Complete cDNA sequences and phylogenetic analyses of the Th1 and Th2 cytokines of the bactrian camel (Camelus bactrianus)

Quantification of camelid cytokine mRNA expression in PBMCs by microfluidic qPCR technology

Camelids are economically and socially important in several parts of the world and might carry pathogens with epizootic or zoonotic potential. However, biological research in these species is limited due to lack of reagents. Here, we developed RT-qPCR assays to quantify a panel of camelid innate and adaptive immune response genes, which can be monitored in a single run. The assays were validated with PHA, PMA-ionomycin, and Poly I:C-stimulated PBMCs from alpaca, dromedary camel and llama, including normalization by multiple reference genes. Further, comparative gene expression analyses for the different camelid species were performed by a unique microfluidic qPCR assay. Compared to unstimulated controls, PHA and PMA-ionomycin stimulation elicited robust Th1 and Th2 responses in PBMCs from camelid species. Additional activation of type I and type III IFN signalling pathways was described exclusively in PHA-stimulated dromedary lymphocytes, in contrast to those from alpaca and llama. We also found that PolyI:C stimulation induced robust antiviral response genes in alpaca PBMCs. The proposed methodology should be useful for the measurement of immune responses to infection or vaccination in camelid species.

Recent Advances in Camel Immunology

Camels are domesticated animals that are highly adapted to the extreme desert ecosystem with relatively higher resistance to a wide range of pathogens compared to many other species from the same geographical region. Recently, there has been increased interest in the field of camel immunology. As the progress in the analysis of camel immunoglobulins has previously been covered in many recent reviews, this review intends to summarize published findings related to camel cellular immunology with a focus on the phenotype and functionality of camel leukocyte subpopulations. The review also describes the impact of different physiological (age and pregnancy) and pathological (e.g. infection) conditions on camel immune cells. Despite the progress achieved in the field of camel immunology, there are gaps in our complete understanding of the camel immune system. Questions remain regarding innate recognition mechanisms, the functional characterization of antigen-presenting cells, and the characterization of camel NK and cytotoxic T cells.

Identification of interleukin-26 in the dromedary camel (Camelus dromedarius): Evidence of alternative splicing and isolation of novel splice variants

Interleukin-26 (IL-26) is a member of the IL-10 family of cytokines. Though conserved across vertebrates, the IL-26 gene is functionally inactivated in a few mammals like rat, mouse and horse. We report here the identification, isolation and cloning of the cDNA of IL-26 from the dromedary camel. The camel cDNA contains a 516 bp open reading frame encoding a 171 amino acid precursor protein, including a 21 amino acid signal peptide. Sequence analysis revealed high similarity with other mammalian IL-26 homologs and the conservation of IL-10 cytokine family domain structure including key amino acid residues. We also report the identification and cloning of four novel transcript variants produced by alternative splicing at the Exon 3-Exon 4 regions of the gene. Three of the alternative splice variants had premature termination codons and are predicted to code for truncated proteins. The transcript variant 4 (Tv4) having an insertion of an extra 120 bp nucleotides in the ORF was predicted to encode a full length protein product with 40 extra amino acid residues. The mRNA transcripts of all the variants were identified in lymph node, where as fewer variants were observed in other tissues like blood, liver and kidney. The expression of Tv2 and Tv3 were found to be up regulated in mitogen induced camel peripheral blood mononuclear cells. IL-26-Tv2 expression was also induced in camel fibroblast cells infected with Camel pox virus in-vitro. The identification of the transcript variants of IL-26 from the dromedary camel is the first report of alternative splicing for IL-26 in a species in which the gene has not been inactivated.

Molecular cloning, sequence, and phylogenetic analysis of T helper 1 cytokines of Pashmina goats

Cytokines play an important role in regulation of immune responses either in health or disease. In the present study, the cDNAs encoding mature Interleukin (IL)-2, interferon gamma (IFN-γ), and IL-12 p35 and p40 of Pashmina goat were cloned and sequenced. The amino acid sequence was deduced from nucleotide sequence and compared with those available in GeneBank. Mature forms of goat IL-2, IFN-γ, IL-12 p35, and IL-12 p40 composed of 135, 143, 196, and 305 amino acid residues, respectively. Comparison of amino acid sequence of goat IL-2 with sheep, buffalo, cattle, pig, camel, cat, and human sequences showed homology percentages of 100, 97.8, 96.3, 72.4, 72.4, 67.2, and 64.7, respectively. Amino acid sequence of goat IFN-γ showed 98.6, 95.8, 81.1, 81.8, 80.4, and 62.9 percent homology with sheep, bovine, pig, horse, dog, and humans, respectively. Homology ranging from 81.6 to 99% for IL-12 p35 sequences and 85.6 to 100% for IL-12 p40 sequences at amino acid level were observed across these species. Multiple sequence alignment and phylogenetic analysis of goat cytokines revealed close relationship with sheep sequence.

