Bartha-K61 vaccine protects nursery pigs against challenge with novel european and asian strains of suid herpesvirus 1.

The present study investigates the pathogenicity of two recently isolated strains of Suid herpesvirus 1 (SuHV1), the Greek strain Hercules and the Chinese strain HeN1, in unvaccinated pigs and in pigs vaccinated with a Bartha-K61 strain. In an experiment performed in negative pressure kiosks (isolators), 45-day old seronegative pigs previously oronasally /intramuscularly vaccinated with the Bartha-K61 vaccine strain, along with unvaccinated controls, were challenged either with the Hercules strain or the HeN1 strain of SuHV1. All animals were observed daily for clinical signs and body temperature and nasal swabs, faeces, blood and bodyweight were collected up to a maximum period of 20 days post-challenge (dpc). The results showed that, in the unvaccinated pigs, HeN1 strain was more virulent than the Hercules strain, with increased mortality, shorter time to death and higher group clinical score (p < 0.05). However, after vaccination with the Bartha-K61 vaccine, there was a drastic reduction in morbidity, mortality, bodyweight loss and virus excretion to almost a similar extent in both strains (p < 0.05). No significant differences were seen among the pigs of the two vaccinated groups compared to unvaccinated unchallenged controls, except a slight elevation in body temperature and in clinical score in the HeN1 vaccinees at 2 and 3 dpc, while bodyweight gain was similar to that of the negative control pigs. Our study showed that despite differences in virulence, the standard vaccination scheme with the Bartha-K61 strain could equally protect nursery pigs against both the European and Chinese strains.

The effect of temperature on persistence of SARS-CoV-2 on common surfaces.

BACKGROUND: The rate at which COVID-19 has spread throughout the globe has been alarming. While the role of fomite transmission is not yet fully understood, precise data on the environmental stability of SARS-CoV-2 is required to determine the risks of fomite transmission from contaminated surfaces. METHODS: This study measured the survival rates of infectious SARS-CoV-2, suspended in a standard ASTM E2197 matrix, on several common surface types. All experiments were carried out in the dark, to negate any effects of UV light. Inoculated surfaces were incubated at 20 °C, 30 °C and 40 °C and sampled at various time points. RESULTS: Survival rates of SARS-CoV-2 were determined at different temperatures and D-values, Z-values and half-life were calculated. We obtained half lives of between 1.7 and 2.7 days at 20 °C, reducing to a few hours when temperature was elevated to 40 °C. With initial viral loads broadly equivalent to the highest titres excreted by infectious patients, viable virus was isolated for up to 28 days at 20 °C from common surfaces such as glass, stainless steel and both paper and polymer banknotes. Conversely, infectious virus survived less than 24 h at 40 °C on some surfaces. CONCLUSION: These findings demonstrate SARS-CoV-2 can remain infectious for significantly longer time periods than generally considered possible. These results could be used to inform improved risk mitigation procedures to prevent the fomite spread of COVID-19.

Comparative analysis of cytokine transcript profiles within mediastinal lymph node compartments of pigs after infection with porcine reproductive and respiratory syndrome genotype 1 strains differing in pathogenicity.

Porcine reproductive and respiratory syndrome virus (PRRSV) induces a weak immune response enabling it to persist in different organs of infected pigs. This has been attributed to the ability of PRRSV to influence the induction of cytokine responses. In this study, we investigated the cytokine transcriptional profiles in different compartments of the mediastinal lymph node of pigs infected with three genotype 1 PRRSV strains of differing pathogenicity: the low virulence prototype Lelystad virus (LV), and UK field strain 215-06 and the highly virulent subtype 3 SU1-Bel isolate from Belarus. We have used a combination of laser capture micro-dissection (LCM) followed by real time quantitative PCR (RT-qPCR) and immunohistochemical (IHC) detection of immune cell markers (CD3, CD79a and MAC387) and RT-qPCR quantification of PRRSV and cytokine transcripts. Compared to mock infected pigs, we found a significant downregulation of TNF-α and IFN-α in follicular and interfollicular areas of the mediastinal lymph node from 3 days post-infection (dpi) in animals infected with all three strains. This was accompanied by a transient B cell depletion and T cell and macrophage infiltration in the follicles together with T cell depletion in the interfollicular areas. A delayed upregulation of IFN-γ and IL-23p19 was observed mainly in the follicles. The PRRSV load was higher in all areas and time-points studied in the animals infected with the SU1-Bel strain. This paper describes the first application of LCM to study the cytokine transcript profiles and virus distribution in different compartments of the lymph node of pigs.

