Two serine protease inhibitors (serpins) that induce a bovine protective immune response against Rhipicephalus appendiculatus ticks.
We have previously undertaken preliminary characterization of two Rhipicephalus appendiculutus serine protease inhibitors (RAS-1 and -2) as anti-tick vaccine candidates. In this study, to clarify this hypothesis, we generated and further characterized recombinant RAS-1 and -2 (rRAS-1 and -2) and tested their potency as a cocktail anti-tick vaccine in cattle. RT-PCR analysis showed that RAS-1 and -2 mRNA transcripts are expressed during all life cycle stages of ticks, independent of sex. As judged by SDS-PAGE rRAS-1 and -2 migrated as a molecular weight of around 64 and 60 kDa protein, respectively, considering that the expression vector produced a recombinant protein fused with 18-22 kDa TRX protein. RAS-1 and -2 were found not to be secreted into the bite site as determined by the reactivity of anti-tick saliva sera to rRAS-1 and -2, suggesting that both proteins are concealed antigens. Vaccination of cattle with a combination of rRAS-1 and -2 conferred significant protective immunity against ticks, resulting in 61.4% reduction in nymph engorgement rate, and in 28 and 43% increased mortality rate in adult female and male ticks, respectively. This is the first report on an anti-tick vaccine trial using a combination of two different serpins derived from R. appendiculatus, and using cattle as a natural host.
Imamura
Saiki
S
Department of Infectious Diseases, Graduate School of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Sapporo 060-0818, Hokkaido, Japan.
Namangala
Boniface
B
Tajima
Tomoko
T
Tembo
Mwase Enala
ME
Yasuda
Jun
J
Ohashi
Kazuhiko
K
Onuma
Misao
M
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000517:prevention & control*; D005260:Female; D008297:Male; D012333:RNA, Messenger / Q000032:analysis; D011817:Rabbits; D011994:Recombinant Proteins / Q000096:biosynthesis; D015842:Serine Proteinase Inhibitors / Q000276:immunology*; D015843:Serpins / Q000276:immunology*; D013984:Tick Infestations / Q000517:prevention & control / Q000662:veterinary*; D013987:Ticks / Q000276:immunology*; D014611:Vaccination; D014614:Vaccines, Synthetic / Q000276:immunology*
D012333:RNA, Messenger; D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; D015843:Serpins; D014614:Vaccines, Synthetic