Bluetongue Virus NS4 Protein Is an Interferon Antagonist and a Determinant of Virus Virulence.

UNLABELLED: Bluetongue virus (BTV) is the causative agent of bluetongue, a major infectious disease of ruminants with serious consequences to both animal health and the economy. The clinical outcome of BTV infection is highly variable and dependent on a variety of factors related to both the virus and the host. In this study, we show that the BTV nonstructural protein NS4 favors viral replication in sheep, the animal species most affected by bluetongue. In addition, NS4 confers a replication advantage on the virus in interferon (IFN)-competent primary sheep endothelial cells and immortalized cell lines. We determined that in cells infected with an NS4 deletion mutant (BTV8ΔNS4), there is increased synthesis of type I IFN compared to cells infected with wild-type BTV-8. In addition, using RNA sequencing (RNA-seq), we show that NS4 modulates the host IFN response and downregulates mRNA levels of type I IFN and interferon-stimulated genes. Moreover, using reporter assays and protein synthesis assays, we show that NS4 downregulates the activities of a variety of promoters, such as the cytomegalovirus immediate-early promoter, the IFN-ß promoter, and a promoter containing interferon-stimulated response elements (ISRE). We also show that the NS4 inhibitory activity on gene expression is related to its nucleolar localization. Furthermore, NS4 does not affect mRNA splicing or cellular translation. The data obtained in this study strongly suggest that BTV NS4 is an IFN antagonist and a key determinant of viral virulence. IMPORTANCE: Bluetongue is one of the main infectious diseases of ruminants and is caused by bluetongue virus (BTV), an arthropod-borne virus transmitted from infected to susceptible animals by Culicoides biting midges. Bluetongue has a variable clinical outcome that can be related to both virus and host factors. It is therefore critical to understand the interplay between BTV and the host immune responses. In this study, we show that a nonstructural protein of BTV (NS4) is critical to counteract the innate immune response of the host. Infection of cells with a BTV mutant lacking NS4 results in increased synthesis of IFN-ß and upregulation of interferon-stimulated genes. In addition, we show that NS4 is a virulence factor for BTV by favoring viral replication in sheep, the animal species most susceptible to bluetongue.

Rift Valley Fever Virus among Wild Ruminants, Etosha National Park, Namibia, 2011.

After a May 2011 outbreak of Rift Valley fever among livestock northeast of Etosha National Park, Namibia, wild ruminants in the park were tested for the virus. Antibodies were detected in springbok, wildebeest, and black-faced impala, and viral RNA was detected in springbok. Seroprevalence was high, and immune response was long lasting.

Multiple genome segments determine virulence of bluetongue virus serotype 8.

UNLABELLED: Bluetongue virus (BTV) causes bluetongue, a major hemorrhagic disease of ruminants. In order to investigate the molecular determinants of BTV virulence, we used a BTV8 strain minimally passaged in tissue culture (termed BTV8L in this study) and a derivative strain passaged extensively in tissue culture (BTV8H) in in vitro and in vivo studies. BTV8L was pathogenic in both IFNAR(-/-) mice and in sheep, while BTV8H was attenuated in both species. To identify genetic changes which led to BTV8H attenuation, we generated 34 reassortants between BTV8L and BTV8H. We found that partial attenuation of BTV8L in IFNAR(-/-) mice was achieved by simply replacing genomic segment 2 (Seg2, encoding VP2) or Seg10 (encoding NS3) with the BTV8H homologous segments. Fully attenuated viruses required at least two genome segments from BTV8H, including Seg2 with either Seg1 (encoding VP1), Seg6 (encoding VP6 and NS4), or Seg10 (encoding NS3). Conversely, full reversion of virulence of BTV8H required at least five genomic segments of BTV8L. We also demonstrated that BTV8H acquired an increased affinity for glycosaminoglycan receptors during passaging in cell culture due to mutations in its VP2 protein. Replication of BTV8H was relatively poor in interferon (IFN)-competent primary ovine endothelial cells compared to replication of BTV8L, and this phenotype was determined by several viral genomic segments, including Seg4 and Seg9. This study demonstrated that multiple viral proteins contribute to BTV8 virulence. VP2 and NS3 are primary determinants of BTV pathogenesis, but VP1, VP5, VP4, VP6, and VP7 also contribute to virulence. IMPORTANCE: Bluetongue is one of the major infectious diseases of ruminants, and it is listed as a notifiable disease by the World Organization for Animal Health (OIE). The clinical outcome of BTV infection varies considerably and depends on environmental and host- and virus-specific factors. Over the years, BTV serotypes/strains with various degrees of virulence (including nonpathogenic strains) have been described in different geographical locations. However, no data are available to correlate the BTV genotype to virulence. This study shows that BTV virulence is determined by different viral genomic segments. The data obtained will help to characterize thoroughly the pathogenesis of bluetongue. The possibility to determine the pathogenicity of virus isolates on the basis of their genome sequences will help in the design of control strategies that fit the risk posed by new emerging BTV strains.