Molecular cloning and characterization of Th1 and Th2 cytokines of African buffalo (Syncerus caffer)

The African buffalo (Syncerus caffer) has been implicated as the reservoir of several bovine infectious agents. However, there is insufficient information on the protective immune responses in the African buffalo, particularly in infected animals. In this study, we analysed Th1 cytokines IL-2 and IFN-γ, and Th2 cytokines IL-4 and IL-10. The cloned cDNA of IL-2, IL-4, IL-10 and IFN-γ contained an open reading frame of 468, 501, 408 and 540 nucleotides, encoding polypeptides of 155, 166, 135 and 179 amino acids, respectively. Nucleotide sequence homology of IL-2, IFN-γ and IL-4 was more than 98% between the African buffalo and cattle, which resulted in identical polypeptides. Meanwhile, IL-10 gene of African buffalo and cattle had 95% homology in nucleotide sequence, corresponding to thirteen amino acid residues substitution. Cysteine residues and potential glycosylation sites were conserved within the family Bovinae. Phylogenetic analyses including cytokines of the African buffalo placed them within a cluster comprised mainly of species belonging to the order Artiodactyla, including cattle, water buffalo, sheep, goat, pig and artiodactyl wildlife. A deeper understanding of the structure of these cytokines will shed light on their protective role in the disease-resistant African buffalo in comparison with other closely related species.

Cloning and sequence analysis of IL-2, IL-4 and IFN-γ from Indian Dromedary camels (Camelus dromedarius)

The cDNAs of three cytokines, viz., IL-2, IL-4 and IFN-γ from Dromedary camels were amplified by PCR using Bactrian camel sequences and subsequently cloned for sequence analysis. Relationship based on amino acid sequences revealed that Dromedary camel IL-2 shared 99.5% and 99.3% identity at the nucleotide and amino acid levels with Bactrian camel IL-2. In the case of IL-4, the identity of Dromedary camel was 99.7% and 99.2% at the nucleotide and amino acid levels, respectively with that of Bactrian camel. The Dromedary camel IFN-γ shared 100% identity both at nucleotide and amino acid levels with Bactrian camel IFN-γ. Phylogenetic analysis based on amino acid sequences indicated the close relationship in these cytokine genes between the Dromedary camel and other camelids.

Modulation of cytokine-induced prostaglandin E₂ production in cultures of articular chondrocytes obtained from carpal joints of camels (Camelus dromedarius)

OBJECTIVE

To determine whether camel articular chondrocytes can be maintained in tissue culture without phenotype loss and whether the response to cytokine stimulation can be modulated.

SAMPLE POPULATION

Cartilage from 4 carpal joints of healthy adult dromedary camels (Camelus dromedarius).

PROCEDURES

Chondrocytes were evaluated for type II collagen and aggrecan production They were incubated with control media or with 2 test mixtures (alone and then in combination) that have anti-inflammatory activity (avocado-soybean unsaponifiables, glucosamine, and chondroitin sulfate [ie, ASU + GLU + CS] and pentosan polysulfate and N-acetyl glucosamine [ie, PPS + NG]). Cells were then stimulated with interleukin-1β and tumor necrosis factor-α to determine prostaglandin (PG) E₂ production and nuclear factor (NF)-κB activation.

RESULTS

Chondrocytes proliferated in media used for propagating equine chondrocytes; they produced type II collagen and aggrecan. Cytokine stimulation induced PGE₂ production and translocation of NF-κB. Incubation with each test mixture significantly inhibited PGE₂ production. The combination of ASU + GLU + CS and PPS + NG significantly potentiated PGE₂ inhibition and disrupted NF-κB translocation, compared with effects for either mixture alone.

CONCLUSIONS AND CLINICAL RELEVANCE

Chondrocytes proliferated without loss of the cartilage phenotype. Responses to cytokines were significantly inhibited by the mixtures of ASU + GLU + CS and PPS + NG, which indicated that this response can be modulated. This culture technique can be used to study the functional properties of camel chondrocytes and identify agents that may potentially be used to treat and manage joint inflammation.