Abstract
Ticks and tick-borne pathogens affect health and welfare of companion animals worldwide, and some human tick-borne diseases are associated with exposure to domestic animals. Vaccines are the most environmentally friendly alternative to acaracides for the control of tick infestations, and to reduce the risk for tick-borne diseases affecting human and animal health. However, vaccines have not been developed or successfully implemented for most vector-borne diseases. The main limitation for the development of effective vaccines is the identification of protective antigens. To address this limitation, in this study we used an experimental approach combining vaccinomics based on transcriptomics and proteomics data with vaccination trials for the identification of tick protective antigens. The study was focused on Ixodes ricinus and Dermacentor reticulatus that infest humans, companion animals and other domestic and wild animals, and transmit disease-causing pathogens. Tick larvae and adult salivary glands were selected for analysis to target tick organs and developmental stages playing a key role during tick life cycle and pathogen infection and transmission. Two I. ricinus (heme lipoprotein and uncharacterized secreted protein) and five D. reticulatus (glypican-like protein, secreted protein involved in homophilic cell adhesion, sulfate/anion exchanger, signal peptidase complex subunit 3, and uncharacterized secreted protein) proteins were identified as the most effective protective antigens based on the criteria of vaccine E > 80%. The putative function of selected protective antigens, which are involved in different biological processes, resulted in vaccines affecting multiple tick developmental stages. These results suggested that the combination of some of these antigens might be considered to increase vaccine efficacy through antigen synergy for the control of tick infestations and potentially affecting pathogen infection and transmission. These antigens were proposed for commercial vaccine development for the control of tick infestations in companion animals, and potentially in other hosts for these tick species.
Highlights
Tick-borne pathogens cause medically important infections affecting dogs and other pet species worldwide (Liu et al, 2018; Skotarczak, 2018), and some human tick-borne diseases are associated with exposure to domestic animals (Estrada-Peña et al, 2008; Kwit et al, 2018; Escárcega-Ávila et al, 2019)
The hypothesis was that the genes encoding for functionally important secreted proteins that are highly represented in both L and SG would result in good candidate tick protective antigens
The algorithm included the generation of transcriptomics and proteomics data in tick L and SG, and selection of gene transcripts and proteins highly represented in both samples and encoding for predicted functionally important secreted proteins
Summary
Tick-borne pathogens cause medically important infections affecting dogs and other pet species worldwide (Liu et al, 2018; Skotarczak, 2018), and some human tick-borne diseases are associated with exposure to domestic animals (Estrada-Peña et al, 2008; Kwit et al, 2018; Escárcega-Ávila et al, 2019). Vaccines have not been developed or successfully implemented for most vector-borne diseases (VBD) affecting humans and animals (de la Fuente et al, 2017b). Traditional control methods for arthropod vector infestations are based on the use of chemical acaricides with associated drawbacks such as selection of arthropod-resistant strains and contamination of both the environment and animal products (de la Fuente and Kocan, 2003; de la Fuente et al, 2017b). Vaccines could be developed to target different tick developmental stages and functions on various hosts with the advantage of avoiding environmental contamination and selection of pesticide resistant arthropod vectors while improving animal welfare and production (de la Fuente et al, 2017b; de la Fuente, 2018). The hypothesis behind tick vaccine protective capacity is that ticks feeding on immunized hosts ingest antibodies specific for the target antigen that could reduce its levels and biological activity and/or interact with conserved epitopes in other proteins resulting in reduced tick feeding, development and reproduction (de la Fuente et al, 2011, 2017b; Moreno-Cid et al, 2011; de la Fuente, 2018)
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