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

Abstract

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.

The evaluation of cystatin protein vaccines based on the stress response of ticks triggered by low‐temperature and toxin stress in Haemaphysalis doenitzi

“…47 The rHlHK protein vaccines reduce engorged weight and egg mass weight in female ticks. 24 Fructose-1,6-bisphosphate aldolase protein vaccines have the same efficiency but do not have an impact on engorged time. 23 Differences in the efficiencies of the cystatin may be attributed to differences in the structure of the antigens and the effects of adjuvants.…”

“…The experiment was repeated three times and in total 18 rabbits were involved in the vaccination trial. 24 Rabbits were analyzed for antibody levels at 0, 7, 14, 21, 28, and 35 days after the first immunization by blood sampling from an ear vein. In the immunized serum, the OD value of the same dilution was measured by enzyme-linked immunosorbent assay (ELISA) to reflect the antibody level.…”

The potential of type 2 cystatin in blood feeding and innate immunity of the tick Haemaphysalis doenitzi (Acari: Ixodidae)

“…These areas present exciting opportunities for future research. Furthermore, investigating the target speci city of cystatin variants such as HDcyst-1, HDcyst-2, HDcyst-3, and HDcyst-4, and the development of anti-tick vaccines, represents intriguing avenues for upcoming studies (Wang et al 2023).…”

Iron regulatory protein from the hard tick Haemaphysalis longicornis: characterization, function and assessment as a protective antigen

“…The rHlIRP was identified using liquid chromatography with tandem mass spectrometry (LC-MS/MS) on a linear ion trap mass spectrometer (Thermo Fisher Scientific) according to established protocols. 16 2.5 Properties of rHlIRP 2.5.1 Aconitase assay The aconitase activity of rHlIRP was investigated using the method described by Cairo et al 17 and an aconitase assay kit (Solarbio Science & Technology, Beijing, China). Briefly, samples were diluted to 1.5 mg mL −1 and activated by adding a solution containing 2.5 mM cysteine hydrochloride and 25 μM ferrous ammonium sulfate.…”

“…Serum antibody levels were assessed 7 days after each immunization using indirect ELISA. 16 Individual serum samples were evaluated, with all reactions performed in triplicate. Ten days after the third inoculation, rabbits were subcutaneously challenged with 23 female and 23 male ticks.…”