Antigens of Amblyomma americanum Ticks Recognized by Repeatedly Infested Sheep

Abstract

Sera were taken from 3 sheep that had been infested 5 times with Amblyomma americanum and that exhibited manifestations of humoral depression to homologous antigens and anti-tick resistance. Proteins extracted from the intestine or salivary glands of unfed ticks or salivary glands from partially (3-day) fed ticks were analyzed by polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate-PAGE. Antigens recognized by the sheep in the same materials before and after each infestation were analyzed by western blots. The sheep responded to 44 antigens. Nine to 23 antigens were recognized by the preinfestation sera and the sera of 2 gnotobiotic sheep. Four antigens (34,000, 36,500, 38,000, and 115,000 MW) were revealed conspicuously by the serum of the first infestation but very weakly or not at all by the sera of the third infestation onward. Two antigens (35,500 and 29,000 MW) from fed salivary glands were revealed only by sera taken after manifestations of resistance had appeared. These antigens may be responsible for anti-tick protection. The 29,900 MW antigen was present also in salivary extracts of Boophilus microplus.

The Central Role of Salivary Metalloproteases in Host Acquired Resistance to Tick Feeding

“…The production of anti-salivary gland-specific antibodies against Amblyomma variegatum and I. ricinus ticks was reported in rabbits (Jongejan et al, 1989;Schorderet and Brossard, 1993). Furthermore, sera from sheep that were exposed to a repeated infestation of Amblyomma americanum ticks were shown to recognize multiple tick antigens ( Barriga et al, 1991). The presence of specific antitick antibodies has been correlated with the inability of ticks to feed and/or reproduce, leading to the concept of acquired resistance to ticks in sensitive host species (Bowessidjaou et al, 1977).…”

Refinement of an established large-animal model to understand the tick-pathogen-host interface

“…Further, repeated infestation induced an immune response in different breeds of cattle that reacts with two-dimensional western blots of tick antigens (288). Several investigations have sought to identify antigens responsible for the phenotype of reduced tick performance after repeated infestation, but without success (294)(295)(296). The only internationally available commercial anti-tick vaccine, Gavac, is based upon a concealed midgut glycoprotein, Bm86 (157,194,199).…”