Characterization of coccidial proteins by two-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis

From the Macro to the Micro: Gel Mapping to Differentiate between Sporozoites of Two Immunologically Distinct Strains of Eimeria maxima (Strains M6 and Guelph)

Two immunologically distinct strains of E. maxima were examined in this study: the M6 strain and the Guelph strain. The differential expression between the sporozoites of the two strains of E. maxima was determined by image analysis of 100 μg of protein from each strain separated by standard one- and conventional two-dimensional polyacrylamide gel electrophoresis. In addition to differences in both molecular weight and the electrophoretic mobility, differences in the intensity of polypeptide bands for example, GS 136.4 and M6 169 were explored. Pooled gels were prepared from each strain. A representative 2D-PAGE gel spanning a non-linear pH range of 3-10 of E. maxima strain M6 consisted of approximately 694 polypeptide spots with about 67 (9.6%) of the polypeptide spots being unique relative to the other strain. E. maxima strain GS had about 696 discernable polypeptide spots with 69 spots (9.9%) that differed from those of the M6 strain. In-depth characterization of the variable polypeptide spots; unique polypeptide spots (absence or presence) and shared polypeptide spots with modifications may lead to novel vaccine target in the form of multi-component, multi-stage, multi-immunovariant strains, multi-species subunit vaccine, and diagnostic probe for E. maxima.

Immunoproteomic technology offers an extraordinary diagnostic approach for Toxoplasma gondii infection

Immunoproteomic technology offers an exceptional tool to fill the blanks that still exist in diagnosis of Toxoplasma gondii infection despite its annotated sequence. The pitfalls of serological assays and current immunoproteomic approaches are accentuated, and new approaches are presented to improve the signal and to eliminate the noise produced by blocking-specific background. This review also highlights examples where immunoproteomic studies have contributed to broaden our understanding of toxoplasmosis diagnosis. Further promising solutions, which immunoproteomic technology can grant for toxoplasmosis diagnosis are part of an intense discussion.

A selective review of advances in coccidiosis research

Coccidiosis is a widespread and economically significant disease of livestock caused by protozoan parasites of the genus Eimeria. This disease is worldwide in occurrence and costs the animal agricultural industry many millions of dollars to control. In recent years, the modern tools of molecular biology, biochemistry, cell biology and immunology have been used to expand greatly our knowledge of these parasites and the disease they cause. Such studies are essential if we are to develop new means for the control of coccidiosis. In this chapter, selective aspects of the biology of these organisms, with emphasis on recent research in poultry, are reviewed. Topics considered include taxonomy, systematics, genetics, genomics, transcriptomics, proteomics, transfection, oocyst biogenesis, host cell invasion, immunobiology, diagnostics and control.

Cross-reactivity among antisera raised against five avian Eimeria species in the natural host and in rabbits

Water- and SDS-soluble antigens were prepared from purified sporulated oocysts of Eimeria acervulina, E. maxima, E. necatrix, E. praecox and E. tenella. Reactivity of . chicken hyperimmune anti-Eimeria sera, rabbit anti-oocyst and rabbit anti-sporozoite sera with the homologous and heterologous oocyst antigens were determined and cross-reactivities were expressed as a percentage of those homologous sera. The results demonstrated that the antisera from chickens infected naturally with Eimeria species differed in their reactivities from those of the rabbit antisera. Occurrence of a high level cross-reactivity among the chicken antisera may suggest that the development of parasites inside the host cells, or the production of substances during the life-cycle, affect the extent of immune responses and that most non-protective antibodies are cross-reactive.

Protein profiles of five avian Eimeria species

SDS-PAGE fingerprint studies of oocyst antigens of five major Eimeria species including E. acervulina, E. maxima, E. necatrix, E. praecox and E. tenella demonstrated that their protein patterns are different, but there are some shared proteins between species and at least one protein band (45 kDa) was conserved among the five species. In Western blot studies, some species-specific as well as a few shared immunogenic bands were identified and chicken anti-E.maxima sera reacted with the conserved protein band in oocyst antigens of all these species.

