Evaluation of glycoproteins purified from adult and larval camel ticks (Hyalomma dromedarii) as a candidate vaccine

Abstract

In order to identify antigens that can help prevent camel tick infestations, three major glycoproteins (GLPs) about 97, 66 and 40 kDa in size were purified from adult and larval Egyptian ticks, Hyalomma (H.) dromedarii, using a single-step purification method with Con-A sepharose. The purified GLPs were evaluated as vaccines against camel tick infestation in rabbits. The rabbits received three intramuscular inoculations of GLPs (20 µg/animal) on days 0, 14, and 28. In the immunoblot analysis, Sera from the immunized rabbits recognized the native GLPs and other proteins from larval and adult H. dromedarii ticks along with those from other tick species such as Rhipicephalus sanguineus but not Ornithodoros moubata. The effects of immunity induced by these GLPs were determined by exposing rabbits to adult H. dromedarii ticks. These results demonstrated that GLP immunization led to a slightly decreased reproductive index and significantly reduced rates of egg hatchability. These results demonstrated that immunization with the purified GLPs can provide protection against infestation by H. dromedarii and some other tick species. Further studies are needed to confirm the effectiveness of immunization with GLPs against other tick species.

Fig. 1

Affinity chromatography of Hyalomma (H.) dromedarii adult proteins (60 mg) using a Con-A sepharose column.

Fig. 2

Affinity chromatography of H. dromedarii larval proteins (130 mg) using a Con-A sepharose column.

Fig. 3

12% SDS-PAGE of the isolated adult and larval GLPs and proteins. Lane 1: molecular weight marker, Lane 2: whole H. dromedarii adult proteins, Lane 3: unbound whole H. dromedarii adult proteins from the Con-A sepharose column, Lane 4: adult glycoproteins (AGLPs), Lane 5: H. dromedarii larval proteins, Lane 6: unbound H. dromedarii larval proteins from the Con-A sepharose column, Lane 7: larval glycoproteins (LGLPs).

Fig. 4

Immunoblot analysis of different H. dromedarii protein extracts. The following samples were analyzed: H. dromedarii LGLPs (1), H. dromedarii AGLPs (2), H. dromedarii total larval proteins (3), and H. dromedarii adult total proteins (4). The blots were probed with rabbit anti-H. dromedarii LGLPs antisera (A), rabbit anti-H. dromedarii AGLPs antisera (B), and normal rabbit serum (C).

Fig. 5

Immunoblot analysis of total protein extracts from different tick species. The samples from the following species were analyzed: Rhipicephalus (R.) annulatus (1), R. sanguineus (2), and Ornithodoros moubata (3). The blots were probed with rabbit anti-H. dromedarii LGLPs antisera (A), and rabbit anti-H. dromedarii AGLPs antisera (B).