Tailoring freshwater diets towards boosted immunity and pancreas disease infection robustness in Atlantic salmon post smolts

The aim of the current study was to investigate how freshwater diets impact on immunity in Atlantic salmon smolts in freshwater, during transfer to seawater and in post smolts during the seawater stage with and without pancreas disease (PD) infection. Three specific freshwater diets were prepared: (i) A diet similar in composition to commercial salmon freshwater diets (Standard diet); (ii) A diet composed of vegetable oils (rapeseed, palm and linseed oils) mimicking the fat composition in aquatic insects - the natural diet of wild salmon in freshwater (Fatty acid diet); (iii) A diet enriched with possible immune modulating amino acids including dl-methionine, l-lysine, l-threonine and taurine (Amino acid diet). After seawater transfer, all fish were fed the same commercial diet. Head kidneys were extracted, and their leukocytes isolated from smolts right before transfer to seawater, from post smolts one and six weeks after transfer to seawater, and from post smolts in seawater after 8 weeks of ongoing PD infection. In addition, to provoke bacterial or virus induced inflammation in vitro, the individual leukocyte suspension from all fish were stimulated by lipopolysaccharide (LPS) or polyinosinic acid: polycytidylic acid (PIC). The transfer of smolts from fresh-to seawater changed the transcription of several types of genes. Particularly in isolates from fish fed the Standard or Fatty acid diet in freshwater, overall gene transcription (IL-1β, CD83, INF-γ, cox2, cd36, MGAT2, catalase) declined. However, the Amino acid diet stimulated the LPS induced gene transcription of IL-1β, CD83, Cox2, and INF-γ at this stage. In freshwater smolts, PIC stimulated leukocytes showed higher transcription level of Mx and viperin in the Fatty acid and Amino acid diet groups compared to the Standard diet group. In seawater post smolts, Mx and viperin responded similarly to PIC challenge in all diet groups. Furthermore, leukocytes isolated from PD infected fish, continued responding to PIC, regardless of freshwater diet.

Effect of vaccines against pancreas disease in farmed Atlantic salmon

Pancreas disease (PD) caused by salmonid alphavirus (SAV) continues to negatively impact salmon farming. To assess the effect on growth and mortality of three vaccines against PD, two controlled field designs were employed: one controlled field study with individual marked fish (PIT tag) assessing three PD vaccines and three controls groups, and a second controlled field study with group marked fish (Maxilla) comparing two PD vaccines against controls. In addition, a descriptive study using whole cages compared fish immunized with two different PD vaccines against controls. The target populations experienced a natural PD outbreak where both SAV 2 and SAV 3 were identified. Only one of the PD vaccines provided statistically significant improvements in harvest weight of 0.43 kg (CI: 0.29-0.57) and 0.51 kg (CI: 0.36-0.65) compared with the control in the PIT tag and the Maxilla study, respectively. In the latter, a significant reduction in mortality of 1.31 (CI:0.8-1.8) per cent points was registered for the same vaccine compared with controls. These results aligned with the growth and PD-specific mortality registered in the descriptive Cage study. The data in this study show a difference in the efficacy of PD vaccines in farmed Atlantic salmon.

Implications of SARS-CoV-2 infection for neurogastroenterology

BACKGROUND

Coronavirus disease 2019 (COVID-19) is associated with gastrointestinal and hepatic manifestation in up to one fifth of patients. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiologic agent of COVID-19, infects gastrointestinal epithelial cells expressing angiotensin-converting enzyme 2 (ACE2) receptors triggering a cascade of events leading to mucosal and systemic inflammation. Symptomatic patients display changes in gut microbiota composition and function which may contribute to intestinal barrier dysfunction and immune activation. Evidence suggests that SARS-CoV-2 infection and related mucosal inflammation impact on the function of the enteric nervous system and the activation of sensory fibers conveying information to the central nervous system, which, may at least in part, contribute symptom generation such as vomiting and diarrhea described in COVID-19. Liver and pancreas dysfunctions have also been described as non-respiratory complications of COVID-19 and add further emphasis to the common view of SARS-CoV-2 infection as a systemic disease with multiorgan involvement.

PURPOSE

The aim of this review was to highlight the current knowledge on the pathophysiology of gastrointestinal SARS-CoV-2 infection, including the crosstalk with the gut microbiota, the fecal-oral route of virus transmission, and the potential interaction of the virus with the enteric nervous system. We also review the current available data on gastrointestinal and liver manifestations, management, and outcomes of patients with COVID-19.

SARS-CoV-2 infects and replicates in cells of the human endocrine and exocrine pancreas

Infection-related diabetes can arise as a result of virus-associated β-cell destruction. Clinical data suggest that the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing the coronavirus disease 2019 (COVID-19), impairs glucose homoeostasis, but experimental evidence that SARS-CoV-2 can infect pancreatic tissue has been lacking. In the present study, we show that SARS-CoV-2 infects cells of the human exocrine and endocrine pancreas ex vivo and in vivo. We demonstrate that human β-cells express viral entry proteins, and SARS-CoV-2 infects and replicates in cultured human islets. Infection is associated with morphological, transcriptional and functional changes, including reduced numbers of insulin-secretory granules in β-cells and impaired glucose-stimulated insulin secretion. In COVID-19 full-body postmortem examinations, we detected SARS-CoV-2 nucleocapsid protein in pancreatic exocrine cells, and in cells that stain positive for the β-cell marker NKX6.1 and are in close proximity to the islets of Langerhans in all four patients investigated. Our data identify the human pancreas as a target of SARS-CoV-2 infection and suggest that β-cell infection could contribute to the metabolic dysregulation observed in patients with COVID-19.

Effect of a novel DNA vaccine against pancreas disease caused by salmonid alphavirus subtype 3 in Atlantic salmon (Salmo salar)

Pancreas disease (PD) caused by salmonid alphavirus subtype 3 (SAV3) is a serious disease with large economic impact on farmed Norwegian Atlantic salmon production despite years of use of oil-adjuvanted vaccines against PD (OAVs). In this study, two commercially available PD vaccines, a DNA vaccine (DNAV) and an OAV, were compared in an experimental setting. At approximately 1040° days (dd) at 12 °C post immunization, the fish were challenged with SAV3 by cohabitation 9 days after transfer to sea water. Sampling was done prior to challenge and at 19, 54, and 83 days post-challenge (dpc). When compared to the OAV and control (Saline) groups, the DNAV group had significantly higher SAV3 neutralizing antibody titers after the immunization period, significantly lower SAV3 viremia levels at 19 dpc, significantly reduced transmission of SAV3 to naïve fish in the latter part of the viremic phase, significantly higher weight gain post-challenge, and significantly reduced prevalence and/or severity of SAV-induced morphologic changes in target organs. The DNAV group had also significantly higher post-challenge survival compared to the Saline group, but not to the OAV group. The data suggest that use of DNAV may reduce the economic impact of PD by protecting against destruction of the pancreas tissue and subsequent growth impairment which is the most common and costly clinical outcome of this disease.

Pancreatic Injury in COVID-19 Patients

BACKGROUND AND AIM

Coronavirus disease 2019 (COVID 2019) outbreak caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may cause multisystem dysfunction. We studied pancreatic injury (serum amylase and serum lipase levels) in COVID-19 patients.

METHODS

A retrospective study involving 42 COVID-19 patients (diagnosed by real-time PCR) admitted to a tertiary care hospital was conducted. Serum amylase and serum lipase levels were analysed in relation to severity of COVID-19 and mortality.

