High gene expression of inflammatory markers and IL-17A correlates with severity of injection site reactions of Atlantic salmon vaccinated with oil-adjuvanted vaccines

<p>Abstract</p> <p>Background</p> <p>Two decades after the introduction of oil-based vaccines in the control of bacterial and viral diseases in farmed salmonids, the mechanisms of induced side effects manifested as intra-abdominal granulomas remain unresolved. Side effects have been associated with generation of auto-antibodies and autoimmunity but the underlying profile of inflammatory and immune response has not been characterized. This study was undertaken with the aim to elucidate the inflammatory and immune mechanisms of granuloma formation at gene expression level associated with high and low side effect (granuloma) indices.</p> <p>Groups of Atlantic salmon parr were injected intraperitoneally with oil-adjuvanted vaccines containing either high or low concentrations of <it>Aeromonas salmonicida </it>or <it>Moritella viscosa </it>antigens in order to induce polarized (severe and mild) granulomatous reactions. The established granulomatous reactions were confirmed by gross and histological methods at 3 months post vaccination when responses were known to have matured. The corresponding gene expression patterns in the head kidneys were profiled using salmonid cDNA microarrays followed by validation by real-time quantitative PCR (qPCR). qPCR was also used to examine the expression of additional genes known to be important in the adaptive immune response.</p> <p>Results</p> <p>Granulomatous lesions were observed in all vaccinated fish. The presence of severe granulomas was associated with a profile of up-regulation of innate immunity-related genes such as complement factors C1q and C6, mannose binding protein, lysozyme C, C-type lectin receptor, CD209, Cathepsin D, CD63, LECT-2, CC chemokine and metallothionein. In addition, TGF-β (p = 0.001), IL-17A (p = 0.007) and its receptor (IL-17AR) (p = 0.009) representing T_H17 were significantly up-regulated in the group with severe granulomas as were arginase and IgM. None of the genes directly reflective of T_H1 T cell lineage (IFN-γ, CD4) or T_H2 (GATA-3) responses were differentially expressed.</p> <p>Conclusions</p> <p>Granulomatous reactions following vaccination with oil-based vaccines in Atlantic salmon have the profile of strong expression of genes related to innate immune responses. The expression of TGF-β, IL-17A and its receptor suggests an involvement of T_H17 T cell lineage and is in conformity with strong infiltration of neutrophils and macrophages into inflamed areas. Arginase upregulation shows that macrophages in these reactions are alternatively activated, indicating also a T_H2-profile. To what extent the expression of IL-17A and its receptor reflects an autoimmune vaccine-based reaction remains elusive but would be in conformity with previous observations of autoimmune reactions in salmon when vaccinated with oil-based vaccines.</p

Antigen dose and humoral immune response correspond with protection for inactivated infectious pancreatic necrosis virus vaccines in Atlantic salmon (Salmo salar L)

An enduring challenge in the vaccinology of infectious pancreatic necrosis virus (IPNV) is the lack of correlation between neutralizing antibodies and protection against mortality. To better understand the immunological basis of vaccine protection, an efficacy trial including Atlantic salmon (Salmo salar L.) vaccinated with a high antigen (HiAg) or low antigen (LoAg) dose vaccine was carried out in a cohabitation challenge model using the highly virulent Norwegian Sp strain NVI015. To pinpoint the immunological basis of vaccine protection, pathogenic mechanisms of IPNV were unraveled in control fish while obtaining feedback on mechanisms of protection in the vaccinated fish. During the incubation period, infection rates were highest in control fish, followed by the LoAg group with the lowest infections being in the HiAg group. Although both the liver and pancreas are target organs prone to tissue damage, infection in the liver was delayed until acute infection in most fish. A correlate of pathology determined as the cutoff threshold of viral copy numbers linked to tissue damage in target organs was estimated at ≥ 107.0, which corresponded with an increase in mortality. The kinetics of IFNα and Mx expression suggests that these genes can be used as biomarkers of IPNV infection progression. Mechanisms of vaccine protection involved reducing infection rates, preventing infection of the liver and reducing virus replication in target organs to levels below the correlate of pathology. Overall, the study shows that antigen dose corresponds with vaccine efficacy and that antibody levels can be used as a signature of protective immunity against pathological disease and mortality

Gene expression studies of host response to Salmonid alphavirus subtype 3 experimental infections in Atlantic salmon

