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

BACKGROUND: Ticks, which are obligate blood-feeding parasites, transmit a wide range of pathogens during their hematophagic process. Certain enzymes and macromolecules play a crucial role in inhibition of several tick physiological processes, including digestion and reproduction. In the present study, genes encoding type 2 cystatin were cloned and characterized from Haemaphysalis doenitzi, and the potential role of cystatin in tick control was further assessed. RESULTS: Two cystatin genes, HDcyst-1 and HDcyst-2, were successfully cloned from the tick H. doenitzi. Their open reading frames are 390 and 426 base pairs, and the number of coding amino acids are 129 and 141, respectively. In the midgut, salivary glands, Malpighian tubules and ovaries of ticks, the relative expression of HDcyst-1 was higher in the midgut and Malpighian tubules, and HDcyst-2 was higher in the salivary glands of H. doenitzi, respectively. Lipopolysaccharide (LPS) injection and low-temperature stress elevated cystatin expression in ticks. Enzyme-linked immunosorbent assay showed that both rHDcyst-1 and rHDcyst-2 protein vaccines increased antibody levels in immunized rabbits. A vaccination trial in rabbits infected with H. doenitzi showed that both recombinant cystatin proteins significantly reduced tick engorgement weights and egg mass weight, in particular, rHDcyst-1 significantly prolonged tick engorgement time by 1 day and reduced egg hatching rates by 16.9%. In total, rHDcyst-1 and rHDcyst-2 protein vaccinations provided 64.1% and 51.8% protection to adult female ticks, respectively. CONCLUSION: This is the first report on the immunological characterization of the cystatin protein and sequencing of the cystatin gene in H. doenitzi. Cystatin proteins are promising antigens that have the potential to be used as vaccines for infestation of H. doenitzi control. © 2024 Society of Chemical Industry.

Morphological environment survey and hydrodynamic modeling of a large bifurcation-confluence complex in Yangtze River, China.

Since the establishment of the world-class Three Gorges Dam (TGD) across the Yangtze River, China, the downstream reach has experienced a long-term adjustment with regard to the river morphology and hydrodynamics, imposing a profound impact on the environmental conditions of human living and aquatic ecosystem. This study presents an investigation on the river channel morphological characteristics and hydrodynamic environment of a large bifurcation-confluence complex downstream of the TGD through detailed field survey and numerical modeling. Results show that the main stem, before being bifurcated into two sub-channels (the North Channel and the South Channel), experiences a meander, leading to the severe bed scouring near the outer bank (pools) resulted from a high flow mass flux and bed shear stress. Because of being bifurcated, the river width with largely growing may result in the reduction of flow velocity and sediment deposition (riffles), and thereby two plugbars are formed near the entrance of two sub-channels. In the meantime, the velocity-reversal phenomenon (flow velocity and friction velocity) is identified when low flows are transited into high flows. The flow mass flux, however, is always larger in pool regions, which is highly related to water depth. As a result, the topographic steering of flows by riffles, bars and floodplains may have more impact on flow path under low flow conditions, while the bankline shape would become more important under high flows. Furthermore, the topographic steering could play a key role in the pattern of flow separations near the confluence. More interestingly, the confluence flow separation only occurs under low flow conditions and its occurring location shifts upwards the tributary (the North Channel), which differs from observations in previous studies. The visualized numerical results of friction velocity distribution indicate that sediment is more likely to deposit in the North Channel (entrance) with lower friction velocity, implying the potential closure of the sub-channel.