Host species barriers to Jaagsiekte sheep retrovirus replication and carcinogenesis.

Understanding the factors governing host species barriers to virus transmission has added significantly to our appreciation of virus pathogenesis. Jaagsiekte sheep retrovirus (JSRV) is the causative agent of ovine pulmonary adenocarcinoma (OPA), a transmissible lung cancer of sheep that has rarely been found in goats. In this study, in order to further clarify the pathogenesis of OPA, we investigated whether goats are resistant to JSRV replication and carcinogenesis. We found that JSRV induces lung tumors in goats with macroscopic and histopathological features that dramatically differ from those in sheep. However, the origins of the tumor cells in the two species are identical. Interestingly, in experimentally infected lambs and goat kids, we revealed major differences in the number of virus-infected cells at early stages of infection. These differences were not related to the number of available target cells for virus infection and cell transformation or the presence of a host-specific immune response toward JSRV. Indeed, we also found that goats possess transcriptionally active endogenous retroviruses (enJSRVs) that likely influence the host immune response toward the exogenous JSRV. Overall, these results suggest that goat cells, or at least those cells targeted for viral carcinogenesis, are not permissive to virus replication but can be transformed by JSRV.

Whole-Genome Sequence and Assembly of Eight Africa Horse Sickness Virus Strains Collected in Namibia and South Africa.

In this report, we describe eight complete genome sequences of African horse sickness virus (AHSV) strains belonging to four different serotypes, namely, AHSV-5, AHSV-6, AHSV-8, and AHSV-9. Samples were collected in Namibia and South Africa from infected horses between 2000 and 2011. As expected, phylogenetic analyses of the variable outer capsid protein VP2 genomic sequences of AHSV-6 and AHSV-8 show higher nucleotide identity between the isolated viruses than that of the relevant reference strains. The full-genome sequence of AHSV will provide useful information on its geographical origin, and it will also be instrumental for comparing the distribution of the Namibian isolate with that of global isolates.

Tick Species Diversity and Molecular Identification of Spotted Fever Group Rickettsiae Collected from Migratory Birds Arriving from Africa.

The role of migratory birds in the spread of ticks and tick-borne pathogens along their routes from Africa to Europe is increasingly emerging. Wild birds can host several tick species, often infected by bacteria responsible for zoonoses. The aim of the study is to assess the possible introduction of exotic ticks carried by migratory birds into Italy from Africa and to detect the presence of Rickettsia species and Coxiella burnetii they may harbor. During a two-year survey, we collected ticks from migratory birds captured during their short stop-over on Ventotene Island. Specimens were first identified by morphology or sequencing molecular targets when needed, and then tested by real-time PCR for the presence of selected pathogens. A total of 91% of the collection consisted of sub-Saharan ticks, more than 50% of which were infected by Rickettsia species belonging to the spotted fever group, mainly represented by R. aeschlimannii. In contrast, the suspected C. burnetii detected in two soft ticks were confirmed as Coxiella-like endosymbionts and not the pathogen. Although there are still gaps in the knowledge of this dispersal process, our findings confirm the role of migratory birds in the spread of ticks and tick-borne pathogens, suggesting the need for a continuous surveillance to monitor the potential emergence of new diseases in Europe.

Culicoides species responsible for the transmission of Epizootic Haemorrhagic Disease virus (EHDV) serotype 8 in Italy.