Development and validation of an ELISA for detecting antibodies to Eimeria tenella in chickens

The aim of this study was to develop and validate an ELISA for detecting chicken antibodies to Eimeria tenella. An initial comparison of merozoite and sporozoite antigen preparations revealed few differences in their ability to monitor the onset, kinetics and magnitude of the antibody response suggesting that both antigens would be equally useful for development of an ELISA. Furthermore the cross-reactivity of these antigens with sera from birds infected with chicken Eimeria species was similar. The merozoite antigen was selected for further evaluation because it was easier to prepare. Discrimination between sera from birds experimentally infected with E. tenella and birds maintained in an Eimeria-free isolation facility was excellent. In sera collected from free-range layers and commercial broilers there also appeared to be clear discrimination between infected and uninfected birds. The ELISA should prove useful for monitoring infectivity in vaccination programmes in layer and breeder flocks and for assessing the effectiveness of biosecurity measures in broiler flocks.

Global protein expression analysis in apicomplexan parasites: Current status

Members of the phylum Apicomplexa are important protozoan parasites that cause some of the most serious, and in some cases, deadly diseases in humans and animals. They include species from the genus Plasmodium, Toxoplasma, Eimeria, Neospora, Cryptosporidium, Babesia and Theileria. The medical, veterinary and economic impact of these pathogens on a global scale is enormous. Although chemo- and immuno-prophylactic strategies are available to control some of these parasites, they are inadequate. Currently, there is an urgent need to design new vaccines or chemotherapeutics for apicomplexan diseases. High-throughput global protein expression analyses using gel or non-gel based protein separation technologies coupled with mass spectrometry and bioinformatics provide a means to identify new drug and vaccine targets in these pathogens. Protein identification based proteomic projects in apicomplexan parasites is currently underway, with the most significant progress made in the malaria parasite, Plasmodium falciparum. More recently, preliminary two-dimensional gel electrophoresis maps of Toxoplasma gondii and Neospora caninum tachyzoites and Eimeria tenella sporozoites, have been produced, as well as for micronemes in E. tenella. In this review, the status of proteomics in the analysis of global protein expression in apicomplexan parasites will be compared and the challenges associated with these investigations discussed.

Analysis of cross-reactivity of five new chicken monoclonal antibodies which recognize the apical complex of Eimeria using confocal laser immunofluorescence assay

For Apicomplexa (members) the host cell invasion is realized with the help of the organelles located at the apical tip of parasites. In this research paper the characterization of five chicken monoclonal antibodies (mabs) produced against Eimeria acervulina sporozoites is described. All mabs reacted with molecules belonging to the apical complex of chicken Eimeria sporozoites. On immunofluorescence assay (IFA) one mab, 8E-1, recognized an apical tip molecule present on all chicken Eimeria sporozoites, two mabs (8D-2 and HE-4) recognized an antigen present on the apical tip of the same two Eimeria species (E. acervulina and E. brunetti), another mab (5D-11) recognized an antigen present on the apical tip of other two species (E. acervulina and E. maxima) while one mab (8C-3) identified antigens present on the sporozoites and sporocysts wall of only E. acervulina. Besides the apical tip antigens, two mabs (HE-4 and 8D-2) recognized some proteins located in the anterior half of the sporozoites. Collectively, these mabs proved that the apical complex of chicken Eimeria sporozoites share one or more antigens that are expected to play a role in host cell recognition and invasion.

Mapping and expression of microneme genes in Eimeria tenella

Microneme organelles are located at the apical tip of invading stages of all apicomplexan parasites and they contain proteins that are critical for parasite adhesion to host cells. In this paper, we have utilised the process of oocyst sporulation in Eimeria tenella to investigate the timing of expression of components of the microneme organelle, at both mRNA and protein levels. Two time-course studies showed that there is a high level of synchrony in the sporulation process, especially during the time period when sporozoites are formed. Western blotting showed that the expression of five microneme proteins (EtMIC1-5) is differentially regulated and highly co-ordinated during sporulation with the proteins being detected only towards the end of the process, as the sporozoites matured within the sporocysts. In contrast, mRNA for all five of these microneme proteins was detected some 10-12 h earlier in sporulation than when the corresponding proteins were seen. Overall these data suggest that the expression of proteins destined for the microneme is regulated both at the transcriptional and translational level. The single copy genes encoding EtMIC1-5 are not clustered on the genome, but are found on four different chromosomes.

