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.

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

Haemaphysalis longicornis is an obligate haematophagous ectoparasite, transmitting a variety of pathogens, which brings great damage to human health and animal husbandry development. Lipocalins (LIP) are a family of proteins that transport small hydrophobic molecules and also involve in immune regulation, such as the regulation of cell homeostasis, inhibiting the host's inflammatory response and resisting the contractile responses in host blood vessels. Therefore, it is one of the candidate antigens for vaccines. Based on previous studies, we constructed the recombinant plasmid pcDNA3.1-HlLIP of LIP homologue from H. longicornis (HlLIP). ELISA results showed that rabbits immunized with pcDNA3.1-HlLIP produced higher anti-rHlLIP antibody levels compared with the pcDNA3.1 group, indicating that pcDNA3.1-HlLIP induced the humoral immune response of host. Adult H. longicornis infestation trial in rabbits demonstrated that the engorgement weight, oviposition and hatchability of H. longicornis fed on rabbits immunized with pcDNA3.1-HlLIP decreased by 7.07%, 14.30% and 11.70% respectively, compared with that of the pcDNA3.1 group. In brief, DNA vaccine of pcDNA3.1-HlLIP provided immune protection efficiency of 30% in rabbits. This study demonstrated that pcDNA3.1-HlLIP can partially protect rabbits against H. longicornis, and it is possible to develop a new candidate antigen against ticks.

Characterization and evaluation of a new triosephosphate isomerase homologue from Haemaphysalis longicornis as a candidate vaccine against tick infection.

Haemaphysalis longicornis is an obligate hematophagous ectoparasite that transmits a variety of pathogens causing life­threatening diseases in humans and animals. Triosephosphate isomerase (TIM) is a key enzyme in glycometabolism, making in an interesting anti-tick vaccine candidate antigen. In this study, the open reading frame (ORF) of the TIM homologue from H. longicornis (HlTIM) was shown to consist of 747 bp encoding a protein of 248 amino acids. HlTIM gene expression was detected in all developmental stages and in all tissues of the unfed female tick by quantitative real-time PCR. The HlTIM gene was cloned and inserted into pET-32a (+) to obtain the recombinant HlTIM protein (rHlTIM) and its immunogenicity was confirmed by Western blot. ELISA results showed that rabbits immunized with rHlTIM produced a humoral immune response. A vaccine trial in rabbits against H. longicornis infestation demonstrated that the engorgement weight, oviposition and hatchability of ticks from the rH1TIM group was decreased by 8.6%, 35.4% and 17.3% respectively, compared to the histidine-tagged thioredoxin (Trx) control group. Considering the cumulative effect of vaccination on the evaluated parameters, results showed 50.9% efficacy in the rHlTIM group. The data reported here demonstrate that rHlTIM has potential for further development of a new candidate vaccine for tick control.

Palladium-catalyzed one-pot synthesis of diazoles via tert-butyl isocyanide insertion.

An efficient one-pot palladium-catalyzed reaction for the synthesis of diazoles from readily available hydrazides and aryl halide via isocyanide insertion/cyclization sequence has been developed. This methodology efficiently constructs diazoles in good to excellent yields with the advantages of wide functional group tolerance and operational simplicity.