Vaccination With Recombinant Adenoviruses Expressing the Bluetongue Virus Subunits VP7 and VP2 Provides Protection Against Heterologous Virus Challenge

Immuno-informatics study identifies conserved T cell epitopes in non-structural proteins of Bluetongue virus serotypes: formulation of a computationally optimized next-generation broad-spectrum multi-epitope vaccine

Introduction

Bluetongue (BT) poses a significant threat to the livestock industry, affecting various animal species and resulting in substantial economic losses. The existence of numerous BT virus (BTV) serotypes has hindered control efforts, highlighting the need for broad-spectrum vaccines.

Methodology

In this study, we evaluated the conserved amino acid sequences within key non-structural (NS) proteins of BTV and identified numerous highly conserved murine- and bovine-specific MHC class I-restricted (MHC-I) CD8+ and MHC-II-restricted CD4+ epitopes. We then screened these conserved epitopes for antigenicity, allergenicity, toxicity, and solubility. Using these epitopes, we developed in silico-based broad-spectrum multiepitope vaccines with Toll-like receptor (TLR-4) agonists. The predicted proinflammatory cytokine response was assessed in silico using the C-IMMSIM server. Structural modeling and refinement were achieved using Robetta and GalaxyWEB servers. Finally, we assessed the stability of the docking complexes through extensive 100-nanosecond molecular dynamics simulations before considering the vaccines for codon optimization and in silico cloning.

Results

We found many epitopes that meet these criteria within NS1 and NS2 proteins and developed in silico broad-spectrum vaccines. The immune simulation studies revealed that these vaccines induce high levels of IFN-γ and IL-2 in the vaccinated groups. Protein-protein docking analysis demonstrated promising epitopes with strong binding affinities to TLR-4. The docked complexes were stable, with minimal Root Mean Square Deviation and Root Mean Square Fluctuation values. Finally, the in silico-cloned plasmids have high % of GC content with > 0.8 codon adaptation index, suggesting they are suitable for expressing the protein vaccines in prokaryotic system.

Discussion

These next-generation vaccine designs are promising and warrant further investigation in wet lab experiments to assess their immunogenicity, safety, and efficacy for practical application in livestock. Our findings offer a robust framework for developing a comprehensive, broad-spectrum vaccine, potentially revolutionizing BT control and prevention strategies in the livestock industry.

Cytokine mRNA Expression Profile in Target Organs of IFNAR (-/-) Mice Infected with African Horse Sickness Virus

African horse sickness (AHS) is a highly severe disease caused by a viral etiological agent, African horse sickness virus (AHSV). It is endemic in sub-Saharan Africa, while sporadic outbreaks have occurred in North Africa, Asia, and Europe, with the most recent cases in Thailand. AHSV transmission between equines occurs primarily by biting midges of the genus Culicoides, especially C. imicola, with a wide distribution globally. As research in horses is highly restricted due to a variety of factors, small laboratory animal models that reproduce clinical signs and pathology observed in natural infection of AHSV are highly needed. Here, we investigated the expression profile of several pro-inflammatory cytokines in target organs and serum of IFNAR (-/-) mice, to continue characterizing this established animal model and to go deep into the innate immune responses that are still needed.

Comprehensive immune profiling reveals that Orbivirus infection activates immune checkpoints during acute T cell immunosuppression

Bluetongue virus (BTV) is an arbovirus transmitted by the bite of infected Culicoides midges that affects domestic and wild ruminants producing great economic losses. The infection induces an IFN response, followed by an adaptive immune response that is essential in disease clearance. BTV can nonetheless impair IFN and humoral responses. The main goal of this study was to gain a more detailed understanding of BTV pathogenesis and its effects on immune cell populations. To this end, we combined flow cytometry and transcriptomic analyses of several immune cells at different times post-infection (pi). Four sheep were infected with BTV serotype 8 and blood samples collected at days 0, 3, 7 and 15pi to perform transcriptomic analysis of B-cell marker+, CD4+, CD8+, and CD14+ sorted peripheral mononuclear cells. The maximum number of differentially expressed genes occurred at day 7pi, which coincided with the peak of infection. KEGG pathway enrichment analysis indicated that genes belonging to virus sensing and immune response initiation pathways were enriched at day 3 and 7 pi in all 4 cell population analyzed. Transcriptomic analysis also showed that at day 7pi T cell exhaustion pathway was enriched in CD4+ cells, while CD8+ cells downregulated immune response initiation pathways. T cell functional studies demonstrated that BTV produced an acute inhibition of CD4+ and CD8+ T cell activation at the peak of replication. This coincided with PD-L1 upregulation on the surface of CD4+ and CD8+ T cells as well as monocytes. Taken together, these data indicate that BTV could exploit the PD1/PD-L1 immune checkpoint to impair T cell responses. These findings identify several mechanisms in the interaction between host and BTV, which could help develop better tools to combat the disease.