RESULTS

Mean age of patients was 50 ± 16 years, with male to female ratio of 3.7:1. Serum amylase was elevated in 14 patients (33%). Serum lipase was elevated in 7 out of 29 patients (24.1%). Mortality was seen in 18 patients (42.8%). Serum amylase or lipase did not correlate with severity of COVID-19 or its mortality. However, both patients who had high lipase (>3times) died.

CONCLUSION

The prevalence of hyperamylasemia in patients of COVID-19 was 33%, while that of elevated lipase was 24.1%. Pancreatic injury failed to show any statistically significant relation to severity or outcome of COVID-19.

Detection of specific Atlantic salmon antibodies against salmonid alphavirus using a bead-based immunoassay

Salmonid alphavirus (SAV) is the etiological cause of pancreas disease (PD) in Atlantic salmon (Salmo salar). Several vaccines against SAV are in use, but PD still cause significant mortality and concern in European aquaculture, raising the need for optimal tools to monitor SAV immunity. To monitor and control the distribution of PD in Norway, all salmonid farms are regularly screened for SAV by RT-qPCR. While the direct detection of SAV is helpful in the early stages of infection, serological methods could bring additional information on acquired SAV immunity in the later stages. Traditionally, SAV antibodies are monitored in neutralization assays, but they are time-consuming and cumbersome, thus alternative assays are warranted. Enzyme-linked immunosorbent assays (ELISAs) have not yet been successfully used for anti-SAV antibody detection in aquaculture. We aimed to develop a bead-based immunoassay for SAV-specific antibodies. By using detergent-treated SAV particles as antigens, we detected SAV-specific antibodies in plasma collected from both a SAV challenge trial and a field outbreak of PD. Increased levels of SAV-specific antibodies were seen after most fish had become negative for viral RNA. The bead-based assay is time saving compared to virus neutralization assays, and suitable for non-lethal testing due to low sample size requirements. We conclude that the bead-based immunoassay for SAV antibody detection is a promising diagnostic tool to complement SAV screening in aquaculture.

Pancreatic injury in COVID-19: pathogenesis and challenges

Apart from the mechanisms reported by Fernandes et al, the thromboembolic pathogenesis should also be taken into account in patients with severe COVID-19 and prophylaxis with low molecular weight heparin should be implemented.

Effect of pancreas disease caused by SAV 2 on protein and fat digestion in Atlantic salmon

Salmonid alphavirus (SAV) causes pancreas disease (PD) in farmed Atlantic salmon (Salmo salar L.), and exocrine pancreas tissue is a primary target of the virus. Digestive enzymes secreted by the exocrine pancreas break down macromolecules in feed into smaller molecules that can be absorbed. The effect of SAV infection on digestion has been poorly studied. In this study, longitudinal observations of PD outbreaks caused by SAV subtype 2 (SAV2) in Atlantic salmon at two commercial sea sites were performed. The development of PD was assessed by measurement of SAV2 RNA load and evaluation of histopathological lesions typical of PD. Reduced digestion of both protein and fat co-varied with the severity of PD lesions and viral load. Also, the study found that during a PD outbreak, the pen population comprise several subpopulations, with different likelihoods of being sampled. The body length of sampled fish deviated from the expected increase or steady state over time, and the infection status in sampled fish deviated from the expected course of infection in the population. Both conditions indicate that disease status of the individual fish influenced the likelihood of being sampled, which may cause sampling bias in population studies.

Molecular tracing confirms that infection with infectious pancreatic necrosis virus follows the smolt from hatchery to grow-out farm

Infectious pancreatic necrosis (IPN) is an important restraint to production of salmonids in aquaculture globally. In order to implement efficacious mitigation strategies for control of this disease, it is important to understand infection routes under current production systems. IPN virus has been shown to be transmitted vertically in Rainbow trout, from broodstock to fingerlings in hatcheries, and there is circumstantial evidence suggesting that vertical transmission can also occur in Atlantic salmon, in addition to horizontal transmission between grow-out fish in farms. In this study, we show that the smolt carries infection with IPN from hatchery to the marine farm. We do this by comparing sequences from fish groups taken both in hatcheries and on corresponding marine grow-out farms. We use statistical analysis to prove that sequences obtained from the same fish group in both hatchery and marine farm are more similar than sequences obtained from random fish groups on hatcheries and marine farms.

Selective precipitation reaction: a novel diagnostic test for tissue pathology in Atlantic salmon, Salmo salar, infected with salmonid alphavirus (SAV3)

While investigating biomarkers for infection with salmonid alphavirus (SAV), the cause of pancreas disease (PD), a selective precipitation reaction (SPR) has been discovered in serum which could be an on-farm qualitative test and an in-laboratory quantitative assay for health assessments in aquaculture. Mixing serum from Atlantic salmon, Salmo salar, with SAV infection with a sodium acetate buffer caused a visible precipitation which does not occur with serum from healthy salmon. Proteomic examination of the precipitate has revealed that the components are a mix of muscle proteins, for example enolase and aldolase, along with serum protein such as serotransferrin and complement C9. The assay has been optimized for molarity, pH, temperature and wavelength so that the precipitation can be measured as the change in optical density at 340 nm (Δ₃₄₀ ). Application of the SPR assay to serum samples from a cohabitation trial of SAV infection in salmon showed that the Δ₃₄₀ in infected fish rose from undetectable to a maximum at 6 weeks post-infection correlating with histopathological score of pancreas, heart and muscle damage. This test may have a valuable role to play in the diagnostic evaluation of stock health in salmon.

Type 1 Diabetes and Type 1 Interferonopathies: Localization of a Type 1 Common Thread of Virus Infection in the Pancreas

Type 1 diabetes (T1D) has been associated with both genetic and environmental factors. Increasing incidence of T1D worldwide is prompting researchers to adopt different approaches to explain the biology of T1D, beyond the presence and activity of autoreactive lymphocytes. In this review, we propose inflammatory pathways as triggers for T1D. Within the scope of those inflammatory pathways and in understanding the pathogenesis of disease, we suggest that viruses, in particular Coxsackieviruses, act by causing a type 1 interferonopathy within the pancreas and the microenvironment of the islet. As such, this connection and common thread represents an exciting platform for the development of new diagnostic, treatment and/or prevention options.

Immune gene profiles in Atlantic salmon (salmo salar L.) post-smolts infected with SAV3 by bath-challenge show a delayed response and lower levels of gene transcription compared to injected fish

Salmonid alphavirus (SAV) causes pancreatic disease (PD) in salmonids in Northern Europe which results in large economic losses within the aquaculture industry. In order to better understand the underlying immune mechanisms during a SAV3 infection Atlantic salmon post-smolts were infected by either i.m.-injection or bath immersion and their immune responses compared. Analysis of viral loads showed that by 14 dpi i.m.-injected and bath immersion groups had 95.6% and 100% prevalence respectively and that both groups had developed the severe pathology typical of PD. The immune response was evaluated by using RT-qPCR to measure the transcription of innate immune genes involved in the interferon (IFN) response as well as genes associated with inflammation. Our results showed that IFNa transcription was only weakly upregulated, especially in the bath immersion group. Despite this, high levels of the IFN-stimulated genes (ISGs) such as Mx and viperin were observed. The immune response in the i.m.-injected group as measured by immune gene transcription was generally faster, and more pronounced than the response in the bath immersion group, especially at earlier time-points. The response in the bath immersion group started later as expected and appeared to last longer often exceeding the response in the i.m-injected fish at later time-points. High levels of transcription of many genes indicative of an active innate immune response were present in both groups.

