title: Genes encoding two Theileria parva antigens recognized by CD8+ T-cells exhibit sequence diversity in South Sudanese cattle populations but the majority of alleles are similar to the Muguga component of the live vaccine cocktail.
abstract: East Coast fever (ECF), caused by Theileria parva infection, is a frequently fatal disease of cattle in eastern, central and southern Africa, and an emerging disease in South Sudan. Immunization using the infection and treatment method (ITM) is increasingly being used for control in countries affected by ECF, but not yet in South Sudan. It has been reported that CD8+ T-cell lymphocytes specific for parasitized cells play a central role in the immunity induced by ITM and a number of T. parva antigens recognized by parasite-specific CD8+ T-cells have been identified. In this study we determined the sequence diversity among two of these antigens, Tp1 and Tp2, which are under evaluation as candidates for inclusion in a sub-unit vaccine. T. parva samples (n = 81) obtained from cattle in four geographical regions of South Sudan were studied for sequence polymorphism in partial sequences of the Tp1 and Tp2 genes. Eight positions (1.97%) in Tp1 and 78 positions (15.48%) in Tp2 were shown to be polymorphic, giving rise to four and 14 antigen variants in Tp1 and Tp2, respectively. The overall nucleotide diversity in the Tp1 and Tp2 genes was π = 1.65% and π = 4.76%, respectively. The parasites were sampled from regions approximately 300 km apart, but there was limited evidence for genetic differentiation between populations. Analyses of the sequences revealed limited numbers of amino acid polymorphisms both overall and in residues within the mapped CD8+ T-cell epitopes. Although novel epitopes were identified in the samples from South Sudan, a large number of the samples harboured several epitopes in both antigens that were similar to those in the T. parva Muguga reference stock, which is a key component in the widely used live vaccine cocktail.
authors.affiliation: Biosciences eastern and central Africa-International Livestock Research Institute Hub (BecA-ILRI Hub), Nairobi, Kenya.|Central Veterinary Research Laboratory, Khartoum, Sudan.
authors.forename: Diaeldin A
authors.identifier: http://orcid.org/0000-0002-4278-9754
authors.initials: DA
authors.lastname: Salih
authors.affiliation: Biosciences eastern and central Africa-International Livestock Research Institute Hub (BecA-ILRI Hub), Nairobi, Kenya.
authors.forename: Roger
authors.initials: R
authors.lastname: Pelle
authors.affiliation: School of Life Sciences, Centre for Genetics and Genomics, University of Nottingham, Nottingham, United Kingdom.
authors.forename: Joram M
authors.initials: JM
authors.lastname: Mwacharo
authors.affiliation: Biosciences eastern and central Africa-International Livestock Research Institute Hub (BecA-ILRI Hub), Nairobi, Kenya.
authors.forename: Moses N
authors.initials: MN
authors.lastname: Njahira
authors.affiliation: Biosciences eastern and central Africa-International Livestock Research Institute Hub (BecA-ILRI Hub), Nairobi, Kenya.|Ministry of Animal Resources and Fisheries, Juba, South Sudan.
authors.forename: Wani L
authors.initials: WL
authors.lastname: Marcellino
authors.affiliation: International Livestock Research Institute (ILRI), Nairobi, Kenya.
authors.forename: Henry
authors.initials: H
authors.lastname: Kiara
authors.affiliation: Ministry of Animal Resources and Fisheries, Juba, South Sudan.
authors.forename: Agol K
authors.initials: AK
authors.lastname: Malak
authors.affiliation: Central Veterinary Research Laboratory, Khartoum, Sudan.
authors.forename: Abdel Rahim M
authors.initials: AR
authors.lastname: El Hussein
authors.affiliation: International Livestock Research Institute (ILRI), Nairobi, Kenya.
authors.forename: Richard
authors.initials: R
authors.lastname: Bishop
authors.affiliation: Biosciences eastern and central Africa-International Livestock Research Institute Hub (BecA-ILRI Hub), Nairobi, Kenya.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Skilton
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D000940:Antigenic Variation; D000953:Antigens, Protozoan / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002417:Cattle / Q000276:immunology / Q000469:parasitology*; D018984:Epitopes, T-Lymphocyte / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D017125:Genes, Protozoan; D014644:Genetic Variation; D010802:Phylogeny; D011110:Polymorphism, Genetic; D016052:Protozoan Vaccines / Q000276:immunology*; D016415:Sequence Alignment; D016797:Theileria parva / Q000235:genetics / Q000276:immunology*; D013801:Theileriasis / Q000276:immunology* / Q000469:parasitology* / Q000517:prevention & control; D014613:Vaccines, Attenuated / Q000276:immunology
chemical_list: D000953:Antigens, Protozoan; D018984:Epitopes, T-Lymphocyte; D016052:Protozoan Vaccines; D014613:Vaccines, Attenuated