Camelid type I interferons: Identification and functional characterization of interferon alpha from the dromedary camel (Camelus dromedarius)

First report of a chemokine from camelids: Dromedary CXCL8 is induced by poxvirus and heavy metal toxicity

Low molecular weight proteins, known as chemokines, facilitate the migration and localization of immune cells to the site of infection and injury. One of the first chemokines identified, CXCL8 functions as a key neutrophil activator, recruiting neutrophils to sites of inflammation. Several viral infections, including zoonotic coronaviruses and poxviruses, have been reported to induce the expression of CXCL8. Dromedary camels are known to harbor several potentially zoonotic pathogens, but critical immune molecules such as chemokines remain unidentified. We report here the identification of CXCL8 from the dromedary camel - the first chemokine identified from camelids. The complete dromedary CXCL8 cDNA sequence as well as the corresponding gene sequence from dromedary and two New World camelids - alpaca and llama were cloned. CXCL8 mRNA expression was relatively higher in PBMC, spleen, lung, intestine, and liver. Poly(I:C) and lipopolysaccharide stimulated CXCL8 expression in vitro, while interferon treatment inhibited it. In vitro infection with potentially zoonotic camelpox virus induced the expression of CXCL8 in camel kidney cells. Toxicological studies on camelids have been limited, and no biomarkers have been identified. Hence, we also evaluated CXCL8 mRNA expression as a potential biomarker to assess heavy metal toxicity in camel kidney cells in vitro. CXCL8 expression was increased after in vitro exposure to heavy metal compounds of cobalt and cadmium, suggesting potential utility as a biomarker for renal toxicity in camels. The results of our study demonstrate that camel CXCL8 plays a significant role in immunomodulatory and induced toxicity responses in dromedary camels.

The one-humped camel: The animal of future, potential alternative red meat, technological suitability and future perspectives

The 2020 world population data sheet indicates that world population is projected to increase from 7.8 billion in 2020 to 9.9 billion by 2050 (Increase of more than 25%). Due to the expected growth in human population, the demand for meats that could improve health status and provide therapeutic benefits is also projected to rise. The dromedary also known as the Arabian camel, or one-humped camel ( Camelus dromedarius), a pseudo ruminant adapted to arid climates, has physiological, biological and metabolic characteristics which give it a legendary reputation for surviving in the extreme conditions of desert environments considered restrictive for other ruminants. Camel meat is an ethnic food consumed across the arid regions of Middle East, North-East Africa, Australia and China. For these medicinal and nutritional benefits, camel meat can be a great option for sustainable meat worldwide supply. A considerable amount of literature has been published on technological aspects and quality properties of beef, lamb and pork but the information available on the technological aspects of the meat of the one humped camel is very limited. Camels are usually raised in less developed countries and their meat is as nutritionally good as any other traditional meat source. Its quality also depends on the breed, sex, age, breeding conditions and type of muscle consumed. A compilation of existing literature related to new technological advances in packaging, shelf-life and quality of camel meat has not been reviewed to the best of our knowledge. Therefore, this review attempts to explore the nutritional composition, health benefits of camel meat, as well as various technological and processing interventions to improve its quality and consumer acceptance. This review will be helpful for camel sector and highlight the potential for global marketability of camel meat and to generate value added products.

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.

Viperin from the dromedary camel: First report of an antiviral interferon-responsive gene from camelids

Viral infections activate pattern recognition receptors in the host, triggering an innate immune response that involves the production of interferons, which, in turn, stimulates the expression of antiviral effector genes. Viperin is one of the most highly induced interferon-stimulated genes and displays broad antiviral activity, especially against tick-borne viruses. Of late, camelid-borne zoonotic viruses have been on the rise in the Arabian Peninsula, but research into camelid antiviral effector genes has been limited. This is the first report of an interferon-responsive gene from the mammalian suborder Tylopoda to which modern camels belong. From camel kidney cells treated with dsRNA mimetic, we cloned viperin cDNA encoding 361 amino acid protein. Sequence analysis of camel viperin reveals high levels of amino acid conservation, particularly within the RSAD domain. Compared to kidney, the relative mRNA expression of viperin was higher in blood, lung, spleen, lymph nodes, and intestines. The in-vitro expression of viperin was induced by poly(I:C) and interferon treatment in camel kidney cell lines. Viperin expression was subdued in camel kidney cells infected with the camelpox virus during the early stages of infection, suggesting possible suppression by the virus. Overexpression of camel viperin through transient transfection significantly enhanced the resistance of cultured camel kidney cell lines to infection with camelpox virus. Research into the role of viperin in host immunity against emerging viral pathogens of camels will provide insight into novel mechanisms of antiviral activity of the protein, viral immune evasion strategies, and enable the development of better antivirals.