The epidemiology of pancreas disease in salmonid aquaculture: a summary of the current state of knowledge

Pancreas disease (PD) is a viral disease caused by Salmonid alphavirus (SAV) that affects farmed Atlantic salmon (Salmo salar L.) and rainbow trout (Oncorhynchus mykiss (Walbaum)) in the seawater phase. Since its first description in Scotland in 1976, a large number of studies have been conducted relating to the disease itself and to factors contributing to agent spread and disease occurrence. This paper summarizes the currently available, scientific information on the epidemiology of PD and its associated mitigation and control measures. Available literature shows infected farmed salmonids to be the main reservoir of SAV. Transmission between seawater sites occurs mainly passively by water currents or actively through human activity coupled with inadequate biosecurity measures. All available information suggests that the current fallowing procedures are adequate to prevent agent survival within the environment through the fallowing period and thus that a repeated disease outbreak at the same site is due to a new agent introduction. There has been no scientific evaluation of currently used on-site biosecurity measures, and there is limited information on the impact of available mitigation measures and control strategies.

Antiviral Activity of Oroxylin A against Coxsackievirus B3 Alleviates Virus-Induced Acute Pancreatic Damage in Mice

The flavonoids mosloflavone, oroxylin A, and norwogonin, which were purified from Scutellaria baicalensis Georgi, significantly protected Vero cells against Coxsackievirus B3 (CVB3)-induced cell death. To investigate the in vivo antiviral activity of oroxylin A, we intraperitoneally inoculated CVB3 into 4-week-old BALB/c mice. Body weights and blood glucose levels of the mice were decreased after CVB3 infection, and these changes were attenuated by the administration of oroxylin A. Importantly, treatment of mice with oroxylin A reduced viral titers in the pancreas and decreased the serum levels of the inflammatory cytokines including interleukin-6 (IL-6) and tumor necrosis factor (TNF)-α. Additionally, the administration of oroxylin A mitigated the histological pancreatic lesions and apoptotic cell death induced by CVB3 infection and increased the levels of phospho-eIF2α in infected pancreata. The results suggest that oroxylin A may represent a potent antiviral agent against CVB3 infection.

Liquid fat, a potential abiotic vector for horizontal transmission of salmonid alphavirus?

Viral diseases represent serious challenge in marine farming of Atlantic salmon (Salmo salar L). Pancreas disease (PD) caused by a salmonid alphavirus (SAV) is by far the most serious in northern Europe. To control PD, it is necessary to identify virus transmission routes. One aspect to consider is whether the virus is transported as free particles or associated with potential vectors. Farmed salmonids have high lipid content in their tissue which may be released into the environment from decomposing dead fish. At the seawater surface, the effects of wind and ocean currents are most prominent. The aim of this study was primarily to identify whether the lipid fraction leaking from dead infected salmon contains SAV. Adipose tissue from dead SAV-infected fish from three farming sites was submerged in beakers with sea water in the laboratory and stored at different temperature and time conditions. SAV was identified by real-time RT-PCR in the lipid fractions accumulating at the water surface in the beakers. SAV-RNA was also present in the sea water. Lipid fractions were transferred to cell culture, and viable SAV was identified. Due to its hydrophobic nature, fat with infective pathogenic virus at the surface may contribute to long-distance transmission of SAV.

Comparison of transcriptomic responses to pancreas disease (PD) and heart and skeletal muscle inflammation (HSMI) in heart of Atlantic salmon (Salmo salar L)

Pancreas disease (PD) and heart and skeletal muscle inflammation (HSMI) are viral diseases associated with SAV (salmonid alphavirus) and PRV (piscine reovirus), which induce systemic infections and pathologies in cardiac and skeletal muscle tissue of farmed Atlantic salmon (Salmo salar L), resulting in severe morbidity and mortality. While general features of the clinical symptoms and pathogenesis of salmonid viral diseases are relatively well studied, much less is known about molecular mechanisms associated with immunity and disease-specific changes. In this study, transcriptomic analyses of heart tissue from PD and HSMI challenged Atlantic salmon were done, focusing on the mature phases of both diseases at respectively 28-35 and 42-77 days post infection. A large number of immune genes was activated in both trials with prevalence of genes associated with early innate antiviral responses, their expression levels being slightly higher in PD challenged fish. Activation of the IFN axis was in parallel with inflammatory changes that involved diverse humoral and cellular factors. Adaptive immune response genes were more pronounced in fish with HSMI, as suggested by increased expression of a large number of genes associated with differentiation and maturation of B lymphocytes and cytotoxic T cells. A similar down-regulation of non-immune genes such as myofiber and mitochondrial proteins between diseases was most likely reflecting myocardial pathology. A suite of genes important for cardiac function including B-type natriuretic peptide and four neuropeptides displayed differential expression between PD and HSMI. Comparison of results revealed common and distinct features and added to the understanding of both diseases at their mature phases with typical clinical pictures. A number of genes that showed disease-specific changes can be of interest for diagnostics.

Clinical manifestations of pancreas disease outbreaks in Norwegian marine salmon farming - variations due to salmonid alphavirus subtype

Pancreas disease (PD) in Norwegian salmonid aquaculture has traditionally been caused by salmonid alphavirus (SAV) subtype 3. Following the isolation of a novel SAV subtype in 2010, marine SAV2, two separate endemic areas have developed. It has been debated whether disease outbreaks due to marine SAV2 result in milder clinical manifestations compared to outbreaks caused by SAV3. The aim of this study was to descriptively investigate site-level differences in the clinical manifestations of marine SAV2 and SAV3 at Norwegian seawater sites diagnosed with PD in 2012. The findings suggest that Norwegian PD outbreaks caused by marine SAV2 result in lower mortality and milder clinical signs compared to outbreaks caused by SAV3. For sites without reported PD-related mortality, there was no difference in the mortality levels between sites infected by marine SAV2 and SAV3. The results also indicate that there are no differences in grading quality at slaughter between the SAV subtypes.

An experimental means of transmitting pancreas disease in Atlantic salmon Salmo salar L. fry in freshwater

A challenge model for pancreas disease in Atlantic salmon, Salmo salar L. fry, was developed comparing two salmonid alphavirus (SAV) subtypes: SAV1 and SAV5. Viral doses of 3 × 10(5) TCID50  mL(-1) for SAV1 and 3 × 10(4) for SAV5 were tested in triplicate tanks, each containing 450 salmon fry. Cumulative mortalities of 1.2% were recorded. Titres of virus recovered from the mortalities ranged from 10(2) to 10(7) TCID50  mL(-1) . Fry were sampled at 3, 5 and 7.5 weeks post-challenge. Sampling after 3 weeks revealed a high prevalence of infection in the absence of clinical signs, and infectious virus was recovered from 80% and 43% of sampled fry infected with SAV1 and SAV5, respectively. After 5 weeks pancreas, heart and red skeletal muscle lesions were generally observed, whilst degeneration in white skeletal muscle was observed only in fish infected with SAV1. In situ hybridisation confirmed the presence of viral genome in infected pancreas, heart and muscle. After 7.5 weeks, infectious virus (both isolates) was recovered from 13.3% of the fish sampled, with a viral titre of 10(2) TCID50  mL(-1) . Clearly, salmon fry are susceptible to SAV infection and pancreas disease.

