David G. Westcott

Incursion of RHDV2-like variant in Great Britain.

RABBIT haemorrhagic disease virus (RHDV) causes an acute, fulminating and generally fatal disease in the European rabbit ( Oryctolagus cuniculus ). It was first discovered in China in 1984 and then confirmed in the UK in 1992, at …

Evaluation of a prototype sub-unit vaccine against equine arteritis virus comprising the entire ectodomain of the virus large envelope glycoprotein (G L ): induction of virus- neutralizing antibody and assessment of protection in ponies

An Escherichia coli-expressed recombinant protein (6hisG(L)ecto) comprising the entire ectodomain (aa 18-122) of equine arteritis virus (EAV) glycoprotein G(L), the immunodominant viral antigen, induced higher neutralizing antibody titres than other G(L)-derived polypeptides when compared in an immunization study in ponies. The potential of the recombinant G(L) ectodomain to act as a sub-unit vaccine against EAV was evaluated further in three groups of four ponies vaccinated with doses of 35, 70 or 140 microg of protein. All vaccinated animals developed a virus-neutralizing antibody (VNAb) response with peak titres 1-2 weeks after the administration of a booster on week 5 (VNAb titres of 1.8-3.1), 13 (VNAb titres of 1.4-2.9) or 53 (VNAb titres of 1.2-2.3). Vaccinated and unvaccinated control ponies were infected with EAV at different times post-vaccination to obtain information about the degree of protection relative to the levels of pre-challenge VNAb. Vaccination conferred varying levels of protection, as indicated by reduced or absent pyrexia, viraemia and virus excretion from the nasopharynx. The degree of protection correlated well with the levels of pre-challenge VNAb and, in particular, with levels of virus excretion. These results provide the first evidence that a sub-unit vaccine protects horses against EAV. The use of the sub-unit vaccine in combination with a differential diagnostic test based on other EAV antigens would enable serological discrimination between naturally infected and vaccinated equines.

Porcine reproductive and respiratory syndrome virus: genetic diversity of recent British isolates.

Porcine reproductive and respiratory syndrome (PRRS) continues to be a significant problem for European pig producers, contributing to porcine respiratory disease complex, neonatal piglet mortality, infertility and occasional abortion storms. PRRS virus (PRRSV), a member of the arterivirus family with two defined major genotypes, has been shown to be quite genetically diverse. In the present study, genetic analysis of multiple gene regions of over 100 viruses isolated in Britain between 2003 and 2007 revealed that the diversity of British strains is now far greater than during the early 1990s. All isolates belong to genotype 1 (European). While some recent isolates are still very similar to early isolates, a wide range of more diverse viruses is now also circulating. Interestingly, some isolates were found to be very similar to a modified-live vaccine strain, and it is suggested that use of the vaccine has affected the evolution pattern of PRRS virus strains in Britain. Evidence of deletions in one viral gene, ORF3, and of genome recombination was also seen. A molecular clock model using the ORF7 sequences estimates the rate of substitution as 3.8 × 10(-3) per site per year, thereby dating the most recent common ancestor of all British viruses to 1991, coincident with the first outbreak of disease. Our findings therefore have implications for both the diagnostic and prophylactic methods currently being used, which are discussed.

Porcine reproductive and respiratory syndrome virus: Antigenic and molecular diversity of British isolates and implications for diagnosis

Porcine reproductive and respiratory syndrome (PRRS) is an endemic disease of pigs, caused by PRRS virus, a member of the Arteriviridae family. First seen in Britain in 1991, the disease continues to be a significant economic and welfare problem for pig producers. To date, only PRRSV genotype 1 has been found in Britain. At the genetic level, a considerable increase has been reported in the diversity of PRRS viruses isolated in Britain between 2003 and 2007, versus the early 1990 s. In this study, the diversity has been shown to extend to the antigenic level too, with potential consequences for diagnostic methods. Antigenic diversity was assessed using a panel of twelve monoclonal antibodies, only one of which reacted with all isolates tested. Nine diverse viruses were compared as potential antigens in immunoperoxidase monolayer assays, where each one produced quite different results for a common panel of sera. As a single virus is used in each diagnostic assay, results must therefore be interpreted cautiously. For a real-time RT-PCR assay, published oligonucleotide primer and probe sequences were evaluated against available genetic sequences of British and European viruses, and were re-designed where considerable mismatches were found. The multiplex assay incorporating these modified primers to detect genotype 1 and 2 PRRS viruses was then validated for use with diagnostic sera and tissues. As the increasing degree of diversity exhibited by British strains is mirrored in other countries, PRRSV will continue to provide an ongoing challenge to diagnosis at a global, as well as national level.

