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-ß 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-ß 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-ß expression in camel kidney cells. Induction of IFN-ß expression upon infection with camelpox virus was late and subdued when compared to poly(I:C) treatment. Prokaryotically expressed recombinant dromedary IFN-ß induced expression of IFN-responsive genes in camel kidney cells. Further, recombinant IFN-ß conferred antiviral resistance to camel kidney cells against the cytopathic effects of the camelpox virus, an endemic zoonotic pathogen. IFN-ß 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.

Nucleic Acid and Immunological Diagnostics for SARS-CoV-2: Processes, Platforms and Pitfalls.

Accurate diagnosis at an early stage of infection is essential for the successful management of any contagious disease. The coronavirus disease 2019 (COVID-19), caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) virus is a pandemic that has affected 214 countries affecting more than 37.4 million people causing 1.07 million deaths as of the second week of October 2020. The primary diagnosis of the infection is done either by the molecular technique of RT-qPCR by detecting portions of the RNA of the viral genome or through immunodiagnostic tests by detecting the viral proteins or the antibodies produced by the host. As the demand for the test increased rapidly many naive manufacturers entered the market with novel kits and more and more laboratories also entered the diagnostic arena making the test result more error-prone. There are serious debates globally and regionally on the sensitivity and specificity of these tests and about the overall accuracy and reliability of the tests for decision making on control strategies. The significance of the test is also complexed by the presence of asymptomatic carriers, re-occurrence of infection in cured patients as well as by the varied incubation periods of the infection and shifting of the viral location in the host tissues. In this paper, we review the techniques available for SARS-CoV-2 diagnosis and probable factors that can reduce the sensitivity and specificity of the different test methods currently in vogue. We also provide a checklist of factors to be considered to avoid fallacious practices to reduce false positive and false negative results by the clinical laboratories.

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

Investigations into the molecular immune response of dromedary camel, a key livestock species of the arid, have been limited due to the lack of species-specific reagents. Here we describe for the first time, the identification and characterization of type I IFNs of dromedary camel, which are the most important cytokines in the innate host immune response against viruses. We cloned camel IFN-α coding sequences and identified a total of eleven subtypes. The canonical IFN-α subtype designated as IFN-α1 contained a 555-bp Open Reading Frame encoding a protein of 184 amino acids. Recombinant IFN-α1 protein was produced in E. coli and purified from inclusion bodies. Recombinant camel IFN-α1 induced the mRNA expression of interferon-stimulated genes (ISGs) in camel kidney cells. The purified protein also showed potent in-vitro antiviral activity against Camelpox Virus in kidney cells. The identified camel IFN-α protein and the subtypes will facilitate a better understanding of the host immune response to viral infections in camel and the development of potential antiviral biologicals for zoonotic diseases for which camel act as a reservoir.

Protective immunity induced by systemic and mucosal delivery of DNA vaccine expressing glycoprotein B of pseudorabies virus.

A murine model immunized by systemic and mucosal delivery of plasmid DNA vaccine expressing glycoprotein B (pCIgB) of pseudorabies virus (PrV) was used to evaluate both the nature of the induced immunity and protection against a virulent virus. With regard to systemic delivery, the intramuscular (i.m.) immunization with pCIgB induced strong PrV-specific IgG responses in serum but was inefficient in generating a mucosal IgA response. Mucosal delivery through intranasal (i.n.) immunization of pCIgB induced both systemic and mucosal immunity at the distal mucosal site. However, the levels of systemic immunity induced by i.n. immunization were less than those induced by i.m. immunization. Moreover, i.n. genetic transfer of pCIgB appeared to induce Th2-biased immunity compared with systemic delivery, as judged by the ratio of PrV-specific IgG isotypes and Th1- and Th2-type cytokines produced by stimulated T cells. Moreover, the immunity induced by i.n. immunization did not provide effective protection against i.n. challenge of a virulent PrV strain, whereas i.m. immunization produced resistance to viral infection. Therefore, although i.n. immunization was a useful route for inducing mucosal immunity at the virus entry site, i.n. immunization did not provide effective protection against the lethal infection of PrV.

Low-dose antigen-experienced CD4+ T cells display reduced clonal expansion but facilitate an effective memory pool in response to secondary exposure.

The strength and duration of an antigenic signal at the time of initial stimulation were assumed to affect the development and response of effectors and memory cells to secondary stimulation with the same antigen. To test this assumption, we used T-cell receptor (TCR)-transgenic CD4+ T cells that were stimulated in vitro with various antigen doses. The primary effector CD4+ T cells generated in response to low-dose antigen in vitro exhibited reduced clonal expansion upon secondary antigenic exposure after adoptive transfer to hosts. However, the magnitude of their contraction was much smaller than both those generated by high-dose antigen stimulation and by naïve CD4+ T cells, resulting in higher numbers of antigen-specific CD4+ T cells remaining until the memory stage. Moreover, secondary effectors and memory cells developed by secondary antigen exposure were not functionally impaired. In hosts given the low-dose antigen-experienced CD4+ T cells, we also observed accelerated recall responses upon injection of antigen-bearing antigen-presenting cells. These results suggest that primary TCR stimulation is important for developing optimal effectors during initial antigen exposure to confer long-lasting memory CD4+ T cells in response to secondary exposure.

