Establishment of the HPLC fluorescence detection method for plasma trace ivermectin and its pharmacokinetics in Bactrian camel

BACKGROUND AND OBJECTIVE

Ivermectin (IVM), a widely used veterinary anthelmintic, lacks recommended doses for Bactrian camels. This study aims to establish its pharmacokinetics in Bactrian camels, comparing with other livestock.

METHODS

A method for high-performance liquid chromatography fluorescence detection of IVM in plasma was developed.

RESULTS

IVM exhibited linear scaling (y = 0.6946x + 0.0088, R2 = 0.9988) within 0.025-5 ng/mL, with a lower limit of quantification of 25.00 pg/mL, high recovery (>70%) and low RSD (<7%). In Bactrian camels, IVM injection showed a low Cmax, extended Tmax and apparent secondary absorption compared to cattle and sheep.

CONCLUSIONS

Slow absorption and widespread distribution were observed, with peak concentration and area under the curve correlating positively with the dose. This study provides insights into IVM pharmacokinetics in Bactrian camels, informing dose determination and highlighting potential metabolic differences compared to other livestock.

Effects of Muscle Type and Aging on Glycolysis and Physicochemical Quality Properties of Bactrian camel (Camelus bactrianus) Meat

Poor tenderness of camel meat has seriously hampered the development of the camel meat industry. This study investigated the effects of muscle fiber composition and ageing time on meat quality, glycolytic potential, and glycolysis-related enzyme activities. Muscle samples of the longissimus thoracis (LT), psoas major (PM), and semitendinosus (ST) were collected from eight 8-10 year old Sonid Bactrian camels (females). Muscle fiber composition was examined by ATPase staining and immunohistochemistry. Meat quality indexes, glycolytic potential, and activities of major glycolytic enzymes were examined at 4 °C aging for 1, 6, 24, 72, and 120 h. The results showed that LT was mainly composed of type IIb muscle fibers, whereas PM and ST were mainly composed of type I muscle fibers. The PCR results of the myosin heavy chain (MyHC) were consistent with the ATPase staining results. During aging, the shear force of LT muscle was always greater than that of PM and ST, and its glycolysis was the strongest; type IIa, IIb, and IIx muscle fibers were positively correlated with muscle shear force and glycolysis rate, and type I muscle fibers were significantly and negatively correlated with the activities of the key enzymes of glycolysis within 6 h. The results showed that the muscle fibers of LT muscle had the greatest glycolysis capacity. These results suggest that an excessive type IIb muscle fiber number percentage and area in camel meat accelerated the glycolysis process, but seriously affected the sensory profile of the camel meat. The results of this study provide directions for the camel industry when addressing the poor tenderness of camel meat.

Histological study of Bactrian camel cryptorchidism and expression of immunoglobulin λ light chain in the testicular and epididymis of cryptorchid Bactrian camel

Lambda light chains (λ-LCs) are frequently responsible for triggering the activation of inflammatory factors in autoimmune disorders, and an increase in their levels will cause various pathological changes in serum. The aim of this study was to determine the histological differences between the epididymis and testis of normal and cryptorchid Bactrian camels and the differences in λ-LC expression in the epididymis and testis of normal and cryptorchid Bactrian camels. Haematoxylin and eosin (H&E) staining was used to examine the pathological changes in cryptorchidism. The gene and protein levels of λ-LC were determined using RT-qPCR and western blot. The distribution of λ-LCs was assessed by immunohistochemistry and immunofluorescence. Compared with that in normal Bactrian camels, the diameter of the epididymal lumen and the thickness of the epithelium were decreased in the epididymis of cryptorchidic animals. Additionally, no sperm was detected in the cavity of the cryptorchidic epididymis. Meanwhile, the expression of λ-LC was significantly increased in the cryptorchidic epididymis at both the mRNA and protein levels (p < .05). The highest protein expression of λ-LC was found in epididymal epithelial halo cells and testicular Sertoli cells. These findings suggested that the structural changes observed in the epididymal epithelium of cryptorchidic camels affect its secretory and absorptive functions. Additionally, the high level of λ-LC expression recorded in halo cells suggested that these cells play an important role in epithelial immunity in cryptorchidic Bactrian camels. Furthermore, the high λ-LC expression levels detected in normal testicular Sertoli cells indicated that λ-LCs may be involved in spermatogenesis. The results of this study provide clues for an in-depth study of immunological sterility in cryptorchidic Bactrian camels.

Transcriptome analysis of the Bactrian camel (Camelus bactrianus) reveals candidate genes affecting milk production traits

BACKGROUND

Milk production traits are complex traits with vital economic importance in the camel industry. However, the genetic mechanisms regulating milk production traits in camels remain poorly understood. Therefore, we aimed to identify candidate genes and metabolic pathways that affect milk production traits in Bactrian camels.

METHODS

We classified camels (fourth parity) as low- or high-yield, examined pregnant camels using B-mode ultrasonography, observed the microscopic changes in the mammary gland using hematoxylin and eosin (HE) staining, and used RNA sequencing to identify differentially expressed genes (DEGs) and pathways.

RESULTS

The average standard milk yield over the 300 days during parity was recorded as 470.18 ± 9.75 and 978.34 ± 3.80 kg in low- and high-performance camels, respectively. Nine female Junggar Bactrian camels were subjected to transcriptome sequencing, and 609 and 393 DEGs were identified in the low-yield vs. high-yield (WDL vs. WGH) and pregnancy versus colostrum period (RSQ vs. CRQ) comparison groups, respectively. The DEGs were compared with genes associated with milk production traits in the Animal Quantitative Trait Loci database and in Alashan Bactrian camels, and 65 and 46 overlapping candidate genes were obtained, respectively. Functional enrichment and protein-protein interaction network analyses of the DEGs and candidate genes were conducted. After comparing our results with those of other livestock studies, we identified 16 signaling pathways and 27 core candidate genes associated with maternal parturition, estrogen regulation, initiation of lactation, and milk production traits. The pathways suggest that emerged milk production involves the regulation of multiple complex metabolic and cellular developmental processes in camels. Finally, the RNA sequencing results were validated using quantitative real-time PCR; the 15 selected genes exhibited consistent expression changes.

CONCLUSIONS

This study identified DEGs and metabolic pathways affecting maternal parturition and milk production traits. The results provides a theoretical foundation for further research on the molecular mechanism of genes related to milk production traits in camels. Furthermore, these findings will help improve breeding strategies to achieve the desired milk yield in camels.

Genome-wide identification and characterization of microsatellite markers in Bactrian Camel

Simple sequence repeats (SSRs) have been widely used for parentage testing, marker-assisted selection, and evolutionary studies. The insufficient availability of SSR markers in Bactrian camels partially accounts for the lack of systematic breeding. Therefore, we aimed to establish a comprehensive SSR dataset for the Bactrian camel. Our approach involved genome searching to locate every SSR in the genome, SSR-enriched sequencing to acquire polymorphism information, and literature research to collect published data. The resulting dataset contains 213,711 SSRs and details their characteristics, including genome coordinates, motifs, lengths, annotations, PCR primers, and polymorphism information. The dataset reveals a biased distribution of SSRs in the Bactrian camel genome, reflecting the mutation mechanism and complex evolution of SSRs. In practice, we successfully demonstrated the utility of the dataset through parentage testing using 15 randomly selected SSRs. This comprehensive dataset can facilitate systematic breeding and enable QTL mapping and GWAS of the Bactrian camel.

Similar proteome expression profiles of the aggregated lymphoid nodules area and Peyer's patches in Bactrian camel

BACKGROUND

The presence of Aggregated Lymphoid Nodules Area (ALNA) is a notable anatomical characteristic observed in the abomasum of Bactrian camels. This area is comprised of two separate regions, namely the Reticular Mucosal Folds Region (RMFR) and the Longitudinal Mucosal Folds Region (LMFR). The histological properties of ALNA exhibit significant similarities to those of Peyer's patches (PPs) found in the gastrointestinal system. The functional characteristics of ALNA were examined in relation to mucosal immunity in the gastrointestinal system.

RESULTS

We used iTRAQ-based proteomic analysis on twelve Bactrian camels to measure the amount of proteins expressed in ALNA. In the experiment, we sampled the RMFR and LMFR separately from the ALNA and compared their proteomic quantification results with samples from the PPs. A total of 1253 proteins were identified, among which 39 differentially expressed proteins (DEPs) were found between RMFR and PPs, 33 DEPs were found between LMFR and PPs, and 22 DEPs were found between LMFR and RMFR. The proteins FLNA, MYH11, and HSPB1 were chosen for validation using the enzyme-linked immunosorbent assay (ELISA), and the observed expression profiles were found to be in agreement with the results obtained from the iTRAQ study. The InnateDB database was utilized to get data pertaining to immune-associated proteins in ALNA. It was observed that a significant proportion, specifically 76.6%, of these proteins were found to be associated with the same orthogroups as human immune-related genes. These proteins are acknowledged to be associated with a diverse range of functions, encompassing the uptake, processing and presentation of antigens, activation of lymphocytes, the signaling pathways of T-cell and B-cell receptors, and the control of actin polymerization.

CONCLUSIONS

The experimental results suggest that there are parallels in the immune-related proteins found in ALNA and PPs. Although there are variations in the structures of LMFR and RMFR, the proteins produced in both structures exhibit a high degree of similarity and perform comparable functions in the context of mucosal immune responses.