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.

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.

Analysis of infraspecific variation among five strains of Eimeria maxima from North America

Two laboratory strains from the eastern shore of Maryland 15 years ago and from an Ontario broiler house 23 years ago and three recent field strains of Eimeria maxima (isolated in Maryland, North Carolina and Florida) were examined for phenotypic and genotypic variation using protein profiles, random amplified polymorphic DNA-PCR analysis and DNA sequences obtained from the internal transcribed spacer regions of the rRNA genes. Staining profiles obtained by one-dimensional SDS-PAGE of sporozoite proteins were identical in all five strains. Using random amplified polymorphic DNA-PCR analysis with high %G-C content decamers as primers, we were able to confirm that the five strains are all E. maxima, but were unable to discern any relationships among them because of the limited number of shared polymorphisms identified. In contrast, cloning and sequencing of the internal transcribed spacer-1, 5.8S rDNA and internal transcribed spacer-2 regions of the rRNA genes provided sufficient sequence information to infer phylogenetic relationships among the strains. Almost all of the infraspecific variation was located in the internal transcribed spacer regions. Only two base changes were identified within the 5.8S rRNA gene. Evolutionary relationships among the strains inferred using parsimony analysis of the aligned internal transcribed spacer sequences were well supported, but the hypothesised relationships did not correlate well with the demonstrated immunological cross-reactivities of these strains.

Mapping for B-cell epitopes in the GX3262 antigenic sequence derived from Eimeria tenella sporulated oocysts

Polypropylene pins were impregnated with synthetic overlapping heptapeptides based on the GX3262 Eimeria tenella antigenic sequence (Miller et al., 1989). Using these coated pins as the solid phase of an enzyme immunoassay (EIA), binding of sera from chickens and rabbits infected and immunised respectively with five different species of Eimeria were examined. Antibody reactions to the individual heptapeptides were then analysed by a number of criteria based on the amino acid sequence including hydropathy, chain flexibility and secondary structure.

Identification of Eimeria bovis merozoite cDNAs using differential mRNA display

Differences in gene expression between Eimeria bovis sporozoites and first-generation merozoites were analyzed using the technique of differential mRNA display. Approx. 5% of the sequences detected in first-generation merozoites appear to be unique relative to sporozoites. Several of the bands corresponding to merozoite-specific gene expression were isolated and cloned. Northern blot analysis revealed that the cDNA fragments DMZ-7, DMZ-8 and NMZ-6 hybridized to mRNAs expressed at > 50-fold higher levels in merozoites relative to sporozoites. A fourth cDNA fragment, NMZ-4, hybridized to a mRNA expressed at 3-fold higher levels in merozoites. Further characterization demonstrated that expression of DMZ-8 in E. bovis-infected bovine cells begins as early as 12 h after sporozoite invasion and continues throughout the entire 14 days of first-generation schizogony. Sequence analysis of each of the four merozoite cDNAs failed to identify any significant similarity to any entries in the GenBank database, suggesting that these developmentally regulated genes may be unique to coccidian parasites.

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.

Antigenic diversity of the asexual developmental stages of Eimeria tenella

Total polypeptides from unsporulated and sporulated oocysts, sporozoites and the first two generations of merozoites of Eimeria tenella were fractionated by electrophoresis through polyacrylamide gels. The parasites are complex and the arrays of polypeptides differ for each of the developmental stages indicating that there is stage-specific control of gene expression. In particular, first generation merozoites display a markedly different polypeptide profile to that of either sporozoites or second generation merozoites. Changes in antigenicity during sporulation and the antigenic relationships between the three asexual zoite stages were examined by probing electroblotted polypeptides with a panel of antisera raised in rabbits to purified preparations of each stage. Antigenic cross-reactivity is well maintained throughout sporulation even though the sizes of antibody-reactive polypeptides change. In contrast there is a marked lack of cross-reactive epitopes between sporozoites, first and second generation merozoites.

