In vitro and in vivo effects of recombinant bovine interferon-tau on bovine leukemia virus

First in vitro and in vivo evaluation of recombinant IL-1β protein as a potential immunomodulator against viral infection in fish

IL-1β is an important proinflammatory cytokine with multifaceted modulatory roles in immune responses. In fish, recombinant IL-1β has been employed in the control of bacterial diseases, while the antiviral mechanisms of IL-1β remain largely unknown, and the efficacy of recombinant IL-1β as an immunomodulator to prevent viral diseases is still not determined. This study evaluated the immunomodulatory effects of recombinant grass carp IL-1β against grass carp reovirus (GCRV) in vitro and in vivo. Firstly, the mature form (Ser111-Lys270) of grass carp IL-1β was identified, and its recombinant protein (designated as rgcIL-1β) was prepared through prokaryotic expression. Then, an in vitro evaluation model for rgcIL-1β activity was established in the CIK cells, with the appropriate concentration (600 ng/mL) and effect time (1 h). In vitro, rgcIL-1β could not only induce the production of proinflammatory cytokines such as IL-1β, IL-6, IL-8, and TNF-α but also a series of antiviral factors including IFN-1, IFN-2, IFN-γ, and ISG15. Mechanistically, transcriptome analysis and western blotting confirmed that rgcIL-1β activated multiple transcriptional factors, including NF-κB, IRF1, IRF3, and IRF8, and the signal pathways associated with inflammatory cytokines and antiviral factors expression. Expectedly, rgcIL-1β treatment significantly inhibited GCRV replication in vitro. In vivo administration of rgcIL-1β via intraperitoneal pre-injection significantly aroused an antiviral response to restrict GCRV replication and intense tissue inflammation in grass carp, demonstrating the immunomodulatory effects of rgcIL-1β. More importantly, rgcIL-1β administrated with 10 ng/g and 1 ng/g could improve the survival rate of grass carp during GCRV infection. This study represents the first time to comprehensively reveal the immunomodulatory and antiviral mechanisms of IL-1β in fish and may also pave the way for further developing recombinant IL-1β as an immunotherapy for the prevention and control of fish viral diseases.

Isolation of Bovine leukemia virus from cows with persistent lymphocytosis in Iraq

This is the first study to report on the isolation of bovine leukemia virus (BLV) from peripheral blood mononuclear cells of two cross bred cows in Iraq. The cattle were seropositive by ELISA when selected while being surveyed for the detection of BLV. Among six cows, two were cases of persistent lymphocytosis (PL). Cytopathology was characterized by the formation of multinucleated giant cells (syncytia) and cytoplasmic vacuoles. Moreover, the viruses produced clear plaques on the monolayer of the primary fetal calf kidney (FCK) cells. Inhibition of plaque formation by BLV-antisera suggested a diagnosis of BLV, which was further confirmed by PCR. Cells infected with the isolates were positive to a monoclonal antibody against the viral gp51 trans-membrane glycoprotein by immunocytochemistry. Both isolates replicated and induced cytopathic effects in bovine and human cell line cultures. Phylogenetic analysis based on partial gp51 env gene sequences revealed that Iraqi strain highly homogenous with Turkey strain (100%) and had 1% distance value with other world strains. In conclusion, this present study found that BLV-infected cattle with PL can be a source for viral isolation, and the cytopathological features of the virus infection are arranged and differ depending on the cell type. This is the first study to report on the isolation of the EBL virus in Iraq, and it provides the basis for further studies about a BLV Iraqi strain that can help control this disease.

The chemokines CCL2 and CXCL10 produced by bovine endometrial epithelial cells induce migration of bovine B lymphocytes, contributing to transuterine transmission of BLV infection

Bovine leukemia virus (BLV) causes a lymphoproliferative disease in cattle and is transmitted horizontally and vertically via infected lymphocytes. Although transplacental infection is considered the predominant route of vertical transmission of BLV, the molecular mechanisms of this process remain to be elucidated. Notably, how BLV passes through the blood-placental barrier remains unclear, given that BLV is transmitted primarily by cell-to-cell contact. One hypothesis is that B cell migration to the placenta may be induced by certain endometrium-expressed chemokines. To test this hypothesis, we performed an in vitro cell migration assay using bovine B cell lines and endometrial epithelial cells. Cell migration assays showed that two bovine B cell lines, BL2M3 and BL3.1 cells, were attracted to the supernatant of bovine endometrial epithelial cells (BEnEpCs). Quantitative real-time RT-PCR showed that expression levels of mRNAs encoding the chemokines CCL2 and CXCL10 were higher in BEnEpCs than in MDBK cells. Additionally, an inhibition assay using immune serum against CCL2 and CXCL10 showed suppression of migration of bovine B cell lines. A syncytium assay showed that cells expressing BLV envelope (Env) protein fused with BEnEpCs. Here we found that bovine B cells are attracted by chemokines produced in the endometrium and that cells expressing BLV Env protein fused with endometrium epithelial cells. These results explain part of the molecular mechanism of transplacental transmission during BLV infection, although further analysis will be required. Advances in these areas are expected to contribute to controlling the spread of BLV.