Sequencing and Characterization of αs2-Casein Gene (CSN1S2) in the Old-World Camels Have Proven Genetic Variations Useful for the Understanding of Species Diversification

The CSN1S2 gene encodes αs2-casein, the third most abundant protein in camel milk. Despite its importance in foals, human nutrition, and dairy processing, the CSN1S2 gene in camels has received little attention. This study presents the first complete characterization of the CSN1S2 gene sequence in Old-World camels (Camelus bactrianus and Camelus dromedarius). Additionally, the gene promoter, consisting of 752 bp upstream of exon 1, was analyzed. The entire gene comprises 17 exons, ranging in length from 24 bp (exons 4, 8, 11, and 13) to 280 bp (exon 17). Interesting was the identification of the exon 12 in both species. The promoter analysis revealed 24 putative binding sites in the Bactrian camel and 22 in dromedary camel. Most of these sites were typical elements associated with milk protein, such as C/EBP-α, C/EBP-β, Oct-1, and AP1. The SNP discovery showed relatively high genetic diversity compared to other camel casein genes (CSN1S1, CSN2, and CSN3), with a total of 34 polymorphic sites across the two species. Particularly noteworthy is the transition g.311G>A in the CSN1S2 promoter, creating a new putative consensus binding site for a C/EBP-β in the Bactrian camel. At the exon level, two novel variants were found. One was detected in exon 6 of the Bactrian camel (g.3639C>G), resulting in an amino acid replacement, p.36Ile>Met. The second variant was found in noncoding exon 17 of dromedary CSN1S2 (g.1511G>T). Although this mutation occurs in the 3'-UnTranslated Region, it represents the first example of exonic polymorphism in the CSN1S2 for this species. This SNP also affects the binding sites of different microRNAs, including the seed sequence of the miRNA 4662a-3p, highlighting its role as a regulatory factor for CSN1S2 gene. A PCR-RFLP was set up for genotyping a dromedary Tunisian population (n = 157), and the minor allele frequency was found to be 0.27 for the G allele, indicating a potential yield improvement margin. The interspersed elements (INEs) analysis revealed 10 INEs covering 7.34% and 8.14% of the CSN1S2 sequence in the Bactrian and dromedary camels, respectively. Furthermore, six elements (A, B, F, H, I, and L) are shared among cattle and camels and are partially found in other ruminants, suggesting a common ancestral origin of these retrotransposons. Conversely, elements C, D, E, and G are specific to camels.

Analysis of Genetic Diversity and Population Structure of Tarim and Junggar Bactrian Camels Based on Simplified GBS Genome Sequencing

In view of the severe reduction in Bactrian camel germplasm resources, scientific evaluation, protection, and utilization is particularly important. Therefore, it is necessary to investigate the genetic diversity and genetic structure of this species, and identify the genes that have played important roles in its evolution. In this study, 21,971 SNPs were identified in 118 domestic Bactrian camels from the Tarim (n = 60) and Junggar (n = 58) populations using simplified GBS genome sequencing. The results show that Tarim and Junggar Bactrian camels have high nucleotide diversity. A phylogenetic tree constructed using structural analysis, principal component analysis (PCA), and the adjacency method (NJ) showed that Tarim and Junggar Bactrian camels were clustered together. The selection signals revealed that the Tarim and Junggar Bactrian camels shared 108 genes under positive selection, including WNT1, WNT10B, CD14, SEC61A2, DPAGT1, FOXO6, etc. These selected genes were widely involved in the immune system, embryonic development, lipid metabolism, and other processes. From a genomic analysis perspective, the genetic relationship between TLM and ZGE camels is close, with an average Fst of 0.048 and a relatively low average differentiation coefficient between the two populations. In addition, shared selected genes in the long-term depression pathway were significantly enriched in Tarim and Junggar. These findings will offer support and assistance for the exploration of genetic resource preservation, economically significant traits, and the mechanisms underlying biological characteristics, molecular breeding, and disease.

Gas/Liquid Chromatography-Mass Spectrometry Analysis of Key Functional Substances Regulating Poll Gland Secretion in Male Camels during Seasonal Estrus

Increased poll gland secretion is a major characteristic and indicator of estrus in male Bactrian camels; however, research on these poll glands and their secretion is extremely rare. In this study, we determine the chemical composition of poll gland secretions and identify the key functional substances that regulate seasonal estrus in male camels. A GC/LC-MS dual platform was used to analyze ventral hair (control) and neck mane samples containing poll gland secretions from male Bactrian camels during estrus. Multidimensional and single-dimensional analyses were used to screen differentially expressed metabolites (DEMs) between groups. Functional prediction of enriched metabolites was performed using a Human Metabolome Database comparison and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis, which were then compared with a behavioral analysis of male Bactrian camels in estrus. A total of 1172 DEMs and 34 differential metabolic pathways were identified. One metabolite group was found to relate to steroid synthesis and metabolism, and another metabolite group was associated with neural metabolism. Therefore, we speculate that steroids and neurochemicals jointly regulate estrous behavior in male Bactrian camels, thus providing theoretical insights into the development and function of poll glands in Bactrian camels.

Hormone measurements and histomorphological observations in male Bactrian camels

The aim of this study was to investigate the effect of age on the hypothalamic-pituitary-gonadal (HPG) axis hormones and to determine the morphological changes of the testis. The Bactrian camels were divided into two groups based on their ages. The results showed that the testicular weight was significantly heavier in adult male camels than in pubertal male camels (P < 0.05). There were also significant differences between testicular length, testicular width, and testicular volume (P < 0.05). In the testes of both pubertal and adult male camels, Sertoli cells, spermatogonia, spermatocytes, round spermatids, and elongated spermatids were observed. Adult male camels had more Sertoli cells (P < 0.01) and elongated spermatids (P < 0.05). The concentrations of testosterone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) were higher in the plasma and testes of adult camels than in pubertal camels (P < 0.05). E2 concentrations were lower in adult camels than in pubertal camels (P < 0.05). The testosterone levels in testicular tissue were higher than in blood plasma in both adult and pubertal stage (P < 0.05). In conclusion, these findings provide supportive knowledge and show the significant differences in terms of testicular volume, testicular hormone concentrations, and testicular morphology between different developmental stages in Bactrian camels.

Construction and Characterization of Immortalized Fibroblast Cell Line from Bactrian Camel

Immortalized cell lines with many advantages are widely used in various experimental contexts by many different labs. However, the absence of available cell lines poses difficulties for research in some species, such as camels. To establish an immortalized Bactrian camel fibroblast (iBCF) cell line and understand its biological characteristics, primary fibroblast cells from Bactrian camels were isolated and purified using enzymatic digestion in this study, and telomerase reverse transcriptase (hTERT) vectors were introduced into primary BCF (pBCF) for continuous passage to 80 generations after screening with G418. The cell morphology of different generations was examined under a microscope. Cell cycle and viability were evaluated by flow cytometry and CCK-8 assay, respectively. Cellular genes expression was monitored by qPCR, immunofluorescence, and Western blot, respectively. Chromosomes were determined by karyotyping. The results showed that like most other cells, both pBCF and iBCF were sensitive to nutrient concentrations and adapted to culture in the medium with 4.5 g/L glucose and 10% fetal bovine serum (FBS) concentration. hTERT gene was introduced and stably expressed in iBCF cells, which promoted BCF cell immortalization. The fibroblast specific marker vimentin (VIM) is expressed in both pBCF and iBCF, but epithelial marker cytokeratin18 (CK18) expression is weak in BCF cells. Proliferation and viability detection showed that hTERT-induced iBCF exhibits faster growth rates and higher viability than pBCF. Karyotyping showed that iBCF maintained the same number and morphology of chromosomes as the pBCF. This study demonstrated that we have successfully constructed an immortalized Bactrian camel fibroblast cell line, which was named BCF23. The establishment of the BCF23 cell line provides a foundation for expanding camel-related research.

Transcriptome analysis to identify candidate genes related to mammary gland development of Bactrian camel (Camelus bactrianus)

Introduction

The demand for camel milk, which has unique therapeutic properties, is increasing. The mammary gland is the organ in mammals responsible for the production and quality of milk. However, few studies have investigated the genes or pathways related to mammary gland growth and development in Bactrian camels. This study aimed to compare the morphological changes in mammary gland tissue and transcriptome expression profiles between young and adult female Bactrian camels and to explore the potential candidate genes and signaling pathways related to mammary gland development.

Methods

Three 2  years-old female camels and three 5  years-old adult female camels were maintained in the same environment. The parenchyma of the mammary gland tissue was sampled from the camels using percutaneous needle biopsy. Morphological changes were observed using hematoxylin-eosin staining. High-throughput RNA sequencing was performed using the Illumina HiSeq platform to analyze changes in the transcriptome between young and adult camels. Functional enrichment, pathway enrichment, and protein-protein interaction networks were also analyzed. Gene expression was verified using quantitative real-time polymerase chain reaction (qRT-PCR).

Results

Histomorphological analysis showed that the mammary ducts and mammary epithelial cells in adult female camels were greatly developed and differentiated from those in young camels. Transcriptome analysis showed that 2,851 differentially expressed genes were obtained in the adult camel group compared to the young camel group, of which 1,420 were upregulated, 1,431 were downregulated, and 2,419 encoded proteins. Functional enrichment analysis revealed that the upregulated genes were significantly enriched for 24 pathways, including the Hedgehog signaling pathway which is closely related to mammary gland development. The downregulated genes were significantly enriched for seven pathways, among these the Wnt signaling pathway was significantly related to mammary gland development. The protein-protein interaction network sorted the nodes according to the degree of gene interaction and identified nine candidate genes: PRKAB2, PRKAG3, PLCB4, BTRC, GLI1, WIF1, DKK2, FZD3, and WNT4. The expression of fifteen genes randomly detected by qRT-PCR showed results consistent with those of the transcriptome analysis.

Discussion

Preliminary findings indicate that the Hedgehog, Wnt, oxytocin, insulin, and steroid biosynthesis signaling pathways have important effects on mammary gland development in dairy camels. Given the importance of these pathways and the interconnections of the involved genes, the genes in these pathways should be considered potential candidate genes. This study provides a theoretical basis for elucidating the molecular mechanisms associated with mammary gland development and milk production in Bactrian camels.