Production and characterization of monoclonal antibodies directed against Eimeria falciformis and cross-reactive with sporozoites from two species of avian coccidia

Monoclonal antibodies (mAbs) were obtained against the surface antigens of the Eimeria falciformis sporozoite by immunizing mice with whole homogenized sporozoite. The hybridomas were selected by their reactivities against oocyst extracts, then against glutaraldehyde-treated sporozoites. Three mAbs recognized both the surface of E. falciformis, E. tenella, and E. acervulina and their refractile bodies, whereas a fourth mAb recognized only one epitope on the refractile bodies. All mAbs bound to the same immunoaffinity-purified antigens in Western-blot analysis (P27 for E. falciformis and P25 for E. tenella and E. acervulina). Thus, the mAbs define at least two shared epitopes between sporozoite antigens from different eimerian species. Two of these mAbs are involved in the in vitro phagocytosis of E. falciformis sporozoites by macrophages and also in their lysis by neutrophils. Altogether, these properties showed that the four mAbs came from different activated B-cells. The P27 antigen recognized by our mAbs represents a major target of the in vitro destructive immune response.

Developmental gene expression in Eimeria bovis

By differential screening of stage-specific cDNA libraries of Eimeria bovis, we have identified and isolated a large set of genes that are regulated during development of the sporozoites and merozoites. Duplicate lifts of cDNA libraries constructed from partially sporulated oocysts and merozoites were probed with radioactively labeled first-strand cDNA prepared from partially sporulated oocyst and merozoite mRNA. Out of 60,000 plaques screened in each case, over 250 plaques from the partially sporulated oocyst library preferentially hybridized with the oocyst cDNA probe and 67 plaques from the merozoite library preferentially hybridized with the merozoite cDNA probe. Three of the oocyst phage and 7 of the merozoite phage were selected for further characterization. Northern analysis revealed a common pattern of mRNA expression for the oocyst cDNA clones. Consistent with the results of the differential screen, no hybridization to merozoite RNA was detected with any of these 3 oocyst cDNA clones. The expression of the merozoite cDNA clones was more complex, with 3 different classes of merozoite genes being identified based on their pattern of developmental regulation. Although each of the merozoite clones was expressed to some extent during sporulation, in all cases, expression was higher in merozoites than in partially sporulated oocysts, consistent with the restriction of expression defined by the differential screen. Sequence analysis revealed that 2 of the merozoite cDNA clones encode elongation factor 1 alpha and the ubiquitin/ribosomal protein fusion, and 1 of the sporozoite cDNAs displays a significant identity to insulin-degrading enzyme. The developmental expression of E. bovis genes involved in protein synthesis and degradation provides additional evidence for the importance of regulation of protein metabolism during parasite development.

Variant proteins associated with ionophore resistance in sporozoites of Eimeria tenella (Coccidia)

Protein samples prepared from sporozoites of two ionophore-sensitive strains (WIS and Penn St) and three resistant strains (FS139, FS459, and FS462) of Eimeria tenella were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), native polyacrylamide gel electrophoresis (native PAGE), or two-dimensional electrophoresis with native PAGE and SDS-PAGE. Variant proteins that might be associated with ionophore resistance were observed in resistant field strains on native PAGE. When two-dimensional electrophoresis was conducted, four over-expressed peptides with approximate molecular weights of 97, 71, 70, and 50 kDa were observed in the FS139 field strain in comparison with the WIS laboratory strain.

Fractionation and antigenic characterization of organelles of Eimeria tenella sporozoites

Sporozoites of Eimeria tenella were disrupted by sonication and subcellular fractions were separated by sucrose gradient ultracentrifugation. Fractions from gradients were characterized by electron microscopical appearance and their polypeptide and antigenic profiles determined by PAGE and Western blotting with antisera to sporozoites and 1st- and 2nd-generation merozoites. Fractions containing micronemes, rhoptries or membranes showed markedly different polypeptide content and antigenic reactivity. Microneme epitopes were strongly conserved between sporozoites and 2nd-generation merozoites whereas the majority of rhoptry epitopes and many membrane epitopes were sporozoite specific. The only polypeptide of sporozoites which was strongly recognized by antisera raised to 1st generation merozoites was a microneme antigen of molecular weight approximately 100 kDa.