Seasonal increase in sea temperature triggers pancreas disease outbreaks in Norwegian salmon farms

Pancreas disease (PD) is a viral disease causing negative impacts on economy of salmon farms and fish welfare. Its transmission route is horizontal, and water transport by ocean currents is an important factor for transmission. In this study, the effect of temperature changes on PD dynamics in the field has been analysed for the first time. To identify the potential time of exposure to the virus causing PD, a hydrodynamic current model was used. A cohort of salmon was assumed to be infected the month it was exposed to virus from other infective cohorts by estimated water contact. The number of months from exposure to outbreak defined the incubation period, which was used in this investigation to explore the relationship between temperature changes and PD dynamics. The time of outbreak was identified by peak in mortality based on monthly records from active sites. Survival analysis demonstrated that cohorts exposed to virus at decreasing sea temperature had a significantly longer incubation period than cohorts infected when the sea temperature was increasing. Hydrodynamic models can provide information on the risk of being exposed to pathogens from neighbouring farms. With the knowledge of temperature-dependent outbreak probability, the farmers can emphasize prophylactic management, avoid stressful operations until the sea temperature is decreasing and consider removal of cohorts at risk, if possible.

The serum proteome of Atlantic salmon, Salmo salar, during pancreas disease (PD) following infection with salmonid alphavirus subtype 3 (SAV3)

Salmonid alphavirus is the aetological agent of pancreas disease (PD) in marine Atlantic salmon, Salmo salar, and rainbow trout, Oncorhynchus mykiss, with most outbreaks in Norway caused by SAV subtype 3 (SAV3). This atypical alphavirus is transmitted horizontally causing a significant economic impact on the aquaculture industry. This histopathological and proteomic study, using an established cohabitational experimental model, investigated the correlation between tissue damage during PD and a number of serum proteins associated with these pathologies in Atlantic salmon. The proteins were identified by two-dimensional electrophoresis, trypsin digest and peptide MS/MS fingerprinting. A number of humoral components of immunity which may act as biomarkers of the disease were also identified. For example, creatine kinase, enolase and malate dehydrogenase serum concentrations were shown to correlate with pathology during PD. In contrast, hemopexin, transferrin, and apolipoprotein, amongst others, altered during later stages of the disease and did not correlate with tissue pathologies. This approach has given new insight into not only PD but also fish disease as a whole, by characterisation of the protein response to infection, through pathological processes to tissue recovery.

BIOLOGICAL SIGNIFICANCE

Salmonid alphavirus causes pancreas disease (PD) in Atlantic salmon, Salmo salar, and has a major economic impact on the aquaculture industry. A proteomic investigation of the change to the serum proteome during PD has been made with an established experimental model of the disease. Serum proteins were identified by two-dimensional electrophoresis, trypsin digest and peptide MS/MS fingerprinting with 72 protein spots being shown to alter significantly over the 12week period of the infection. The concentrations of certain proteins in serum such as creatine kinase, enolase and malate dehydrogenase were shown to correlate with tissue pathology while other proteins such as hemopexin, transferrin, and apolipoprotein, altered in concentration during later stages of the disease and did not correlate with tissue pathologies. The protein response to infection may be used to monitor disease progression and enhance understanding of the pathology of PD.

Immune parameters correlating with reduced susceptibility to pancreas disease in experimentally challenged Atlantic salmon (Salmo salar)

Two strains of Atlantic salmon (Salmon salar) with different susceptibility to infectious salmon anaemia (ISA) were challenged with salmon pancreas disease virus (SPDV), the etiological agent of salmon pancreas disease (PD), by cohabitation. Serum and tissues were sampled at 0, 1, 3, 6 and 8 weeks post-challenge. Experimental challenge with SAV did not cause mortality, but virus loads and assessment of histopathology indicated that the fish more resistant to ISAV (ISAHi) also was more resistant to PD. Eight weeks post-challenge, the ISAHi strain had higher titres of SAV-neutralising antibodies than the less resistant strain (ISALo). Transcript levels of four adaptive and six innate immune parameters were analysed by real-time RT-PCR in heart, head kidney (HK) and gills of both strains. Secretory IgM (sIgM) and CD8 levels differed most between the two salmon strains. The ISAHi strain had significantly higher levels of sIgM in HK at all samplings, and significantly higher CD8 levels in gills at most samplings. In heart, both sIgM and CD8 levels increased significantly during the challenge, but the increase appeared earlier for the ISALo strain. By hierarchical clustering analysis of mRNA levels, a clear segregation was observed between the two strains prior to the virus challenge. As the viral infection developed, the clustering divide between fish strains disappeared, first for innate and later for adaptive parameters. At eight weeks post-challenge, the divide had however reformed for adaptive parameters. Possible pair-wise correlation between transcript levels of immune parameters was evaluated by a non-parametric statistical test. For innate parameters, the extent of correlation peaked at 3 wpc in all tissues; this came rapidly for ISALo and more gradual for ISAHi. The ISAHi strain tended to show higher correlation for innate parameters in heart and gill than ISALo at early sampling times. For adaptive immune parameters, little correlation was observed in general, except for ISAHi in heart at 6 wpc. Overall, the observed differences in immune parameters may provide important clues to the causes underlying the observed difference in susceptibility to PD.

Stress-induced reversion to virulence of infectious pancreatic necrosis virus in naïve fry of Atlantic salmon (Salmo salar L.)

We have studied stress-induced reversion to virulence of infectious pancreatic necrosis virus (IPNV) in persistently infected Atlantic salmon (Salmo salar L.) fry. Naïve fry were persistently infected with a virulent strain (T₂₁₇A₂₂₁ of major structural virus protein 2, VP2) or a low virulent (T₂₁₇T₂₂₁) variant of IPNV. The fry were infected prior to immunocompetence as documented by lack of recombination activating gene-1, T-cell receptor and B-cell receptor mRNA expression at time of challenge. The fish were followed over 6 months and monitored monthly for presence of virus and viral genome mutations. No mutation was identified in the TA or TT group over the 6 months period post infection. Six months post infection TA and TT infected groups were subject to daily stress for 7 days and then sampled weekly for an additional period of 28 days post stress. Stress-responses were documented by down-regulation of mRNA expression of IFN-α1 and concomitant increase of replication levels of T₂₁₇T₂₂₁ infected fish at day 1 post stress. By 28 days post stress a T221A reversion was found in 3 of 6 fish in the T₂₁₇T₂₂₁ infected group. Sequencing of reverted isolates showed single nucleotide peaks on chromatograms for residue 221 for all three isolates and no mix of TA and TT strains. Replication fitness of reverted (TA) and non-reverted (TT) variants was studied in vitro under an antiviral state induced by recombinant IFN-α1. The T₂₁₇A₂₂₁ reverted variant replicated to levels 23-fold higher than the T₂₁₇T₂₂₁ strain in IFN-α1 treated cells. Finally, reverted TA strains were virulent when tested in an in vivo trial in susceptible salmon fry. In conclusion, these results indicate that stress plays a key role in viral replication in vivo and can facilitate conditions that will allow reversion from attenuated virus variants of IPNV.

Transcriptomic analysis of the host response to early stage salmonid alphavirus (SAV-1) infection in Atlantic salmon Salmo salar L

Salmon pancreas disease, caused by salmonid alphavirus (SAV) of the family Togaviridae, is an economically important disease affecting farmed Atlantic salmon (Salmo salar L.) in Scotland, Norway, and Ireland. The virus causes characteristic lesions in the pancreas, heart, kidney and skeletal muscle of infected fish. The mechanisms responsible for the pathology and the immune responses elicited in infected Atlantic salmon are not fully understood. A microarray-based study was therefore performed to evaluate the host transcriptomic response during the early stages of an experimentally-induced SAV-1 infection. Atlantic salmon parr were injected intra-peritoneally with viral cell culture supernatant or cell culture supernatant without virus. RNA, extracted from head kidney sampled from infected and control fish at 1, 3 and 5 days post-injection (d.p.i.), was interrogated with the 17 k TRAITS/SGP cDNA microarray. The greatest number of significantly differentially expressed genes was recorded at 3 d.p.i., mainly associated with immune and defence mechanisms, including genes involved in interferon I pathways and Major Histocompatibility Complex Class I and II responses. Genes associated with apoptosis and cellular stress were also found to be differentially expressed between infected and uninfected individuals, as were genes involved in inhibiting viral attachment and replication. The microarray results were validated by follow-on analysis of eight genes by real-time PCR. The findings of the study reflect mechanisms used by the host to protect itself during the early stages of SAV-1 infection. In particular, there was evidence of rapid induction of interferon-mediated responses similar to those seen during mammalian alphavirus infections, and also early involvement of an adaptive immune response. This study provides essential knowledge to assist in the development of effective control and management strategies for SAV-1 infection.

