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ABSTRACT: Lymphoblastoid cell lines 265(L) and 990(O) are monoclonal lymphomas, derived respectively from liver and ovarian tumours, generated in inbred P-line (MHC B(19)/B(19)) chickens infected with RB-1B strain of Marek's disease virus (MDV) and pRB-1B5 BAC clone respectively. These were inoculated into inbred, MDV-susceptible, P-line chickens by intra-venous or intra-abdominal routes. Additional groups of birds were vaccinated using 1000 plaque-forming units of CVI988 vaccine 8 days prior to inoculation of the cell lines. Non-vaccinated birds developed visceral Marek's disease tumours with an increased rate 30 to 60 days post inoculation. Vaccination prevented tumour and disease development in challenged birds. TCRβ repertoire analysis by spectratyping and sequencing of the inoculum was used to track tumour identity in primary tumours and tumour cell lines derived from inoculated birds. These data revealed that the tumours were a consequence of de novo virus infection and not metastasis and expansion of the inoculated tumour cells. Moreover, the data showed that the two MDV-derived cell lines were not transplantable even in syngeneic P-line birds. The data also demonstrated the application of spectratyping as a tool to track tumour identity in lymphoma transplantation studies.
Avian Pathology 12/2012; 41(6):589-98. · 1.71 Impact Factor
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Damer P Blake,
Halimah Alias,
Karen J Billington,
Emily L Clark,
Mohd-Noor Mat-Isa,
Ahmad-Fuad-Hilmi Mohamad,
Mohd-Rashdi Mohd-Amin,
Yea-Ling Tay, Adrian L Smith,
Fiona M Tomley,
Kiew-Lian Wan
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ABSTRACT: Apicomplexan parasites are serious pathogens of animals and man that cause diseases including coccidiosis, malaria and toxoplasmosis. The importance of these parasites has prompted the establishment of genomic resources in support of developing effective control strategies. For the Eimeria species resources have developed most rapidly for the reference Eimeria tenella Houghton strain (http://www.genedb.org/Homepage/Etenella). The value of these resources can be enhanced by comparison with related parasites. The well characterised immunogenicity and genetic diversity associated with Eimeria maxima promote its use in genetics-led studies on coccidiosis and recommended its selection for sequencing. Using a combination of sequencing technologies a first draft assembly and annotation has been produced for an E. maxima Houghton strain-derived clone (EmaxDB; http://www.genomemalaysia.gov.my/emaxdb/). The assembly of a draft genome sequence for E. maxima provides a resource for comparative studies with Eimeria and related parasites as demonstrated here through the identification of genes predicted to encode microneme proteins in E. maxima.
Molecular and Biochemical Parasitology 03/2012; 184(1):48-51. · 2.55 Impact Factor
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ABSTRACT: Lymphoid oncogenesis is a life threatening complication associated with a number of persistent viral infections (e.g. EBV and HTLV-1 in humans). With many of these infections it is difficult to study their natural history and the dynamics of tumor formation. Marek's Disease Virus (MDV) is a prevalent α-herpesvirus of poultry, inducing CD4+ TCRαβ+ T cell tumors in susceptible hosts. The high penetrance and temporal predictability of tumor induction raises issues related to the clonal structure of these lymphomas. Similarly, the clonality of responding CD8 T cells that infiltrate the tumor sites is unknown. Using TCRβ repertoire analysis tools, we demonstrated that MDV driven CD4+ T cell tumors were dominated by one to three large clones within an oligoclonal framework of smaller clones of CD4+ T cells. Individual birds had multiple tumor sites, some the result of metastasis (i.e. shared dominant clones) and others derived from distinct clones of transformed cells. The smaller oligoclonal CD4+ cells may represent an anti-tumor response, although on one occasion a low frequency clone was transformed and expanded after culture. Metastatic tumor clones were detected in the blood early during infection and dominated the circulating T cell repertoire, leading to MDV associated immune suppression. We also demonstrated that the tumor-infiltrating CD8+ T cell response was dominated by large oligoclonal expansions containing both "public" and "private" CDR3 sequences. The frequency of CD8+ T cell CDR3 sequences suggests initial stimulation during the early phases of infection. Collectively, our results indicate that MDV driven tumors are dominated by a highly restricted number of CD4+ clones. Moreover, the responding CD8+ T cell infiltrate is oligoclonal indicating recognition of a limited number of MDV antigens. These studies improve our understanding of the biology of MDV, an important poultry pathogen and a natural infection model of virus-induced tumor formation.
