Theileria parva candidate vaccine antigens recognized by immune bovine cytotoxic T lymphocytes.
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ABSTRACT:
SUBMITTER: Graham SP
PROVIDER: S-EPMC1413922 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Theileria parva is a protozoan parasite transmitted by the brown ear tick Rhipicephalus appendiculatus that causes East Coast fever (ECF) in cattle, resulting in substantial economic losses in the regions of southern, eastern and central Africa. The schizont form of the parasite transforms the bovine host lymphocytes into actively proliferating cancer-like cells. However, how T. parva causes bovine host cells to proliferate and maintain a cancerous phenotype following infection is still poorly understood. On the other hand, current efforts to develop improved vaccines have identified only a few candidate antigens. In the present paper, we report the first comparative transcriptomic analysis throughout the course of T. parva infection. We observed that the development of sporoblast into sporozoite and then the establishment in the host cells as schizont is accompanied by a drastic increase of upregulated genes in the schizont stage of the parasite. In contrast, the ten highest gene expression values occurred in the arthropod vector stages. A comparative analysis showed that 2845 genes were upregulated in both sporozoite and schizont stages compared to the sporoblast. In addition, 647 were upregulated only in the sporozoite whereas 310 were only upregulated in the schizont. We detected low p67 expression in the schizont stage, an unexpected finding considering that p67 has been reported as a sporozoite stage-specific gene. In contrast, we found that transcription of p67 was 20 times higher in the sporoblast than in the sporozoite. Using the expression profiles of recently identified candidate vaccine antigens as a benchmark for selection for novel potential vaccine candidates, we identified three genes with expression similar to p67 and several other genes similar to Tp1-Tp10 schizont vaccine antigens. We propose that the antigenicity or chemotherapeutic potential of this panel of new candidate antigens be further investigated. Structural comparisons of the transcripts generated here with the existing gene models for the respective loci revealed indels. Our findings can be used to improve the structural annotation of the T. parva genome, and the identification of alternatively spliced transcripts.
| S-EPMC6179218 | biostudies-literature
Project description:Theileria parva is a protozoan parasite that causes East Coast fever (ECF), an economically important disease of cattle in Africa. It is transmitted mainly by the tick Rhipicephalus appendiculatus. Research efforts to develop a subunit vaccine based on parasite neutralizing antibodies and cytotoxic T-lymphocytes have met with limited success. The molecular mechanisms underlying T. parva life cycle stages in the tick vector and bovine host are poorly understood, thus limiting progress toward an effective and efficient control of ECF. Transcriptomics has been used to identify candidate vaccine antigens or markers associated with virulence and disease pathology. Therefore, characterization of gene expression throughout the parasite's life cycle should shed light on host-pathogen interactions in ECF and identify genes underlying differences in parasite stages as well as potential, novel therapeutic targets. Recently, the first gene expression profiling of T. parva was conducted for the sporoblast, sporozoite, and schizont stages. The sporozoite is infective to cattle, whereas the schizont is the major pathogenic form of the parasite. The schizont can differentiate into piroplasm, which is infective to the tick vector. The present study was designed to extend the T. parva gene expression profiling to the piroplasm stage with reference to the schizont. Pairwise comparison revealed that 3,279 of a possible 4,084 protein coding genes were differentially expressed, with 1,623 (49%) genes upregulated and 1,656 (51%) downregulated in the piroplasm relative to the schizont. In addition, over 200 genes were stage-specific. In general, there were more molecular functions, biological processes, subcellular localizations, and pathways significantly enriched in the piroplasm than in the schizont. Using known antigens as benchmarks, we identified several new potential vaccine antigens, including TP04_0076 and TP04_0640, which were highly immunogenic in naturally T. parva-infected cattle. All the candidate vaccine antigens identified have yet to be investigated for their capacity to induce protective immune response against ECF.
| S-EPMC7296165 | biostudies-literature
Project description:The extent of sequence diversity among the genes encoding 10 antigens (Tp1-10) known to be recognized by CD8+ T lymphocytes from cattle immune to Theileria parva was analysed. The sequences were derived from parasites in 23 buffalo-derived cell lines, three cattle-derived isolates and one cloned cell line obtained from a buffalo-derived stabilate. The results revealed substantial variation among the antigens through sequence diversity. The greatest nucleotide and amino acid diversity were observed in Tp1, Tp2 and Tp9. Tp5 and Tp7 showed the least amount of allelic diversity, and Tp5, Tp6 and Tp7 had the lowest levels of protein diversity. Tp6 was the most conserved protein; only a single non-synonymous substitution was found in all obtained sequences. The ratio of non-synonymous: synonymous substitutions varied from 0.84 (Tp1) to 0.04 (Tp6). Apart from Tp2 and Tp9, we observed no variation in the other defined CD8+ T cell epitopes (Tp4, 5, 7 and 8), indicating that epitope variation is not a universal feature of T. parva antigens. In addition to providing markers that can be used to examine the diversity in T. parva populations, the results highlight the potential for using conserved antigens to develop vaccines that provide broad protection against T. parva.