Formulations combining CpG containing oliogonucleotides and poly I:C enhance the magnitude of immune responses and protection against pancreas disease in Atlantic salmon

Both CpG oligodeoxynucleotides and double-stranded RNA (poly I:C) have documented effects as treatments against several viral diseases in fish. However, as stand-alone treatments their effects have been modest. We have tested here whether CpG and poly I:C, alone or in combination induce protection against Salmonid Alphavirus (SAV), the causative agent of pancreas disease in Atlantic salmon. Our results revealed a significant reduction of viraemia 2 weeks after ip injection of the combined treatment and 1 week after challenge with SAV subtype 3, followed by reduced SAV induced heart pathology 3 weeks later. The SAV titers in blood samples from the combination group were lower as compared to single treatments with either CpG or poly I:C. Surprisingly, reduced SAV levels could also be found in fish as long as 7 weeks after receiving the combination treatment. The expression of IFNγ and to a lesser extent IFNa and Mx was up-regulated in head kidney and spleen 5 days after the fish had been treated with CpG and poly I:C. Furthermore, the complement factor C4 was depleted in serum 8 weeks post treatment, suggesting complement activation leading to C4 consumption. We hypothesize that the CpG/poly I:C-induced protection against SAV3 is mediated by mechanisms involving type I and type II IFN induced antiviral activity and complement mediated protective responses.

A comparative study of marine salmonid alphavirus subtypes 1-6 using an experimental cohabitation challenge model

A comparative challenge study of six marine isolates representing subtypes 1-6 of salmonid alphavirus (salmon pancreas disease virus, Genus Alphavirus, Family Togaviridae) was conducted in Atlantic salmon in a fresh water cohabitation trial. Histopathological lesions typical of pancreas disease were observed with all subtypes, and virus was re-isolated from serum of cohabitant fish in each case. Using a virus neutralization (VN) test neutralizing salmonid alphavirus (SAV) subtype 1 strain F93-125, VN antibodies were detected in all challenge groups, consistent with serological cross-reactivity between these subtypes. Using real-time RT-PCR, SAV RNA was detected in heart tissue from 2 to 3 weeks post-challenge (wpc) in all cohabitant groups excluding controls. The results obtained suggested differences in the dynamics of infection between strains of SAV and potentially between subtypes. Results for SAV subtypes 1 and 3 suggested essentially synchronous infection of cohabitant fish. These two study groups also had the highest virus load in heart tissue as measured by quantitative RT-PCR and also had the most extensive histopathological changes. In contrast, results for SAV subtypes 2 and 6 strains were consistent with asynchronous infection in the cohabitant fish and were characterized by slow spread, low virus loads and mild histopathological changes. The SAV subtype 4 and 5 strains occupied an intermediate position in this regard. Despite the use of concentration procedures, it was not possible to detect SAV RNA in water samples from selected study tanks. However, testing of faeces from the SAV subtypes 1, 3 and 6 challenge groups found positive signals in each beginning at 1-3 wpc and remaining detectable for a further 2-3 weeks. Parallel testing of mucus samples found these became positive at 2-3 wpc and remained positive for a further 1-3 weeks. These results demonstrate for the first time that shedding and transmission of virus may occur by both these routes and suggest that dispersal in these matrices should be included in any disease transmission models.

Lack of evidence for vertical transmission of SAV 3 using gametes of Atlantic salmon, Salmo salar L., exposed by natural and experimental routes

Pancreas disease (PD) is an important cause of losses in farmed salmonids in Norway, the United Kingdom and Ireland. As the spread of salmonid alphavirus (SAV), the causal agent, to naïve populations is of major concern to the farming industry, it is important to uncover the transmission routes of the virus. This study was conducted to investigate the potential for vertical transmission of SAV subtype 3. Progeny of broodstock with signs of late-stage PD and persistent RT-PCR signals for SAV were followed from fertilization to smoltification in an experimental facility. Fertilized ova were either not disinfected or taken through one of three different disinfection regimes. Also, ova and milt from uninfected broodfish from a different population were exposed to a cell-cultured strain of SAV 3 immediately before fertilization to simulate a viraemic phase in parent fish. A group of uninfected controls were also included in the study. Fertilized ova from bath exposed and negative control groups were double disinfected. Following fertilization, experimental fish went through a normal freshwater phase. However, fry were stressed at first feeding to enhance replication of possibly latent virus. Smoltification was induced by an artificial light regime, and experimental fish were followed to the late smoltification phase. Selected samples were investigated by real-time RT-PCR for SAV, by histology for evidence of PD and by serology for neutralising antibodies against SAV. All analysed samples of progeny were negative. This result shows that SAV 3 is not readily transmitted vertically from parents to offspring. Additional negative PCR results from salmon sampled in commercial hatcheries support these findings. Also, recent studies have shown that risk factors for the horizontal transmission route explain the vast majority of PD outbreaks in Norway. It is concluded that if it happens at all, vertical transmission is of minor importance in the spread of SAV 3.

Detection of salmonid alphavirus RNA in wild marine fish: implications for the origins of salmon pancreas disease in aquaculture

Salmonid alphaviruses (SAVs), which include the aetiological agents of salmon pancreas disease (SPD) in farmed Atlantic salmon Salmo salar L. and sleeping disease (SD) in rainbow trout Oncorhynchus mykiss (Walbaum), are significant viral pathogens of European salmonid aquaculture. SAV is horizontally transmitted and the virus can survive for extended periods in seawater. A lack of convincing evidence for vertical transmission coupled to the fact that the SPD virus (SPDV) occurs in historically infected sites irrespective of fallow period duration suggests that a substantial reservoir of infection exists in the marine environment. We used a highly sensitive real-time PCR (qPCR) assay targeting a region of the SAV nsP1 gene to screen wild marine fish species for the presence of SAV in an attempt to identify such a potential reservoir. Screened fish species were caught in the vicinity of aquaculture activity in an area with a previous history of SAV infection (Shetland Isles, Scotland). SAV RNA was detected in internal organs (kidney and heart) from the flatfish species common dab Limanda limanda, long rough dab Hippoglossoides platessoides, and plaice Pleuronectes platessa. Based on these findings, sampling was extended to an area remote from aquaculture activity (Stonehaven Bay, NE coast of Scotland) from where heart tissues obtained from common dab also tested positive. While no virus could be cultivated from these samples, qPCR detections were shown to be SAV-specific by sequencing of an alternative gene region (E2) to that targeted by the qPCR assay. Analysis of these nucleotide sequences revealed minor differences to those previously obtained from farmed salmon, and subsequent phylogenetic analysis of an E2 dataset demonstrated a subtype V-like sequence.