PLoS Pathogens 05/2011; 7(5):e1001337. · 9.13 Impact Factor
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ABSTRACT: Apicomplexan parasites are responsible for a myriad of diseases in humans and livestock; yet despite intensive effort, development of effective sub-unit vaccines remains a long-term goal. Antigenic complexity and our inability to identify protective antigens from the pool that induce response are serious challenges in the development of new vaccines. Using a combination of parasite genetics and selective barriers with population-based genetic fingerprinting, we have identified that immunity against the most important apicomplexan parasite of livestock (Eimeria spp.) was targeted against a few discrete regions of the genome. Herein we report the identification of six genomic regions and, within two of those loci, the identification of true protective antigens that confer immunity as sub-unit vaccines. The first of these is an Eimeria maxima homologue of apical membrane antigen-1 (AMA-1) and the second is a previously uncharacterised gene that we have termed 'immune mapped protein-1' (IMP-1). Significantly, homologues of the AMA-1 antigen are protective with a range of apicomplexan parasites including Plasmodium spp., which suggest that there may be some characteristic(s) of protective antigens shared across this diverse group of parasites. Interestingly, homologues of the IMP-1 antigen, which is protective against E. maxima infection, can be identified in Toxoplasma gondii and Neospora caninum. Overall, this study documents the discovery of novel protective antigens using a population-based genetic mapping approach allied with a protection-based screen of candidate genes. The identification of AMA-1 and IMP-1 represents a substantial step towards development of an effective anti-eimerian sub-unit vaccine and raises the possibility of identification of novel antigens for other apicomplexan parasites. Moreover, validation of the parasite genetics approach to identify effective antigens supports its adoption in other parasite systems where legitimate protective antigen identification is difficult.
PLoS Pathogens 01/2011; 7(2):e1001279. · 9.13 Impact Factor
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ABSTRACT: Eimeria maxima is one of the seven Eimeria spp. that infect the chicken and cause the disease coccidiosis. The well characterised immunogenicity and genetic diversity associated with E. maxima promote its use in genetics-led studies on avian coccidiosis. The development of a genetic map for E. maxima, presented here based upon 647 amplified fragment length polymorphism markers typed from 22 clonal hybrid lines and assembled into 13 major linkage groups, is a major new resource for work with this parasite. Comparison with genetic maps produced for other coccidial parasites indicates relatively high levels of genetic recombination. Conversion of ∼14% of the markers representing the major linkage groups to sequence characterised amplified region markers can provide a scaffold for the assembly of future genomic sequences as well as providing a foundation for more detailed genetic maps. Comparison with the Eimeria tenella genetic map produced 10years ago has revealed a less biased marker distribution, with no more than nine markers mapped within any unresolved heritable unit. Nonetheless, preliminary bioinformatic characterisation of the three largest publicly available genomic E. maxima sequences suggest that the feature-poor/feature-rich structure which has previously been found to define the first sequenced E. tenella chromosome also defines the E. maxima genome. The significance of such a segmented genome and the apparent potential for variation in genetic recombination will be relevant to haplotype stability and the longevity of future anticoccidial strategies based upon multiple loci targeted by novel chemotherapeutic drugs or recombinant subunit vaccines.
International journal for parasitology 10/2010; 41(2):263-70. · 3.39 Impact Factor
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ABSTRACT: The repertoire of gut associated T cells is shaped by exposure to microbes, including the natural enteric microflora. Previous studies compared the repertoire of gut associated T cell populations in germ free (GF) and conventional mammals often focussing on intra-epithelial lymphocyte compartments. Using GF, conventional and monocolonised (gnotobiotic) chickens and chicken TCRbeta-repertoire analysis techniques, we determined the influence of microbial status on global and regional enteric TCRbeta repertoires. The gut of conventionally reared chickens exhibited non-Gaussian distributions of CDR3-lengths with some shared over-represented peaks in neighbouring gut segments. Sequence analysis revealed local clonal over-representation. Germ-free chickens exhibited a polyclonal, non-selected population of T cells in the spleen and in the gut. In contrast, gnotobiotic chickens exhibited a biased repertoire with shared clones evident throughout the gut. These data indicate the dramatic influence of enteric microflora complexity on the profile of TCRbeta repertoire in the gut at local and global levels.