Effects of plasma-derived exosomes from the normal and thin Bactrian camels on hepatocellular carcinoma and their differences at transcriptome and proteomics levels

Background

Hepatocellular carcinoma (HCC) is a common malignant primary tumor. Bactrian camels have high economic and social values, but their potential medical value has not been studied. This study aimed to investigate the effects of Bactrian camel plasma-derived exosomes on HCC.

Methods

Plasma was obtained from thin and normal Bactrian camels, and used to isolate exosomes by ultracentrifugation. The exosomes were then characterized by transmission electron microscopy and Nano particle tracking analyzer. In vivo imaging of nude mice and hematoxylin eosin (HE) staining of liver tissues were used to explore the effects of the exosomes on tumor growth. Finally, the differences of the two exosomes were further analyzed using small RNA sequencing and proteomics.

Results

In vivo imaging and HE staining showed that no significant differences were found in fluorescence value and liver tissue morphology between the control mice and the mice treated with the exosomes from thin Bactrian camels; while the fluorescence value and the live histology changes were alleviated in the mice with the exosomes from normal Bactrian camels. After sequencing and proteomic analysis, 40 differentially expressed miRNAs (DE-miRNAs, 15 down-regulated and 25 up-regulated) and 172 differentially expressed proteins (DEPs, 77 up-regulated and 95 down-regulated) were identified in the plasma-derived exosomes from normal Bactrian camels. These identified DE-miRNAs and DEPs were significantly enriched in many signaling pathways.

Conclusions

Normal Bactrian camel plasma-derived exosomes may inhibit the growth of HCC cells through regulating pathways of Ras, Ras-Association Proximate 1 (Rap1), phosphoinositide 3-kinase-protein kinase B (PI3K-Akt), mitogen-activated protein kinase (MAPK), adenosine monophosphate-activated protein kinase (AMPK), and canonical Wnt signaling pathways.

Establishment of Bactrian Camel Induced Pluripotent Stem Cells and Prediction of Their Unique Pluripotency Genes

Induced pluripotent stem cells (iPSCs) can differentiate into all types of cells and can be used in livestock for research on biological development, genetic breeding, and in vitro genetic resource conservation. The Bactrian camel is a large domestic animal that inhabits extreme environments and holds value in the treatment of various diseases and the development of the local economy. Therefore, we transferred four mouse genes (Oct4, Sox2, Klf4, and c-Myc) into Bactrian camel fetal fibroblasts (BCFFs) using retroviruses with a large host range to obtain Bactrian camel induced pluripotent stem cells (bciPSCs). They were comprehensively identified based on cell morphology, pluripotency gene and marker expression, chromosome number, transcriptome sequencing, and differentiation potential. The results showed the pluripotency of bciPSCs. However, unlike stem cells of other species, late formation of stem cell clones was observed; moreover, the immunofluorescence of SSEA1, SSEA3, and SSEA4 were positive, and teratoma formation took four months. These findings may be related to the extremely long gestation period and species specificity of Bactrian camels. By mining RNA sequence data, 85 potential unique pluripotent genes of Bactrian camels were predicted, which could be used as candidate genes for the production of bciPSC in the future. Among them, ASF1B, DTL, CDCA5, PROM1, CYTL1, NUP210, Epha3, and SYT13 are more attractive. In conclusion, we generated bciPSCs for the first time and obtained their transcriptome information, expanding the iPSC genetic information database and exploring the applicability of iPSCs in livestock. Our results can provide an experimental basis for Bactrian camel ESC establishment, developmental research, and genetic resource conservation.

Discovery of novel Mamastroviruses in Bactrian camels and dromedaries reveals complex recombination history

Virus emergence may occur through interspecies transmission and recombination of viruses coinfecting a host, with potential to pair novel and adaptive gene combinations. Camels are known to harbor diverse ribonucleic acid viruses with zoonotic and epizootic potential. Among them, astroviruses are of particular interest due to their cross-species transmission potential and endemicity in diverse host species, including humans. We conducted a molecular epidemiological survey of astroviruses in dromedaries from Saudi Arabia and Bactrian camels from Inner Mongolia, China. Herein, we deployed a hybrid sequencing approach coupling deep sequencing with rapid amplification of complementary deoxyribonucleic acid ends to characterize two novel Bactrian and eight dromedary camel astroviruses, including both partial and complete genomes. Our reported sequences expand the known diversity of dromedary camel astroviruses, highlighting potential recombination events among the astroviruses of camelids and other host species. In Bactrian camels, we detected partially conserved gene regions bearing resemblance to human astrovirus types 1, 4, and 8 although we were unable to recover complete reading frames from these samples. Continued surveillance of astroviruses in camelids, particularly Bactrian species and associated livestock, is highly recommended to identify patterns of cross-species transmission and to determine any epizootic threats and zoonotic risks posed to humans. Phylogenomic approaches are needed to investigate complex patterns of recombination among the astroviruses and to infer their evolutionary history across diverse host species.

Preparation of IgE Antibody and Distribution of IgE+ Secretory Cells in the Palatine Tonsil of Bactrian Camel

BACKGROUND

Allergic diseases induced by dust have seriously threatened human health, while Bactrian camels can live in a sandy environment for a long time.

OBJECTIVE

To prepare rabbit anti-Bactrian camel IgE antibody and explore the distribution characteristics of IgE⁺ secretory cells in the palatine tonsils, which lays a theoretical foundation for the distribution of local antibodies in the palatal tonsils of Bactrian camel and the study of immune function.

METHODS

In this study, the amino acid sequences of Bactrian camel IgE, IgA, IgM and IgG heavy chain constant regions were compared, and a specific IgE gene fragment were selected (447 bp). The recombinant plasmid pET-28a-IgE was induced in Escherichia coli BL21(DE3) by IPTG and its expression conditions were optimized. The antibody was prepared by immunizing rabbits with purified IgE recombinant protein, its titer and specificity were detected by indirect ELISA and Western blotting. Immunohistochemical and statistical methods investigated the distribution of IgE⁺ secretory cells in the palatine tonsils.

RESULTS

The IgE recombinant protein was expressed in the form of inclusion bodies with a size of 16 kDa. The optimal IPTG induction concentration was 0.7 mmol/L and the induction time was 8 h. The titer of the antibody was 1:16000 by ELISA, and the antibody could specifically bind to the recombinant protein by Western blotting. IgE⁺ secretory cells were mainly distributed in the subepithelial compartments of reticulated crypt epithelium of the palatine tonsil of the Bactrian camel, followed by the subepithelial compartments of stratified squamous epithelium and occasionally in the extrafollicular region.

CONCLUSION

The rabbit anti-Bactrian camel IgE polyclonal antibody was successfully prepared. It is confirmed that IgE exists in the palatine tonsils of Bactrian camels under normal living conditions. In addition, IgE⁺ secretory cells are mainly distributed in the subepithelial compartments of reticulated crypt epithelium of the palatine tonsil, which is consistent with the distribution characteristics of IgG⁺ and sIgA⁺ secretory cells in the palatal tonsils of the Bactrian camel.

Characterization of heavy-chain antibody gene repertoires in Bactrian camels

Camelids are the only mammals that can produce functional heavy-chain antibodies (HCAbs). Although HCAbs were discovered over 30 years ago, the antibody gene repertoire of Bactrian camels remains largely underexplored. To characterize the diversity of variable genes of HCAbs (VHHs), germline and rearranged VHH repertoires are constructed. Phylogenetics analysis shows that all camelid VHH genes are derived from a common ancestor and the nucleotide diversity of VHHs is similar across all camelid species. While species-specific hallmark sites are identified, the non-canonical cysteines specific to VHHs are distinct in Bactrian camels and dromedaries compared with alpacas. Though low divergence at the germline repertoire between wild and domestic Bactrian camels, higher expression of VHHs is observed in some wild Bactrian camels than that of domestic ones. This study not only adds our understanding of VHH repertoire diversity across camelids, but also provides useful resources for HCAb engineering.

The distribution of SIgA and IgG antibody-secreting cells in the large intestine of Bactrian camels (Camelus bactrianus)

BACKGROUND

Mucosal immunoglobulin comprises mainly secretory immunoglobulin A (SIgA) which mainly participates in the intestinal mucosal pathogenspecific immune response. Immunoglobulin G (IgG) is another common immunoglobulin. Bactrian camels' gastrointestinal mucosal tissue has a special mucosal immune system. However, the distribution characteristics of these two antibody-secreting cells (ASCs) in Bactrian camel's large intestine mucosal immunity system remain largely unknown. This study was aimed to describe the distribution characteristics and density of SIgA and IgG ASCs in the mucosal immunity tissues of Bactrian camel large intestine.

MATERIALS AND METHODS

Tissue samples were collected from different parts of the large intestines of 10 healthy adult Chinese Alashan Bactrian camels. Immunohistochemistry technology was used to determine the distribution of SIgA and IgG ASCs in the large intestine samples and the image-Pro Plus 6.0 was employed to calculate their densities.

RESULTS

SIgA and IgG ASCs were distributed in lamina propria of the large intestine mucosa with some ASCs aggregating around the intestinal glands. The SIgA density increased from ileocecal orifice to the caecum and decreased from the colon to the rectum. The largest number of SIgA ASCs was observed in the caecum, followed by anterior colonic segments, ileocecal orifice, posterior colonic segments, and rectum, and the number of SIgA ASCs in the caecum was significantly larger than that in other four positions (p < 0.05). Similarly, the number of IgG ASCs was also the largest in the caecum, which was significantly higher than that in ileocecal orifice, anterior, posterior colonic segments, and rectum (p < 0.05).

CONCLUSIONS

Our findings suggest that SIgA and IgG ASCs are mainly distributed in intestinal mucosal immunity effector sites. These distribution characteristics provide evidence to support that SIgA and IgG supply effective protection and maintain homeostasis in the large intestinal mucosa.