At Least Three Doses of Leading Vaccines Essential for Neutralisation of SARS-CoV-2 Omicron Variant.

Plasma samples taken at different time points from donors who received either AstraZeneca (Vaxzevria) or Pfizer (Comirnaty) or Moderna (Spikevax) coronavirus disease-19 (COVID-19) vaccine were assessed in virus neutralization assays against Delta and Omicron variants of concern and a reference isolate (VIC31). With the Pfizer vaccine there was 6-8-fold reduction in 50% neutralizing antibody titres (NT50) against Delta and VIC31 at 6 months compared to 2 weeks after the second dose; followed by 25-fold increase at 2 weeks after the third dose. Neutralisation of Omicron was only consistently observed 2 weeks after the third dose, with most samples having titres below the limit of detection at earlier timepoints. Moderna results were similar to Pfizer at 2 weeks after the second dose, while the titres for AstraZeneca samples derived from older donors were 7-fold lower against VIC31 and below the limit of detection against Delta and Omicron. Age and gender were not found to significantly impact our results. These findings indicate that vaccine matching may be needed, and that at least a third dose of these vaccines is necessary to generate sufficient neutralising antibodies against emerging variants of concern, especially Omicron, amidst the challenges of ensuring vaccine equity worldwide.

Characterisation and natural progression of SARS-CoV-2 infection in ferrets.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the infectious disease COVID-19, which has rapidly become an international pandemic with significant impact on healthcare systems and the global economy. To assist antiviral therapy and vaccine development efforts, we performed a natural history/time course study of SARS-CoV-2 infection in ferrets to characterise and assess the suitability of this animal model. Ten ferrets of each sex were challenged intranasally with 4.64 × 104 TCID50 of SARS-CoV-2 isolate Australia/VIC01/2020 and monitored for clinical disease signs, viral shedding, and tissues collected post-mortem for histopathological and virological assessment at set intervals. We found that SARS-CoV-2 replicated in the upper respiratory tract of ferrets with consistent viral shedding in nasal wash samples and oral swab samples up until day 9. Infectious SARS-CoV-2 was recovered from nasal washes, oral swabs, nasal turbinates, pharynx, and olfactory bulb samples within 3-7 days post-challenge; however, only viral RNA was detected by qRT-PCR in samples collected from the trachea, lung, and parts of the gastrointestinal tract. Viral antigen was seen exclusively in nasal epithelium and associated sloughed cells and draining lymph nodes upon immunohistochemical staining. Due to the absence of clinical signs after viral challenge, our ferret model is appropriate for studying asymptomatic SARS-CoV-2 infections and most suitable for use in vaccine efficacy studies.

Highly Thermotolerant SARS-CoV-2 Vaccine Elicits Neutralising Antibodies against Delta and Omicron in Mice.