Developmental and comparative immunology 11/2009; 34(4):406-17. · 3.29 Impact Factor
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ABSTRACT: The development of quantitative real-time polymerase chain reaction (PCR) assays specific to Eimeria acervulina, Eimeria maxima, Eimeria necatrix and Eimeria tenella is described and validated. The PCR templates adopted include a fragment of a gene encoding a microneme protein and previously characterized species-specific random amplified polymorphic DNA (RAPD) sequences. The sensitivity of each assay allowed the consistent detection of between one and 10 parasite genomes, equivalent to between one or two sporulated oocysts or a fraction of a single mature schizont, unaffected by the presence of chicken (host) or other Eimeria species DNA. Regression coefficients in excess of 0.99 over linear ranges of at least six orders of magnitude, together with comparable PCR efficiencies, demonstrated the robust reproducibility of each assay and suggest that two or more may be successfully multiplexed. The species-specific assays described here, combined with a previously published generic Eimeria species real-time PCR, provide valuable components in a "tool box" to accurately quantify the presence of specific Eimeria species in environmental or within-host phases of the lifecycle with little specialist knowledge. The application of these assays may benefit chicken husbandry, veterinary practice, quality control of live vaccine production and scientific research.
Avian Pathology 03/2008; 37(1):89-94. · 1.71 Impact Factor
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ABSTRACT: Human enteritis resulting from the consumption of poultry products contaminated with serovars of Salmonella enterica remains a major public-health concern. Reducing food contamination by preventing or controlling infection in the chicken during rearing is an attractive solution. An accurate understanding of the mechanisms of immunity to Salmonella infection in the chicken will help to focus the development of vaccines for birds and prevent contaminated products from entering the human food chain. Infection is primarily restricted to the intestinal lumen when chickens are infected with S. enterica serovars Typhimurium or Enteritidis, where they persist for many weeks. High titers of Salmonella-specific antibodies are observed following infection and demonstrate a high degree of cross-reactivity against other serovars. However, depletion of B cells and, therefore, removal of the capacity for antibody production in the chicken does not exacerbate the infection following either primary or secondary challenge.
Expert Review of Anticancer Therapy 11/2007; 5(5):873-81. · 3.28 Impact Factor
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ABSTRACT: Eimeria species infect livestock in a host-specific manner and are the cause of the disease, coccidiosis. Control of Eimeria species is essential and is currently dominated by chemotherapy; with vaccination using formulations of live wild-type or attenuated parasites an increasing option. A new generation of subunit, live-vector or DNA vaccination strategies is being sought and determining the identity of suitable antigens remains difficult. Some past and present methods of controlling avian coccidia are discussed briefly and we describe progress with a novel approach to identify immunoprotective antigens as vaccine candidates.
Vaccine 08/2007; 25(30):5540-7. · 3.77 Impact Factor
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ABSTRACT: The Peyer's patches (PP) and mesenteric lymph nodes (MLN) are structural components of the gut-associated lymphoid tissues and contribute to the induction of immune responses toward infection in the gastrointestinal tract. These secondary lymphoid organs provide structural organization for efficient cellular interactions and the initiation of primary adaptive immune responses against infection. Immunity against primary infection with the enteric apicomplexan parasite, Eimeria vermiformis, depends on the rapid induction of local Th1 responses. Lymphotoxin (LT)-deficient mice which have various defects in secondary lymphoid organs were infected with E. vermiformis. The relative susceptibility of LTalpha(-/-), LTbeta(-/-), LTalpha(+/-)beta(+/-) mice and bone marrow chimeras, indicated that rapid protective Th1 responses required both PP and MLN. Moreover, the timing of Th1 induction in both MLN and gut was dependent on the presence of PP suggesting a level of cooperation between immune responses induced in these distinct lymphoid structures. The delay in Th1 induction was attributable to the delayed arrival of a broad range of dendritic cell subsets in the MLN and a substantial reduction of CD8alpha(-)CD11b(high) B220(-) dendritic cells in PP-deficient mice.
The Journal of Immunology 07/2006; 176(12):7533-41. · 5.79 Impact Factor
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ABSTRACT: Salmonella enterica serovar Typhimurium colonizes the gut of chickens and is cleared from the intestine within about 3 weeks. Infection induces high levels of specific antibody, but B cells do not play an essential role in clearance of primary infection or in the enhanced clearance after secondary challenge.
