Rhipicephalus appendiculatus: Immunochemical isolation, identification and characterization of tick gut antigens recognized by IgGs derived from rabbits repeatedly infested with ticks

Abstract

Immune resistance to infestation by the brown ear tick, Rhipicephalus appendiculatus Neumann, was induced in rabbits by repeated tick feeding. Antibodies from the rabbits resistant to ticks were purified and used to isolate tick midgut antigens. Purified immunoglobulin G (IgGs) from rabbits immune to tick infestations demonstrated, by immunoblotting, nine protein subunits with molecular weights ranging from 12,000 to 92,000 daltons. Immuno-adsorption studies revealed an aggregated native protein with a molecular weight greater than 500,000 daltons as resolved by polyacrylamide gel electrophoresis (PAGE). Sodium dodecyl sulphate (SDS)-PAGE of this protein molecule revealed the presence of 14 protein subunits similar to some of those detected by the immunoblots. Their molecular weights ranged from 14,000 to 165,000 daltons. Sera from rabbits immunized with the 500,000 dalton molecule formed a weak precipitating arc in the immunodiffusion test, confirming its immunogenicity. The reproductive potential of ticks fed on rabbits immunized with the purified protein molecule was slightly affected compared to controls. The protein molecule also had the capacity to induce immediate and delayed type skin reactions when injected into rabbits resistant to adult R. appendiculatus , as opposed to control tick-naive rabbits.