mortality rate from day 0 to 28. The incidences of minor coccidiosis were higher (P < 0.05) in vaccinated birds than in nonvaccinated birds. Diet supplementation with BAC or tested encapsulated essential oils showed comparable effects on the coccidiosis incidences. Similar to BAC, CIN and its combination with CIT reduced both incidence and severity of necrotic enteritis (P < 0.05). No treatment effects were observed on the cecal microbiota at the phyla level. At the genus level, significant differences between vaccination and treatment groups were observed for 5 (Lactobacillus, Ruminococcus, Faecalibacterium, Enterococcus, and Clostridium) of 40 detected genera (P < 0.05). The genus Lactobacillus was more abundant in broilers fed with CIT, while Clostridium and Enterococcus were less abundant in broilers fed with CIN, CIT, or CIN + CIT in both the vaccinated and nonvaccinated groups. Results from this study suggested that CIN alone or in combination with CIT in feed could improve chicken growth performance to the level comparable with BAC and alter cecal microbiota composition.

Construction of DNA vaccines and their induced protective immunity against experimental Eimeria tenella infection

In an attempt to construct a DNA vaccine against chicken coccidiosis, the TA4 gene of Eimeria tenella strain BJ was ligated to the mammalian expression vector pcDNA3.1/Zeo(+) to give pcDNA3.1-TA4 (pcDT). Then, Et1A (E. tenella refractile body gene) was ligated to it, upstream, aiming to be expressed in fusion with TA4, giving pcDNA3.1-Et1A-TA4 (pcDET). The constructed DNA vaccines were given to broilers intramuscularly 10-15 min after the breasts had been pre-treated with 25% sucrose solution. At 7 days after the second vaccination, chickens were challenged with 3 x 10(4) sporulated oocysts of E. tenella BJ. The chickens were killed and the lesion scores of the ceca, the relative body-weight gains and the numbers of oocysts in the ceca of each group of chickens were calculated at day 8 post-inoculation. Results indicated that both pcDT and pcDET could induce protective immunity against coccidial challenge. Their use could obviously reduce oocyst output and alleviate chicken body-weight decrease due to coccidial infection. An anti-coccidial index of 160 was achieved with a treatment of 50 microg pcDET and 100 microg pcDT.

B-cell epitope mapping within the MA16 antigenic sequence found in Eimeria acervulina merozoites and sporozoites

Overlapping heptapeptides derived from the MA16 Eimeria acervulina antigenic sequence (Castle et al., 1991) were synthesised on polypropylene pins ('pepskan' technique, Cambridge Research Biochemicals, UK). Binding of antibodies from chickens and rabbits infected and immunised respectively with various species of Eimeria oocysts (E. acervulina, E. tenella, E praecox, E. necatrix and E. maxima), was examined using the coated pins as the solid phase of an enzyme immunoassay (EIA). Antigenicity of the overlapping synthetic heptapeptides was then analysed using a number of algorithms based on the amino acid sequence to predict secondary protein structure, hydrophilicity, acrophilicity and chain flexibility profiles. The antigenicity of this sequence appears to be quite different from that found for the E. tenella GX3264 antigenic sequence (Bhogal et al., 1992) whose profile was similarly examined (Talebi and Mulcahy, 1994) using the same rabbit and chicken anti-Eimeria oocyst sera.

High-resolution mapping of B-cell epitopes within an antigenic sequence from Eimeria tenella

Overlapping hexapeptides representing part of an Eimeria tenella antigenic sequence, shown to induce partial immunity to homologous challenge in chickens, were synthesized on polypropylene pins (Pepskan technique; Cambridge Research Biochemicals, Cambridge, United Kingdom). The binding to these hexapeptides of antibodies from chickens infected and rabbits immunized with five species of Eimeria was studied, using the coated pins as the solid phase of an enzyme-linked immunoassay. Antibody binding to most regions of the sequence was demonstrated, with peak areas of antigenicity correlating with the most hydrophilic regions. A particularly hydrophilic and antigenic area towards the N terminus of the sequence consists of a peptide motif repeated five times in the native antigen. Homologous antisera (chicken and rabbit anti-E. tenella antisera) differed in their pattern of reactivity from heterologous sera raised against other Eimeria species. While the former bound to fewer of the hexapeptides than the latter, they did so very strongly, indicating affinity maturation of the antibody response to E. tenella-specific sequences. No antibody reactivity to two regions of the sequence was detected. These regions occur in relatively hydrophilic areas and so are unlikely to be situated in transmembrane domains or in the interior of globular proteins. Synthetic peptides, as used in these experiments, make possible analysis of the fine specificity of immune responses and thus have a role to play in the development of novel vaccines for the control of coccidiosis.