Increased Clinical Signs and Mortality in IFNAR(-/-) Mice Immunised with the Bluetongue Virus Outer-Capsid Proteins VP2 or VP5, after Challenge with an Attenuated Heterologous Serotype

Bluetongue is an economically important disease of domesticated and wild ruminants caused by bluetongue virus (BTV). There are at least 36 different serotypes of BTV (the identity of which is determined by its outer-capsid protein VP2), most of which are transmitted by Culicoides biting midges. IFNAR^(-/-) mice immunised with plant-expressed outer-capsid protein VP2 (rVP2) of BTV serotypes -1, -4 or -8, or the smaller outer-capsid protein rVP5 of BTV-10, or mock-immunised with PBS, were subsequently challenged with virulent strains of BTV-4 or BTV-8, or with an attenuated clone of BTV-1 (BTV-1RG_C7). The mice that had received rVP2 generated a protective immune response against the homologous BTV serotype, reducing viraemia (as detected by qRT-PCR), the severity of clinical signs and mortality levels. No cross-serotype protection was observed after challenge with the heterologous BTV serotypes. However, the severity of clinical signs, viraemia and fatality levels after challenge with the attenuated strain of BTV-1 were all increased in mice immunised with rVP2 of BTV-4 and BTV-8, or with rVP5 of BTV10. The possibility is discussed that non-neutralising antibodies, reflecting serological relationships between the outer-capsid proteins of these different BTV serotypes, could lead to 'antibody-dependent enhancement of infection' (ADE). Such interactions could affect the epidemiology and emergence of different BTV strains in the field and would therefore be relevant to the design and implementation of vaccination campaigns.

Vaccination as a Strategy to Prevent Bluetongue Virus Vertical Transmission

Bluetongue virus (BTV) produces an economically important disease in ruminants of compulsory notification to the OIE. BTV is typically transmitted by the bite of Culicoides spp., however, some BTV strains can be transmitted vertically, and this is associated with fetus malformations and abortions. The viral factors associated with the virus potency to cross the placental barrier are not well defined. The potency of vertical transmission is retained and sometimes even increased in live attenuated BTV vaccine strains. Because BTV possesses a segmented genome, the possibility of reassortment of vaccination strains with wild-type virus could even favor the transmission of this phenotype. In the present review, we will describe the non-vector-based BTV infection routes and discuss the experimental vaccination strategies that offer advantages over this drawback of some live attenuated BTV vaccines.

The Interplay between Bluetongue Virus Infections and Adaptive Immunity

Viral infections have long provided a platform to understand the workings of immunity. For instance, great strides towards defining basic immunology concepts, such as MHC restriction of antigen presentation or T-cell memory development and maintenance, have been achieved thanks to the study of lymphocytic choriomeningitis virus (LCMV) infections. These studies have also shaped our understanding of antiviral immunity, and in particular T-cell responses. In the present review, we discuss how bluetongue virus (BTV), an economically important arbovirus from the Reoviridae family that affects ruminants, affects adaptive immunity in the natural hosts. During the initial stages of infection, BTV triggers leucopenia in the hosts. The host then mounts an adaptive immune response that controls the disease. In this work, we discuss how BTV triggers CD8⁺ T-cell expansion and neutralizing antibody responses, yet in some individuals viremia remains detectable after these adaptive immune mechanisms are active. We present some unpublished data showing that BTV infection also affects other T cell populations such as CD4⁺ T-cells or γδ T-cells, as well as B-cell numbers in the periphery. This review also discusses how BTV evades these adaptive immune mechanisms so that it can be transmitted back to the arthropod host. Understanding the interaction of BTV with immunity could ultimately define the correlates of protection with immune mechanisms that would improve our knowledge of ruminant immunology.

Inhibition of the IFN Response by Bluetongue Virus: The Story So Far

Bluetongue virus (BTV) is the prototypical orbivirus that belongs to the Reoviridae family. BTV infection produces a disease in ruminants, particularly in sheep, that results in economic losses through reduced productivity. BTV is transmitted by the bite of Culicoides spp. midges and is nowadays distributed globally throughout subtropical and even temperate regions. As most viruses, BTV is susceptible to the IFN response, the first line of defense employed by the immune system to combat viral infections. In turn, BTV has evolved strategies to counter the IFN response and promote its replication. The present review we will revise the works describing how BTV interferes with the IFN response.