| S-EPMC6126638 | biostudies-literature
Project description:Immunity against the bovine intracellular protozoan parasite Theileria parva has been shown to be mediated by CD8 T cells. Six antigens targeted by CD8 T cells from T. parva-immune cattle of different major histocompatibility complex (MHC) genotypes have been identified, raising the prospect of developing a subunit vaccine. To facilitate further dissection of the specificity of protective CD8 T-cell responses and to assist in the assessment of responses to vaccination, we set out to identify the epitopes recognized in these T. parva antigens and their MHC restriction elements. Nine epitopes in six T. parva antigens, together with their respective MHC restriction elements, were successfully identified. Five of the cytotoxic-T-lymphocyte epitopes were found to be restricted by products of previously described alleles, and four were restricted by four novel restriction elements. Analyses of CD8 T-cell responses to five of the epitopes in groups of cattle carrying the defined restriction elements and immunized with live parasites demonstrated that, with one exception, the epitopes were consistently recognized by animals of the respective genotypes. The analysis of responses was extended to animals immunized with multiple antigens delivered in separate vaccine constructs. Specific CD8 T-cell responses were detected in 19 of 24 immunized cattle. All responder cattle mounted responses specific for antigens for which they carried an identified restriction element. By contrast, only 8 of 19 responder cattle displayed a response to antigens for which they did not carry an identified restriction element. These data demonstrate that the identified antigens are inherently dominant in animals with the corresponding MHC genotypes.
| S-EPMC2223472 | biostudies-literature
Project description:Theileria parva is a tick-transmitted protozoan parasite that infects and transforms bovine lymphocytes. We have previously shown that Theileria parva Chitongo is an isolate with a lower virulence than that of T. parva Muguga. Lower virulence appeared to be correlated with a delayed onset of the logarithmic growth phase of T. parva Chitongo-transformed peripheral blood mononuclear cells after in vitro infection. In the current study, infection experiments with WC1(+) γδ T cells revealed that only T. parva Muguga could infect these cells and that no transformed cells could be obtained with T. parva Chitongo sporozoites. Subsequent analysis of the susceptibility of different cell lines and purified populations of lymphocytes to infection and transformation by both isolates showed that T. parva Muguga sporozoites could attach to and infect CD4(+), CD8(+), and WC1(+) T lymphocytes, but T. parva Chitongo sporozoites were observed to bind only to the CD8(+) T cell population. Flow cytometry analysis of established, transformed clones confirmed this bias in target cells. T. parva Muguga-transformed clones consisted of different cell surface phenotypes, suggesting that they were derived from either host CD4(+), CD8(+), or WC1(+) T cells. In contrast, all in vitro and in vivo T. parva Chitongo-transformed clones expressed CD8 but not CD4 or WC1, suggesting that the T. parva Chitongo-transformed target cells were exclusively infected CD8(+) lymphocytes. Thus, a role of cell tropism in virulence is likely. Since the adhesion molecule p67 is 100% identical between the two strains, a second, high-affinity adhesin that determines target cell specificity appears to exist.
| S-EPMC3294644 | biostudies-literature
Project description:As part of an international effort to develop vaccines for Theileria lestoquardi, we undertook a limited screen to test T. lestoquardi orthologues of antigens recognised by CD8+ T lymphocyte responses against T. annulata and T. parva in cattle. Five MHC defined sheep were immunized by live T. lestoquardi infection and their CD8+ T lymphocyte responses determined. Thirteen T. lestoquardi orthologues of T. parva and T. annulata genes, previously shown to be targets of CD8+ T lymphocyte responses of immune cattle, were expressed in autologous fibroblasts and screened for T cell recognition using an IFN? assay. Genes encoding T. lestoquardi antigens Tl8 (putative cysteine proteinase, 349 aa) or Tl9 (hypothetical secreted protein, 293 aa) were recognise by T cells from one animal that displayed a unique MHC class I genotype. Antigenic 9-mer peptide epitopes of Tl8 and Tl9 were identified through peptide scans using CD8+ T cells from the responding animal. These experiments identify the first T. lestoquardi antigens recognised by CD8+ T cell responses linked to specific MHC class I alleles.
| S-EPMC5017765 | biostudies-literature
Project description:East Coast fever (ECF) is an acute fatal tick-borne disease of cattle caused by Theileriaparva. It causes major losses in exotic and crossbreed cattle, but this could be prevented by a vaccine of T. parva if the vaccine is selected properly based on information from molecular epidemiology studies. The Muguga cocktail (MC) vaccine (Muguga, Kiambu 5 and Serengeti-transformed strains) has been used on exotic and crossbreed cattle. A total of 254 T. parva samples from vaccinated and unvaccinated cattle were used to understand the genetic diversity of T. parva in Malawi using partial sequences of the Tp1 and Tp2 genes encoding T. parva CD8+ antigens, known to be immunodominant and current candidate antigens for a subunit vaccine. Single nucleotide polymorphisms were observed at 14 positions (3.65%) in Tp1 and 156 positions (33.12%) in Tp2, plus short deletions in Tp1, resulting in 6 and 10 amino acid variants in the Tp1 and Tp2 genes, respectively. Most sequences were either identical or similar to T. parva Muguga and Kiambu 5 strains. This may suggest the possible expansion of vaccine components into unvaccinated cattle, or that a very similar genotype already existed in Malawi. This study provides information that support the use of MC to control ECF in Malawi.
