Cross-reaction of tick salivary antigens in the Boophilus microplus-cattle system

Immunoproteomic identification of antigenic salivary biomarkers detected by Ixodes ricinus-exposed rabbit sera

Ixodes ricinus, the primary vector of tick-borne disease in Europe, is currently expanding its distribution area and its activity in many countries. Antibody responses to tick salivary antigens have been proposed as an alternative marker of exposure to tick bites. However, the identification of the I. ricinus corresponding antigens remains elusive. Using rabbits artificially exposed to I. ricinus and 2 other European tick species (Rhipicephalus sanguineus and Dermacentor reticulatus) as controls, a cross-comparison of IgG profiles was performed against protein salivary gland extracts (pSGE) from these 3 tick species using immunoblots. Immunoblot analysis highlighted a singularity in the immune patterns according to tick species exposure and pSGE antigen source. Two protein bands were detected against I. ricinus pSGE only in rabbits exposed to I. ricinus bites. An immunoproteomic approach based on a fluorescence detection method was developed to unambiguously identify corresponding antigenic spots on 2-D gels. Among the unique I. ricinus salivary antigenic proteins detected by sera from rabbits exposed to this tick species, I. ricinus calreticulin was identified. Although tick calreticulin was previously proposed as a potential antigenic marker following exposure to ticks (particularly in North American tick species), the present study suggested that Ixodes calreticulin does not appear to be cross-recognized by the 2 other tick genera tested. Additional experiments are needed to confirm the use of I. ricinus calreticulin salivary protein as a potential discriminant antigenic biomarker to Ixodes tick exposure.

Analysis of the specificity of the salivary antigens of Ornithodoros erraticus for the purpose of serological detection of swine farms harbouring the parasite

In Spain, considerable efforts are currently being devoted to the eradication of Ornithodoros erraticus from the swine farms harbouring this parasite, the European vector of African swine fever (ASF). However, to do so, a preliminary requirement is to determine on which farms it is present. Of all possible methods for discovering this, the only one feasible for large scale application is the serological detection of swine bearing anti-O. erraticus antibodies. To apply serology it was necessary to check the specificity of extracts from the salivary glands (SGE) from O. erraticus. For this, indirect ELISA, competitive ELISA and Western blot were used to assay the SGE from O. erraticus and their corresponding antisera against the SGE and respective antisera from 4 ixodidae, one mange mite, one louse and a mosquito. The results obtained show that only the anti-ixodidae sera are able to react against the SGE from O. erraticus. The cause of this reaction are the somatic antigens present in the SGE of the argasid but not its soluble (secretory) antigens. It is proposed that the anti-cement antibodies present in the anti-ixodidae sera are those that react with the somatic antigens of O. erraticus.

The development of Amblyomma americanum and Dermacentor variabilis (Acari: Ixodidae) fed on rabbits immunized with tick hemolymph

The possibility of interfering with the normal function of tick hemolymph using antihemolymph antibodies taken in with the bloodmeal, was investigated. Cell free hemolymph from replete Amblyomma americanum and Dermacentor variabilis ticks was used to immunize rabbits. Immunized rabbits developed high antihemolymph antibody titers (ca. 10(5)) and had no ill side effects. Rabbits were simultaneously infested with larvae, nymphs, and adult ticks. The biological performance of ticks fed on immunized rabbits was virtually identical to that of ticks fed on nonimmunized rabbits. Usually, the mean engorgement weights of nymphs and females and the weights of the egg masses of both species were slightly higher for ticks fed on the nonimmunized rabbits but differences were not significant (P greater than 0.05) due to a large standard deviation. The possibility of deactivating a single hemolymph component with specific antibodies is discussed.

The interaction between the immune response of rabbits to heterologous antigens and a primary infestation with Rhipicephalus evertsi evertsi

Rhipicephalus evertsi evertsi feeding on hosts inoculated with sheep red blood cells (SRBC) and bovine serum albumin (BSA) suppressed the primary antibody response to the two antigens. In addition, while the ticks paralysed most hosts in the studies, fatality associated with this toxicosis occurred only in rabbits which had received SRBC, either alone or with BSA. Only those hosts inoculated with BSA developed any resistance against the ticks, manifested by a slight reduction of engorged weights and development of anti-tick antibodies. These results suggest that R. e. evertsi infestation induces a degree of reduced host immune responsiveness to heterologous antigens.

The effects of non-specifically activated immunity in rabbits on primary infestation with Rhipicephalus evertsi evertsi

The secondary antibody response to sheep red blood cells and bovine serum albumin (BSA) was measured in rabbits infested with adult Rhipicephalus evertsi evertsi. The response was reduced (particularly for BSA) but still displayed anamnestic characteristics. Resistance against ixodid ticks associated with antibodies detected by gel diffusion and enzyme linked immunosorbent assay techniques early in the primary challenge was acquired by the immunized hosts only. This suggests that a non-specifically activated immune system enables hosts to develop rapid resistance against tick parasitism.