G. Habibi - 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 CD۸+ T Lymphocytes is vital for the development of recombinant and subunit vaccines. Herein, sequences of the genes encoding Ta۹, which is an important antigenrecognized by bovine CD۸+ T cells specific for T. annulata, in Iranian S۱۵ vaccine strains, several Iranian isolates, as well as reference Ta۹ 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 Ta۹ 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 Ta۹ gene for CD۸+ 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 Ta۹ antigen for developing novel subunit vaccines.

Antigen, Iran, Polymorphism, Ta۹, Theileria annulata, vaccine