Pancreas disease (PD) in sea-reared Atlantic salmon, Salmo salar L., in Norway; a prospective, longitudinal study of disease development and agreement between diagnostic test results

A prospective longitudinal study was performed on three cages at each of three Norwegian Atlantic salmon seawater sites that experienced outbreaks of pancreas disease (PD). Once salmonid alphavirus (SAV) ribonucleic acid (RNA) was detected by real-time RT-PCR (Rt RT-PCR) at a site, it became detected in all studied cages and was persistently found until the end of the study period up to 19 months after first detection. SAV-specific antibodies were detected at all sites until the end of the study period and were also found at a high prevalence in broodfish at the time of stripping. No evidence of increased viral activity was detected in these broodfish. One site tested negative over several months prior to the first detection of SAV by Rt RT-PCR and SAV-specific antibody, which occurred 1 month prior to clinical manifestations of PD. Moribund fish or thin fish/runts that were sampled after the first PD diagnosis had almost twice the risk of testing positive by one or more diagnostic tests compared to that of randomly selected apparently healthy individuals. This paper describes the first detailed investigation of the disease development of PD at site and cage level in Norway, as well as an assessment of the performance and agreement of the commonly used diagnostic tests.

Salmonid alphavirus (SAV) and pancreas disease (PD) in Atlantic salmon, Salmo salar L., in freshwater and seawater sites in Norway from 2006 to 2008

A cohort study was initiated in the spring of 2006 to investigate epidemiological aspects and pathogenesis of salmonid alphavirus (SAV) subtype 3 infections and pancreas disease (PD). The aims were to assess involvement of the freshwater production phase, the extent and frequency of subclinical infections and to follow PD-affected populations throughout the entire seawater production cycle, as well as investigate possible risk factors for PD outbreaks. Fish groups from 46 different Atlantic salmon freshwater sites in six counties were sampled once prior to seawater transfer and followed onto their seawater sites. A total of 51 Atlantic salmon seawater sites were included, and fish groups were sampled three times during the seawater production phase. SAV subtype 3 was not identified by real-time RT-PCR from samples collected in the freshwater phase, nor were any SAV-neutralizing antibodies or histopathological changes consistent with PD. In the seawater phase, SAV was detected in samples from 23 of 36 (63.9%) studied sites located within the endemic region. No SAV subtype 3 was detected in samples from seawater sites located outside the endemic region. The cumulative incidence of PD during the production cycle amongst sites with SAV detected was 87% (20 of 23 sites). Average fish weight at time of PD diagnosis ranged from 461 to 5978 g, because of a wide variation in the timing of disease occurrence throughout the production cycle. Mortality levels following a PD diagnosis varied greatly between populations. The mean percentage mortality was 6.9% (+/-7.06) (range 0.7-26.9), while the mean duration of increased mortality following PD diagnosis was 2.8 months (+/-1.11) (range 1-6).

Integration of hydrodynamics into a statistical model on the spread of pancreas disease (PD) in salmon farming

Pancreas disease (PD) is an emerging disease in salmon farming caused by the salmonid alphavirus (SAV). SAV is evidently spread horizontally between neighbouring salmon farms, but whether such transmission occurs by passive drift in the water current or via fomites is not known. We tested whether hydrodynamic modelling contributes to explain the spread of PD, in which case SAV is likely to spread by passive drift. We present a simple logistic regression model that accounts for the effect of PD in the neighbourhood on the probability of acquiring PD in cohorts of farmed salmonids from an area on the west coast of Norway between 2005 and 2008. For a given cohort, we calculated infection pressure (IP) based on Euclidean distance, seaway distance or estimated water contact to sites with PD, and compared the amount of variance explained in the regression model by the different variants of IP. Water contact between a discharging farm site and a receiving site was calculated by simulating particle discharge using a hydrodynamic model. IP estimated by water contact was the best predictor of PD cases and controls in the model, which performed significantly better than IP estimated by seaway distance or Euclidean distance. Since the spread of PD in the study area was best explained by modelled water velocity, we conclude that PD is likely to be spread by passive drift of SAV in the water current.

Pancreas disease in farmed Atlantic salmon, Salmo salar L., and rainbow trout, Oncorhynchus mykiss (Walbaum), in Norway

The present paper describes, for the first time, clinical signs and pathological findings of pancreas disease (PD) in farmed Atlantic salmon, Salmo salar L., and rainbow trout, Oncorhynchus mykiss (Walbaum), in sea water in Norway. Similarities and differences with reports of PD from Ireland and Scotland are discussed. Samples of 68 rainbow trout from disease outbreaks on 14 farms and from 155 Atlantic salmon from outbreaks on 20 farms collected from 1996 to 2004 were included in the present study. The histopathological findings of PD in Atlantic salmon and rainbow trout in sea water were similar. Acute PD, characterized by acute necrosis of exocrine pancreatic tissues, was detected in nine Atlantic salmon and three rainbow trout. Salmonid alphavirus (SAV) was identified in acute pancreatic necroses by immunohistochemistry. Most fish showed severe loss of exocrine pancreatic tissue combined with chronic myositis. Myocarditis was often but not consistently found. Kidneys from 40% and 64% of the rainbow trout and Atlantic salmon, respectively, had cells along the sinusoids that were packed with cytoplasmic eosinophilic granules. These cells resembled hypertrophied endothelial cells or elongated mast cell analogues. Histochemical staining properties and electron microscopy of these cells are presented. SAV was identified by RT-PCR and neutralizing antibodies against SAV were detected in blood samples.

Prevalence and clinical course of BK virus nephropathy in pancreas after kidney transplant patients

The influence of BK virus nephropathy (BKVN) in pancreas after kidney (PAK) transplantation is unclear. A retrospective analysis of PAK transplants performed at our center was conducted to determine the impact of BKVN. Among 40 PAK transplants performed using sequential immunosuppression, four patients developed BKVN, as defined by a >20% rise in serum creatinine and BK viremia (BK plasma load >4 log copies/mL), at a median of 19 months following PAK. In all four patients, treatment of BKVN consisted of reduction in tacrolimus, cessation of mycophenolate mofetil, and introduction of leflunomide. With this approach, two patients experienced improvement or stabilization of renal function. The remaining two patients progressed to dialysis dependence despite treatment. Plasma BK load < or =5 log copies/mL was associated with graft preservation. Gender, age, delay between transplants, cumulative Thymoglobulin dose, and type of kidney donor were not associated with BK virus infection. Pancreas graft rejection or dysfunction was not observed with the above immunosuppression modification. Mean amylase and lipase > or =6 months following BKVN treatment remained normal. BKVN is an important cause of kidney allograft loss in PAK patients. Screening and early treatment of BKVN may enable preservation of kidney and pancreas grafts.

Epidemiological observations of pancreas disease of farmed Atlantic salmon, Salmo salar L., in Ireland

Epidemiological investigations into the pancreas disease (PD) of farmed salmon were conducted on populations of Atlantic salmon reared in Ireland during 2003 and 2004. The investigations surveyed all marine salmon farms operating in Ireland through a detailed questionnaire with follow-up farm visits. Information was gathered on 21 populations of fish in 2003 and 14 populations in 2004. Thirteen of the 21 populations suffered PD in 2003 and 12 of the 14 in 2004. The mean mortality due to PD on affected farms was 18.8% in 2003 and 14.8% in 2004 and the loss of growth due to PD was estimated at 11.4% over the 2-year period. The highest risk periods for outbreaks of PD were early summer and early autumn and the farms most seriously affected by PD mortality were in the western counties of Ireland. Factors which showed an indication of association with a PD outbreak or high mortality during a PD outbreak were: livestock movement to another sea site, high feeding rate prior to any PD outbreak, the presence of another PD positive farm in the same water body, greater than 250000 fish on a site, a previous history of PD on a site, a high sea lice burden, and sites located in the western regions of Ireland which reared a specific strain of salmon.

