Tick- host- pathogen interactions and vaccine development for the control of tick-borne diseases

Resumen

Tick-borne diseases have a negative impact on human and animal health worldwide. Ticks are the most important vectors of pathogens that cause different diseases in humans, domestic and wild animals. Traditional tick control methods are primarily based on the use of chemical acaricides, which can result in the selection of resistant ticks, environmental pollution, and contamination of milk and meat products with residues affecting in particular the cattle industry. Chapter I: General introduction Content: Chapter I is a review paper [de la Fuente, J., and Contreras, M. (2015). Tick vaccines: current status and future directions. Expert. Rev. Vaccines. 14, 1367-1376] that constitute an introduction for this thesis by reviewing the importance of tick vaccines as an alternative environmentally sound approach for the control of tick infestations and pathogen infection and transmission. This chapter also describes critical issues, and recommendations for future directions towards developing improved and effective tick vaccines. The results with commercial vaccines for the control of cattle tick infestations support the efficacy of tick vaccines under field conditions. Future strategies include the vaccinomics pipeline developed by our group for the identification and characterization of tick protective antigens. Vaccinomics is a holistic approach based on the use of genome-scale or omics technologies integrated in a systems biology approach to characterize tick-host-pathogen interactions for the development of next-generation vaccines. In vaccinomics, the integration of “omics” technologies can improve the probability of identifying new candidate protective antigens, therefore advancing the development of effective vaccines. Furthermore, we propose that the combination of tick-derived and pathogen-derived protective antigens could result in more effective vaccines for the prevention and control of tick-borne diseases. Chapter II: Vaccinomics for the identification and characterization of candidate protective antigens Content: In chapter II, the intracellular bacterium, Anaplasma phagocytophilum, which causes human and animal granulocytic anaplasmosis, and its tick vectors, Ixodes scapularis and I. ricinus are used as models for the identification of tick-derived and pathogen-derived candidate protective antigens using a vaccinomics approach. The sequence, assembly and annotation of the I. scapularis genome were recently released, and transcriptomics studies in I. ricinus suggest that these tick species are genetically closely related [Genomic Resources Development Consortium, Contreras, M., de la Fuente, J., Estrada-Peña, A., Grubhoffer, L., and Tobes, R. (2014). Transcriptome sequence divergence between Lyme disease tick vectors, Ixodes scapularis and Ixodes ricinus. Genomic Resources Notes accepted 1 April 2014 – 31 May 2014. Mol. Ecol. Resour. 14: 1095]. The vaccinomics pipeline was developed based on quantitative transcriptomics and proteomics data from uninfected and A. phagocytophilum-infected I. scapularis nymphs, adult female midguts and salivary glands [Contreras, M., Villar, M., Alberdi, P., and de la Fuente, J. (2016). Vaccinomics approach to tick vaccine development. Methods. Mol. Biol. 1404, 275-286]. This approach resulted in the identification of the candidate tick protective antigens, lipocalin (ISCW005600) and lectin pathway inhibitor (AAY66632) for the control of vector infestations and A. phagocytophilum infection [Contreras, M., Alberdi, P., Fernández de Mera, I.G., Krull, C., Nijhof, A., Villar, M., de la Fuente, J. (2017). Vaccinomics approach to the identification of candidate protective antigens for the control of vector infestations and pathogen infection. Front. Cell. Infect. Microbiol., 7:360. doi:10.3389/fcimb.2017.00360]. Additionally, the characterization of protein-protein interactions at the host-pathogen interface are characterized in order to discover and design new pathogen-derived protective antigens [Contreras, M., Alberdi, P., Mateos-Hernández, L., Fernández de Mera, I.G., García-Pérez, A.L., Vancová, M., et al. (2017). Anaplasma phagocytophilum MSP4 and HSP70 proteins are involved in interactions with host cells during pathogen infection. Front. Cell. Infect. Microbiol. 7: 307]. The results show that A. phagocytophilum MSP4-HSP70 are involved in interaction and infection of host cells, but were only partially protective against pathogen infection in sheep. However, these antigens may constitute candidate protective antigens for the development of vaccines against tick borne diseases when used in combination with other antigens. Chapter III: Vaccination trails with tick protective antigens Chapter III describes vaccination trials that were conducted to evaluate the protective capacity of tick protective antigens for the control of tick infestations. The efficacy of the Q38 chimera, containing Subolesin (SUB) and Akirin (AKR) conserved protective epitopes, was evaluated on I. ricinus and Dermacentor reticulatus. It was demonstrated that Q38 vaccination had an efficacy of 99.9% and 46.4% on the control of I. ricinus and D. reticulatus larvae, respectively [Contreras, M., de la Fuente, J. (2016). Control of Ixodes ricinus and Dermacentor reticulatus tick infestations in rabbits vaccinated with the Q38 Subolesin/Akirin chimera. Vaccine 34: 3010-3013]. In a second trial, vaccination with the I. ricinus aquaporin (IrAQP) and a tick aquaporin conserved region (CoAQP) on I. ricinus larvae infestations had an efficacy of 32% and 80%, respectively [Contreras, M., de la Fuente, J. (2017). Control of infestations by Ixodes ricinus tick larvae in rabbits vaccinated with aquaporin recombinant antigens. Vaccine 35: 1323-1328]. Finally, the characterization, composition and immunogenicity of the membrane-bound SUB-Anaplasma marginale MSP1a chimeric antigen is presented [Contreras, M., Moreno-Cid, J.A., Domingos, A., Canales, M., Díez-Delgado, I., Pérez de la Lastra, J.M., Sánchez, E., Merino, O., López Zavala, R., Ayllón, N., Boadella, M., Villar, M., Gortázar, C., de la Fuente, J. (2015). Bacterial membranes enhance the immunogenicity and protective capacity of the surface exposed tick Subolesin-Anaplasma marginale MSP1a chimeric antigen. Ticks and Tick-Borne Diseases 6: 820-828]. The SUB-MSP1a chimeric antigen was produced in Escherichia coli as a membrane-bound and exposed protein and used to protect vaccinated cattle against tick infestations. In this study, lipidomics and proteomics characterization showed the presence of components with potential adjuvant effect in the bacterial membrane, enhancing the immunogenicity of the SUB-MSP1a antigen in mouse and pig vaccination models. In addition, this system provides a simple and cost-effective approach, to produce tick protective chimera antigens on the E. coli membrane, with endotoxin levels within the limits acceptable for recombinant vaccine formulations. Chapter IV: General discussion Chapter IV is presented as a general discussion with an overview of the challenges to the control of tick-borne diseases through vaccine intervention, and also the current status of vaccines for the control of tick-borne diseases [de la Fuente, J., Contreras, M., Estrada-Peña, A., Cabezas-Cruz, A. (2017). Targeting a global health problem: Vaccine design and challenges for the control of tick-borne diseases. Vaccine, (35) 5089–5094]. These vaccines could constitute the safest and most effective intervention for the control of tick-borne diseases, inducing a long-lasting immunity, and reducing or even preventing tick infestation, pathogen infection and transmission in humans, domestic and wild animals.