A preliminary evaluation of tick cement-cone protein extract for a vaccine against Hyalomma infestation

Abstract

Background: Vaccines have been widely exploited to prevent tick-borne infections in cattle. Most vaccines have faced failure in the field because of inconsistency in an immune response. It is presumed that the cement-cone proteins of ticks that participate in the acquisition of blood meal for ticks possess strong immune-stimulating properties and, hence, could be a useful candidate in vaccine development.

Aims: We evaluated cement-cone proteins of tick Hyalomma anatolicum as a vaccine candidate against infestations of H. anatolicum and H. aegyptium in cattle.

Methods: The cement-cone proteins were extracted from H. anatolicum to develop stage-reactive and immunogenic cross-reactive vaccine against the infestation of two species of ticks H. anatolicum and H. aegyptium. The immune response of the vaccine was tested against cement-cone proteins starved, partially fed, and richly fed ticks.

Results: The findings of the present study demonstrated the cross-reactivity among the two species of ticks that belonged to the same genus (Hyalomma). The antigenic similarity between the two ticks species suggests that a common antigen may possibly be suitable for a vaccine against the two different species of ticks. The results have also indicated that the 23 kDa cement-cone protein of H. anatolicum and H. aegyptium may be responsible for the induction, or elicitation of immunogenic, common stage reactive, and cross-reactive host immune responses with consistent intensity throughout the life stages of ticks.

Conclusion: The vaccine based upon cement-cone proteins of ticks may be a useful deterrent against tick-borne infections in cattle in countries like Pakistan.

Keywords: Cattle; Cement-cone; Cross-reactive; Tick; Vaccine.

Fig. 1

SDS-PAGE Western blotting of immune reactivity of tick cement-cone proteins with the serum of cattle Bos primigenius immunized against cement-cone protein extract of H. anatolicum. (A) Recognition of 23 kDa (intense) and 45 kDa (weak intensity) proteins in cement-cone protein extracts of tick H. anatolicum by bovine antisera. M: Pre-stained markers, A: Adult, N: Nymph, and L: Larva of tick, and (B) Represents the feed stage cross reactivity of 23 kDa cement-cone protein of larva of H. aegyptium tick against the serum of cattle immunized by cement-cone protein extracts of the larva of H. anatolicum. 1: Unfed, 2: Partially fed, and 3: Fully fed ticks

Fig. 2

Serum anti-body response of cows against cement-cone proteins of tick H. anatolicum. The anti-body response was evaluated through ELISA. The cows of both control and vaccinated groups were infested with equal numbers (100/instar) of ticks (adults, larvae, nymphs). The secondary response was three times greater than control. Arrow signs indicate primary, secondary, and tertiary responses

Fig. 3

Eosinophil stimulation index as a measure of antigen-specific response in cows. Eosinophils index was measured against cement-cone proteins of tick H. anatolicum during the course of infestation with ticks H. anatolicum. Arrows indicate primary, secondary, and tertiary infestations. Controls were only given Montanide ISA-50 adjuvant

Fig. 4

Mean skin reactivity of cows injected by crude cement-cone proteins of tick H. anatolicum. Measurement was done at the injection site

Fig. 5

Post immunization cutaneous-hypersensitivity induced by cement-cone proteins. Cows were sensitized through infestation with larvae and nymphs on the ear. The arrow indicates a significant difference between nymphs and control means (P<0.05)

Fig. 6

Mean weight of eggs produced by tick H. anatolicum in weeks. Ticks were reared on cows vaccinated with crude cement-cone protein extracts. Series 1 vaccinated cows and series 2 control cows (P<0.01)