Epizootic haemorrhagic disease (EHD) is a viral disease transmitted by Culicoides biting midges that affects wild and domestic ruminants. The causative agent, EHD virus (EHDV), belongs to the family Sedoreoviridae, genus Orbivirus. The virus has never been reported in Europe until October 2022, when the virus was for the first time detected in Sicily and Sardinia. After the first clinical cases, an intensive entomological field activity was carried out in five EHD affected farms located in Sardinia, with the aim of assessing the EHDV vector competence in European species of Culicoides. EHDV­8 was detected in C. imicola, C. obsoletus/scoticus, C. newsteadi, C. pulicaris ss, and C. bysta. The first 4 species have also been demonstrated to be able to transmit bluetongue virus (BTV). According to these results, it is likely that EHDV­8, sharing the same transmission patterns of BTV, can also spread to Europe.

Evaluation of next generation sequencing approaches for SARS-CoV-2.

Within public health control strategies for SARS-CoV-2, whole genome sequencing (WGS) is essential for tracking viral spread and monitoring the emergence of variants which may impair the effectiveness of vaccines, diagnostic methods, and therapeutics. In this manuscript different strategies for SARS-CoV-2 WGS including metagenomic shotgun (SG), library enrichment by myBaits® Expert Virus-SARS-CoV-2 (Arbor Biosciences), nCoV-2019 sequencing protocol, ampliseq approach by Swift Amplicon® SARS-CoV-2 Panel kit (Swift Biosciences), and Illumina COVIDSeq Test (Illumina Inc.), were evaluated in order to identify the best approach in terms of results, labour, and costs. The analysis revealed that Illumina COVIDSeq Test (Illumina Inc.) is the best choice for a cost-effective, time-consuming production of consensus sequences.

Determinants of bluetongue virus virulence in murine models of disease.

Bluetongue is a major infectious disease of ruminants that is caused by bluetongue virus (BTV). In this study, we analyzed virulence and genetic differences of (i) three BTV field strains from Italy maintained at either a low (L strains) or high (H strains) passage number in cell culture and (ii) three South African "reference" wild-type strains and their corresponding live attenuated vaccine strains. The Italian BTV L strains, in general, were lethal for both newborn NIH-Swiss mice inoculated intracerebrally and adult type I interferon receptor-deficient (IFNAR(-/-)) mice, while the virulence of the H strains was attenuated significantly in both experimental models. Similarly, the South African vaccine strains were not pathogenic for IFNAR(-/-) mice, while the corresponding wild-type strains were virulent. Thus, attenuation of the virulence of the BTV strains used in this study is not mediated by the presence of an intact interferon system. No clear distinction in virulence was observed for the South African BTV strains in newborn NIH-Swiss mice. Full genomic sequencing revealed relatively few amino acid substitutions, scattered in several different viral proteins, for the strains found to be attenuated in mice compared to the pathogenic related strains. However, only the genome segments encoding VP1, VP2, and NS2 consistently showed nonsynonymous changes between all virulent and attenuated strain pairs. This study established an experimental platform for investigating the determinants of BTV virulence. Future studies using reverse genetics will allow researchers to precisely map and "weight" the relative influences of the various genome segments and viral proteins on BTV virulence.

Survey of Bartonella species in cats from Abruzzo region, Italy.

Cat scratch disease (CSD) is a zoonotic disease, caused predominantly by Bartonella henselae and transmitted to humans through a scratch or bite of the cat. Cat represents the principal reservoir and healthy carrier of Bartonella, which is mainly transmitted, among cats, by the flea Ctenocephalides felis. During 2014, fifty­two samples of whole blood and sera were collected randomly from cats in Abruzzo region and were examined by real-time PCR and IFAT tests, respectively. Seven samples out of fifty­two (13.5%) resulted positive for Bartonella spp. in both tests, while six specimens (11.5%) resulted real-time PCR negative but IgG positive; thirty­nine were instead both real-time PCR and IFAT negative (75%). Sequence analysis of a fragment of DNA identified B. henselae and B. clarridgeiae in four and in two real­time PCR positive samples, respectively.

Usutu virus in Italy: an emergence or a silent infection?

