Characterization of tick antigens inducing host immune resistance. II. Description of rabbit-acquired immunity to Amblyomma americanum ticks and identification of potential tick antigens by Western blot analysis.
Feeding by adult Amblyomma americanum ticks induced a level of immunity in rabbits to subsequent tick feeding that resulted in a significant decrease in tick feeding success and fecundity. Histological analysis of tick feeding sites in hosts expressing resistance revealed a predominant eosinophil response, with weak basophil and neutrophil infiltrates. While the basophil was never the dominant granulocyte at the tick feeding sites in resistant hosts, this cell exhibited the greatest increase in density (tenfold) over levels observed in hosts experiencing their first infestation; eosinophils and neutrophils exhibited increases of five- and twofold, respectively. Serum from animals that expressed resistance was tested for the presence of anti-tick antibodies to tick-derived salivary gland substances (SGA) by Western blotting. Western blot analysis of female-derived SGA compared to male-derived SGA, using the Avidin/Biotin technique, resulted in the identification of approximately 25 proteins from the female preparation, but only seven from the male. The use of 125I labeled protein-A as the probe for anti-tick antibody in Western blot analysis resulted in fewer recognized proteins. Serum from rabbits immunized with A. americanum-derived SGA emulsified with complete (CFA) Freund's adjuvant recognized most of the proteins identified by active serum, whereas serum from animals immunized with SGA in incomplete (IFA) Freund's adjuvant did not. Furthermore, both sera recognized a multiplicity of proteins from extracts of larval A. americanum Dermacentor variabilis and Boophilus microplus ticks, suggesting the presence of common antigens between these distantly related ticks. The results from this study demonstrate that rabbits acquire a strong immunity to A. americanum ticks characterized by the production of antibody. Furthermore, ticks secrete a number of substances into rabbits during feeding, as seen by Western blot analysis but only three may be crucial to the induction of host immunity; proteins at 41, 40 and 39 kDa. The purified anti-tick antibody will be used for subsequent isolation and characterization of crucial antigens.
Brown
S J
SJ
Department of Biology, Loyola Marymount University, Los Angeles, CA 90045.
D000818:Animals; D000941:Antigens / Q000032:analysis*; D003870:Dermacentor / Q000276:immunology; D005260:Female; D005620:Freund's Adjuvant; D007111:Immunity, Cellular; D007158:Immunologic Techniques; D008297:Male; D011817:Rabbits / Q000276:immunology / Q000469:parasitology*; D012471:Salivary Proteins and Peptides / Q000276:immunology; D012737:Sex Factors; D013984:Tick Infestations / Q000276:immunology / Q000473:pathology / Q000662:veterinary*; D013987:Ticks / Q000276:immunology*
D000941:Antigens; D012471:Salivary Proteins and Peptides; D005620:Freund's Adjuvant