As existing vaccines fail to completely prevent COVID-19 infections or community transmission, there is an unmet need for vaccines that can better combat SARS-CoV-2 variants of concern (VOC). We previously developed highly thermo-tolerant monomeric and trimeric receptor-binding domain derivatives that can withstand 100 °C for 90 min and 37 °C for four weeks and help eliminate cold-chain requirements. We show that mice immunised with these vaccine formulations elicit high titres of antibodies that neutralise SARS-CoV-2 variants VIC31 (with Spike: D614G mutation), Delta and Omicron (BA.1.1) VOC. Compared to VIC31, there was an average 14.4-fold reduction in neutralisation against BA.1.1 for the three monomeric antigen-adjuvant combinations and a 16.5-fold reduction for the three trimeric antigen-adjuvant combinations; the corresponding values against Delta were 2.5 and 3.0. Our findings suggest that monomeric formulations are suitable for upcoming Phase I human clinical trials and that there is potential for increasing the efficacy with vaccine matching to improve the responses against emerging variants. These findings are consistent with in silico modelling and AlphaFold predictions, which show that, while oligomeric presentation can be generally beneficial, it can make important epitopes inaccessible and also carries the risk of eliciting unwanted antibodies against the oligomerisation domain.

In vitro characterisation of SARS-CoV-2 and susceptibility of domestic ferrets (Mustela putorius furo).

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is an emerging virus that has caused significant human morbidity and mortality since its detection in late 2019. With the rapid emergence has come an unprecedented programme of vaccine development with at least 300 candidates under development. Ferrets have proven to be an appropriate animal model for testing safety and efficacy of SARS-CoV-2 vaccines due to quantifiable virus shedding in nasal washes and oral swabs. Here, we outline our efforts early in the SARS-CoV-2 outbreak to propagate and characterize an Australian isolate of the virus in vitro and in an ex vivo model of human airway epithelium, as well as to demonstrate the susceptibility of domestic ferrets (Mustela putorius furo) to SARS-CoV-2 infection following intranasal challenge.

Host inhibits replication of European porcine reproductive and respiratory syndrome virus in macrophages by altering differential regulation of type-I interferon transcriptional response.

Porcine reproductive and respiratory syndrome (PRRS) is an infectious disease caused by a positive RNA strand arterivirus. PRRS virus (PRRSV) interacts primarily with lung macrophages. Little is known how the virus subverts the innate immune response to initiate its replication in alveolar macrophages. Large-scale transcriptional responses of macrophages with different levels of susceptibility to PRRSV infection were compared over 30 h of infection. This study demonstrates a rapid and intense host transcriptional remodelling during the early phase of the replication of the virus which correlates with transient repression of type-I interferon transcript as early as 8 h post-infection. These results support the suggestion from previous studies that host innate immune response inhibits replication of European porcine reproductive and respiratory syndrome virus in macrophages by altering differential regulation of type-I interferon transcriptional response.

ChAdOx1 nCoV-19 (AZD1222) vaccine candidate significantly reduces SARS-CoV-2 shedding in ferrets.

Vaccines against SARS-CoV-2 are likely to be critical in the management of the ongoing pandemic. A number of candidates are in Phase III human clinical trials, including ChAdOx1 nCoV-19 (AZD1222), a replication-deficient chimpanzee adenovirus-vectored vaccine candidate. In preclinical trials, the efficacy of ChAdOx1 nCoV-19 against SARS-CoV-2 challenge was evaluated in a ferret model of infection. Groups of ferrets received either prime-only or prime-boost administration of ChAdOx1 nCoV-19 via the intramuscular or intranasal route. All ChAdOx1 nCoV-19 administration combinations resulted in significant reductions in viral loads in nasal-wash and oral swab samples. No vaccine-associated adverse events were observed associated with the ChAdOx1 nCoV-19 candidate, with the data from this study suggesting it could be an effective and safe vaccine against COVID-19. Our study also indicates the potential for intranasal administration as a way to further improve the efficacy of this leading vaccine candidate.

Supporting pandemic response using genomics and bioinformatics: A case study on the emergent SARS-CoV-2 outbreak.

