Identification and characterization of a cathepsin L-like cysteine protease from Rhipicephalus (Boophilus) annulatus

Borrelia theileri infections in Rhipicephalus annulatus ticks from the north of Iran

Ticks serve as vectors and reservoirs of various Borrelia species, potentially causing diseases in humans and animals. Mazandaran, a fertile green land in northern Iran, provides ample grazing grounds for livestock and harbors at least 26 hard tick species. This study investigated Borrelia infection in hard ticks from forest areas in this region and compared their genetic identity with the species data in the GenBank database. A total of 2,049 ticks were collected manually from mammalian hosts or using dragging and flagging methods. These ticks were then grouped into 190 pools and 41 individuals based on host, species, developmental stage, and gender. A real-time PCR (qPCR) detected Borrelia DNA in 26 pools from female, male, and nymph of Rhipicephalus annulatus (n = 17) and Ixodes ricinus (n = 9) ticks and one individual female Haemaphysalis punctata tick. The generated partial flaB and glpQ sequences from qPCR-positive Rh. annulatus ticks exhibited the highest identities of 98.1-100% and 98.2% with Borrelia theileri and closely related undefined isolates. Additionally, in phylogenetic analysis, these sequences clustered within well-supported clades with B. theileri and the closely related undefined isolates from various geographic regions, confirming the presence of B. theileri in the north of Iran. Divergence in B. theileri flaB and glpQ sequences across various geographical areas suggests potential subspeciation driven by adaptations to different tick species. This divergence in our flaB sequences implies the possible introduction of B. theileri-infected ticks from different geographical origins into Iran.

Characterization of cysteine proteases from poultry red mite, tropical fowl mite, and northern fowl mite to assess the feasibility of developing a broadly efficacious vaccine against multiple mite species

Infestation with poultry red mites (PRM, Dermanyssus gallinae) causes anemia, reduced egg production, and death in serious cases, resulting in significant economic losses to the poultry industry. As a novel strategy for controlling PRMs, vaccine approaches have been focused upon and several candidate vaccine antigens against PRMs have been reported. Tropical (TFM, Ornithonyssus bursa) and northern (NFM, Ornithonyssus sylviarum) fowl mites are also hematophagous and cause poultry industry problems similar to those caused by PRM. Therefore, ideal antigens for anti-PRM vaccines are molecules that cross-react with TFMs and NFMs, producing pesticidal effects similar to those against PRMs. In this study, to investigate the potential feasibility of developing vaccines with broad efficacy across mite species, we identified and characterized cysteine proteases (CPs) of TFMs and NFMs, which were previously reported to be effective vaccine antigens of PRMs. The open reading frames of CPs from TFMs and NFMs had the same sequences, which was 73.0% similar to that of PRMs. Phylogenetic analysis revealed that the CPs of TFMs and NFMs clustered in the same clade as CPs of PRMs. To assess protein functionality, we generated recombinant peptidase domains of CPs (rCP-PDs), revealing all rCP-PDs showed CP-like activities. Importantly, the plasma obtained from chickens immunized with each rCP-PD cross-reacted with rCP-PDs of different mites. Finally, all immune plasma of rCP-PDs reduced the survival rate of PRMs, even when the plasma was collected from chickens immunized with rCP-PDs derived from TFM and NFM. Therefore, CP antigen is a promising, broadly efficacious vaccine candidate against different avian mites.

Pathogenesis and defense mechanism while Beauveria bassiana JEF-410 infects poultry red mite, Dermanyssus gallinae

The poultry red mite, Dermanyssus gallinae (Mesostigmata: Dermanyssidae), is a major pest that causes great damage to chicken egg production. In one of our previous studies, the management of red mites using entomopathogenic fungi was evaluated, and the acaricidal fungus Beauveria bassiana JEF-410 was selected for further research. In this study, we tried to elucidate the pathogenesis of B. bassiana JEF-410 and the defense mechanisms of red mites at a transcriptome level. Red mites collected from a chicken farm were treated with B. bassiana JEF-410. When the mortality of infected red mites reached 50%, transcriptome analyses were performed to determine the interaction between B. bassiana JEF-410 and red mites. Uninfected red mites and non-infecting fungus served as controls. In B. bassiana JEF-410, up-regulated gene expression was observed in tryptophan metabolism and secondary metabolite biosynthesis pathways. Genes related to acetyl-CoA synthesis were up-regulated in tryptophan metabolism, suggesting that energy metabolism and stress management were strongly activated. Secondary metabolites associated with fungal up-regulated DEGs were related to the production of substances toxic to insects such as beauvericin and beauveriolide, efflux pump of metabolites, energy production, and resistance to stress. In red mites, physical and immune responses that strengthen the cuticle against fungal infection were highly up-regulated. From these gene expression analyses, we identified essential factors for fungal infection and subsequent defenses of red mites. These results will serve as a strong platform for explaining the interaction between B. bassiana JEF-410 and red mites in the stage of active infection.

