Response of Leucine-Rich Repeat Domain-Containing Protein in Haemaphysalis longicornis to Babesia microti Infection and Its Ligand Identification

Expression characteristics and inhibitory activity of a leucine-rich repeat (LRR)-only protein in the Chinese mitten crab, Eriocheir sinensis

The leucine-rich repeat (LRR) domain is a crucial structure in a variety of immune related proteins and displays multiple immune functions. In this study, the open reading frame (ORF) of an LRR-only protein was cloned from the Chinese mitten crab, Eriocheir sinensis (EsLRRop1). The protein sequence of EsLRRop1 contained seven LRR motifs, three LRR-TYP motifs and an LRRCT motif. Tissue distribution exhibited that EsLRRop1 mainly expressed in nervous tissues including thoracic ganglion, eyestalk and brain while showed relatively lower transcriptional level in hemocyte. Based on the above expression characteristics, the responses of EsLRRop1 to the challenge of Vibrio parahaemolyticus and Staphylococcus aureus were tested. The result showed that the transcript of EsLRRop1 in thoracic ganglion and eyestalk up-regulated after being challenged with S. aureus, while it decreased post injection with V. parahaemolyticus. The transcript of EsLRRop1 in hemocytes up-regulated sharply at 3 h and decreased at 12 h and 24 h after being challenged with V. parahaemolyticus, while it decreased at 12 h and 24 h post injection with S. aureus. The recombinant protein of EsLRRop1 (His-EsLRRop1) displayed binding activities to V. alginolyticus, V. harveyi, V. parahaemolyticus, S. aureus, Corynebacterium glutamicum and Micrococcus lysodeikticus as well as lipopolysaccharide (LPS) and peptidoglycan (PGN). Moreover, the His-EsLRRop1 exhibited inhibitory activity against V. parahaemolyticus and V. harveyi with minimum inhibitory concentration (MIC) of 3.57-7.14 μM and 7.14-14.28 μM, respectively. These results provide theoretical basis for the application of EsLRRop1 in inhibiting bacteria in aquaculture practice.

Molecular Detection of Tick-Borne Bacterial and Protozoan Pathogens in Haemaphysalis longicornis (Acari: Ixodidae) Ticks from Free-Ranging Domestic Sheep in Hebei Province, China

Ticks and tick-borne pathogens significantly threaten human and animal health worldwide. Haemaphysalis longicornis is one of the dominant tick species in East Asia, including China. In the present study, 646 Ha. longicornis ticks were collected from free-ranging domestic sheep in the southern region of Hebei Province, China. Tick-borne pathogens of zoonotic and veterinary importance (i.e., Rickettsia, Anaplasma, Ehrlichia, Borrelia, Theileria, and Hepatozoon spp.) were detected in the ticks using PCR assays and sequence analysis. The prevalence rates of these pathogens were 5.1% (33/646), 15.9% (103/646), 1.2% (8/646), 17.0% (110/646), 0.15% (1/646), and 0.15% (1/646), respectively. For Rickettsia spp., R. japonica (n = 13), R. raoultii (n = 6), and Candidatus R. jingxinensis (n = 14) were detected for the first time in the province, while several Anaplasma spp. were also detected in the ticks, including A. bovis (n = 52), A. ovis (n = 31), A. phagocytophilum (n = 10), and A. capra (n = 10). A putative novel Ehrlichia spp. was also found with a prevalence of 1.2% in the area. The present study provides important data for effectively controlling ticks and tick-borne diseases in the Hebei Province region of China.

Saliva proteome of partially- and fully-engorged adult female Haemaphysalis flava ticks

Tick saliva is a reservoir of bioactive proteins. Saliva protein compositions change dynamically during blood-feeding. Decipherment of protein profiles in different blood-feeding stages may bring deeper insight into tick feeding physiology and provide targets for immunologic control alternatives. However, having the infancy of tick genome sequencing, assembly, annotation, and limited knowledge of tick salivary proteins restrain the data interpretation. Here, we aimed to depict the saliva protein profile in partially- (PE) and fully-engorged (FE) Haemaphysalis flava ticks, with a special focus on the analysis of those uncharacterized proteins. Saliva was collected from PE and FE adult female H. flava ticks. Saliva proteins were analyzed by high-performance liquid chromatography-tandem mass spectrometry (HPLC/MS-MS). MS data were searched against an in-house salivary gland transcriptome library for identification of tick-derived proteins. Abundances of proteins were compared between PE and FE ticks. The uncharacterized proteins detected in saliva were further bioinformatically analyzed. In total, 614 proteins were identified including 94 host proteins and 520 tick-derived proteins. The 226 tick-derived high-confidence proteins were classified into 10 categories: transporters, enzymes, protease inhibitors, immunity-related proteins, lipocalins, glycine-rich proteins, muscle proteins, secreted proteins, uncharacterized proteins and others. A total of 98 proteins were shared in both PE and FE with 74 only in PE and 54 only in FE. Abundances of 24 shared proteins were significantly higher in PE. The profile of top 15 most abundant proteins was also different between PE and FE ticks. The 65 uncharacterized proteins detected in tick saliva were branched into subclusters 1 A, 1B, 2, 3 A, 3B and 3 C based on particular motifs like RGD, LRR, indicating their diverse predicted functions like anti-coagulation, regulation of innate immune, or other functions. This study provides and compares saliva proteomes of H. flava ticks in two feeding stages with special cluster analysis on the uncharacterized proteins. Further investigations are needed to confirm the roles of these uncharacterized proteins in ticks.