Pre-clinical responses to fast-moving infectious disease outbreaks heavily depend on choosing the best isolates for animal models that inform diagnostics, vaccines and treatments. Current approaches are driven by practical considerations (e.g. first available virus isolate) rather than a detailed analysis of the characteristics of the virus strain chosen, which can lead to animal models that are not representative of the circulating or emerging clusters. Here, we suggest a combination of epidemiological, experimental and bioinformatic considerations when choosing virus strains for animal model generation. We discuss the currently chosen SARS-CoV-2 strains for international coronavirus disease (COVID-19) models in the context of their phylogeny as well as in a novel alignment-free bioinformatic approach. Unlike phylogenetic trees, which focus on individual shared mutations, this new approach assesses genome-wide co-developing functionalities and hence offers a more fluid view of the 'cloud of variances' that RNA viruses are prone to accumulate. This joint approach concludes that while the current animal models cover the existing viral strains adequately, there is substantial evolutionary activity that is likely not considered by the current models. Based on insights from the non-discrete alignment-free approach and experimental observations, we suggest isolates for future animal models.

Experimental and in silico evidence suggests vaccines are unlikely to be affected by D614G mutation in SARS-CoV-2 spike protein.

The 'D614G' mutation (Aspartate-to-Glycine change at position 614) of the SARS-CoV-2 spike protein has been speculated to adversely affect the efficacy of most vaccines and countermeasures that target this glycoprotein, necessitating frequent vaccine matching. Virus neutralisation assays were performed using sera from ferrets which received two doses of the INO-4800 COVID-19 vaccine, and Australian virus isolates (VIC01, SA01 and VIC31) which either possess or lack this mutation but are otherwise comparable. Through this approach, supported by biomolecular modelling of this mutation and the commonly-associated P314L mutation in the RNA-dependent RNA polymerase, we have shown that there is no experimental evidence to support this speculation. We additionally demonstrate that the putative elastase cleavage site introduced by the D614G mutation is unlikely to be accessible to proteases.

Antigenic differentiation of classical swine fever viruses in China by monoclonal antibodies.

The phylogenetic diversity of classical swine fever virus (CSFV) in China has been extensively studied previously, with the report of the classification of Chinese CSFVs into four subgroups within two of the established genotypes, but the antigenic differences amongst Chinese CSF viruses still remain unknown. To address this issue, 21 CSFV field strains isolated in China between 1996 and 2006 were grown in cell culture and characterized in comparison with two Chinese reference strains: a virulent strain Shimen and a vaccine strain CSF lapinized virus (hog cholera lapinized virus in China, HCLV), by indirect immunofluorescence assay (IFA) with a panel of 28 monoclonal antibodies (mAbs) against four pestiviruses, CSFV, bovine viral diarrhoea virus-1 (BVDV-1), bovine viral diarrhoea virus-2 (BVDV-2) and border disease virus (BDV). All 23 CSFV strains reacted only with CSFV-specific mAbs, not with those raised against BVDV-1, BVDV-2 and BDV. Of the former mAbs, those directed against CSFV E2 protein recognized more isolates than those directed against E(rns) and NS2/3. Of nine CSFV E2-specific mAbs used, WH303 and WH302 reacted with all 23 strains, confirming their value in differentiating CSFV from other pestiviruses. Furthermore, different strains had different patterns of reactivity with CSFV-specific mAbs, and mAbs other than WH303 and WH302 did not recognize all strains. This study provides the first evidence for the existence of antigenic differences among Chinese CSFVs.

Innate immune responses to replication of porcine reproductive and respiratory syndrome virus in isolated Swine alveolar macrophages.

Porcine reproductive and respiratory syndrome (PRRS) is an infectious disease caused by a positive RNA strand arterivirus. PRRS virus (PRRSV) interacts primarily with lung macrophages. Identifying the genetic components involved in host resistance/susceptibility would represent an important step forward in the design of disease control programs. In this study, alveolar macrophages derived from five commercial pig lines were used to study the innate immune response to PRRSV infection in vitro. Analysis by flow cytometry has demonstrated that bronchial alveolar lavage fluid (BALF) preparations were almost exclusively composed of alveolar macrophages and that the pigs tested were free from infection. Macrophages from the Landrace line showed significantly reduced virus replication and poor growth of PRRSV during 30 h of infection. By 72 h, PRRSV viral load was down to 2.5 log(10) TCID(50) compared with an average of 5 log(10) TCID(50) for the other breeds tested. These observations suggest that factors intrinsic to the Landrace breed may be responsible for this reduced or delayed response to PRRSV. Preliminary investigation suggests that the PRRSV coreceptor, sialoadhesin, may not be responsible for the Landrace macrophage phenotype as its abundance and localisation were comparable in all the breeds. Strikingly, we found that the reduced or delayed growth of PRRSV was temporally associated with high levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-8 mRNA accumulation and substantial reduction of secretion of IL-8, suggesting a key contributory role for cytokine synthesis and secretion during the innate immune response to PRRSV infection.

