title: Identification and partial characterization of a gut Rhipicephalus appendiculatus cystatin.
abstract: Vaccines are among the alternative tick control methods expected to replace at least in part the volumes of chemical acaricides currently used worldwide. However, a vaccination approach depends on a host immune response against proteins that are essential to tick physiology. The cystatin family is a protein class recently investigated to compose an effective antigen in a tick vaccine. In this study, a cDNA from Rhipicephalus appendiculatus with high sequence similarity to cystatins type 2 was identified by random sequencing analysis and called R. appendiculatus cystatin 1 (Ra-cyst-1). DNA sequence analysis showed that the cloned Ra-cyst-1 has a 423-bp open reading frame and codified to a 140-amino acid polypeptide. The putative mature protein consists of 115 amino acid residues with a deduced molecular weight of 12.8kDa. The highly conserved G (P-I), QxVxG (P-II), and PW (P-III) type 2 cystatins motifs are present in Ra-cyst-1 cDNA. RT-PCR analysis showed that the Ra-cyst-1 gene is expressed in nymph, male, and female midgut following blood feeding, but not in the salivary glands of fed females. In addition, Western blot revealed that recombinant Ra-cyst-1 was not recognized by sera derived from rabbits infested with ticks, suggesting that this cystatin is not secreted into the host during infestation. We hypothesize that Ra-cyst-1 may play a role in the tick feeding process and could be a concealed antigen candidate in further anti-tick vaccination trials.
authors.affiliation: Department of Infectious Diseases, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido, Japan.
authors.forename: Saiki
authors.initials: S
authors.lastname: Imamura
authors.forename: Satoru
authors.initials: S
authors.lastname: Konnai
authors.forename: Shinji
authors.initials: S
authors.lastname: Yamada
authors.forename: Luís F
authors.initials: LF
authors.lastname: Parizi
authors.forename: Naftaly
authors.initials: N
authors.lastname: Githaka
authors.forename: Itabajara da S
authors.initials: Ida S
authors.lastname: Vaz
authors.forename: Shiro
authors.initials: S
authors.lastname: Murata
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Ohashi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015891:Cystatins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005260:Female; D008297:Male; D008969:Molecular Sequence Data; D048494:Rhipicephalus / Q000145:classification* / Q000378:metabolism*
chemical_list: D015891:Cystatins