Reovirus delays diabetes onset but does not prevent insulitis in nonobese diabetic mice

Mice infected with reovirus develop abnormalities in glucose homeostasis. Reovirus strain type 3 Abney (T3A) was capable of systemic infection of nonobese diabetic (NOD) mice, an experimental model of autoimmune diabetes. Reovirus antigen was detected in pancreatic islets of T3A-infected mice, and primary cultures of pancreatic islets from NOD mice supported T3A growth. Significantly fewer T3A-infected animals compared to uninfected controls developed diabetes. However, despite the alteration in diabetes penetrance, insulitis was evident in T3A-infected mice. These results suggest that viral infection of NOD mice alters autoimmune responses to beta-cell antigens and thereby delays development of diabetes.

In infectious pancreatic necrosis virus carrier Atlantic salmon, Salmo salar L., post-smolts, almost all kidney macrophages ex vivo contain a low level of non-replicating virus

The level of infection by infectious pancreatic necrosis virus (IPNV) of kidney macrophages from 12 asymptomatic carrier Atlantic salmon post-smolts was studied. Kidney leucocytes were fractionated on 34/51% Percoll gradients, allowed to adhere to plastic wells overnight, washed to remove non-adherent cells and cultured for up to 7 days with or without renewal of medium on day 3. On day 1, supernatants were harvested, macrophages were counted, lysed and IPNV in the supernatants and lysates was titred in chinook salmon embryo (CHSE-214) cells. The multiplicity of infection ranged between 1:2.2 and 1:7.4 (virus:macrophages). On day 3, the titres of IPNV in macrophage lysates decreased and in wells where the medium was renewed on day 3, IPNV was no longer detectable on day 7. In the supernatants, one fish was positive for IPNV on day 1, four fish on day 3 but none were detectably positive on day 7. In parallel wells in which the medium was not renewed, on day 7 IPNV was detected in macrophage lysates of three fish and the supernatants were also IPNV positive in two of these fish. This suggests that virus might be shed from infected macrophages and then reinfect other macrophages. When macrophages were serially diluted in wells and cultured for 24 h, IPNV could be cultured from macrophage lysates of wells containing between two and 70 macrophages. These results indicate that a very high proportion of the adherent kidney macrophages must be infected with very few non-replicating virions.

New subtype of salmonid alphavirus (SAV), Togaviridae, from Atlantic salmon Salmo salar and rainbow trout Oncorhynchus mykiss in Norway

In Europe, 2 closely related alphaviruses (Togaviridae) are regarded as the causative agents of sleeping disease (SD) and salmon pancreas disease (SPD): SD virus (SDV) has been isolated from rainbow trout Oncorhynchus mykiss in France and the UK, while SPD virus (SPDV) has been isolated from salmon Salmo salar in Ireland and the UK. Farmed salmonids in western Norway also suffer from a disease called pancreas disease (PD), and this disease is also believed to be caused by an alphavirus. However, this virus has not yet been characterised at the molecular level. We have cultured a Norwegian salmonid alphavirus from moribund fishes diagnosed with cardiac myopathy syndrome (CMS) and fishes diagnosed with PD. The virus has also been found in salmon suffering from haemorrhagic smolt syndrome in the fresh water phase. The genomic organisation of the Norwegian salmonid alphavirus is identical to that in SPDV and SDV, and the nucleotide sequence similarity to the other 2 alphaviruses is 91.6 and 92.9%, respectively. Based on the pathological changes, host species and the nucleotide sequence, we suggest naming this virus Norwegian salmonid alphavirus (NSAV). Together with SPDV and SDV it constitutes a third subtype of salmonid alphavirus (SAV) species within the genus Alphavirus, family Togaviridae.

Gabexate mesilate and/or octreotide in human immunodeficiency virus-associated pancreatic abnormalities

BACKGROUND

Human immunodeficiency virus (HIV)-associated pancreatic alterations are frequent, but poorly investigated, notwithstanding their potential consequences on the course and management of HIV infection. No epidemiological or clinical data on pancreatic alterations have been published since the introduction of highly active antiretroviral therapy, and no indications of the pharmacological management of symptomatic or prolonged laboratory pancreatic abnormalities have been reported.

AIM

To investigate the therapeutic role of gabexate mesilate and octreotide in HIV-infected patients with elevated, symptomatic or instrumentally confirmed pancreatic anomalies persisting for more than 3 months.

METHODS AND RESULTS

An open-label, prospective, 5-year case-control study was conducted involving 185 consecutive patients with pancreatic alterations. Treatment of patients with severe laboratory and/or clinical involvement with low-dose gabexate mesilate and/or somatostatin was effective and safe and led to a lower recurrence rate and a better tolerability of concomitant drug regimens compared with supportive therapy taken by control patients. Combined gabexate-octreotide proved to be more active than single drug administration.

CONCLUSIONS

Epidemiological and therapeutic data on the frequency, risk factors and clinical significance of pancreatic abnormalities during HIV infection are required, as are studies investigating the need for and choice of antisecretory and/or antiprotease compounds.

Comparison of two aquatic alphaviruses, salmon pancreas disease virus and sleeping disease virus, by using genome sequence analysis, monoclonal reactivity, and cross-infection

Cell culture isolates of salmon pancreas disease virus (SPDV) of farmed Atlantic salmon and sleeping disease virus (SDV) of rainbow trout were compared. Excluding the poly(A) tracts, the genomic nucleotide sequences of SPDV and SDV RNAs include 11,919 and 11,900 nucleotides, respectively. Phylogenetic analysis places SPDV and SDV between the New World viruses of Venezuelan equine encephalitis virus and Eastern equine encephalitis virus and the Old World viruses of Aura virus and Sindbis virus. When compared to each other, SPDV and SDV show 91.1% nucleotide sequence identity over their complete genomes, with 95 and 93.6% amino acid identities over their nonstructural and structural proteins, respectively. Notable differences between the two viruses include a 24-nucleotide insertion in the C terminus of nsP3 protein of SPDV and amino acid sequence variation at the C termini of the capsid and E1 proteins. Experimental infections of Atlantic salmon and rainbow trout with SPDV and SDV confirmed that the disease lesions induced by SPDV and SDV were similar in nature. Although infections with SPDV and SDV produced similar levels of histopathology in rainbow trout, SDV induced significantly less severe lesions in salmon than did SPDV. Virus neutralization tests performed with sera from experimentally infected salmon indicated that SPDV and SDV belonged to the same serotype; however, antigenic variation was detected among SDV and geographically different SPDV isolates by using monoclonal antibodies. Although SPDV and SDV exhibit minor biological differences, we conclude on the basis of the close genetic similarity that SPDV and SDV are closely related isolates of the same virus species for which the name Salmonid alphavirus is proposed.

Pathogenesis and immune response in Atlantic salmon (Salmo salar L.) parr experimentally infected with salmon pancreas disease virus (SPDV)

Atlantic salmon parr were injected intraperitoneally with salmon pancreas disease virus (SPDV) grown on CHSE-214 cells. The viraemia, the histopathological changes in target organs and some immune parameters were taken at intervals up to 30 days post-infection (dpi). The earliest kind of lesion was necrosis of exocrine pancreas, appearing as soon as 2 dpi. It progressed towards complete tissue breakdown at 9 dpi before resolving gradually. Concurrent to this necrosis, a strong inflammatory response was in evidence from 9 dpi in the pancreatic area for a majority of fish. A necrosis of the myocardial cells of the ventricle occurred in infected fish mainly at 16 dpi and it faded thereafter. The monitoring of the plasma viral load showed a rapid haematogenous spreading of SPDV, peaking at 4 dpi, but also the absence of a secondary viraemia. No interferon (IFN) was detected following the infection of parr with SPDV, probably owing to an IFN activity in Atlantic salmon below the detection level of the technique. Neutralising antibodies against SPDV were in evidence from 16 dpi and they showed a time-related increasing titre and prevalence. The phagocytic activity in head-kidney leucocytes was always significantly higher in the infected fish than in the control fish, being particularly high by 9 dpi. Lysozyme and complement levels were both increased and they peaked significantly in the infected fish at 9 and 16 dpi respectively. These results demonstrated that an experimental infection of Atlantic salmon parr with SPDV provoked a stimulation of both specific and non-specific immunity with regards to the viraemia and the histopathology.

