A combination of antibodies against Bm86 and Subolesin inhibits engorgement of Rhipicephalus australis (formerly Rhipicephalus microplus) larvae in vitro

Abstract

Background Rhipicephalus microplus is a hard tick species that has a high impact on cattle health and production in tropical and subtropical regions. Recently, ribosomal DNA and morphological analysis resulted in the reinstatement of R. australis as a separate species from R. microplus . Both feed on cattle and can transmit bovine pathogens such as Anaplasma and Babesia species. The current treatment with acaricides is becoming increasingly less effective due to the emergence of resistant tick strains. A promising alternative can be found in the form of anti-tick vaccines. The available commercial vaccines can be used to control tick infestation, but the lack of a knockdown effect (> 90% reduction in tick numbers as seen with effective acaricides) hampers its widespread use, hence higher efficacious vaccines are needed. Instead of searching for new protective antigens, we investigated the efficacy of vaccines that contain more than one (partially) protective antigen. For screening vaccine formulations, a previously developed in vitro feeding assay was used in which R. australis larvae are fed sera that were raised against the candidate vaccine antigens. In the present study, the efficacy of the Bm86 midgut antigen and the cytosolic Subolesin (SUB) antigen were evaluated in vitro . Results Antiserum against recombinant Bm86 (rBm86) partially inhibited larval engorgement, whereas antiserum against recombinant SUB (rSUB) did not have any effect on feeding of larvae. Importantly, when larvae were fed a combination of antiserum against rBm86 and rSUB, a synergistic effect on significantly reducing larval infestations was found. Immunohistochemical analysis revealed that the rBm86 antiserum reacted with gut epithelium of R. australis larvae, whereas the antiserum against rSUB stained salivary glands and rectal sac epithelium. Conclusions Combining anti-Bm86 and anti-subolesin antibodies synergistically reduced R. australis larval feeding in vitro . Rhipicephalus australis is a one host tick, meaning that the larvae develop to nymphs and subsequently adults on the same host. Hence, this protective effect could be even more pronounced when larvae are used for infestation of vaccinated cattle, as the antibodies could then affect all three developmental stages. This will be tested in future in vivo experiments.

Cocktail Anti-Tick Vaccines: The Unforeseen Constraints and Approaches toward Enhanced Efficacies

“…Recently, Trentelman et al [ 66 ] exploited in vitro tick feeding for larval stages to examine the effect of a cocktail anti-tick vaccine serum. They demonstrated that a combination of anti-Bm86 and anti-subolesin serum inhibited the feeding of Rhipicephalus australis larvae, which suggested that the antigens were candidates for a cocktail vaccine.…”

Immunoinformatic Analysis to Identify Proteins to Be Used as Potential Targets to Control Bovine Anaplasmosis

“…In A. marginale, a large number of laboratory studies have focused on the MSPs and the Type Four Secretion System proteins, but none of them have resulted in a vaccine capable of protecting cattle [ 28 , 29 , 30 ]. In the case of R. microplus , several recombinant vaccines have been developed; however, the search for new targets continue [ 6 , 8 ]. In the present work, we have performed an analysis of the complete genome sequences of all Mexican A. marginale strains and extracted the sequences of membrane-associated proteins.…”

“…So far, there are no commercial vaccines against bovine anaplasmosis, and those that have been prepared from freed bacteria (initial bodies) have a limited use due to a wide antigenic diversity of the pathogen, while those prepared from live attenuated organisms carry the risk for the cotransmission of other blood-borne pathogens [ 2 , 5 ]. With regards to tick vaccination, recent studies have shown that antitick recombinant vaccines such as aquaporin, subolesin, and tick gut glycoprotein Bm86 have a synergistic effect in reducing the engorgement of tick larvae in vitro [ 6 , 7 , 8 ]. So, an integral view of the tick-pathogen relationship should be considered to propose not only effective control measures but also successful diagnostic and vaccination methods as those recently reported [ 8 , 9 , 10 ].…”

“…With regards to tick vaccination, recent studies have shown that antitick recombinant vaccines such as aquaporin, subolesin, and tick gut glycoprotein Bm86 have a synergistic effect in reducing the engorgement of tick larvae in vitro [ 6 , 7 , 8 ]. So, an integral view of the tick-pathogen relationship should be considered to propose not only effective control measures but also successful diagnostic and vaccination methods as those recently reported [ 8 , 9 , 10 ].…”

An Improved Method for in Vitro Feeding of Dermanyssus Gallinae (Poultry Red Mite) Using Baudruche Membrane (Goldbeater’s Skin).

“…To our knowledge, this is the rst published report on the use of Baudruche membrane in the feeding of D. gallinae, although it has been used for tick feeding in conjunction with silicone as recently as 2019 [13] and for mosquitoes as early as 1964 [14]. Although chick skin has been used successfully to allow in vitro feeding of PRM [5,8,9] availability and ease of use of arti cial membranes has led to their more frequent use.…”