Abstract
A synthetic 20 amino acid peptide of the ribosomal protein P0 from ticks, when conjugated to keyhole limpet hemocyanin from Megathura crenulata and used as an immunogen against Rhipicephalus microplus and Rhipicephalus sanguineus s.l. species, has shown efficacies of around 90%. There is also experimental evidence of a high efficacy of this conjugate against Amblyomma mixtum and Ixodes ricinus species, which suggest that this antigen could be a good broad-spectrum anti-tick vaccine candidate. In this study, the P0 peptide (pP0) was chemically conjugated to Bm86 as a carrier protein. SDS-PAGE analysis of this conjugate demonstrated that it is highly heterogeneous in size, carrying from 1 to 18 molecules of pP0 per molecule of Bm86. Forty-nine out of the 54 lysine residues and the N-terminal end of Bm86 were found partially linked to pP0 by using LC-MS/MS analysis and the combination of four different softwares. Several post-translational modifications of Bm86 protein were also identified by mass spectrometry. High immunogenicity and efficacy were achieved when dogs and cattle were vaccinated with the pP0–Bm86 conjugate and challenged with R. sanguineus s.l. and R. microplus, respectively. These results encourage the development of this antigen with promising possibilities as an anti-tick vaccine.
Highlights
Ticks cause direct damage to infested hosts by debilitating effects but they may act as vectors of agents that cause diseases that in many cases can be lethal [1]
Many authors agree that the combination of several immunogens, involved in different physiological processes in the same preparation, could contribute to an increase in the efficacy of anti-tick vaccines [35,36,37]
Bm86 nanoparticles produced by P. pastoris yeasts, which are the active pharmaceutical ingredient of GavacTM [38], this protein should be the candidate of choice as a carrier protein for the efficient presentation of pP0 to the host immune system
Summary
Ticks cause direct damage to infested hosts by debilitating effects but they may act as vectors of agents that cause diseases that in many cases can be lethal [1]. As an alternative to acaricides, is based on host immunizations with an antigenic protein derived from ticks. The immune response against these antigens should be able to affect the parasite life cycle, reducing the viable larva “yield” after each generation of parasites fed on vaccinated animals [2]. Many attempts to identify such antigens have been carried out by anti-tick vaccine developers after successful Rhipicephalus microplus immunological control was achieved by cattle vaccination with the concealed antigen Bm86. This is a glycoprotein identified by an Australian group that is located at the epithelial cell membrane of the tick gut [3]
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