Infection and Immunity 03/2006; 74(2):1442-4. · 4.16 Impact Factor
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ABSTRACT: The influence of host genotype on susceptibility to infection with Eimeria species has long been recognised, but beyond monitoring pathological severity or magnitude of oocyst excretion attempts to quantify fluctuations in parasite reproduction within the host have previously relied upon labour-intensive microscopic analysis. The development and application of a quantitative real-time PCR assay has opened this biological 'black box', permitting the sensitive and reproducible enumeration of parasite genomes throughout the course of infection. Generic and species-specific quantitative PCR methods are described, based upon the conserved 5S ribosomal RNA coding sequence of nine avian and murine Eimeria species and the Eimeria maxima MIC1 gene, respectively. These complementary assays have been applied to study the influence of host genotype on resistance to infection with E. maxima, revealing significant differences in parasite load between 'resistant' Line C and 'susceptible' Line 15I inbred chickens 5 days after infection. Parasite DNA remained detectable up to 20 days post-infection; 11 days after the last oocysts had been detected leaving the host.
International Journal for Parasitology 02/2006; 36(1):97-105. · 3.39 Impact Factor
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ABSTRACT: Eimeria maxima, the most immunogenic of the Eimeriidae that infect the chicken, is characterized by the presence of antigenic diversity within field isolates. In priming/challenge experiments immunity to homologous infection is essentially complete while immunity against challenge by a heterologous strain is often only partial. The phenotype "escape from immune protection" is known to be influenced by both host and parasite genotypes but the impact of varied immunization dose and schedule remains poorly documented. In this manuscript we report that an immunizing dose between <or=5 and <or=20 sporulated E. maxima oocysts is consistently capable of stimulating complete (>99.99%) protective immunity against challenge by 100 oocysts of a homologous strain. In contrast, complete immunity against a heterologous strain was never observed, although increasing the immunizing dose size did frequently reduce oocyst production arising from subsequent heterologous challenge. Differences in cross-protective immunizing capacity between two strains of E. maxima were evident as the H strain consistently stimulated a more potent protective immune response than the W strain. Similarly, increasing the number of immunizing doses of the E. maxima W strain (but not the H strain) increased immune protection against subsequent heterologous challenge. When combined with previously published data the results described here suggest that the E. maxima genome encodes a pool of antigens that are capable of stimulating an immune response cross-protective against more than one strain. These antigens supplement a separate restricted pool of antigens that are capable of stimulating stronger, but strain-specific, protective immune responses.
Avian Pathology 01/2006; 34(6):489-94. · 1.71 Impact Factor
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ABSTRACT: Chicken genetics and age affect resistance to enteric infection with Salmonella enterica serovar Typhimurium and were used to identify the immune responses that may contribute to rapid clearance. When birds were infected at 40 days of age, line 6(1) chickens cleared the infection more effectively than line N chickens, whereas when birds were infected at 10 days of age, both chicken lines were highly susceptible to infection. Antibody levels, T-cell responsiveness, and cytokine mRNA levels were all elevated during infection. A negative correlation between resistance and antigen-specific antibody production was observed in older chickens. However, this finding was not replicated for age-related resistance; we found that older chickens exhibited a stronger and more rapid antibody response than younger chickens. The levels of interleukin-1beta (IL-1beta) and gamma interferon (IFN-gamma) mRNA were similar in the spleens and cecal tonsils of both line 6(1) and line N chickens, except for higher levels of IL-1beta in the spleens of line 6(1) chickens at 6 days postinfection. Differences in the levels of IFN-gamma and IL-1beta 1beta mRNA between the lines were more apparent in younger chickens, but while the increases were greater than those observed in the older chickens, the clearance of enteric S. enterica serovar Typhimurium was much slower. The level of antigen-specific proliferation of splenocytes was associated with increased resistance in both experimental systems, and the strongest responses were observed in older and genetically resistant chickens. The data presented here implicate T-cell responses in the clearance of S. enterica serovar Typhimurium from the intestine of infected chickens.
Infection and Immunity 12/2005; 73(11):7509-16. · 4.16 Impact Factor
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ABSTRACT: CD1 molecules play an important role in the immune system, presenting lipid-containing antigens to T and NKT cells. CD1 genes have long been thought to be as ancient as MHC class I and II genes, based on various arguments, but thus far they have been described only in mammals. Here we describe two CD1 genes in chickens, demonstrating that the CD1 system was present in the last common ancestor of mammals and birds at least 300 million years ago. In phylogenetic analysis, these sequences cluster with CD1 sequences from other species but are not obviously like any particular CD1 isotype. Sequence analysis suggests that the expressed proteins bind hydrophobic molecules and are recycled through intracellular vesicles. RNA expression is strong in lymphoid tissues but weaker to undetectable in some nonlymphoid tissues. Flow cytometry confirms expression from one gene on B cells. Based on Southern blotting and cloning, only two such CD1 genes are detected, located approximately 800 nucleotides apart and in the same transcriptional orientation. The sequence of one gene is nearly identical in six chicken lines. By mapping with a backcross family, this gene could not be separated from the chicken MHC on chromosome 16. Mining the draft chicken genome sequence shows that chicken has only these two CD1 genes located approximately 50 kb from the classical class I genes. The unexpected location of these genes in the chicken MHC suggests the CD1 system was present in the primordial MHC and is thus approximately 600 million years old.