Low Genetic Polymorphism in the Immunogenic Sequences of Rhipicephalus microplus Clade C

Rhipicephalus microplus tick highly affects the veterinary sector throughout the world. Different tick control methods have been adopted, and the identification of tick-derived highly immunogenic sequences for the development of an anti-tick vaccine has emerged as a successful alternate. This study aimed to characterize immunogenic sequences from R. microplus ticks prevalent in Pakistan. Ticks collected in the field were morphologically identified and subjected to DNA and RNA extraction. Ticks were molecularly identified based on the partial mitochondrial cytochrome C oxidase subunit (cox) sequence and screened for piroplasms (Theileria/Babesia spp.), Rickettsia spp., and Anaplasma spp. PCR-based pathogens-free R. microplus-derived cDNA was used for the amplification of full-length cysteine protease inhibitor (cystatin 2b), cathepsin L-like cysteine proteinase (cathepsin-L), glutathione S-transferase (GST), ferritin 1, 60S acidic ribosomal protein (P0), aquaporin 2, ATAQ, and R. microplus 05 antigen (Rm05Uy) coding sequences. The cox sequence revealed 100% identity with the nucleotide sequences of Pakistan's formerly reported R. microplus, and full-length immunogenic sequences revealed maximum identities to the most similar sequences reported from India, China, Cuba, USA, Brazil, Egypt, Mexico, Israel, and Uruguay. Low nonsynonymous polymorphisms were observed in ATAQ (1.5%), cathepsin-L (0.6%), and aquaporin 2 (0.4%) sequences compared to the homologous sequences from Mexico, India, and the USA, respectively. Based on the cox sequence, R. microplus was phylogenetically assembled in clade C, which includes R. microplus from Pakistan, Myanmar, Malaysia, Thailand, Bangladesh, and India. In the phylogenetic trees, the cystatin 2b, cathepsin-L, ferritin 1, and aquaporin 2 sequences were clustered with the most similar available sequences of R. microplus, P0 with R. microplus, R. sanguineus and R. haemaphysaloides, and GST, ATAQ, and Rm05Uy with R. microplus and R. annulatus. This is the first report on the molecular characterization of clade C R. microplus-derived immunogenic sequences.

Recombinant cysteine proteinase as anti-tick targeting Hyalomma asiaticum infestation

Cysteine proteases are involved in the digestion of host blood and the degradation of yolk proteins of arthropod ectoparasites. In this study, a cathepsin L-like cysteine proteinase gene (HasCPL) of Hyalomma asiaticum was cloned, and recombinant (r)HasCPL protein was generated for immunization study. Bioinformatic analysis confirmed HasCPL was a member of the papain family (clan CA) and have high sequence identities with CPLs of other Ixodid ticks. The efficacy of immunization against H. asiaticum infestations in rabbits was assessed. Rabbits (n = 3) were immunized three times with rHasCPL before challenged with 250 larvae per rabbit four weeks post-immunization. A high antibody titer was detected in immunized rabbits in comparison to control. Western blot analysis detected CPLs in midgut, salivary gland, and ovary. Increase of rejection percentage of larvae were noted in ticks fed on immunized animals in comparison to control. Overall, a 55.09% protection against larva ticks was noted.