Cross-protection against four species of chicken coccidia with a single recombinant antigen

A cDNA clone, SO7', from an Eimeria tenella cDNA library was inserted into the high-expression vector pJC264 and was expressed in Escherichia coli as a fusion protein, CheY-SO7', with a molecular mass of approximately 36 kDa. By using the purified recombinant antigen to immunize young chicks, it was demonstrated that a single dose, without adjuvant, not only protected against severe coccidiosis induced by infection with E. tenella but also protected chicks challenged with the heterologous species Eimeria acervulina, E. maxima, and E. necatrix. By using rabbit antiserum raised against recombinant CheY-SO7', Western blot (immunoblot) analysis of sporulated oocysts of all seven major species of chicken coccidia showed that all species tested contained proteins characteristic of the B class of antigens, of which CheY-SO7' is representative. It seems likely that a single B antigen could protect chickens against severe coccidiosis caused by infection with any of these Eimeria species. Although chicks exposed to prolonged, natural infection develop antibodies to B antigen, active immunization of young chicks with a protective dose of CheY-SO7' does not elicit a humoral antibody response, suggesting that the partial protection results from cell-mediated effector mechanisms. In addition, the cross-protective nature of the immunity indicates that the response to B antigen is different from that induced by natural infection, which elicits a species-specific immunity. To date, the protection induced by B antigen immunization, although remarkable for a single recombinant protein, is not sufficient to compete with prophylactic chemotherapy.

Protective immunization against the intestinal parasite Eimeria acervulina with recombinant coccidial antigen

The gene encoding an immunodominant Eimeria acervulina merozoite surface antigen (EAMZ250) was expressed in bacteria as a fusion peptide with the galactose-binding protein (GBP) of Escherichia coli. Recombinant and control antigens were administered to 1-wk-old chickens by peroral inoculation with live nonpathogenic bacteria that were expressing GBP-EAMZ250 or GBP protein. The immunization elicited antigen-specific humoral and cellular immune responses as measured by ELISA and T-cell blastogenesis assay. In addition, chickens immunized with recombinant GBP-EAMZ250 exhibited significant protection against weight loss and intestinal lesions after E. acervulina challenge. Bacterial transformants were recoverable from the upper and middle intestine of inoculated chickens for various times after immunization. These data indicate that oral administration of live E. coli expressing a recombinant E. acervulina antigen is an effective means of inducing resistance to coccidiosis.

Development of a genetically engineered vaccine against poultry coccidiosis

Coccidiosis is caused by infection with Eimeria spp. The disease is responsible for major economic loss to the poultry industry unless infections are controlled by anticoccidial drugs. John Ellis and Fiona Tomley discuss recent research on the characterization and cloning of antigens from Eimeria spp and advances towards the development of genetically engineered vaccines against poultry coccidiosis.

Immunization of chickens with live Escherichia coli expressing Eimeria acervulina merozoite recombinant antigen induces partial protection against coccidiosis

Inoculation of chickens with live Escherichia coli N6405 transformants containing a plasmid which encodes ampicillin resistance and an immunodominant p250 surface antigen of Eimeria acervulina merozoites induced partial protection against challenge with live coccidia. The inoculation with E. coli transformants induced antigen-specific immunoglobulin and cell-mediated immune responses. Challenge with infective oocysts of Eimeria acervulina enhanced both immune parameters, indicating that administration of live E. coli transformants served to prime the immune system for recognition of specific epitopes on the 250-kilodalton protein. Although the mechanism of antigen presentation is unclear, the data suggest that in vivo expression of recombinant merozoite antigen is operative. After administration, no E. coli N6405 transformants could be recovered from intestinal or fecal materials of inoculated chickens, as assessed by enumeration on selective medium. However, ampicillin-resistant E. coli originating from the normal flora and harboring the gene sequences for both antibiotic resistance and Eimeria acervulina merozoite surface protein could be recovered from these chickens. Furthermore, normal-flora E. coli transformants were capable of generating functional beta-lactamase product, as evidenced by their resistance to ampicillin, and immunoreactive E. acervulina merozoite recombinant antigen, as revealed by immunofluorescence staining with p250-specific antiserum.

