title: Sequence Polymorphism of Cytochrome b Gene in Theileria annulata Tunisian Isolates and Its Association with Buparvaquone Treatment Failure.
abstract: BACKGROUND
  Buparvaquone (BW 720C) is the major hydroxynaphtoquinone active against tropical theileriosis (Theileria annulata infection). Previous studies showed that buparvaquone, similarly to others hydroxynaphtoquinone, probably acts by binding to cytochrome b (cyt b) inhibiting the electron transport chain in the parasite. Several observations suggested that T. annulata is becoming resistant to buparvaquone in many endemic regions (Tunisia, Turkey and Iran), which may hinder the development of bovine livestock in these areas.
  
  
  RESULTS
  In the present study we sought to determine whether point mutations in T. annulata cytochrome b gene could be associated to buparvaquone resistance. A total of 28 clones were studied in this work, 19 of which were obtained from 3 resistant isolates (ST2/12, ST2/13 and ST2/19) collected at different time after treatment, from a field treatment failure and nine clones isolated from 4 sensitive stocks of T. annulata (Beja, Battan, Jed4 and Sousse). The cytochrome b gene was amplified and sequenced. We identified five point mutations at the protein sequences (114, 129, 253, 262 and 347) specific for the clones isolated from resistant stocks. Two of them affecting 68% (13/19) of resistant clones, are present in the drug-binding site Q02 region at the position 253 in three resistant clones and at the position 262 in 11 out of 19 resistant clones. These two mutations substitute a neutral and hydrophobic amino acids by polar and hydrophilic ones which could interfere with the drug binding capabilities. When we compared our sequences to the Iranian ones, the phylogenetic tree analyses show the presence of a geographical sub-structuring in the population of T. annulata.
  
  
  CONCLUSIONS
  Taken together, our results suggest that the cytochrome b gene may be used as a tool to discriminate between different T. annulata genotypes and also as a genetic marker to characterize resistant isolates of T. annulata.
authors.affiliation: Laboratoire de Parasitologie, École Nationale de Médecine Vétérinaire, Université de la Manouba, 2020 Sidi Thabet, Tunisia; Faculté des Sciences de Bizerte, Université de Carthage, Tunis, Tunisia.
authors.forename: Moez
authors.initials: M
authors.lastname: Mhadhbi
authors.affiliation: Laboratoire de Parasitologie Médicale, Biotechnologies et Biomolécules, Institut Pasteur de Tunis, Tunis, Tunisia.
authors.forename: Melek
authors.initials: M
authors.lastname: Chaouch
authors.affiliation: Laboratoire de Parasitologie Médicale, Biotechnologies et Biomolécules, Institut Pasteur de Tunis, Tunis, Tunisia.
authors.forename: Kaouthar
authors.initials: K
authors.lastname: Ajroud
authors.affiliation: Laboratoire de Parasitologie, École Nationale de Médecine Vétérinaire, Université de la Manouba, 2020 Sidi Thabet, Tunisia.
authors.forename: Mohamed Aziz
authors.initials: MA
authors.lastname: Darghouth
authors.affiliation: Laboratoire de Parasitologie Médicale, Biotechnologies et Biomolécules, Institut Pasteur de Tunis, Tunis, Tunisia.
authors.forename: Souha
authors.initials: S
authors.lastname: BenAbderrazak
mesh_terms: D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology / Q000627:therapeutic use*; D002417:Cattle; D045303:Cytochromes b / Q000235:genetics*; D004351:Drug Resistance; D009285:Naphthoquinones / Q000494:pharmacology / Q000627:therapeutic use*; D017354:Point Mutation; D020641:Polymorphism, Single Nucleotide; D015800:Protozoan Proteins / Q000235:genetics*; D016796:Theileria annulata / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D013801:Theileriasis / Q000188:drug therapy / Q000469:parasitology; D017211:Treatment Failure
chemical_list: D000981:Antiprotozoal Agents; D009285:Naphthoquinones; D015800:Protozoan Proteins; C046326:buparvaquone; D045303:Cytochromes b