Evaluation of anti-tick efficiency in rabbits induced by DNA vaccines encoding Haemaphysalis longicornis lipocalin homologue

Human Tick-Borne Diseases and Advances in Anti-Tick Vaccine Approaches: A Comprehensive Review

This comprehensive review explores the field of anti-tick vaccines, addressing their significance in combating tick-borne diseases of public health concern. The main objectives are to provide a brief epidemiology of diseases affecting humans and a thorough understanding of tick biology, traditional tick control methods, the development and mechanisms of anti-tick vaccines, their efficacy in field applications, associated challenges, and future prospects. Tick-borne diseases (TBDs) pose a significant and escalating threat to global health and the livestock industries due to the widespread distribution of ticks and the multitude of pathogens they transmit. Traditional tick control methods, such as acaricides and repellents, have limitations, including environmental concerns and the emergence of tick resistance. Anti-tick vaccines offer a promising alternative by targeting specific tick proteins crucial for feeding and pathogen transmission. Developing vaccines with antigens based on these essential proteins is likely to disrupt these processes. Indeed, anti-tick vaccines have shown efficacy in laboratory and field trials successfully implemented in livestock, reducing the prevalence of TBDs. However, some challenges still remain, including vaccine efficacy on different hosts, polymorphisms in ticks of the same species, and the economic considerations of adopting large-scale vaccine strategies. Emerging technologies and approaches hold promise for improving anti-tick vaccine development and expanding their impact on public health and agriculture.

Molecular characterization of hexokinase (HK) in Haemaphysalis longicornis and evaluation of HK protein- and DNA-based vaccines against adult ticks

BACKGROUND

Haemaphysalis longicornis is an obligate hematophagous ectoparasite, which transmits various pathogens to humans, livestock and wild animals. Hexokinase (HK) is a key regulatory enzyme of the glycolytic pathway in the organisms. However, little is known about hexokinase and its functions in ticks.

RESULTS

The open reading frame of the H. longicornis HK (HlHK) gene was 1425 bp and encoded a protein of 474 amino acids, containing conserved domains for glucose, glucose 6-phosphate, and adenosine triphosphate. The expression of HlHK gene was detected at different developmental stages and in different tissues of unfed female ticks. Enzyme-linked immunosorbent assay revealed that both HK protein- and DNA-based vaccines increased the antibody levels of the immunized animals. A vaccination trail on rabbits against H. longicornis infestation indicated that the rHlHK protein and HlHK DNA vaccines reduced the number of attached female ticks by 9% and 12%, egg mass weight by 36% and 34%, and egg hatching rate by 41% and 17%, respectively. Overall, protein vaccination conferred 65.6% protection against adult female ticks, whereas the DNA vaccine conferred 51.8% protection.

CONCLUSION

This is the first report of the molecular characterization of the HK protein and sequencing of the HK gene from H. longicornis. Positive results from vaccination trials on rabbits of the recombinant HK protein and HK DNA suggest that these novel anti-tick vaccines potentially can be used as viable tick control tools for the management of the Asian longhorned tick. Additionally, inhibition of glucose metabolism may be a new strategy for tick control. © 2023 Society of Chemical Industry.

Recent Advances in Tick Antigen Discovery and Anti-Tick Vaccine Development

Ticks can seriously affect human and animal health around the globe, causing significant economic losses each year. Chemical acaricides are widely used to control ticks, which negatively impact the environment and result in the emergence of acaricide-resistant tick populations. A vaccine is considered as one of the best alternative approaches to control ticks and tick-borne diseases, as it is less expensive and more effective than chemical controls. Many antigen-based vaccines have been developed as a result of current advances in transcriptomics, genomics, and proteomic techniques. A few of these (e.g., Gavac® and TickGARD®) are commercially available and are commonly used in different countries. Furthermore, a significant number of novel antigens are being investigated with the perspective of developing new anti-tick vaccines. However, more research is required to develop new and more efficient antigen-based vaccines, including on assessing the efficiency of various epitopes against different tick species to confirm their cross-reactivity and their high immunogenicity. In this review, we discuss the recent advancements in the development of antigen-based vaccines (traditional and RNA-based) and provide a brief overview of recent discoveries of novel antigens, along with their sources, characteristics, and the methods used to test their efficiency.