Prediction and validation of cross-protective candidate antigen of Hyalomma asiaticum cathepsin L between H. asiaticum and H. anatolicum

Hyalomma asiaticum and H. anatolicum are tick species in Eurasia and Africa with major medical and veterinary significance. Beside their direct pathogenic effects, H. asiaticum and H. anatolicum are vectors of important diseases of livestock and in some instances of zoonoses. In search of ways to address the increasing incidence of global acaricide resistance, tick control through vaccination is regarded as a sustainable alternative approach. Cathepsin L-like cysteine protease (CPL) is a potent hemoglobinase, and plays important roles in the digestion of blood acquired from a host. CPL from H. anatolicum (HanCPL) with high similarity (> 90%) for H. asiaticum CPL (HasCPL) were aligned by in silico analysis. After further in vitro validation, the anti-HasCPL sera have cross-reactivity between the different total native protein of life stages and tissues for H. asiaticum and H. anatolicum. Furthermore, we further confirmed that recombinant HasCPL (rHasCPL) immunized rabbits were partially cross-protected (54.8%) by H. anatolicum infestation.

In vitro evaluation of a cysteine protease from poultry red mites, Demanyssus gallinae, as a vaccine antigen for chickens

Poultry red mites (PRMs, Dermanyssus gallinae) are hematophagous ectoparasites that negatively affect egg production, which causes serious economic losses to the poultry industry worldwide. Currently, the emergence of acaricide-resistant PRMs has impeded PRM control in poultry farms. Several alternatives for acaricide use have been described for managing PRM-caused problems. Vaccination is among the methods for controlling PRMs in poultry houses. Currently, several candidates for vaccine antigens have been identified. This study identified a cysteine protease, Deg-CPR-2, which differs from 2 other previously reported cysteine proteases in PRMs, from previously obtained data from RNA-sequencing (RNA-seq) analysis. We investigated the characteristics of Deg-CPR-2 and assessed its efficacy as a vaccine antigen in vitro. Phylogenetic analysis revealed that Deg-CPR-2 belonged to a different cluster from those of other cysteine proteases in PRMs. This cluster also included cathepsin L-like proteases, enzymes thought to be involved in hemoglobin digestion in ticks. Expression analysis revealed Deg-CPR-2 expression in midguts and all the life-stages; however, there were differences in the expression levels across the life-stages. The enzyme activity of recombinant Deg-CPR-2 was inhibited in the presence of a cysteine protease inhibitor, which suggests that Deg-CPR-2 functions as a cysteine protease in PRMs. Finally, there was an in vitro increase in the mortality of PRMs, mainly protonymphs that were artificially fed with plasma from chickens immunized with Deg-CPR-2. These findings suggest that Deg-CPR-2 may contribute to protein digestion in the midgut of PRMs and is crucially involved in physiological processes in PRMs. Additionally, immunization with Deg-CPR-2 may reduce the number of protonymphs, and Deg-CPR-2 should be considered as a candidate antigen for anti-PRM vaccine development.

Characterisation of a cysteine protease from poultry red mites and its potential use as a vaccine for chickens

Poultry red mites (PRMs, Dermanyssus gallinae) are ectoparasites that negatively affect farmed chickens, leading to serious economic losses worldwide. Acaricides have been used to control PRMs in poultry houses. However, some PRMs have developed resistance to acaricides, and therefore different approaches are required to manage the problems caused by PRMs. Vaccination of chickens is one of the methods being considered to reduce the number of PRMs in poultry houses. In a previous study, a cysteine protease, Deg-CPR-1, was identified as a candidate vaccine against PRMs distributed in Europe. In this study, we investigated the characteristics of Deg-CPR-1. A phylogenetic analysis revealed that Deg-CPR-1 is closely related to the digestive cysteine proteases of other mite species, and it was classified into a cluster different from that of chicken cathepsins. Deg-CPR-1 of PRMs in Japan has an amino acid substitution compared with that of PRMs in Europe, but it showed efficacy as a vaccine, consistent with previous findings. Deg-CPR-1 exhibited cathepsin L-like enzyme activity. In addition, the Deg-CPR-1 mRNA was expressed in the midgut and in all stages of PRMs that feed on blood. These results imply that Deg-CPR-1 in the midgut may have important functions in physiological processes, and the inhibition of its expression may contribute to the efficacy of a Deg-CPR-1-based vaccine. Further research is required to fully understand the mechanisms of vaccine efficacy.

