title: Hd86 mRNA expression profile in Hyalomma scupense life stages, could it contribute to explain anti-tick vaccine effect discrepancy between adult and immature instars?
abstract: Bm86 midgut protein has been used in order to control ticks of the Hyalomma genus. Previous studies demonstrated the inefficacity of this antigen in the control of Hyalomma scupense, whereas recombinant Hd86 antigen, the Bm86 ortholog in H. scupense produced in Pichia pastoris, was protective against larval H. scupense tick stage infestations but ineffective in the control of the adult stage. One possible explanation for this result is the variation in Hd86 expression levels between these two developmental stages. To test this hypothesis, Hd86 mRNA levels were characterized in H. scupense developmental stages. The expression profile of Hd86 demonstrated a significant variation between tick life stages and showed a significant reduction in the number of transcripts during feeding and, particularly after molting to adults. The most interesting result was noted after molting of engorged nymphs in unfed adults where the expression levels decreased significantly by 12.78 (10.77-17.39) (p<0.001) and 9.25 (5.77-15.72)-fold (p<0.001) in unfed males and unfed females, respectively. Comparing unfed nymphs to unfed adult ticks, the Hd86 expression levels decreased by 13.82 (5.39-24.45) (p=0.035) and 9.93 (2.87-22.08)-fold (p=0.038) in males and females respectively. Lower Hd86 mRNA levels in adult ticks should result in lower protein levels and thus less antibody-antigen interactions necessary for vaccine efficacy in ticks fed on vaccinated animals. Thus, the observed differences in Hd86 expression profile between immature and adult stages might explain, in part, the discrepancy of the Hd86 vaccine efficacy against these two life stages of H. scupense.
authors.affiliation: Laboratoire de Parasitologie, Ecole Nationale de Médecine Vétérinaire, 2020 Sidi Thabet, IRESA and La Manouba University, Tunisia.
authors.forename: Mourad
authors.initials: M
authors.lastname: Ben Said
authors.forename: Yousr
authors.initials: Y
authors.lastname: Galaï
authors.forename: Melika
authors.initials: M
authors.lastname: Ben Ahmed
authors.forename: Mohamed
authors.initials: M
authors.lastname: Gharbi
authors.forename: José
authors.initials: J
authors.lastname: de la Fuente
authors.forename: Mohamed
authors.initials: M
authors.lastname: Jedidi
authors.forename: Mohamed Aziz
authors.initials: MA
authors.lastname: Darghouth
mesh_terms: D000818:Animals; D060829:Arthropod Proteins / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D026863:Ixodidae / Q000235:genetics* / Q000254:growth & development; D008018:Life Cycle Stages / Q000502:physiology*; D008297:Male; D012333:RNA, Messenger / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013984:Tick Infestations / Q000517:prevention & control / Q000662:veterinary; D059467:Transcriptome; D014612:Vaccines / Q000276:immunology
chemical_list: D060829:Arthropod Proteins; D018076:DNA, Complementary; D012333:RNA, Messenger; D014612:Vaccines
keywords: Expression profile; Hd86 transcript; Hd86 vaccine; Hyalomma scupense tick species; Immature and adult stages; Quantitative RT-PCR