Abstract Salmonid alphavirus subtype-3 (SAV-3) infection in Atlantic salmon is exclusively found in Norway. The salmonid alphaviruses have been well characterized at the genome level but there is limited information about the host-pathogen interaction phenomena. This study was undertaken to characterize the replication and spread of SAV-3 in internal organs of experimentally infected Atlantic salmon and the subsequent innate and adaptive immune responses. In addition, suitability of a cohabitation challenge model for this virus was also examined. Groups of fish were infected by intramuscular injection (IM), cohabited (CO) or kept uninfected in a separate tank. Samples of pancreas, kidney, spleen, heart and skeletal muscles were collected at 2, 4 and 8 weeks post infection (wpi). Pathological changes were assessed by histology concurrently with viral loads and mRNA expression of immune genes by real time RT-PCR. Pathological changes were only observed in the pancreas and heart (target organs) of both IM and CO groups, with changes appearing first in the pancreas (2 wpi) in the former. Lesions with increasing severity over time coincided with high viral loads despite significant induction of IFN-α, Mx and ISG15. IFN-γ and MHC-I were expressed in all tissues examined and their induction appeared in parallel with that of IL-10. Inflammatory genes TNF-α, IL-12 and IL-8 were only induced in the heart during pathology while T cell-related genes CD3ε, CD4, CD8, TCR-α and MHC-II were expressed in target organs at 8 wpi. These findings suggest that the onset of innate responses came too late to limit virus replication. Furthermore, SAV-3 infections in Atlantic salmon induce Th1/cytotoxic responses in common with other alphaviruses infecting higher vertebrates. Our findings demonstrate that SAV-3 can be transmitted via the water making it suitable for a cohabitation challenge model.</jats:p

The Immunogenicity of Irradiated Theileria Parva( Katete) Sporozoites in the Immunisation of Cattle against Malignant Theileriosis

The effect of irradiation on the Katete stock of Theileria parva sporozoites either directly (stabilate form) or indirectly (in their tick vectors) was compared to the 'infection and treatment' method of immunisation of cattle against malignant theileriosis. Fifteen steers were randomly divided into five groups using a computerised random number generator. The first group comprising three steers was immunised with T. parva sporozoites harvested from Rhipicephalus appendiculatus ticks and then irradiated at 8.4 krads using the Cobalt source. In the second group, four steers were immunised with T. parva sporozoites irradiated at 20 krads in their R. appendiculatus tick vectors. The third and fourth groups consisting of three steers each were immunised with non-irradiated T. parva sporozoites. In addition, the fourth group was also treated with tetracycline (infection and treatment). The fifth group (control) with two steers was introduced during the challenge of immunised animals and was treated with lethal doses of T. parva stabilates only. The steers in all experimental groups, except the control, resisted lethal challenge with homologous T. parva stabilates. Mild and moderate reactions were observed in the group of steers immunised with stabilates produced from T. parva sporozoites irradiated in their tick vectors (group two) and non-irradiated stabilates only (group three), respectively. Steers in the control group died from East Coast fever. The best results were obtained from the groups of steers immunised with directly irradiated T. parva sporozoites and non-irradiated stabilates with concurrent tetracycline therapy. There was no statistically significant difference(P>0.05) between the infection and treatment method of immunisation and that of directly irradiated stabilates. Estimates of costs showed that farmers would save between $0.39 (calf) and$2.39 (adult) per animal if they used irradiated stabilate instead of tetracycline in the immunisation

Sequence similarities of the capsid gene of Chilean and European isolates of infectious pancreatic necrosis virus point towards a common origin

The Chilean salmonid industry was developed by importing breeding materials, a practice still in effect due to deficits in the national supply of roe. Importation of breeding materials is often associated with the transmission of pathogens. The objectives of this study were to compare the infectious pancreatic necrosis virus (IPNV) isolates from Chile to those of European origin and to determine the diversity of the Chilean IPNV. The VP2 genes of IPNV from Chilean fish (whose eggs originated from Scotland, Iceland and Norway) were compared to isolates from fish in Norway and Ireland. The results show that the isolates are identical (97–99 %) and cluster into one genogroup. Our findings support previous reports of association between the trade-in breeding materials and transmission of pathogens. Furthermore, our results demonstrate the genotypic diversity of Chilean IPNV isolates. These findings have important implications for IPNV disease diagnosis and control in Chile.</jats:p