Limited heterogeneity between strains of Eimeria tenella isolated from Britain and Bangladesh

Single-oocyst-derived field strains of Eimeria tenella isolated from Rugby in the United Kingdom (E tenella R) and from Mymensingh and Dhaka in Bangladesh (E tenella M and D, respectively) and a laboratory strain (E tenella, Houghton, H) were compared by isoenzyme electrophoresis, reactivity with antisporozoite monoclonal antibodies and, for some pairs of strains, cross-protection in vivo. The three field strains conformed to one zymodeme with respect to six isoenzymes. For glucose phosphate isomerase (GPI) all field strains were characterised by GPI-9. A panel of six different monoclonal antibodies raised against sporozoites of E tenella H did not discriminate between strains by titration in an immunofluorescence assay against air-dried, acetone fixed sporozoites. In cross-protection experiments involving immunisation and challenge of young chickens, two immunisation schedules were used which, after homologous challenge, provided complete immunity either by the criterion of oocyst output, or by the criterion of weight gain (and more than 94 per cent protection by the criterion of oocyst output). While strain heterogeneity was minimal in the former situation, there was poor cross protection between some strains in the latter case. Under those conditions, heterologous challenge with E tenella M resulted in dysentery and in significantly (P less than 0.05) increased oocyst output and decreased weight gain. The results suggested that E tenella M was immunologically superior to E tenella R and H strains. The results show that a limited degree of immunogenic variability exists between these strains of E tenella and that, unless homologous strain immunity is complete by the criterion of oocyst output, challenge with heterologous strains may result in depressed weight gain.

Protein analysis of Theileria sergenti/buffeli/orientalis piroplasms by two-dimensional polyacrylamide gel electrophoresis

Proteins of the piroplasms of Theileria sergenti, T. buffeli and T. orientalis were analysed by two-dimensional polyacrylamide gel electrophoresis. Protein spot patterns of T. buffeli and T. orientalis were identical except for a few minor proteins, whereas spot patterns of two T. sergenti stocks were differentiated from those of T. buffeli and T. orientalis by a characteristic set of proteins including a major protein of molecular weight 33-34 kDa. This result indicates that Japanese T. sergenti can be phenotypically distinguishable from European and Australia Theileria species; T. orientalis and T. buffeli.

Changes in the messenger RNA population during sporulation of Eimeria maxima

Messenger RNA has been extracted from oocysts of Eimeria maxima. Using the techniques of in vitro translation and SDS-polyacrylamide gel electrophoresis, we have been able to show that major changes in gene transcription occur during sporulation. Following an overall reduction in the abundance of many mRNAs, several genes identified as the result of an increase in the abundance of their transcripts, are highly expressed during the latter stages of sporulation. A study of two genes whose transcription is down-regulated has provided evidence which shows that both single copy and repetitive sequences are regulated during sporulation of the oocyst.

Identification of isolate-specific sporozoite proteins of Cryptosporidium parvum by two-dimensional gel electrophoresis

Five isolates of Cryptosporidium parvum collected from human, horse, and calf sources were compared for differences in sporozoite protein patterns by using two-dimensional gel electrophoresis. Silver-stained two-dimensional gels contained over 300 protein spots from detergent-solubilized sporozoites. A distinguishing 106-kilodalton peptide that shifted in isoelectric point was detected in four of the five isolates. Computerized two-dimensional gel analysis was performed to obtain objective quantitation of the pI shift. Three of these four isolates could be differentiated from one other by the pI shift in this peptide. The fifth isolate was distinguished by the absence of the 106-kilodalton peptide and the presence of a 40-kilodalton peptide that was not observed in any other isolate.