Effects of Age and Muscle Type on the Chemical Composition and Quality Characteristics of Bactrian Camel (Camelus bactrianus) Meat

Camel meat could have health benefits for human consumers due to its nutritional value. The influence of age and muscle type on the chemical composition and quality characteristics of Bactrian camel meat was examined in the present study. Samples of the Longissimus thoracic (LT), Semitendinosus (ST), and Psoas major (PM) muscles were collected from a total of fifteen male camels in three different age groups (3−4 years, 6−7 years, and 9−10 years). The younger camels exhibited higher values of moisture, polyunsaturated fatty acids, ultimate pH, cooking loss, and lightness, but lower fat, shear force, and redness values compared to meat collected from older camels. The LT muscle had higher fat and color parameters (lightness, redness, yellowness) but lower shear force values than the ST and PM muscles (p < 0.05). The ST muscles had a higher content of n-6 polyunsaturated fatty acids and n-3 polyunsaturated fatty acids but lower cooking loss values than the LT and PM muscles. These results indicated that younger camels provide better meat quality traits than older camels. The results of the present study will improve the marketing of Bactrian camel meat products and will provide more information about the most suitable muscles and the optimal slaughter age.

Screening and Identification of Differential Ovarian Proteins before and after Induced Ovulation via Seminal Plasma in Bactrian Camels

Simple Summary

Camelidae are induced ovulators whose ovulation is tightly regulated by multiple factors. Understanding the biological mechanisms underlying follicular development, hormone secretion, and ovulation requires investigating the potential molecular pathways involved in these mechanisms. However, little is known about these molecular pathways in Bactrian camels. To screen and identify candidate biomarkers after seminal plasma (SP)-induced ovulation in the ovaries, we performed comprehensive proteomic and molecular biological analyses of the ovaries from camels that were intramuscularly injected with either seminal plasma or phosphate-buffered saline. Identification of these candidate biomarkers will enable a better understanding of reproduction in Bactrian camels. Our findings suggest candidate proteins for further studies on the molecular mechanisms of induced ovulation.

Abstract

Camelidae are induced ovulators whose ovulation is tightly regulated by multiple factors. Understanding the biological mechanisms underlying follicular development, hormone secretion, and ovulation requires investigating the potential molecular pathways involved. However, little is known about these pathways in Bactrian camels. To screen and identify candidate biomarkers after inducing ovulation, this study performed comprehensive proteomic and molecular biological analyses of the ovaries from two camel groups (n = 6). We identified 5075 expressed ovarian proteins, of which 404 were differentially expressed (264 upregulated, 140 downregulated) (p < 0.05 or p < 0.01), in samples from plasma-induced versus control camels. Gene ontology annotation identified the potential functions of the differentially expressed proteins (DEPs). These results validated the differential expression for a subset of these proteins using Western blot (p < 0.05) and immunofluorescence staining. Three DEPs (FST, NR5A1, and PRL) were involved in neurochemical signal transduction, as well as endocrine and reproductive hormone regulatory processes. The Kyoto Encyclopedia of Genes and Genomes analysis indicated the involvement of several pathways, including the calcium, cAMP, gonadotropin-releasing hormone, MAPK, and neuroactive ligand–receptor signaling pathways, suggesting that induced ovulation depends on the hypothalamic–pituitary–ovarian axis. Identifying these candidate biomarkers enables a better understanding of Bactrian camel reproduction. Ovarian proteomic profiling and the measurement of selected proteins using more targeted methods is a promising approach for studying induced-ovulation mechanisms.

Molecular survey of bovine Babesia species in Bactrian camels (Camelus bactrianus) in Mongolia

Bovine babesiosis, which is caused by species of genus Babesia, is a leading cause of considerable economic losses to the cattle industry each year. Bovine Babesia species have frequently been detected in non-cattle hosts, such as water buffalo (Bubalus bubalis), from which the parasites can be transmitted by ticks to cattle. Therefore, Babesia infections should be minimized not only in cattle but also in non-cattle carriers. In the present study, we surveyed the Bactrian camels (Camelus bactrianus) in Mongolia for three clinically significant bovine Babesia species, including Babesia bovis, B. bigemina, and Babesia sp. Mymensingh, which had been detected previously in Mongolian cattle. We screened blood DNA samples from 305 Bactrian camels in six Mongolian provinces for these species, using parasite-specific PCR assays. Our findings showed that the Bactrian camels in Mongolia were infected with all three Babesia species surveyed. The overall positive rates of B. bovis, B. bigemina, and Babesia sp. Mymensingh were 32.1%, 21.6%, and 24.3%, respectively, whereas 52.5% of the surveyed animals were infected with at least one parasite species. We also found that the female Bactrian camels and the Mongolian native camel breed had significantly higher Babesia positive rates than the male Bactrian camels and the Hos Zogdort breed. In Mongolia, cattle and Bactrian camels usually share common pasture lands for grazing; furthermore, tick species infesting cattle also infest Bactrian camels. Our findings, together with these observations, suggest that the tick transmission of bovine Babesia species might be possible between cattle and Bactrian camels. Therefore, strategies for the control of bovine babesiosis in Mongolia should include methods to minimize bovine Babesia species infections in Bactrian camels.

Molecular identification and biological characterization of Cryptosporidium muris from camels (Camelus bactrianus) in China

BACKGROUND

Cryptosporidium is an opportunistic pathogen that infects a wide variety of vertebrates. The aim of the present study was to characterize Cryptosporidium spp. isolates from Bactrian camels and to foster further understanding of the biological characteristics of the pathogen.

METHODS

Fecal specimens were collected from two 4-year-old Bactrian camels resident at the Kaifeng City Zoo in China and examined for Cryptosporidium. Fecal specimens were screened using the floatation method, and then genomic DNA was extracted from the oocysts and identified by nested-PCR amplification of the small subunit ribosomal RNA (SSU rRNA) gene, the actin gene and the Cryptosporidium oocyst wall-protein (COWP) gene. Subtype analysis was performed based on four minisatellite (MS) loci (MS1, MS2, MS3 and MS16) that were aligned and phylogenetically analyzed to determine the species and subtype of Cryptosporidium. We then established a BALB/c mice infection model and further verified the results through clinical status, pattern of oocyst excretion and histological examination.

RESULTS

Cryptosporidium oocyst isolates from the two Bactrian camels had an average (± standard deviation) size of 7.49 ± 0.13 × 5.70 ± 0.10 μm (n = 50). The sequencing and phylogenetic analysis confirmed the species as C. muris. Multilocus sequence typing analysis indicated that the subtypes were M13, M4, M1 and M5. Following the inoculation of BALB/c mice, we found that the prepatent period and number of oocysts per gram increased with increasing infective dose. Oocysts were first detected in the feces of BALB/c mice at 7-8 days post-infection (dpi), with levels peaking twice thereafter, at 15-16 dpi and 19-20 dpi. Histology and scanning electron microscopy studies showed that the stomach contained gastric pits filled with Cryptosporidium that adhered to the surface of gastric mucosa gland epithelial cells, causing the latter to deform, swell and become disordered.

CONCLUSIONS

The findings of this study indicated that oocysts isolated from Bactrian camels were from C. muris. This is the first report of C. muris isolated from camels in China. More epidemiological data are needed to understand the prevalence and transmission of C. muris in camels in different geographic areas.

Identification and a full genome analysis of novel camel hepatitis E virus strains obtained from Bactrian camels in Mongolia

Hepatitis E virus (HEV) infects humans and a wide variety of other mammalian hosts. Recently, HEV strains belonging to genotype 8 (G8) within the Orthohepevirus A species of the Hepeviridae family, were identified in Bactrian camels (Camelus bactrianus) in China. The Bactrian camel (also known as the Mongolian camel) is native to the steppes of Central Asia. However, the HEV strains of Mongolian camels have not been examined. Among 200 serum samples from domestic Bactrian camels raised on 6 farms, in 6 soums in 3 provinces; 71 (35.5 %) were positive for anti-HEV IgG, with prevalence differing by farm (soum) (4.2-75.0 %); and 2 camels (1.0 %) that had been raised in Bogd, Bayankhongor Province, which had the highest seroprevalence among the six studied areas, were positive for HEV RNA. The two HEV strains (BcHEV-MNG140 and BcHEV-MNG146) obtained from the viremic camels in the present study shared 97.7 % nucleotide identity. They were closest to the reported G8 Chinese camel HEV strains but differed from them by 13.9-14.3 % over the entire genome, with a nucleotide difference of 24.0-26.5 % from the reported G1-G7 HEV strains. A phylogenetic tree indicated that the BcHEV-MNG140 and BcHEV-MNG146 strains were located upstream of a clade consisting of the Chinese camel HEV strains and formed a cluster with them, with a bootstrap value of 100 %, suggesting that they may represent a novel subtype within G8. These results indicate a high prevalence of HEV infection in Mongolian camels and suggest that the variability of camel HEV genomes is markedly high.

Valproic Acid Enhance Reprogramming of Bactrian Camel Cells through Promoting the Expression of Endogenous Gene c-Myc and the Process of Angiogenesis

Background and Objectives

Induced pluripotent stem cells (iPSCs) are usually generated by reprogramming differentiated cells through the introduction of specific transcription factors, but this is a difficult and inefficient process. Valproic acid (VPA) is a histone deacetylase inhibitor that significantly improves the efficiency of iPSC generation. But its role and mechanism are still unclear.

Methods and Results

We transduced Bactrian camel fetal fibroblasts (BCFFs) with retroviruses carrying defined factors (OCT4, SOX2, KLF4, c-MYC and EGFP; OSKMG) in the presence of VPA. Cells were collected (Day 7) and analyzed using RNA-seq technology. Afterwards, different groups of cells and transcriptomics results were detected by PCR and qRT-PCR technology. The results showed that VPA promoted the expression of the endogenous gene c-Myc and inhibited cell proliferation; at the same time, it promoted the expression of VEGF and other genes related to angiogenesis.