| S-EPMC7281522 | biostudies-literature
Project description:Theileria parva is an obligate, intracellular, parasitic protozoan that causes East Coast fever, an acute leukemia-like disease of cattle. T. parva and the related parasite, Theileria annulata, are unique among protozoa in that their intralymphocytic stages induce transformation of bovid lymphocytes. Comparison of in vitro protein kinase activities between uninfected IL-2-dependent T lymphoblasts and T. parva-infected lymphocytes revealed a 4.7- to 12-fold increase in total phosphorylation and the induction of a group of Theileria infection-specific phosphoproteins. The enzyme that phosphorylates these substrates is a serine/threonine kinase with substrate and effector specificities of casein kinase (CK) II. Northern blot analyses revealed a 3.9- to 6.0-fold increase in CKII alpha mRNA in the infected cells relative to the controls. Furthermore, a marked increase of CKII antigen was observed on Western blots of materials prepared from the infected cell lines. The antibovine CKII antibody used in these studies immunoprecipitated a protein kinase that phosphorylated casein in a reaction that was inhibited by low (nM) quantities of heparin. Our data show marked increases of bovine CKII at the transcriptional, translational and functional levels in T. parva-infected lymphocytes, relative to quiescent cells or IL-2-dependent parental lymphoblasts. Bovine CKII thus appears to be constitutively activated in these cells and we propose that this kinase may be an important element in the signal-transducing pathways activated by Theileria in bovid lymphocytes and perhaps in some leukemic cells.
| S-EPMC413376 | biostudies-other
Project description:BackgroundEast Coast fever (ECF) caused by Theileria parva is endemic in Rwanda. In this study, the antigenic and genetic diversity of T. parva coupled with immunization and field challenge were undertaken to provide evidence for the introduction of ECF immunization in Rwanda.MethodsBlood collected from cattle in the field was screened for T. parva using ELISA and PCR targeting the p104 gene. Tp1 and Tp2 gene sequences were generated from field samples and from Gikongoro and Nyakizu isolates. Furthermore, multilocus genotype data was generated using 5 satellite markers and an immunization challenge trial under field conditions using Muguga cocktail vaccine undertaken.ResultsOut of 120 samples, 44 and 20 were positive on ELISA and PCR, respectively. Antigenic diversity of the Tp1 and Tp2 gene sequences revealed an abundance of Muguga, Kiambu and Serengeti epitopes in the samples. A further three clusters were observed on both Tp1 and Tp2 phylogenetic trees; two clusters comprising of field samples and vaccine isolates and the third cluster comprising exclusively of Rwanda samples. Both antigens exhibited purifying selection with no positive selection sites. In addition, satellite marker analysis revealed that field samples possessed both shared alleles with Muguga cocktail on all loci and also a higher proportion of unique alleles. The Muguga cocktail (Muguga, Kiambu and Serengeti) genotype compared to other vaccine isolates, was the most represented in the field samples. Further low genetic sub-structuring (FST = 0.037) coupled with linkage disequilibrium between Muguga cocktail and the field samples was observed. Using the above data to guide a field immunization challenge trial comprising 41 immunized and 40 control animals resulted in 85% seroconversion in the immunized animals and an efficacy of vaccination of 81.7%, implying high protection against ECF.ConclusionsAntigenic and genetic diversity analysis of T. parva facilitated the use of Muguga cocktail vaccine in field conditions. A protection level of 81.7% was achieved, demonstrating the importance of combining molecular tools with field trials to establish the suitability of implementation of immunization campaigns. Based on the information in this study, Muguga cocktail immunization in Rwanda has a potential to produce desirable results.
| S-EPMC7487574 | biostudies-literature
Project description:The objective of this study was to assess whether cytotoxic T cells (CTL) generated by the live vaccine, known as "ITM Muguga cocktail", which is used for the cattle disease East Cost fever (ECF) in Sub-Saharan Africa, showed a broad reactivity against many different strains of the causative parasite Theileria parva. We also assessed whether immune responses were similar in cattle expressing the same MHC class I haplotypes.The antigenic specificity of CTL from MHC class I-matched cattle vaccinated with the Muguga cocktail were different. Three cattle of MHC class I haplotype A18, one A18/A19 and two haploidentical (A18v/A12) animals, showed differential recognition of autologous cells infected with a panel of T. parva isolates. This could have implications in the field where certain strains could break through the vaccine. Furthermore, neither of the haploidentical cattle recognized the CTL epitope (Tp1214-224), presented by the A18 haplotype, in contrast to the third animal, showing differences in immunodominance in animals of the same haplotype A18. This suggests that the CTL specificities following immunization with the Muguga cocktail can vary even between haploidentical individuals and that some parasite strains may break through immunity generated by the Muguga cocktail.
| S-EPMC5773172 | biostudies-literature