In silico analysis of Ta9 gene polymorphism in an Iranian Theileria annulata schizont-infected cell line S15 vaccine strain and native isolates

Document Type : Original Articles


Department of Parasite Vaccine Research and Production, Razi Vaccine and Serum Research Institute, Karaj, Iran


Bovine theileriosis is a tick-borne disease caused by obligate intracellular parasites related to the genus Theileria. Cellular immune responses protect cattle against pathogens through the activation of immune cells. Nowadays, live, attenuated vaccine of Theileria annulata (T. annulata) is being produced in Iran and is recommended for active cattle immunization. Detection of the immunogenic  antigens and epitopes recognized by CD8+ T Lymphocytes is vital for the development of recombinant and subunit vaccines. Herein, sequences of the genes encoding Ta9, which is an important antigenrecognized by bovine CD8+ T cells specific for T. annulata, in Iranian S15 vaccine strains, several Iranian isolates, as well as reference Ta9 DNA sequences registered in GeneBank were compared through polymerase chain reaction (PCR). The obtained data from DNA sequences were analyzed by using "Nucleotide", "Blast n", "BioEdit" and "IEDB" softwares. The results showed high level of variation in nucleotides and amino acids level. The observed polymorphism in Ta9 gene sequences of Iranian vaccine strains and some isolates from Iran demonstrated that this antigen contains polymorphic sequences and is active along with the specific major histocompatibility complex (MHC) of the host. Polymorphic sequences and specific epitopes of Ta9 gene for CD8+ T cell provides an explanation for incomplete protection observed after inoculation of heterologous parasites in vaccinated cattle. These results have important implications for the application of Ta9 antigen for developing novel subunit vaccines.


Main Subjects

Article Title [French]

Analyse in silico du polymorphisme du gène Ta9 dans une souche iranienne de vaccin S15 infectée par le schizonte Theileria annulata et d’isolats indigènes

Abstract [French]

La theilériose bovine est une infection transmise par des tiques et causée par des parasites obligatoires, intracellulaires appartenant au genre Theileria. La réponse immune cellulaire protège les bovins de ces pathogènes à travers l’activation de cellules immunes spécifiques. Aujourd’hui, le vaccin vivant atténué de Theileria annulata (T. annulata) est produit en Iran et est recommandé pour l’immunisation active des bovins. La détection des antigènes immunogènes et des épitopes reconnus par les lymphocytes T CD8+ est vitale dans le développement de vaccins recombinants ou sous-unitaires. Dans cette étude, les séquences des gènes codant pour Ta9, un antigène majeur reconnu par les cellules T CD8+ bovines et spécifique à l’espèce T. annulata, ont été analysés par réaction en chaine à la polymerase (PCR). Les résultats obtenus pour les souches iraniennes du vaccin S15 et plusieurs isolats iraniens ont été comparés à la séquence ADN de référence du gène Ta9 enregistré dans GeneBank. Les séquences ADN issus de nos analyses ont été étudiées avec les logiciels "Nucleotide", "Blast n", "BioEdit" et "IEDB". Nos résultats montrent un degré important de variation au niveau des séquences nucléotidiques et d’acides aminés. Le polymorphisme observé dans les séquences du gène Ta9 des souches iraniennes du vaccin S15 ainsi que dans plusieurs isolats iraniens montrent que cet antigène contient des séquences fortement polymorphiques et actives au niveau du complexe majeur d’histocompatibilité (CMH) spécifique de l’hôte. Le polymorphisme des séquences et des épitopes spécifiques au gène Ta9 pour les cellules T CD8+ pourrait donc expliquer la protection partielle observée après l’inoculation de parasites hétérologues par les bovins vaccinés. Ces résultats pourraient donc avoir des implications importantes pour le développement de nouveaux vaccins sous-unitaires à partir de l’antigène Ta9.

Keywords [French]

  • Antigène
  • Iran
  • Polymorphisme
  • Ta9
  • Theileria annulata
  • Vaccin
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