Equine Encephalosis Virus in Israel

We wish to draw your attention to an outbreak of equine encephalosis virus (EEV) in Israel. Between October 2008 and January 2009, a febrile horse disease was observed in more than 60 equine premises across the country. Clinical signs included: raised body temperatures, unrest, decreased appetite, edema of the neck, legs, lips and eyelids, accelerated pulse and breathing rates, and congested mucosae. The morbidity ranged from 2% to 100% but there were no fatalities. In the affected stables, the disease infected all breeds, ages and sexes and the duration of illness lasted from between 7 and 30 days. The initial diagnostic investigation was performed by the Kimron Veterinary Institute (KVI), Israel, on nasal swabs, blood and serum samples from affected animals. The tests for WNV and EHV-1 were negative. Initial serological results indicated that the disease was equine viral arteritis (EAV), but no EAV virus could be isolated and PCR tests were also negative. The virus isolates and original sample material were passed on to the Veterinary Laboratories Agency (VLA) in the UK for further investigation. Based on the clinical signs and possible suspect diagnosis, the VLA performed PCR tests for EAV, Togaviruses (Getah, WEE, EEE, VEE, Ross River), and Flaviviruses (Tick Borne Encephalitis, WN, Usutu, Louping ill, Dengue, Japanese encephalitis), with all tests being negative. Using a novel DNA array technique, with subsequent RT-PCR and sequence analysis, the virus was finally identified as EEV. While further characterization of the virus is underway and an extended description of the investigation will be provided in due course, we feel obliged to alert the scientific community of this important disease and the implications involved. Equine encephalosis virus is member of the Orbivirus genus, thus transmitted by midges of the Culicoides family and is related to African horse sickness; all equids (horses, donkeys, zebras) being susceptible to infection. This disease has never been diagnosed in Israel or anywhere else North of Southern Africa before (van Niekerk et al., 2003). In the future, it will now be important to distinguish EEV from other diseases such as EAV and Getah, which can have similar clinical signs. In this context, we would wish to recommend further testing of equines in the region, in order to obtain a better knowledge of the distribution of this virus.

Functional analysis of the porcine USP18 and its role during porcine arterivirus replication.

Emerging evidence places deubiquitylation at the core of a multitude of regulatory processes, ranging from cell growth to innate immune response and health, such as cancer, degenerative and infectious diseases. Little is known about deubiquitylation in pig and arterivirus infection. This report provides information on the biochemical and functional role of the porcine USP18 during innate immune response to the porcine respiratory and reproductive syndrome virus (PRRSV). We have shown that UBP gene is the ortholog of the murine USP18 (Ubp43) gene and the human ubiquitin specific protease 18 (USP18) gene and encodes a biochemically functional de-ubiquitin enzyme which inhibits signalling pathways that lead to IFN-stimulating response element (ISRE) promotor regulation. Furthermore we have demonstrated that overexpression of the porcine USP18 leads to reduced replication and/or growth of PRRSV. Our data contrast with the conclusion of numerous reports demonstrating that USP18-deficient mice are highly resistant to viral and bacterial infections and to oncogenic transformation by BCR-ABL, and highlight USP18 as a potential target gene that promotes reduced replication of PRRSV.

Dynamic Differential Regulation of Innate Immune Transcripts during the Infection of Alveolar Macrophages by the Porcine Reproductive and Respiratory Syndrome Virus

Porcine reproductive and respiratory syndrome virus (PRRSV), an arterivirus, is the etiologic agent of an infectious disease of that name, characterized by respiratory disorders, abortion in pregnant sows and high mortality in piglets, resulting in significant economic losses in the pig industry worldwide. In order to identify whether genetic differences in PRRSV response may exist in pigs, alveolar macrophages were used to assess the progression of the type-I interferon (IFN) transcript response in porcine alveolar macrophages infected by PRRSV. Our results suggest that a dynamic differential regulation of the type-I IFN and chemokine transcripts may operate during the first hours of infection with and entry of the virus in alveolar macrophages, and provide a compelling mechanism for the establishment of PRRSV replication in susceptible cells.

Correction: Evidence for the Circulation of Equine Encephalosis Virus in Israel since 2001.

[This corrects the article on p. e70532 in vol. 8.].