Systemic and mucosal immunity induced by oral somatic transgene vaccination against glycoprotein B of pseudorabies virus using live attenuated Salmonella typhimurium.

Glycoprotein B mediates the absorption and penetration of the pseudorabies virus in the form of an immunodominant Ag, and represents a major target for the development of new vaccines. This study evaluated the efficiency of live attenuated Salmonella typhimurium SL7207 for the oral delivery of DNA vaccine encoding the pseudorabies virus glycoprotein B (pCI-PrVgB) in vivo, leading to the generation of both systemic and mucosal immunity against the pseudorabies virus Ag. An oral transgene vaccination of pCI-PrVgB using a Salmonella carrier produced a broad spectrum of immunity at both the systemic and mucosal sites, whereas the intramuscular administration of a naked DNA vaccine elicited no mucosal immunoglobulin (Ig)A response. Interestingly, the Salmonella-mediated oral transgene vaccination of the pseudorabies virus glycoprotein B biased the immune responses to the Th2-type, as determined by the IgG2a/IgG1 ratio and the cytokine production profile. However, oral vaccination mediated by Salmonella harbouring pCI-PrVgB showed inferior protection to systemic immunization against virulent pseudorabies virus infection. The expression of transgene delivered by Salmonella bacteria in antigen-presenting cells of both the systemic and mucosal-associated lymphoid tissues was further demonstrated. These results highlight the potential use of live attenuated S. typhimurium for an oral transgene pseudorabies virus glycoprotein B vaccination to induce broad immune responses.

Investigation of pseudorabies virus latency in nervous tissues of seropositive pigs exposed to field strain.

The prevalence and quantity of latent pseudorabies virus (PrV) in nervous tissues of pigs exposed to field strain in Korea was investigated by nested and real-time PCR. Nervous tissues including trigeminal ganglion (TG), olfactory bulb (OB), and brain stem (BS) were collected from 94 seropositive pigs. PrV latent infection in nervous tissues was initially investigated by nested PCR targeting three glycoprotein genes (gB, gE, and gG). Based on the obtained result, latent infection was detected in 95.7% of screened animals. Furthermore, it was revealed that the examined tissues harbored different copy numbers of latent PrV genome ranging from <10(2.0) to 10(7.1) copies per microgram of genomic DNA in real-time PCR analysis. These results show that under normal conditions, levels of latent PrV in the nervous tissues of pigs can vary across a wide range. Therefore, the data presented here provides information regarding control of the endemic state of PrV in Korea.

Inhibition of Anatid Herpes Virus-1 replication by small interfering RNAs in cell culture system.

RNA interference (RNAi) mediated by double stranded small interfering RNA (siRNA) is a novel mechanism of post-transcriptional gene silencing. It is projected as a potential tool to inhibit viral replication. In the present paper, we demonstrate the suppression of replication of an avian herpes virus (Anatid Herpes Virus-1, AHV-1) by siRNA mediated gene silencing in avian cells. The UL-6 gene of AHV-1 that codes for a protein involved in viral packaging was targeted. Both cocktail and unique siRNAs were attempted to evaluate the inhibitory potential of AHV-1 replication in duck embryo fibroblast (DEF) cell line. DEF cells were chemically transfected with different siRNAs in separate experiments followed by viral infection. The observed reduction in virus replication was evaluated by cytopathic effect, viral titration and quantitative real time PCR (QRT-PCR). Among the three siRNA targets used the unique siRNA UL-B sequence was found to be more potent in antiviral activity than the cocktail and UL6-A-siRNA sequences.

Molecular survey of latent pseudorabies virus infection in nervous tissues of slaughtered pigs by nested and real-time PCR.

In this study, the prevalence and quantity of a latent pseudorabies virus (PrV) infection in the nervous tissues of randomly selected pigs was determined via nested and real-time PCR. The nervous tissues, including the trigeminal ganglion (TG), olfactory bulb (OB), and brain stem (BS), were collected from the heads of 40 randomly selected pigs. The majority of the nervous tissues from the selected pigs evidenced a positively amplified band on nested PCR. In particular, nested PCR targeted to the PrV glycoprotein B (gB) gene yielded positive results in all of the BS samples. Nested PCR for either the gE or gG gene produced positive bands in a less number of nervous tissues (57.5% and 42.5%, respectively). Real-time PCR revealed that the examined tissues harbored large copy numbers of latent PrV DNA, ranging between 10(0.1) and 10(7.2) (1-1.58 x 10(7)) copies per 1 microg of genomic DNA. Real-time PCR targeted to the PrV gE gene exhibited an accumulated fluorescence of reporter dye at levels above threshold, thereby indicating a higher prevalence than was observed on the nested PCR (100% for BS, 92% for OB, and 85% for TG). These results indicate that a large number of farm-grown pigs are latently infected with a field PrV strain with a variety of copy numbers. This result is similar to what was found in association with the human herpes virus.