Conclusions

When VPA is added to the culture medium, only the cells that have begun to reprogram can break the G2/M repression through the expression of the endogenous gene c-Myc, and use the nutrients and space in the culture dish to proliferate normally, which can achieve the purpose of directly improving the efficiency of reprogramming. Another new discovery for Bactrian camels, VPA significantly increased the expression of VEGFC and other genes, promoting the transformation of fibroblasts to endothelial cells (different from the mesenchymal-to-epithelial transition process of other species) to accelerate the early induction of Bactrian camels iPSc process. Overall, this study proved the new mechanism of VPA in enhancing the induction of pluripotency from the transcriptome level.

Middle East Respiratory Syndrome-Coronavirus Seropositive Bactrian Camels, Mongolia

Middle East respiratory syndrome coronavirus (MERS-CoV) is a zoonotic disease that was first identified in humans in 2012 in Saudi Arabia. MERS-CoV causes acute and severe respiratory disease in humans. The mortality rate of MERS in humans is ∼35% and >800 deaths have been reported globally as of August 2020. Dromedary camels are a natural host of the virus and the source of zoonotic human infection. In experimental studies, Bactrian camels are susceptible to MERS-CoV infection similar to dromedary camels; however, neither the virus, viral RNA, nor virus-specific antibodies were detected in Bactrian camel field samples so far. The aim of our study was to survey Mongolian camels for MERS-CoV-specific antibodies. A total of 180 camel sera, collected in 2016 and 2017, were involved in this survey: 17 of 180 sera were seropositive with an initial enzyme-linked immunosorbent assay (ELISA) test performed at the State Central Veterinary Laboratory in Mongolia. These 17 positive sera plus 53 additional negative sera were sent to the Rocky Mountain Laboratories, NIAID/NIH, and tested for the presence of antibodies with a similar ELISA, an indirect immunofluorescence assay (IFA), and a virus neutralization test (VNT). In these additional tests, a total of 21 of 70 sera were positive with ELISA and 10 sera were positive with IFA; however, none was positive in the VNT. Based on these results, we hypothesize that the ELISA/IFA-positive antibodies are (1) non-neutralizing antibodies or (2) directed against a MERS-CoV-like virus circulating in Bactrian camels in Mongolia.

and Coxiella burnetii collected from Hyalomma asiaticum in Bactrian camels (Camelus bactrianus) in inner Mongolia of China

The purpose of the present study was to determine the presence of Rickettsia sp. and Coxiella burnetii in Hyalomma asiaticum collected from Bactrian camels (Camelus bactrianus) in Inner Mongolia of China. A total of 385 H. asiaticum adults collected from Bactrian camels from Alxa in Inner Mongolia from 2017 to 2018 were examined using PCR combined with sequencing. The results indicated that 18 (4.7 %) and 5 (1.3 %) samples tested positive for Rickettsia and C. burnetii, respectively. The corresponding nucleotide identities among detected genes ranged between 99.7 % and 100 % for the sequences of 17 kD and ompB from Rickettsia and 16S rRNA and FtsX from C. burnetii. Two representative strains-Rickettsia IMA-1 strain and C. burnetii IMA-1 strain-were used for subsequent analysis. NCBI BLAST and phylogenetic analyses demonstrated that the detected strain Rickettsia IMA-1 may represent a novel species of spotted fever group (SFG) rickettsiae. The C. burnetii IMA-1 strain was grouped with Coxiella burnetii str. RSA439 (GenBank: CP040059.1). In addition, the Rickettsia sp. was successfully isolated from the ticks in Vero cells incubated at 28 °C. These findings indicate that the H. asiaticum collected off Bactrian camels in Inner Mongolia carried SFG Rickettsia species and C. burnetii and could contribute to the etiology of febrile illness in animals and humans.

Morphometric, haematological and physio-biochemical characterization of Bactrian (Camelus bactrianus) camel at high altitude

BACKGROUND

Biochemical and haematological parameters have not been determined in Bactrian camels kept at high altitude. Therefore, this study was undertaken to characterise different physiological, haematological, biochemical, and morphometric parameters of Bactrian camels of high altitude. For this, total fourteen high altitude healthy Bactrian camels were selected from Leh-Ladakh, India, a high altitude area, and thereafter divided into three age groups (N = 3 young; N = 6 adult; N = 5 old camels) to characterise for above parameters. All the results were compared with Lowlander Bactrian camels.

RESULTS

Morphometric measurement showed significant difference in body height, body length, front-hump height and girth, back-hump height and girth, abdomen girth, neck length, and circumference of the shank in the young age group camels as compared to other age groups of Bactrian camels (p < 0.05). Furthermore, all the physiological and haematological parameters were similar in all the age groups of camels (p < 0.05). However, the leukocyte, erythrocyte, Hb, platelets, monocyte, and ESR level were towards the higher side of the normal reference range of Lowlander Bactrian camels. Whereas, the biochemical analysis revealed a significant increase in triglycerides and decrease in protein levels in the younger age group as compared to other age groups (p < 0.05). Although, albumin, aspartate aminotransferase, iron, magnesium, urea, and creatinine levels were insignificant among the different groups, but observed towards the higher side of the low altitude reference range. Interestingly, the glucose levels in all the groups were observed towards the lower side of the range, which showed metabolic adaptation to high altitude.

CONCLUSION

These findings suggested there is morphometric and biochemical variation in Bactrian camel of high altitude. The results further helped in establishing novel reference ranges for these parameters in Highlander Bactrian camel. Hence, this study will be the basis of future research on a Bactrian camel from high-altitude cold desert and helpful for better camel husbandry and health management in high altitude.

Development of Genomic Resources and Identification of Genetic Diversity and Genetic Structure of the Domestic Bactrian Camel in China by RAD Sequencing

The domestic Bactrian camel is indispensable to agricultural production in the desertification area of China owning to its endurance to hunger and thirst, cold resistance, drought resistance, and good long-distance transportation. Therefore, it is necessary to investigate the genetic diversity, genetic structure, and genes with important roles in the evolution of this species. In this study, 1,568,087 SNPs were identified in 47 domestic Bactrian camels inhabiting four regions of China, namely Inner Mongolia, Gansu, Qinghai, and Xinjiang, by restriction site associated DNA sequencing (RAD-seq). The SNP data were used for nucleotide diversity analysis (π) and linkage disequilibrium (LD) attenuation analysis to elucidate the genetic diversity of the domestic Bactrian camel in the four regions studied. Results showed that Xinjiang camels had the highest nucleotide diversity and the fastest decay rate of the LD coefficient; therefore, Xinjiang camels had the highest genetic diversity. Structure analysis, principal component analysis (PCA), and phylogenetic tree construction by the neighbor-joining (NJ) method showed that Qinghai camels clustered separately, at a larger phylogenetic distance from camels in the other regions. Through analyses of selection signals, it was found that the number of selected genes shared by Inner Mongolia camels, Qinghai camels, Xinjiang camels, and Gansu camels was 7, 24, 25, and 113, respectively. The shared selected genes of the domestic Bactrian camel in the four regions were further analyzed, and three shared genes (GRIA3, XIAP, and THOC2) of the domestic Bactrian camel in China were identified. Gene Ontology (GO) classification and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis were performed on the shared selected genes of the domestic Bactrian camel in all four regions studied. Across all regions, genes involved in the cellular process were the most abundant subcategory under biological process. Cell and cell part represented the main proportion of genes under cellular component. Binding represented the main molecular function. In addition, the shared selected genes of the domestic Bactrian camel in the four regions of China were significantly enriched in the long-term depression pathway. The research should enable further study of the genetic resources of the domestic Bactrian camel, as well as the conservation of these resources.

Bactrian camel serum albumins-based nanocomposite as versatile biocargo for drug delivery, biocatalysis and detection of hydrogen peroxide

In response to extreme environmental conditions, Bactrian camels with largest population in China have evolved with the unique and extraordinary stress-tolerant mechanism in the bodies, in which the most abundantly secreted serum albumins contribute to an important role in diverse physiological activities such as maintaining osmotic pressure and transporting endogenous/exogenous molecules. In this study, we have for the first time purified Chinese Bactrian camel serum albumins (CSA) aimed at exploring their biomedical application. The mass spectrometric as well as structural analysis of CSA have revealed the sequence consensus and alpha-helix abundant structures among its heterologous proteins. Using desolvation methods, CSA-based nanoparticles have been prepared to encapsulate two substrate molecules including Doxorubicin (Dox) and hemin, which confers the versatility of nanocomposite. As drug delivery matrix, the Dox-loaded CSA nanoparticles displayed sustained release behaviors of DOX with the decreased cytotoxicity detected by both CCK-8 assay and real-time cell analysis. The CSA-hemin nanoparticles exhibited superior catalytic activities in the oxidation of Orange II comparable with horse radish peroxidase following a ping-pong mechanism. Furthermore, the constructed CSA-hemin nanoparticles were applied for the spectroscopic detection of H₂O₂ resulting in a wide linear calibration curve ranging from 5 to 400 μM with a detection limit of 3.32 μM.