A hemocyte-specific cathepsin L-like cysteine protease is involved in response to 20-hydroxyecdysone and microbial pathogens stimulation in silkworm, Bombyx mori

Cathepsin L protease belongs to the papain-like cysteine proteases family, plays indispensable roles in animals' pathological and physiological processes. However, little is known about Cathepsin L in silkworm, Bombyx mori. Herein, a novel Cathepsin L-like (Cat L-like) was cloned and identified from silkworm by the rapid amplification of cDNA ends (RACE). Cat L-like contains an intact open reading frame (ORF) of 1 668 bp and encodes 556 amino acid residues, consisting of a signal peptide, typical cathepsins' inhibitor_I29, and pept_C1 domain. Cat L-like is specifically and highly expressed in hemocytes. The cathepsin (including Cathepsin L, B, and H) crude extract from hemocytes had typical substrate specific catalytic activities and were sensitive to pH and temperature. Cat L-like up-regulated considerably after 20-hydroxyecdysone (20-E) administration, indicating that Cat L-like may be regulated by insect hormone. The responses of Cat L-like against bacterial infection suggest it may play essential roles in silkworm immunity. Overall, our studies provide a theoretical basis and insights to further investigate the functions of Cat L-like and in insects' innate immunity mechanisms.

De novo transcriptome sequencing and comparative analysis of Haemaphysalis flava Neumann, 1897 at larvae and nymph stages

Haemaphysalis flava Neumann, 1897 (H. flava) is of public health significance due to its capability of transmitting several pathogens such as Rickettsia, Ehrlichia, Bartonella and Francisella tularensis. However, lack of complete genome, transcriptome and proteome information limits the understanding of the biology of H. flava. Here, the total RNA of H. flava was collected separately at larvae and nymph stages and analyzed with high-throughput RNA sequencing technology. The obtained data were assembled and annotated based on the near origin species in the Nr database. The functions of the unigenes were annotated and classified by seven databases, including Nr, Nt, Pfam, KOG, Swiss-Prot, GO and KEGG. A total of 61,850,967 and 79,579,368 clean reads were obtained with a data bulk of 9.28 G and 11.94 G in larvae and nymph stages, respectively. The number of unigenes was 440,896, with 48.6% of them being matched to the Nr database and 51.4% remaining unknown. Additionally, 1,776,404 SNPs were identified in the unigenes. Differential analysis revealed 80 differentially expressed genes (DEGs), including 56 up-regulated genes and 24 down-regulated genes in the nymph versus larvae. qPCR confirmed 4 of the 56 up-regulated genes and 4 of the down-regulated genes. KEGG analysis of the DEGs showed that aldehyde dehydrogenase and sorbitol dehydrogenase, two up-regulated unigenes in nymph versus larvae, were both matched to the top three enriched pathways: "chloroalkane and chloroalkene degradation", "fatty acid degradation" and "glycolysis and gluconeogenesis". This is the first report on the whole transcriptome of H. flava at larvae and nymph stages. This study contributes to the understanding of H. flava at the gene expression level in different developmental stages and provides a theoretical basis for the development of vaccines against H. flava.

A role of cathepsin L gene in innate immune response of crayfish (Procambarus clarkii)

Cathepsin L is one of the crucial enzyme superfamilies and involved in the immune responses. In the present study, cathepsin L gene from the red crayfish Procambarus clarkii, named PcCTSL, was cloned and characterized. The cDNA fragment of PcCTSL was 1026 bp in length, which encoded a putative protein of 341 amino acid residues with a molecular weight of 37.884 kDa. The theoretical isoelectric point was 5.218. The prepro-cathepsin L was comprised of a typical signal peptide (Met₁-Ala₁₈), a prodomain proregion peptide (Trp₂₉-Phe₈₉) and a mature peptide (Leu₁₂₄-Leu₃₄₀). Homology analysis indicated that PcCTSL exhibited 53.2%-87.1% identity to other selected species. The recombinant protein of PcCTSL was successfully expressed in Escherichia coli and rabbit anti-PcCTSL polyclonal antibodies were prepared. Real-time quantitative reverse transcription-PCR (qPCR) analysis revealed that the PcCTSL was expressed in all examined tissues, while the greatest mRNA level was observed in hepatopancreas. The expression of PcCTSL mRNA was clearly up regulated in hepatopancreas after challenge by lipopolysaccharide (LPS) and polyriboinosinic polyribocytidylic acid (Poly I:C). RNA interference of PcCTSL affected the gene expression of members of the Toll pathway. Our results suggest that the PcCTSL may play an important role to defend P. clarkii against the pathogens infection.