Production and characterisation of monoclonal antibodies to salmon pancreas disease virus

Six mouse monoclonal antibodies (mAbs) specific to salmon pancreas disease virus (SPDV) were produced following immunisation with purified virus preparations. These mAbs and 2 mAbs resulting from an earlier investigation were characterised. None of the mAbs possessed virus neutralising activity but all reacted with 4 geographically different SPDV isolates as determined by indirect immunofluorescence. Three mAbs produced positive immunostaining with Western blots of SPDV proteins. The 4H1 mAb reacted with the 53 kDa structural E1 glycoprotein present in virus-infected cells and in gradient-purified virus. Two mAbs, 5A5 and 7B2, which exhibited unusual immunofluorescence staining of the nuclear margin, reacted with a 35 kDa protein, which is present in gradient-purified virus and which is considered to be the capsid protein. A sandwich ELISA, based on the use of mAb 2D9 for capture and a biotinylated conjugate of mAb 7A2 for detection, detected SPDV antigen in virus-infected Chinook salmon embryo-214 cells and gradient-purified virus. These mAbs may be of use in pathogenesis studies and in diagnostic test development.

Isolation of salmon pancreas disease virus (SPDV) in cell culture and its ability to protect against infection by the 'wild-type' agent

A Scottish salmon pancreas disease virus (SPDV) has been isolated and its optimum growth conditions determined. Although several fish cell lines have been tested, successful culture was achieved only with CHSE-214 cells. Cytopathic effects were observed after 5 days. The highest virus titres, calculated by microtitration assay, were reached at 15 degrees C. After 7-9 days post-inoculation, CHSE-214 cell supernatants contained between 10(7)-10(5) TCID50 ml(-1) The cultured isolate is chloroform- and pH 3.0-sensitive, and virions are 50-60 nm in diameter. These characteristics are similar to the Irish SPDV isolates. The culture isolate induced typical pancreas disease (PD) lesions in experimentally infected Atlantic salmon and convalescent fish were resistant to experimental infection with PD-infective kidney homogenates obtained by serial in vivo passages from a PD-infected farmed salmon (termed wild-type SPDV). Furthermore, fish immunised with the inactivated cultured virus were protected against a cohabitation challenge with the wild-type virus. Immunised fish sera showed virus-neutralising activity before challenge (7 weeks post-immunisation) and from 3-6 weeks post-challenge, when sera from non-immunised fish did not neutralise the virus. At 6 weeks post-cohabitation challenge, previously immunised fish had neutralising titres of up to 1:65. Following intraperitoneal (i.p.) challenge, immunised fish showed neutralising titres as high as 1:226 at 8 weeks post-challenge. Non-immunised fish injected i.p. with the wild-type virus developed serum-neutralising activity against the cultured isolate when sampled 8 weeks after infection, confirming an antigenic relationship between the wild-type and cultured virus. The results demonstrate that the tissue culture-adapted isolate of SPDV could be successfully used to protect against challenge by the wild-type virus and could therefore have potential use as an inactivated vaccine against PD.

Comparative study of in-situ cell death induced by the viruses of viral haemorrhagic septicaemia (VHS) and infectious pancreatic necrosis (IPN) in rainbow trout

The causative viruses of two diseases of rainbow trout, viral haemorrhagic septicaemia (VHS) and infectious pancreatic necrosis (IPN), exert much of their cytopathogenic effect in cell culture through the induction of apoptosis. In the present study, the TUNEL procedure was used to investigate the presence of apoptotic cells in different organs of rainbow trout infected with the viruses of VHS and IPN. VHS viral infection resulted in massive apoptosis in renal lymphoid tissue, where viral antigens were also detected. Large numbers of viral particles were observed in close proximity to apoptotic cells. Apoptosis was not detected in excretory cells of the renal tubules or in infected muscle cells. IPN virus did not induce apoptosis in the pancreas. However, the DNA degradation associated with apoptotic nuclei was observed in muscle lesions. Taken together, these results indicated that induction of apoptosis in vivo was critically influenced by the species of virus and the cell type. Moreover, it would seem likely that apoptosis contributed to the nature of the two diseases and to mortality.

Inflammatory pseudotumour of the pancreas in a child

We describe a 4-year-old girl with an inflammatory pseudotumour of the pancreas, which was preceded by varicella-zoster infection. Inflammatory pseudotumour may involve a variety of tissues, the lungs and liver being typical sites of predilection. Imaging and laboratory tests are nonspecific, and for this reason the diagnosis of inflammatory pseudotumour is rarely made prior to surgery. These benign but locally aggressive masses simulate malignancy in the majority of cases. Inflammatory pseudotumour should, therefore, be considered when a mass arises in an unusual location in the paediatric age group.

Gastrointestinal manifestations of HIV infection

Since the beginning of the AIDS pandemic, gastrointestinal (GI) problems have been among the most common features of the disease. Despite the introduction of highly active antiretroviral therapy (HAART) in 1995 and 1996, most HIV-infected patients continue to have GI complications. The clinician must be able to diagnose and treat the opportunistic gastrointestinal infections and neoplasms that occur in the advanced AIDS patient, as well as the treatment-induced symptoms and non-HIV-related GI disorders that predominate in early HIV disease. This review addresses the GI manifestations of HIV, with particular emphasis on new developments in the era of highly effective therapy.

Biochemical characterization of salmon pancreas disease virus

Salmon pancreas disease virus (SPDV) has been shown to cause severe economic losses in farmed Atlantic salmon (Salmo salar) and has been reported to occur in Europe, Scandinavia and the United States. This paper describes the biochemical characterization of SPDV in terms of its RNA and protein composition. SPDV was purified by precipitation from infected Chinook salmon embryo (CHSE-214) cell-culture supernatant and sucrose density-gradient centrifugation. Fractions containing virus were identified by an immunodot blot assay using an SPDV-specific MAb. Two major proteins with molecular masses of approximately 55 and 50 kDa, putatively identified as the E1 and E2 alphavirus glycoproteins respectively, were detected when purified virus preparations were analysed by PAGE. Radiolabelling experiments indicated that SPDV infection of CHSE-214 cells did not shut-off host-cell protein synthesis, making attempts to identify virus-specific proteins unsuccessful. However, radioimmunoprecipitation assay (RIPA) experiments showed that two SPDV-specific MAbs reacted with a protein in the 50-55 kDa range. Northern blot hybridization with cloned cDNA probes indicated that infected cells contained RNA species of approximately 11.4 and 4 kb, which correspond to the genomic and subgenomic RNAs specified by SPDV. The results described are consistent with SPDV being characterized as an alphavirus.

Localized lymphoplasmacellular pancreatitis forming a pancreatic inflammatory pseudotumor

Inflammatory pseudotumors (IPTs) of the pancreas are rare. To our knowledge, we report the first case of a pancreatic IPT composed of dense lymphocytic and plasmacellular infiltrates that histologically resembled a primary lymphoplasmacytic lymphoma of the pancreas. In addition, it is the first pancreatic IPT analyzed for latent Epstein-Barr virus, an agent implicated in the pathogenesis of IPTs of the liver and spleen.