Immunoblotting of Amblyomma cajennense antigens using sera from sensitized goats. Cross reactivity with A. hebraeum

Abstract

Species: Ruminants The control of ticks has been a major concern because of the very high costs of the chemical methods of control usually practiced, the environmental contamination they produce, and the development of tick resistance problems. Antigenic extracts derived from whole tick body homogenates of both adult and immature instars and of internal organs as salivary gland and gut of partially fed female ticks were already tested and demonstrated to induce various degrees of resistance to ticks in several hosts. This approach is promising as an alternative method for tick control. In addition, preliminary results of the laboratory showed that goats acquire partial resistance against nymphs of the lone-star tick Amblyomma cajennense after repeated infestations. With the aim to search for antigens from A. cajennense recognized by sera from repeatedly infested goats, five animals aged 6 months, of both sexes, were infested thrice with 100 A. cajennense nymphs at 30 days interval. Sera from these goats were collected before the infestation and 30 days after both the 1st and 3rd infestations and used in western blot analysis to identify potential antigens from unfed nymphal extract homogenate. Sera collected from goats infested at same conditions with A. hebraeum ticks were used to search for cross-reactivity between tick antigens from the ixodid species. These later sera revealed nine polypeptides of 12, 19, 24, 34, 46, 52, 66, 83 and 160kDa while those collected from goats infested once and thrice with A. cajennense nymphs revealed eight common polypeptides of 26, 36,5, 37,5, 55, 72, 86, 98, and 170kDa. At non-infested animals’ blots, it was observed reactive polypeptides as well, revealing the existence of cross reactivity with antigens from ectoparasites other than ticks. However, it should be stressed that three polypeptides of 14, 11 and 7kDa related to A. cajennense nymphs observed only when used sera were from animals infested thrice could play an important role in inducing resistance in goats to such tick species. Finally, the presence of close polypeptides reactive to A. hebraeum serum probably reveals the existence of cross reactivity between the two ixodid species, but forward studies are needed to confirm it.