Middle East Respiratory Syndrome Coronavirus Antibodies in Bactrian and Hybrid Camels from Dubai

So far, dromedary camels are the only known animal reservoir for Middle East respiratory syndrome (MERS) coronavirus (MERS-CoV). Previous published serological studies showed that sera of Bactrian camels were all negative for MERS-CoV antibodies. However, a recent study revealed that direct inoculation of Bactrian camels intranasally with MERS-CoV can lead to infection with abundant virus shedding and seroconversion. In this study, we examined the presence of MERS-CoV antibodies in Bactrian and hybrid camels in Dubai, the United Arab Emirates (where dromedaries are also present), and Bactrian camels in Xinjiang, China (where dromedaries are absent). For the 29 serum samples from Bactrian camels in Dubai tested by the MERS-CoV spike (S) protein-based enzyme-linked immunosorbent assay (S-ELISA) and neutralization antibody test, 14 (48%) and 12 (41%), respectively, were positive for MERS-CoV antibodies. All the 12 serum samples that were positive with the neutralization antibody test were also positive for the S-ELISA. For the 11 sera from hybrid camels in Dubai tested with the S-ELISA and neutralization antibody test, 6 (55%) and 9 (82%), respectively, were positive for MERS-CoV antibodies. All the 6 serum samples that were positive for the S-ELISA were also positive with the neutralization antibody test. There was a strong correlation between the antibody levels detected by S-ELISA and neutralizing antibody titers, with a Spearman coefficient of 0.6262 (P < 0.0001; 95% confidence interval, 0.5062 to 0.7225). All 92 Bactrian camel serum samples from Xinjiang were negative for MERS-CoV antibodies tested using both S-ELISA and the neutralization antibody test. Bactrian and hybrid camels are potential sources of MERS-CoV infection.IMPORTANCE Since its first appearance in 2012, Middle East respiratory syndrome (MERS) has affected >25 countries, with >2,400 cases and an extremely high fatality rate of >30%. The total number of mortalities due to MERS is already greater than that due to severe acute respiratory syndrome. MERS coronavirus (MERS-CoV) has been confirmed to be the etiological agent. So far, dromedaries are the only known animal reservoir for MERS-CoV. Previously published serological studies showed that sera of Bactrian camels were all negative for MERS-CoV antibodies. In this study, we observed that 41% of the Bactrian camel sera and 55% of the hybrid camel sera from Dubai (where dromedaries are also present), but none of the sera from Bactrian camels in Xinjiang (where dromedaries are absent), were positive for MERS-CoV antibodies. Based on these results, we conclude that in addition to dromedaries, Bactrian and hybrid camels are also potential sources of MERS-CoV infection.

Screening for reproductive biomarkers in Bactrian camel via iTRAQ analysis of proteomes

Bactrian camel is an ancient and precious species of livestock; that is, unique resources exist in the desert and have important economic and scientific value. In recent years, the number of Bactrian camels has declined sharply. Due to its long reproductive cycle and seasonal oestrus, the mechanism of oestrus is unknown. To identify candidate biomarkers of reproduction, we performed a comprehensive proteomic analysis of serum from Bactrian camel in oestrus and non-oestrus, using isobaric tags for relative and absolute quantitation (iTRAQ) coupled with tandem mass spectrometry. We identified 359 proteins, of which 32 were differentially expressed: 11 were up-regulated and 21 were down-regulated in samples from camels in oestrus. We validated the differential expression of a subset of these proteins using qPCR and Western blot. Gene ontology annotation identified that the differentially expressed proteins function in cellular processes, metabolic processes and immune system processes. Notably, five of the differentially expressed proteins, PCGF5, histone H1.2, RBP4, FOLR1 and ANTXR2, are involved in reproductive regulatory processes in other animals. KEGG enrichment analysis demonstrated significant enrichment in several cardiac-related pathways, such as 'dilated cardiomyopathy', 'hypertrophic cardiomyopathy', 'cardiac muscle contraction' and 'adrenergic signalling in cardiomyopathy'. Our results suggest that candidate biomarker (PCGF5, histone H1.2, RBP4, FOLR1 and ANTXR2) discovery can aid in understanding reproduction in Bactrian camels. We conclude that the profiling of serum proteomes, followed by the measurement of selected proteins using more targeted methods, offers a promising approach for studying mechanisms of oestrus.

Camelids: new players in the international animal production context

The Camelidae family comprises the Bactrian camel (Camelus bactrianus), the dromedary camel (Camelus dromedarius), and four species of South American camelids: llama (Lama glama), alpaca (Lama pacos) guanaco (Lama guanicoe), and vicuña (Vicugna vicugna). The main characteristic of these species is their ability to cope with either hard climatic conditions like those found in arid regions (Bactrian and dromedary camels) or high-altitude landscapes like those found in South America (South American camelids). Because of such interesting physiological and adaptive traits, the interest for these animals as livestock species has increased considerably over the last years. In general, the main animal products obtained from these animals are meat, milk, and hair fiber, although they are also used for races and work among other activities. In the near future, climate change will likely decrease agricultural areas for animal production worldwide, particularly in the tropics and subtropics where competition with crops for human consumption is a major problem already. In such conditions, extensive animal production could be limited in some extent to semi-arid rangelands, subjected to periodical draughts and erratic patterns of rainfall, severely affecting conventional livestock production, namely cattle and sheep. In the tropics and subtropics, camelids may become an important protein source for humans. This article aims to review some of the recent literature about the meat, milk, and hair fiber production in the six existing camelid species highlighting their benefits and drawbacks, overall contributing to the development of camelid production in the framework of food security.

Effects of Geographic Region on the Composition of Bactrian Camel Milk in Mongolia

Summary

Camels are known to occupy arid and desert countries. These pastoralist areas and conditions make it difficult to estimate camel milk production. Camel milk is considered to have anti-cancer, hypo-allergic and anti-diabetic properties. A high content of unsaturated fatty acids contributes to its overall dietary quality. The low quantity of β-casein and the lack of β-lactoglobulin are linked to the hypo-allergic effect of camel milk. Although the Bactrian camel is an important domestic animal in Mongolia, few studies have focused on Bactrian camel milk in this country. Our study characterizes the amino acid and fatty acid compositions of Bactrian camel milk collected from several geographical areas in Mongolia. The findings establish a theoretical basis for additional studies on the composition of milk from Bactrian camels in Mongolia.

Abstract

Camel milk is considered as an essential source of nutrition for desert people. However, few studies have investigated how geography affects Bactrian camel milk in Mongolia. In this study, we evaluated the differences in gross composition, fatty acid composition, and amino acid composition among Bactrian camel milk samples collected from 102 Bactrian camels in five different Mongolian regions. The proportion of long-chain fatty acids, out of total fatty acids, was high in all samples of Bactrian camel milk. The primary fatty acids detected in the samples were palmitic acid (23.99–30.72%), oleic acid (17.21–24.24%), and stearic acid (11.13–16.49%), while the dominant amino acids were leucine, lysine, valine, and aspartic acid. Cysteine was the least common amino acid detected in the Bactrian camel milk samples. Considerable differences in the fatty acid and amino acid compositions were observed among Bactrian camel milk from different regions of Mongolia. The findings suggest that geography strongly affects the composition of camel milk.

The Major Histocompatibility Complex of Old World Camels-A Synopsis

This study brings new information on major histocompatibility complex (MHC) class III sub-region genes in Old World camels and integrates current knowledge of the MHC region into a comprehensive overview for Old World camels. Out of the MHC class III genes characterized, TNFA and the LY6 gene family showed high levels of conservation, characteristic for MHC class III loci in general. For comparison, an MHC class II gene TAP1, not coding for antigen presenting molecules but functionally related to MHC antigen presenting functions was studied. TAP1 had many SNPs, even higher than the MHC class I and II genes encoding antigen presenting molecules. Based on this knowledge and using new camel genomic resources, we constructed an improved genomic map of the entire MHC region of Old World camels. The MHC class III sub-region shows a standard organization similar to that of pig or cattle. The overall genomic structure of the camel MHC is more similar to pig MHC than to cattle MHC. This conclusion is supported by differences in the organization of the MHC class II sub-region, absence of functional DY genes, different organization of MIC genes in the MHC class I sub-region, and generally closer evolutionary relationships of camel and porcine MHC gene sequences analyzed so far.

Effects of CYP1A enzyme specific inhibitor on pharmacokinetics of para-acetaminophen in Bactrian camel

The effects of CYP1A enzyme on the pharmacokinetics of p-acetaminophen were studied in Bactrian camel. Twelve Bactrian camels were divided into 2 groups, then given a single dose of p-acetaminophen only or with the enzyme inhibitor lomefloxacin. Blood samples were collected after different intervals, and p-acetaminophen concentration was determined by high-performance liquid chromatography. Pharmacokinetic parameters were analyzed by Phoenix WinNonLin v.7.0. The results show that lomefloxacin can significantly inhibit Bactrian camel CYP1A enzyme, as evidenced by the prolonged elimination half-life, increased maximum plasma concentration and area under the curve values and the shortened time to peak concentration for p-acetaminophenol in the substrate with inhibitor group. The results lay a foundation for revealing the particular characteristics of the CYP1A enzyme in Bactrian camels.

Population genetic analysis of the domestic Bactrian camel in China by RAD-seq

Restriction site-associated DNA sequencing (RAD-seq) is one of the most effective high-throughput sequencing technologies for SNP development and utilization and has been applied to studying the origin and evolution of various species. The domestic Bactrian camels play an important role in economic trade and cultural construction. They are precious species resources and indispensable animals in China's agricultural production. Recently, the rapid development of modern transportation and agriculture, and the deterioration of the environment have led to a sharp decline in the number of camels. Although there have been some reports on the evolution history of the domestic Bactrian camel in China, the origin, evolutionary relationship, and genetic diversity of the camels are unclear due to the limitations of sample size and sequencing technology. Therefore, 47 samples of seven domestic Bactrian camel species from four regions (Inner Mongolia, Gansu, Qinghai, and Xinjiang) were prepared for RAD-seq analysis to study the evolutionary relationship and genetic diversity. In addition, seven domestic Bactrian camel species are located in different ecological zones, forming different characteristics and having potential development value. A total of 6,487,849 SNPs were genotyped. On the one hand, the filtered SNP information was used to conduct polymorphism mapping construction, LD attenuation analysis, and nucleotide diversity analysis. The results showed that the number of SNPs in Dongjiang camel was the highest, the LD coefficient decayed the fastest, and the nucleotide diversity was the highest. It indicates that Dongjiang camel has the highest genetic diversity. On the other hand, the filtered SNPs information was used to construct the phylogenetic tree, and F ST analysis, inbreeding coefficient analysis, principal component analysis, and population structure analysis were carried out. The results showed that Nanjiang camel and Beijiang camels grouped together, and the other five Bactrian camel populations gathered into another branch. It may be because the mountains in the northern part of Xinjiang and the desert in the middle isolate the two groups from the other five groups.

