Two serine protease inhibitors (serpins) that induce a bovine protective immune response against Rhipicephalus appendiculatus ticks

Vaccine. 2006 Mar 20;24(13):2230-7. doi: 10.1016/j.vaccine.2005.10.055. Epub 2005 Nov 10.


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.

MeSH terms

  • Animals
  • Cattle
  • Cattle Diseases / prevention & control*
  • Female
  • Male
  • RNA, Messenger / analysis
  • Rabbits
  • Recombinant Proteins / biosynthesis
  • Serine Proteinase Inhibitors / immunology*
  • Serpins / immunology*
  • Tick Infestations / prevention & control
  • Tick Infestations / veterinary*
  • Ticks / immunology*
  • Vaccination
  • Vaccines, Synthetic / immunology*


  • RNA, Messenger
  • Recombinant Proteins
  • Serine Proteinase Inhibitors
  • Serpins
  • Vaccines, Synthetic