Production and evaluation of multiantigenic tick vaccine formulations against Rhipicephalus microplus

Author(s)

Natalia Serra Mendes

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina de Ribeirão Preto (PCARP/BC)
• Defense date: 2024-07-24

Examining board members

Beatriz Rossetti Ferreira; Luiz Gustavo Araujo Gardinassi; Ricardo Tostes Gazzinelli; Sandra Regina Costa Maruyama

• Advisor: Beatriz Rossetti Ferreira

Abstract

Ticks are important vectors capable of parasitizing nearly all classes of vertebrates and transmitting a variety of infectious diseases. In the agricultural scenario, the Rhipicephalus microplus tick is particularly harmful to cattle in tropical and subtropical areas worldwide, representing a significant limiting factor for bovine productivity. The control of R. microplus ticks is mainly achieved through the application of chemical acaricides. However, the indiscriminate use of acaricides for ticks has led to environmental contamination and contamination of animal products, as well as the selection of tick populations resistant to the active ingredients used. It is increasingly necessary to develop more sustainable and efficient options for controlling bovine ticks, such as vaccines. In this study, a clinical trial of vaccine immunization was conducted on 30 Holstein Friesian heifers using a combination of ten recombinant proteins derived from R. microplus saliva (formulation V1.0). Additionally, a group of animals was immunized with two multiantigenic (chimeric) proteins adjuvanted with aluminum hydroxide (formulation V2.0). Thirty-five days after the last immunization, the animals were subjected to a challenge infestation with R. microplus ticks. The data obtained did not indicate protection in the immunized animals compared to the control group, although antigen-specific seroconversion occurred for almost all proteins in formulation V1.0. It is inferred that the experimental management adopted did not allow the ticks to complete their natural feeding cycle, affecting the evaluation of vaccine formulation efficacy. Furthermore, the 100 g dose of chimeric formulation V2.0 used in this study may have been insufficient to induce an effective immune response and confer protection to the animals against ticks. At the end of this work, new chimeric proteins with lower molecular mass were designed and produced, demonstrating an approximately fourfold higher yield than the proteins used in formulation V2.0. In addition, an in silico analysis of B cell epitope prediction was performed, revealing that most epitopes present in individual proteins are retained in the chimeric proteins. These results indicate that the new chimeric multiantigenic proteins will likely be recognized and induce a similar immune response to that observed with individual use in formulation V1.0. (AU)

• FAPESP's process: 20/04990-9 - Characterization of the local and systemic immune response of immunized cattle with a multi-antigenic anti-R. microplus vaccine for the determination of immunological markers of tick protection
• Grantee: Natalia Serra Mendes
• Support Opportunities: Scholarships in Brazil - Doctorate