A Recombinant Adenovirus Expressing Ovine Interferon Tau Prevents Influenza Virus-Induced Lethality in Mice

Ovine interferon tau (IFN-τ) is a unique type I interferon with low toxicity and a broad host range in vivo. We report the generation of a nonreplicative recombinant adenovirus expressing biologically active IFN-τ. Using the B6.A2G-Mx1 mouse model, we showed that single-dose intranasal administration of recombinant Ad5-IFN-τ can effectively prevent lethality and disease induced by highly virulent hv-PR8 influenza virus by activating the interferon response and preventing viral replication.

Potential applications for antiviral therapy and prophylaxis in bovine medicine

Viral disease is one of the major causes of financial loss and animal suffering in today's cattle industry. Increases in global commerce and average herd size, urbanization, vertical integration within the industry and alterations in global climate patterns have allowed the spread of pathogenic viruses, or the introduction of new viral species, into regions previously free of such pathogens, creating the potential for widespread morbidity and mortality in naïve cattle populations. Despite this, no antiviral products are currently commercially licensed for use in bovine medicine, although significant progress has been made in the development of antivirals for use against bovine viral diarrhea virus (BVDV), foot and mouth disease virus (FMDV) and bovine herpesvirus (BHV). BVDV is extensively studied as a model virus for human antiviral studies. Consequently, many compounds with efficacy have been identified and a few have been successfully used to prevent infection in vivo although commercial development is still lacking. FMDV is also the subject of extensive antiviral testing due to the importance of outbreak containment for maintenance of export markets. Thirdly, BHV presents an attractive target for antiviral development due to its worldwide presence. Antiviral studies for other bovine viral pathogens are largely limited to preliminary studies. This review summarizes the current state of knowledge of antiviral compounds against several key bovine pathogens and the potential for commercial antiviral applications in the prevention and control of several selected bovine diseases.

Interferon-tau: current applications and potential in antiviral therapy

Interferon-tau (IFN-tau) was initially identified as an ovine pregnancy protein. Produced by the trophoblast, it is important in preventing degradation of the corpus luteum and has been used as an early marker for ovine pregnancy. As a member of the family of type I interferons, IFN-tau has demonstrated promising antiviral activity against human viral infections in vitro. Additionally, it displays high species cross-reactivity despite its absence in humans. To date, IFN-tau has shown efficacy in reducing replication of human immunodeficiency virus, feline immunodeficiency virus, and human papillomavirus. While IFN-tau shares similar antiviral activity to IFN-alpha, the current interferon of choice for treatment of viral infections, it lacks the associated toxicity. This may make IFN-tau an attractive alternative to IFN-alpha for the treatment of viral infections.

Effect of type-I interferon on retroviruses

Type-I interferons (IFN-I) play an important role in the innate immune response to several retroviruses. They seem to be effective in controlling the in vivo infection, though many of the clinical signs of retroviral infection may be due to their continual presence which over-stimulates the immune system and activates apoptosis. IFN-I not only affect the immune system, but also operate directly on virus replication. Most data suggest that the in vitro treatment with IFN-I of retrovirus infected cells inhibits the final stages of virogenesis, avoiding the correct assembly of viral particles and their budding, even though the mechanism is not well understood. However, in some retroviruses IFN-I may also act at a previous stage as some retroviral LTRs posses sequences homologous to the IFN-stimulated response element (ISRE). When stimulated, ISREs control viral transcription. HIV-1 displays several mechanisms for evading IFN-I, such as through Tat and Nef. Besides IFN-α and IFN-β, some other type I IFN, such as IFN-τ and IFN-ω, have potent antiviral activity and are promising treatment drugs.

Mechanisms of leukemogenesis induced by bovine leukemia virus: prospects for novel anti-retroviral therapies in human

In 1871, the observation of yellowish nodules in the enlarged spleen of a cow was considered to be the first reported case of bovine leukemia. The etiological agent of this lymphoproliferative disease, bovine leukemia virus (BLV), belongs to the deltaretrovirus genus which also includes the related human T-lymphotropic virus type 1 (HTLV-1). This review summarizes current knowledge of this viral system, which is important as a model for leukemogenesis. Recently, the BLV model has also cast light onto novel prospects for therapies of HTLV induced diseases, for which no satisfactory treatment exists so far.