A two year study (2008-2009) was carried out to monitor the Usutu virus (USUV) circulation in Italy. Sentinel horses and chickens, wild birds and mosquitoes were sampled and tested for the presence of USUV and USUV antibodies within the WND National Surveillance plan. Seroconversion evidenced in sentinel animals proved that in these two years the virus has circulated in Tuscany, Emilia Romagna, Veneto and Friuli Venezia Giulia regions. In Veneto USUV caused a severe blackbird die-off disease involving at least a thousand birds. Eleven viral strains were detected in organs of 9 blackbirds (52.9%) and two magpies (0.5%) originating from Veneto and Emilia Romagna regions. USUV was also detected in a pool of Culex pipiens caught in Tuscany. According to the alignment of the NS5 partial sequences, no differences between the Italian USUV strains isolated from Veneto, Friuli and Emilia Romagna regions were observed. The Italian North Eastern strain sequences were identical to those of the strain detected in the brain of a human patient and shared a high similarity with the isolates from Vienna and Budapest. Conversely, there were few differences between the Italian strains which circulated in the North Eastern regions and the USUV strain detected in a pool of C. pipiens caught in Tuscany. A high degree of similarity at both nucleotide and amino acid level was also found when the full genome sequence of the Italian North Eastern isolate was compared with that of the strains circulating in Europe. The North Eastern Italian strain sequence exhibited 97% identity to the South African reference strain SAAR-1776. The deduced amino acid sequences of the Italian strain differed by 10 and 11 amino-acids from the Budapest and Vienna strains, respectively, and by 28 from the SAAR-1776 strain. According to this study two strains of USUVs are likely to have circulated in Italy between 2008 and 2009. They have developed strategies of adaptation and evolution to spread into new areas and to become established.

Use of real-time RT-PCR as a rapid molecular approach for differentiation of field and vaccine strains of bluetongue virus serotypes 2 and 9.

Since 2000 severe, long-lasting epidemics of bluetongue virus (BTV) have been described in Italy, caused by BTV serotypes 2, 4, 9 and 16. Vaccination programs have been applied extensively to control the infection, in spite of concerns about the potential dissemination of attenuated vaccine strains of BTV in susceptible animals. Accordingly, rapid and reliable differentiation between vaccine and field strains is paramount in routine diagnosis of BTV to evaluate the extent of this phenomenon. In the present study, we report the development of two real-time RT-PCR assays able to recognise BTV serotypes 2 and 9, respectively, and we evaluated the use of the assays for discrimination between field and vaccine strains. A total of 65 samples collected in Italy from 2000 to 2006 and diagnosed as positive for either BTV-2 or -9 were analysed by the TaqMan assays. Both the assays were found to be highly sensitive and reproducible, ensuring correct serotype characterisation and prediction of the origin of the strains, as confirmed by characterisation using virus neutralisation and sequencing.

Real-time polymerase chain reaction to detect bluetongue virus in blood samples.

The authors describe a real-time reverse transcriptase polymerase chain reaction (RT-PCR) to detect bluetongue viruses (BTV) in blood samples. The primers and Taqman probes used were specific for a conserved region of BTV RNA segment 5, which encodes non-structural protein NS1. The method was able to detect strains of BTV serotypes 2, 4, 9 and 16 isolated in Italy, and their respective vaccine strains. The limit of detection was 5.0x10-(3) TCID(50) per ml of sample. The assay did not amplify RNA from other Orbiviruses, including epizootic haemorrhagic disease virus (EHDV) or African horse sickness virus (AHSV), or from viruses in the Reoviridae family or those that cause a similar clinical picture to that of BTV. Its accuracy was evaluated on 104 blood samples in ethylenediamine tetra-acetic acid (EDTA) and the results were compared with those obtained with the conventional RT-PCR used in routine diagnosis. Both tests gave negative results on 40 blood samples from bluetongue-free farms (confidence interval: 95%, 92.5-100%). Real-time PCR detected BTV RNA in 64 sentinel cows that had recently seroconverted to serotypes 2 and 16 (confidence interval: 95%, 95.5-100%), whereas conventional RT-PCR detected only 47 of these (confidence interval: 95%, 61.5-82.7%) (P<0.05). The method is rapid, thereby reducing execution times, and does not require any post-amplification manipulation, thus avoiding the inherent risk of contamination of amplified products.