Optimization of sperm freezability in Bactrian camel using various dilution rates and equilibration times

The effect of different dilution rates and equilibration times on the cryopreservation of Bactrian camel spermatozoa was evaluated in the current study. Semen samples from four healthy adult males were collected, processed and pooled. They were then subjected to a completely randomized 4×2 factorial design including four dilution rates (DR; 1:1, 1:2, 1:4 or 1:8; v:v with SHOTOR diluent) and two equilibration times (ET; 1 or 2 h at 5ºC). After freezing and thawing, sperm kinematic parameters as well as viability, plasma membrane integrity, abnormality and seminal malondialdehyde level were assessed. According to the results, four-fold diluted samples recorded significantly higher values (P < 0.05) for sperm total (39.58 vs 31.83 and 33.33,%) and progressive motility (19.50 vs 14.00 and 14.25,%), viability (55.37 vs 43.50 and 48.75,%) and plasma membrane integrity (46.75 vs 37.25 and 37.37,%) than those of both less (1:1) and high (1:8) concentrated samples, respectively. By contrast, the percentage of abnormal spermatozoa and the concentration of seminal malondialdehyde were comparable among all treated groups. Moreover, ET revealed that 1 h equilibration had significantly higher sperm motility (37.04 vs 33.33%), linearity (42.29 vs 32.26%), beat cross-frequency (13.15 vs 8.70 Hz), plasma membrane integrity (42.25 vs 39.75%) and viability (51.37 vs 48.12%) compared with 2 h of ET (P < 0.05). Taken together, a four-fold dilution along with 1 h equilibration can be an optimal procedure to cryopreserve Bactrian camel sperm.

Old World camels in a modern world - a balancing act between conservation and genetic improvement

Old World camels have served humans in cross‐continental caravans, transporting people and goods, connecting different cultures and providing milk, meat, wool and draught since their domestication around 3000–6000 years ago. In a world of modern transport and fast connectivity, these beasts of burden seem to be out‐dated. However, a growing demand for sustainable milk and meat production, especially in countries affected by climate change and increasing desertification, brings dromedaries (Camelus dromedarius) and Bactrian camels (Camelus bactrianus) back onstage and into the focus of animal breeders and scientists. In this review on the molecular genetics of these economically important species we give an overview about the evolutionary history, domestication and dispersal of Old World camels, whereas highlighting the need for conservation of wild two‐humped camels (Camelus ferus) as an evolutionarily unique and highly endangered species. We provide cutting‐edge information on the current molecular resources and on‐going sequencing projects. We cannot emphasise enough the importance of balancing the need for improving camel production traits with maintaining the genetic diversity in two domestic species with specific physiological adaptation to a desert environment.

Bactrian camels shed large quantities of Middle East respiratory syndrome coronavirus (MERS-CoV) after experimental infection. Emerg Microbes Infect 2019;8:717-723. [PMID: 31119984 PMCID: PMC6534258 DOI: 10.1080/22221751.2019.1618687]

In 2012, Middle East respiratory syndrome coronavirus (MERS-CoV) emerged. To date, more than 2300 cases have been reported, with an approximate case fatality rate of 35%. Epidemiological investigations identified dromedary camels as the source of MERS-CoV zoonotic transmission and evidence of MERS-CoV circulation has been observed throughout the original range of distribution. Other new-world camelids, alpacas and llamas, are also susceptible to MERS-CoV infection. Currently, it is unknown whether Bactrian camels are susceptible to infection. The distribution of Bactrian camels overlaps partly with that of the dromedary camel in west and central Asia. The receptor for MERS-CoV, DPP4, of the Bactrian camel was 98.3% identical to the dromedary camel DPP4, and 100% identical for the 14 residues which interact with the MERS-CoV spike receptor. Upon intranasal inoculation with 107 plaque-forming units of MERS-CoV, animals developed a transient, primarily upper respiratory tract infection. Clinical signs of the MERS-CoV infection were benign, but shedding of large quantities of MERS-CoV from the URT was observed. These data are similar to infections reported with dromedary camel infections and indicate that Bactrians are susceptible to MERS-CoV and given their overlapping range are at risk of introduction and establishment of MERS-CoV within the Bactrian camel populations.

Preparation and characterization of a single-domain antibody specific for the porcine epidemic diarrhea virus spike protein

Porcine epidemic diarrhea (PED) is a diarrheal disease of swine caused by porcine epidemic diarrhea virus (PEDV). It is characterized by acute watery diarrhea, dehydration and vomiting in swine of all ages and is especially fatal for neonatal and postweaning piglets. The spike protein of PEDV plays an important role in mediating virus attachment and fusion to target cells, and recent studies also reported that the neutralizing epitopes of the spike protein were mainly located in the S1 subunit, which makes it a candidate for vaccine development and clinical diagnosis. In this study, we successfully constructed an immune phage display single-domain antibody library with a library size of 3.4 × 10⁶. A single-domain antibody, named S7, specific for the spike protein of PEDV was identified from the phage display single-domain antibody library. S7 could be expressed in a soluble form in E. coli, bound to the spike protein of PEDV in ELISA and stained the PEDV virus in Vero cells, but it showed no neutralization activity on PEDV. These results indicated the potent application of the S7 antibody as an imaging probe or as a candidate for the development of a diagnostic assay.

Detection and genotypic characterization of Toxoplasma gondii DNA within the milk of Mongolian livestock

Toxoplasma gondii is a global, zoonotic parasite capable of infecting any warm-blooded host. Toxoplasmosis can cause a variety of illnesses including abortions and congenital defects in humans, sheep, and goats. Congenital toxoplasmosis is considered to have the highest global disease burden of any foodborne illness in humans. This study examined the potential role of milk as a route of T. gondii transmission between livestock and humans within Mongolian herders, a little-studied population which relies heavily on animals. Milk of Mongolian sheep, goats and Bactrian camels was tested for the presence of T. gondii DNA, and a survey was conducted to ascertain what behavioral and environmental factors were present that might potentiate T. gondii infection within these Mongolian communities. T. gondii DNA was detected in samples from one sheep and five camels. Sequence analysis of DNA from camel milk revealed that two were from potentially virulent T. gondii genotypes. This has implications for public health in the region, as milk is an extremely important source of nutrition and our survey results imply that some people believe consumption of raw camel milk carries health benefits. This is the first report of T. gondii DNA in Bactrian camel milk as well as the first genotypic characterization of T. gondii within Mongolia.

Transmission of a Novel Genotype of Hepatitis E Virus from Bactrian Camels to Cynomolgus Macaques

Hepatitis E virus (HEV) is zoonotic and a major cause of acute viral hepatitis worldwide. Recently, we identified a novel HEV genotype 8 (HEV8) in Bactrian camels in Xinjiang, China. However, the epidemiology, pathogenicity, and zoonotic potential of HEV8 are unclear. Here, we present the prevalence of HEV8 in China and investigate its pathogenicity and cross-species transmission in cynomolgus macaques. Fresh fecal and milk samples from Bactrian camels collected from four provinces/regions in China were screened for HEV RNA by reverse transcriptase PCR (RT-PCR). An HEV8-positive sample was used to inoculate two cynomolgus macaques to examine the potential for cross-species infection. The pathogenicity of HEV8 was analyzed by testing HEV markers and liver function during the study period and histopathology of liver biopsy specimens at 3, 13, and 25 weeks postinoculation. Extrahepatic replication was tested by using reverse transcriptase quantitative PCR (RT-qPCR) and immunofluorescence assays. The overall prevalence of HEV8 RNA in Chinese Bactrian camels was 1.4% (4/295), and positive samples were found in three different provinces/regions in China. Histopathology confirmed acute and chronic HEV8 infections in the two monkeys. Multiple tissues were positive for HEV RNA and ORF2 proteins. Renal pathology was observed in the monkey with chronic hepatitis. Whole-genome sequencing showed only 1 to 3 mutations in the HEV8 in the fecal samples from the two monkeys compared to that from the camel. HEV8 is circulating in multiple regions in China. Infection of two monkeys with HEV8 induced chronic and systemic infections, demonstrating the high potential zoonotic risk of HEV8.IMPORTANCE It is estimated that one-third of the world population have been exposed to hepatitis E virus (HEV). In developed countries and China, zoonotic HEV strains are responsible for almost all acute and chronic HEV infection cases. It is always of immediate interest to investigate the zoonotic potential of novel HEV strains. In 2016, we discovered a novel HEV genotype, HEV8, in Bactrian camels, but the epidemiology, zoonotic potential, and pathogenicity of the virus were unknown. In the present study, we demonstrated that HEV8 was circulating in multiple regions in China and was capable of infecting cynomolgus macaques, a surrogate for humans, posing high risk of zoonosis. Chronic hepatitis, systemic infection, and renal pathology were observed. Collectively, these data indicate that HEV8 exhibits a high potential for zoonotic transmission. Considering the importance of Bactrian camels as livestock animals, risk groups, such as camelid meat and milk consumers, should be screened for HEV8 infection.