Eimeria tenella and E. acervulina: lymphokines secreted by an avian T cell lymphoma or by sporozoite-stimulated immune T lymphocytes protect chickens against avian coccidiosis

The role of avian lymphokines as nonspecific immunomodulators of host immunity against the intracellular parasite Eimeria was investigated. Prophylactic treatment of normal chickens with crude cell-free supernatants obtained from JMV-1 culture, concanavalin A (Con A)-stimulated normal spleen cells, or sporozoite-stimulated immune T cells prior to inoculation with E. tenella or E. acervulina conferred significant protection. These crude cell-free culture supernatants also inhibited intracellular development of eimerian parasites in vitro. Avian macrophages pretreated with these supernatant preparations showed inhibitory activity against Eimeria. This inhibitory activity could not be ascribed to anti-Eimeria antibody, complement, or cell-free Marek's disease virus and was therefore considered to be due to immunomodulating lymphokines present in the culture supernatants. These results suggest that JMV-1-transformed T lymphoblastoid cells, immune T lymphocytes, and Con A-stimulated normal spleen cells secrete lymphokines that can enhance host immunity in a nonspecific manner and implicate cell-mediated immunity as a major mechanism of the protective host immune response against eimerian infections.

Characterization of a surface antigen of Eimeria nieschulzi (Apicomplexa, Eimeriidae) sporozoites

A monoclonal antibody (McAb 3C3) reacting with a pellicular antigen of Eimeria nieschulzi sporozoites has been selected among hybridomas produced against this organism by immunofluorescence assay. This antigen has been shown to be located on the zoite surface by immunofluorescence on living organisms. Capping and shedding of antigen-monoclonal antibody immune complexes was observed upon incubation at 37 degrees C. On western immunoblotting, two polypeptides at 22 and 26 kDa were recognized by McAb 3C3, whereas only one polypeptide of 22 kDa was immunoprecipitated by the same antibody after lactoperoxidase surface radio-iodination of sporozoites.

Parasite vaccines versus anti-parasite drugs: rivals or running mates?

Previous articles in this volume have considered the whole question of parasite vaccines from the immunological point of view. A backcloth of general concepts (Roitt, 1989) and strategies in the viral area (Schild, 1989) precedes consideration of problems specific to parasite vaccines (Mitchell, G. F. 1989). This leads on to reviews of progress to date in the development of vaccines for leishmaniasis (Modabber, 1989), malaria (Mitchell, G. H. 1989) and schistosomiasis (Sher, 1989) and in the development and use of veterinary vaccines (Morrison, 1989). I have been asked in this final chapter to take one step back from all of this and provide the alternative, chemotherapeutic, perspective. The reasons for the request are particularly pertinent, though rarely stated: antiparasite drugs already exist; if parasite vaccines are in fact developed, the way these drugs are used and the whole question of whether or not new ones are required, will have to be reconsidered. It is also a timely one: it is clear that the whole concept of a series of vaccines for the control of parasitic diseases has been so well sold, some would say oversold, that it is impacting on the resolve within the pharmaceutical industry to undertake new chemotherapeutic developments, at a time when this is already under severe strain because of financial considerations (Gutteridge, 1987 a). Hence my title: Parasite vaccines versus anti-parasite drugs: rivals or running mates?. I will try to answer it by, in turn, addressing three key questions. Why are we attempting to develop parasite vaccines? Will we be successful? If we are, will there still be a need for chemotherapy?

Characterization of a surface antigen of Eimeria tenella sporozoites and synthesis from a cloned cDNA in Escherichia coli

An antigenic surface protein of Eimeria tenella sporozoites has been identified that is the target of two neutralizing monoclonal antibodies Ptn 7.2A4/4 and Ptn 9.9D12. The antigen as isolated from the parasite is composed of a 17 kDa polypeptide and a 8 kDa polypeptide linked by a disulfide bridge. De novo synthesis of the antigen does not begin until approximately 16-20 h after the initiation of oocyst sporulation. A cDNA library was constructed using mRNA from sporulated oocysts and a clone encoding the antigen was isolated. The Ta4 gene encodes a single polypeptide of 25 kDa which contains the 17 and 8 kDa polypeptides. The protein has been synthesized in Escherichia coli either directly or as part of a beta-galactosidase fusion protein. The products synthesized in E. coli are single polypeptides and are not cleaved to two polypeptides as is seen in the parasite. The products accumulate in bacteria in an insoluble form which can be solubilized and renatured to an immunoreactive form.