Proceedings of the National Academy of Sciences 07/2005; 102(24):8668-73. · 9.68 Impact Factor
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ABSTRACT: Based upon the recognition of antiviral compounds and single stranded viral RNA the Toll-like receptors TLR7 and TLR8 are suggested to play a significant role in initiating antiviral immune responses. Here we report the molecular characterization of the chicken TLR7/8 loci which revealed an intact TLR7 gene and fragments of a TLR8-like gene with a 6-kilobase insertion containing chicken repeat 1 (CR1) retroviral-like insertion elements. The chicken TLR7 gene encodes a 1047-amino-acid protein with 62% identity to human TLR7 and a conserved pattern of predicted leucine-rich repeats. Highest levels of chicken TLR7 mRNA were detected in immune-related tissues and cells, especially the spleen, caecal, tonsil and splenic B cells. Alternative spliced forms of TLR7 mRNA were identified in chicken, mouse and human and expressed in similar tissues and cell types to the major form of chicken TLR7. The chicken TLR7+ HD11 cell line and fresh splenocytes produced elevated levels of interleukin-1beta (IL-1beta) mRNA after exposure to the agonists R848 and loxoribine. Interestingly, none of the TLR7 agonists stimulated increased type I interferon (IFN) mRNA whereas poly(I:C) (a TLR3 agonist) up-regulated both chicken IFN-alpha and chicken IFN-beta mRNA. In contrast, TLR7 agonists, particularly R848 and poly(U) stimulated up-regulation of chicken IL-1beta, and chicken IL-8 mRNAs more effectively than poly(I:C). Stimulation of chicken TLR7 with R848 was chloroquine sensitive, suggesting signalling within an endosomal compartment, as for mammalian TLR7. The deletion of TLR8 in galliforms, accompanied with the differential response after exposure to TLR7 agonists, offers insight into the evolution of vertebrate TLR function.
Immunology 05/2005; 114(4):507-21. · 3.32 Impact Factor
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Muhammad Iqbal,
Victoria J Philbin,
G S K Withanage,
Paul Wigley,
Richard K Beal,
Marianne J Goodchild,
Paul Barrow,
Ian McConnell,
Duncan J Maskell,
John Young,
Nat Bumstead,
Yvonne Boyd, Adrian L Smith
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ABSTRACT: Toll-like receptors (TLRs) are a major component of the pattern recognition receptor repertoire that detect invading microorganisms and direct the vertebrate immune system to eliminate infection. In chickens, the differential biology of Salmonella serovars (systemic versus gut-restricted localization) correlates with the presence or absence of flagella, a known TLR5 agonist. Chicken TLR5 (chTLR5) exhibits conserved sequence and structural similarity with mammalian TLR5 and is expressed in tissues and cell populations of immunological and stromal origin. Exposure of chTLR5+ cells to flagellin induced elevated levels of chicken interleukin-1beta (chIL-1beta) but little upregulation of chIL-6 mRNA. Consistent with the flagellin-TLR5 hypothesis, an aflagellar Salmonella enterica serovar Typhimurium fliM mutant exhibited an enhanced ability to establish systemic infection. During the early stages of infection, the fliM mutant induced less IL-1beta mRNA and polymorphonuclear cell infiltration of the gut. Collectively, the data represent the identification and functional characterization of a nonmammalian TLR5 and indicate a role in restricting the entry of flagellated Salmonella into systemic sites of the chicken.