Risk factors of brucellosis seropositivity in Bactrian camels of Mongolia

BACKGROUND

More information on brucellosis epidemiology in Bactrian camels is needed due to their growing economic and livelihood importance for herders and renewed efforts in Mongolia to eliminate brucellosis through mass vaccination of ruminants excluding camels. Brucellosis prevalence in camels increased over the past two decades. Random multi-stage cluster surveys were done in the Eastern provinces of Dornod and Sukhbaatar in 2013 and 2014 and in the Southern & Western provinces of Dornogobi, Umnogobi and Khovd in 2014 and 2015. A total of 1822 camels, 1155 cattle, and 3023 small ruminant sera were collected and tested with the Rose Bengal Test. In addition, 195 vaginal swabs and 250 milk samples for bacteriological culture were taken from livestock with history of abortion.

RESULTS

The overall apparent seroprevalence in camels was 2.3% (95% confidence interval 1.6-3.3). The main risk factor for camel seropositivity was being in an Eastern province when compared to Southern & Western provinces (odds ratio 13.2, 95% CI 5.3-32.4). Camel seroprevalences were stable over the two consecutive survey years, despite introduction of ruminant vaccination: 5.7% (95% CI 3.1-10.2%) and 5.8% (3.3-10.1%) in Eastern provinces and 0.4% (0.2-1.2%) and 0.5% (0.1-2.0%) in Southern & Western provinces. We isolated Brucella abortus from camels and cattle. Camel seropositivity was associated to keeping cattle together with camels. Monitoring of vaccination campaigns showed that coverage in cattle was insufficient because animals could not be adequately restrained.

CONCLUSIONS

The present study reveals that brucellosis is present with important seroprevalence in Mongolian camels and was endemic in Eastern provinces. Camel herd seropositivity was most closely associated to infection in cattle. Longer term monitoring is needed to assess whether camel seroprevalance decreases with ongoing vaccination in Mongolia. This should be coupled with further confirmation on Brucella spp. isolates. To date, only Brucella abortus was isolated, but camels are also susceptible to Brucella melitensis. Clear verbal and written information on disease prevention in livestock and household members is important, particularly for remote camel herders who had only moderate knowledge on brucellosis epidemiology and preventive measures.

First detection and molecular identification of Borrelia species in Bactrian camel (Camelus bactrianus) from Northwest China

Comprehensive epidemiological surveys for Lyme disease have not been conducted for the Bactrian camel in China. In this study, a total of 138 blood specimens collected from Bactrian camels from Zhangye City in Gansu Province and Yili and Aksu in Xinjiang Province, China, were examined for the presence of Borrelia spp. Species-specificity nested PCR based on the 5S-23S rRNA, OspA, flaB and 16S rRNA genes revealed that the total positive rate of Borrelia spp. was 3.6% (5/138, 95% CI = 0.2–17.9). These results were confirmed by sequence analysis of the positive PCR products or positive colonies. This is the first report of Borrelia pathogens in camels in China. Two Borrelia species that cause Lyme disease and one that causes relapsing fever were identified in the camel blood samples by sequencing. The findings of this study indicate that the Bactrian camel may serve as a potential natural host of Lyme disease and/or relapsing fever in China.

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This is the first report of Borrelia pathogens using molecular tools in Bactrian camel.

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Bactrian camel may play as potential natural host of Lyme disease in China.

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The results revealed that the prevalence of Borrelia spp. were 3.6% based on sequences of four genes.

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A novel Borrelia genespecies belong to Relapsing fever Borrelia spp. was found.

Host specificity of Enterocytozoon bieneusi genotypes in Bactrian camels (Camelus bactrianus) in China

BACKGROUND

Enterocytozoon bieneusi is an obligate, intracellular fungus and is commonly reported in humans and animals. To date, there have been no reports of E. bieneusi infections in Bactrian camels (Camelus bactrianus). The present study was conducted to understand the occurrence and molecular characteristics of E. bieneusi in Bactrian camels in China.

RESULTS

Of 407 individual Bactrian camel fecal specimens, 30.0% (122) were E. bieneusi-positive by nested polymerase chain reaction (PCR) based on internal transcriber spacer (ITS) sequence analysis. A total of 14 distinct E. bieneusi ITS genotypes were obtained: eight known genotypes (genotype EbpC, EbpA, Henan-IV, BEB6, CM8, CHG16, O and WL17), and six novel genotypes (named CAM1 to CAM6). Genotype CAM1 (59.0%, 72/122) was the most predominant genotype in Bactrian camels in Xinjiang, and genotype EbpC (18.9%, 23/122) was the second-most predominant genotype. Phylogenetic analysis revealed that six known genotypes (EbpC, EbpA, WL17, Henan-IV, CM8 and O) and three novel genotypes (CAM3, CAM5 and CAM6) fell into the human-pathogenic group 1. Two known genotypes (CHG16 and BEB6) fell into the cattle host-specific group 2. The novel genotypes CAM1, CAM 2 and CAM4 cluster into group 8.

CONCLUSIONS

To our knowledge, this is the first report of E. bieneusi in Bactrian camels. The host-specific genotype CAM1 was the predominant genotype, which plays a negligible role in the zoonotic transmission of E. bieneusi. However, the second-most predominant genotype, EbpC, has greater zoonotic potential.

Identification of Bactrian camel cell lines using genetic markers

Iranian Bactrian camel population is less than 100 animals. Iranian biological resource center produced more than 50 Bactrian camel fibroblast cell lines as a somatic cell bank for conservation animal genetic resources. We compared two type markers performance, including 14 random amplified polymorphic DNA (RAPDs) (dominant) and eight microsatellite (co-dominant) for cell line identification, individual identification and investigation genetic structure of these samples. Based on clarity, polymorphism, and repeatability, four RAPD primers were selected for future analysis. Four RAPD primers and eight microsatellite markers have generated a total of 21 fragments and 45 alleles, respectively. RAPD primers revealed fragment size between 150 to 2000 bp and gene diversity since 0.27 (IBRD) to 0.46 (GC10), with an average of 0.37. Microsatellite markers generated number of alleles per locus ranged from 3 to 11, with an average of 5.62 alleles. The observed heterozygosity ranged from 0.359 (IBRC02) to 0.978 (YWLL08), and expected heterozygosity ranged from 0.449 (IBRC02) to 0.879 (YWLL08). Bottleneck analysis and curve showed that Bactrian camel population did not experience a low diversity. RAPD profiles were especially suitable for investigation population genetics. All primers generated novel and polymorphic fragments. Briefly, our results show that a multiplex PCR based on these markers can still be valuable and suitable for authentication of cell lines, investigating gene diversity and conservation genetic resources in Bactrian camel, while new technologies are continuously developed.

Impact of aging on distribution of IgA+ and IgG+ cells in aggregated lymphoid nodules area in abomasum of Bactrian camels (Camelus bactrianus)

The aggregated lymphoid nodules area (ALNA) in the abomasum is a special organized lymphoid tissue discovered only in Bactrian camels at present. This study aimed to explore the impact of aging on distribution of IgA⁺ and IgG⁺ cells in ALNA in abomasum of Bactrian camels. Twenty-four Alashan Bactrian camels were divided into the following four age groups: young (1-2years), pubertal (3-5years), middle-aged (6-16years) and old (17-20years). IgA⁺ and IgG⁺ cells in the lamina propria of ALNA were observed and analyzed using immunohistochemical and statistical techniques. The results showed that, in ALNA, the distribution of IgA⁺ and IgG⁺ cells were diffuse, and only a few were in subepithelium dome (SED) and most of them in non-SED. Meanwhile, there were significantly more IgA⁺ cells than IgG⁺ cells in SED from the young to the middle aged group, but which reversed in old group (P<0.05). However, the aging significantly decreased the densities of IgA⁺ and IgG⁺ cells populations in non-SED (P<0.05); in SED, there were no significant differences between the densities of IgA⁺ and IgG⁺ cells, but which were both significantly lower in old group than those in young group (P<0.05). The results demonstrated that, in mucosal effector sites, the aging significantly decreased the densities of IgA⁺ and IgG⁺ cells populations and impacted on the defense barriers formed by IgA and IgG, but had no impact on the scattered characteristics. In inductive sites, the aging dramatically declined their densities, and they should have close relationships with immune memory. These findings lay the foundation for further researching the mucosal immune disorder or decline caused by aging, and especially underscore the importance of researching the impact of aging on the relationship between IgA⁺ and IgG⁺ cells populations and the microbiota colonized in abomasum of Bactrian camels.

Diversity and distribution of CYP gene family in Bactrian camel

Cytochrome P450 (CYP) enzymes belong to a superfamily of monooxygenases which are phase I enzymes responsible for the first pass metabolism of about 90% of drugs in animals. However, these enzymes are often polymorphic and metabolism of the same drug in different species or different individuals is influenced by genetic and non-genetic factors. Bactrian camels are capable of survival in harsh living environments, being able to consume diets that are often toxic to other mammals and can tolerate extreme water and food deprivation. The aim of this study was to investigate whether the Bactrian camel’s special metabolic pathways and unique detoxification capabilities are attributable to particularities of the CYP gene family. The Bactrian camel’s whole genome sequencing data were systemically analyzed and annotated, and then, CYP gene family was searched from the whole protein database and compared with CYP gene families of cattle, horse, chicken, and human. The total of 63 CYP gene copies were found in Bactrian camel’s whole genome and were classified into 17 families and 38 subfamilies. Among them, 9 multi-gene families were found, and CYP2, CYP3, and CPY4 have 27, 6, and 7 subfamilies, accounting for 43, 10, and 11% in camel CYP gene, respectively. In comparison with cattle, chicken, horse, and human, the distribution of CYP gene subfamilies in camel is different, with more CYP2J and CYP3A copies in the Bactrian camel, which may contribute to the Bactrian camel’s specific biological characteristics and metabolic pathways. Comparing to the cow, horse, chicken, and human CYP genes, the distribution of CYP gene subfamilies is distinct in the Bactrian camel. The higher copy number of CYP2J gene and CYP3A gene in Bactrian camel may be the important factors contributing to the distinct biological characteristics and metabolic pathways of Bactrian camels for adaptation to the harsh environments.