Dual use issues in research - A subject of increasing concern?

Dual use is defined as the application of materials, knowledge or technologies for military or terrorist purposes, as well as for good. In biological science, it is considered to be a growing threat as the genetics of pathogenicity traits and toxins are becoming on one hand elucidated in a detail that was not anticipated 20years ago and on the other hand technological advances in genetic engineering and synthetic biology are continually enabling easier access to these technologies. On a theoretical and policy level, much has happened over the past decade, but translating these policies and concepts to operational level awareness and robust processes requires more attention. Where the research is conducted, scientists have to make ethical judgements and account for their data sharing and publication policies. How can we ensure the requirement for dual use review is taken on board, but is not skewing research detrimentally and imposing a disproportionate burden?

Laboratory twinning to build capacity for rabies diagnosis.

In 2009, the UK's OIE Reference Laboratory for rabies, based at the APHA in Weybridge, was awarded a project to twin with the Changchun Veterinary Research Institute in the People's Republic of China to help the institute develop the skills and methods necessary to become an OIE Reference Laboratory itself. Here, Tony Fooks, Trevor Drew and Changchun Tu describe the OIE's twinning project and the success that has since been realised in China.

Factors affecting the infectivity of tissues from pigs with classical swine fever: thermal inactivation rates and oral infectious dose.

Outbreaks of classical swine fever are often associated with ingestion of pig meat or products derived from infected pigs. Assessment of the disease risks associated with material of porcine origin requires knowledge on the likely amount of virus in the original material, how long the virus may remain viable within the resulting product and how much of that product would need to be ingested to result in infection. Using material from pigs infected with CSFV, we determined the viable virus concentrations in tissues that comprise the majority of pork products. Decimal reduction values (D values), the time required to reduce the viable virus load by 90% (or 1 log10), were determined at temperatures of relevance for chilling, cooking, composting and ambient storage. The rate of CSFV inactivation varied in different tissues. At lower temperatures, virus remained viable for substantially longer in muscle and serum compared to lymphoid and fat tissues. To enable estimation of the temperature dependence of inactivation, the temperature change required to change the D values by 90% (Z values) were determined as 13 °C, 14 °C, 12 °C and 10 °C for lymph node, fat, muscle and serum, respectively. The amount of virus required to infect 50% of pigs by ingestion was determined by feeding groups of animals with moderately and highly virulent CSFV. Interestingly, the virulent virus did not initiate infection at a lower dose than the moderately virulent strain. Although higher than for intranasal inoculation, the amount of virus required for infection via ingestion is present in only a few grams of tissue from infected animals.

A comparative study of the local cytokine response in the lungs of pigs experimentally infected with different PRRSV-1 strains: upregulation of IL-1α in highly pathogenic strain induced lesions.