Infection and Immunity 05/2005; 73(4):2344-50. · 4.16 Impact Factor
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ABSTRACT: The Toll-like receptor (TLR) family of cell surface molecules represent a major component of the pattern recognition system, which enables both vertebrates and invertebrates to detect invading microorganisms and mount an anti-microbial response. The TLR repertoire of mouse and man has been intensively studied and in this manuscript we report the identification of ESTs with homology to chTLR5 and chTLR7, and independently confirm the identification of chTLR 1/6/10 and 3 in the EST databases. We have determined the mRNA expression patterns for seven chicken TLRs (chTLR) in a wide range of chicken tissues, isolated immune cell types and cultured cells. Some of the chTLR were expressed in most tissues (chTLR1/6/10, chTLR3, chTLR4 and chTLR5), whereas others exhibited more restricted expression patterns (chTLR2 type 1, type 2 and chTLR7). Similarly distinct patterns of chTLR expression were seen with innate and adaptive immune cell types isolated from peripheral blood or spleen and with cultured cells of somatic or immunological origin. An understanding of the TLR repertoire for different tissues, immune cell subsets and cultured cell types allows more refined interpretation of immune induction in response to chicken pathogens.
Veterinary Immunology and Immunopathology 04/2005; 104(1-2):117-27. · 2.08 Impact Factor
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ABSTRACT: Studies on the biology of the avian species of Eimeria are currently benefiting from the availability of a comprehensive sequence for the nuclear genome of Eimeria tenella. Allied to some recent advances in transgenic technologies and genetic approaches to identify protective antigens, some elements are now being assembled that should be helpful for the development of a new generation of vaccines. In the meantime, control of avian coccidiosis by vaccination represents a major success in the fight against infections caused by parasitic protozoa. Live vaccines that comprise defined populations of oocysts are used routinely and this form of vaccination is based upon the long-established fact that chickens infected with coccidial parasites rapidly develop protective immunity against challenge infections with the same species. Populations of wild-type Eimeria parasites were the basis of the first live vaccines introduced around 50 years ago and the more recent introduction of safer, live-attenuated, vaccines has had a significant impact on coccidiosis control in many areas of the world. In Europe the introduction of vaccination has coincided with declining drug efficacy (on account of drug resistance) and increasing concerns by consumers about the inclusion of in-feed medication and prospects for drug residues in meat. The use of attenuated vaccines throughout the world has also stimulated a greater interest in the vaccines that comprise wild-type parasites and, during the past 3 years worldwide, around 3x10(9) doses of each type of vaccine have been used. The need for only small numbers of live parasites to induce effective protective immunity and the recognition that Eimeria spp. are generally very potent immunogens has stimulated efforts to develop other types of vaccines. None has succeeded except for the licensing, within several countries in 2002, of a vaccine (CoxAbic vaccine; Abic, Israel) that protects via the maternal transfer of immunoglobulin to the young chick. Building on the success of viral vaccines that are delivered via the embryonating egg, an in ovo coccidiosis vaccine (Inovocox, Embrex Inc.) is currently in development. Following successful field trials in 2001, the product will be ready for Food and Drug Administration approval in 2005 and a manufacturing plant will begin production for sale in late 2005. Limited progress has been achieved towards the development of subunit or recombinant vaccines. No products are available and studies to identify potential antigens remain compromised by an absence of effective in vitro assays that correlate with the induction of protective immunity in the host. To date, only a relatively small portfolio of molecules has been evaluated for an ability to induce protection in vivo. Although Eimeria are effective immunogens, it is probable that to date none of the antigens that induce potent protective immune responses during the course of natural infection has been isolated.
Advances in Parasitology 02/2005; 60:285-330. · 4.39 Impact Factor
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ABSTRACT: The genomes of protozoan parasites encode thousands of gene products and identification of the subset that stimulates a protective immune response is a daunting task. Most screens for vaccine candidates identify molecules by capacity to induce immune responses rather than protection. This paper describes the core findings of a strategy developed with the coccidial parasite Eimeria maxima to rationally identify loci within its genome that encode immunoprotective antigens. Our strategy uses a novel combination of parasite genetics, DNA fingerprinting, drug-resistance and strain-specific immunity and centres on two strains of E. maxima that each induce a lethal strain-specific protective immune response in the host and show a differential response to anti-Eimeria chemotherapy. Through classical mating studies with these strains we have demonstrated that loci encoding molecules stimulating strain-specific protective immunity or resistance to the anti-coccidial drug robenidine segregate independently. Furthermore, passage of populations of recombinant parasites in the face of killing in the immune host was accompanied by the elimination of some polymorphic DNA markers defining the parent strain used to immunise the host. Consideration of the numbers of parasites recombinant for the two traits implicates very few antigen-encoding loci. Our data provide a potential strategy to identify putative antigen-encoding loci in other parasites.
Molecular and Biochemical Parasitology 12/2004; 138(1):143-52. · 2.55 Impact Factor