Novel type-I interferons from the dromedary camel: Molecular identification, prokaryotic expression and functional characterization of camelid interferon-delta

The last two decades have seen the emergence of three highly pathogenic coronaviruses with zoonotic origins, which prompted immediate attention to the underlying cause and prevention of future outbreaks. Intensification of camel husbandry in the Middle East has resulted in increased human-camel interactions, which has led to the spread of potentially zoonotic viruses with human spillover risks like MERS-coronavirus, camelpox virus, etc. Type-I interferons function as the first line of defense against invading viruses and are pivotal for limiting viral replication and immune-mediated pathologies. Seven novel dromedary camel interferon delta genes were identified and cloned. Functional characterization of this novel class of IFNs from the mammalian suborder tylopoda is reported for the first time. The camel interferon-delta proteins resemble the reported mammalian counterparts in sequence similarity, conservation of cysteines, and phylogenetic proximity. Prokaryotically expressed recombinant camel interferon-δ1 induced IFN-stimulated gene expression and also exerted antiviral action against camelpox virus, an endemic zoonotic virus. The pre-treatment of camel kidney cells with recombinant camel IFN-δ1 increased cell survival and reduced camelpox virus in a dose-dependent manner. The identification of novel IFNs from species with zoonotic spillover risk such as camels, and evaluating their antiviral effects in-vitro will play a key role in improving immunotherapies against viruses and expanding the arsenal to combat emerging zoonotic pathogens.

Beta interferons from the extant camelids: Unique among eutherian mammals

The COVID-19 pandemic is a wake-up call on the zoonotic viral spillover events and the need to be prepared for future outbreaks. Zoonotic RNA viruses like the Middle East respiratory syndrome coronavirus (MERS-CoV) are potential pathogens that could trigger the next pandemic. Dromedary camels are the only known animal source of MERS-CoV zoonotic infections, but little is known about the molecular antiviral response in this species. IFN-β and other type-I interferons provide the first line of defense against invading pathogens in the host immune response. We identified the IFNB gene of the dromedary camel and all extant members of the family Camelidae. Camelid IFN-β is unique with an even number of cysteines in the mature protein compared to other eutherian mammals with an odd number of cysteines. The viral mimetic poly(I:C) strongly induced IFN-β expression in camel kidney cells. Induction of IFN-β expression upon infection with camelpox virus was late and subdued when compared to poly(I:C) treatment. Prokaryotically expressed recombinant dromedary IFN-β induced expression of IFN-responsive genes in camel kidney cells. Further, recombinant IFN-β conferred antiviral resistance to camel kidney cells against the cytopathic effects of the camelpox virus, an endemic zoonotic pathogen. IFN-β from this unique group of mammals will offer insights into antiviral immune mechanisms and aid in the development of specific antivirals against pathogens that have the potential to be the next zoonotic pandemic.

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.

Parabronema skrjabini (Nematoda: Habronematidae) infection and development in the intermediate host-Haematobia irritans (Linnaeus, 1758) in Inner Mongolia, China

Parabronemosis is a disease that severely threatens camel health, causing huge economic losses to industries involved in camel husbandry. Previous studies have reported that horn flies (Haematobia irritans) act as intermediate hosts of Parabronema skrjabini; however, the infection and developmental processes of P. skrjabini in horn flies remain unclear. In the present study, the infection rates of P. skrjabini were determined in morphologically and molecularly identified horn flies collected from Bactrian camels (Camelus bactrianus) producing regions in Inner Mongolia, China that have high P. skrjabini infection rates. The horn flies were dissected to obtain the nematode larvae at various instar stages. The P. skrjabini found in the different instar stages of horn fly instars were counted and identified to assess the infection and developmental status. Nematode larvae at different developmental stages were obtained from the horn fly instars for further molecular analysis. Sequencing results confirmed that the nematode larvae were P. skrjabini. Furthermore, we found that the mean growth rate of the nematode larva increased as the horn fly instars develops. The results suggested that P. skrjabini infected the horn flies at the larval instar stage, and that the nematode larvae developed simultaneously with the horn fly instars stages. Our findings provide useful information into the elucidation of P. skrjabini infection and life history by studying horn fly development.