Porcine reproductive and respiratory syndrome viruses (PRRSV) show high genetic differences both among and within genotypes. Recently, several highly pathogenic PRRSV (HP-PRRSV) strains have been described. This study compares and characterizes the production of cytokines by pulmonary macrophages in pigs experimentally infected with four different PRRSV-1 strains: two low-virulent strains, Lelystad (LV) and a British field strain (215-06); a HP strain (SU1-bel) from Belarus and the attenuated vaccine strain DV (Porcilis(®) PRRS). Animals were clinically monitored and post-mortem examinations were performed at 3, 7 and 35 days post-infection (dpi). Lung samples were processed for histopathological and immunohistochemical studies by using specific antibodies against PRRSV, IL1-α, IL-6, TNF-α, IL-10 and IFN-γ. SU1-bel infected animals presented the highest mean scores for clinical observations, gross and microscopic lesions as well as for PRRSV expression compared with the other infected groups (p≤0.027). These animals displayed the highest expression of IL1-α at 7dpi, together with the highest score for lung pathology, whereas LV, 215-06 and DV inoculated animals only showed a transient enhancement in some of these cytokines. SU1-bel-infected pigs showed a positive correlation between the amount of PRRSV antigen and IL-1α expression (r=0.645, p<0.001). The highest expression of IL-10 was detected in 215-06-infected animals (p≤0.004), with a positive correlation with the numbers of virus-infected cells (r=0.375, p≤0.013). In conclusion, the HP-PRRSV SU1-bel strain replicated more efficiently in the lung of infected animals and induced a higher expression of IL-1α than the other PRRSV-1-infected groups, which may have played a key role in the onset of the clinical signs and interstitial pneumonia.

Development of a TaqMan PCR assay with internal amplification control for the detection of African swine fever virus.

A closed-tube polymerase chain reaction (PCR) was developed to allow the rapid detection of African swine fever virus (ASFV) DNA. This assay targets the VP72 gene of ASFV and uses the 5'-nuclease assay (TaqMan) system to detect PCR amplicons, avoiding tube opening and potential cross-contamination of post-PCR products. An artificial mimic was engineered with the TaqMan probe site replaced by a larger irrelevant DNA fragment allowing discrimination from ASFV by using two-colour TaqMan probe reporters. When added to the samples, successful amplification of this mimic demonstrated the absence of substances inhibitory to PCR, thereby validating negative results. Assay sensitivity was confirmed by obtaining positive signals with a representative selection of ASFV isolates. Many of the clinical and post-mortem features of ASF resemble those of classical swine fever (CSF) and porcine dermatitis and nephropathy syndrome (PDNS). Therefore, fast and reliable detection of ASFV is essential not only for the implementation of control measures to prevent the spread of ASF, but also in the differential diagnosis from CSF and PDNS. This assay should prove to be a valuable tool in the laboratory diagnosis of ASF and will complement existing molecular methods to provide rapid differential diagnosis in cases of suspected swine fever.

Development and validation of a multiplex, real-time RT PCR assay for the simultaneous detection of classical and African swine fever viruses.

A single-step, multiplex, real-time polymerase chain reaction (RT-PCR) was developed for the simultaneous and differential laboratory diagnosis of Classical swine fever virus (CSFV) and African swine fever virus (ASFV) alongside an exogenous internal control RNA (IC-RNA). Combining a single extraction methodology and primer and probe sets for detection of the three target nucleic acids CSFV, ASFV and IC-RNA, had no effect on the analytical sensitivity of the assay and the new triplex RT-PCR was comparable to standard PCR techniques for CSFV and ASFV diagnosis. After optimisation the assay had a detection limit of 5 CSFV genome copies and 22 ASFV genome copies. Analytical specificity of the triplex assay was validated using a panel of viruses representing 9 of the 11 CSFV subgenotypes, at least 8 of the 22 ASFV genotypes as well as non-CSFV pestiviruses. Positive and negative clinical samples from animals infected experimentally, due to field exposure or collected from the UK which is free from both swine diseases, were used to evaluate the diagnostic sensitivity and specificity for detection of both viruses. The diagnostic sensitivity was 100% for both viruses whilst diagnostic specificity estimates were 100% for CSFV detection and 97.3% for ASFV detection. The inclusion of a heterologous internal control allowed identification of false negative results, which occurred at a higher level than expected. The triplex assay described here offers a valuable new tool for the differential detection of the causative viruses of two clinically indistinguishable porcine diseases, whose geographical occurrence is increasingly overlapping.

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.