Mucosal and Systemic Immune Responses to Salmon Gill Poxvirus Infection in Atlantic Salmon Are Modulated Upon Hydrocortisone Injection
Permanent link
https://hdl.handle.net/10037/24104Date
2021-06-09Type
Journal articleTidsskriftartikkel
Peer reviewed
Author
Amundsen, Marit Måsøy; Tartor, Haitham; Andersen, Kathrine; Sveinsson, Karoline Overn; Thoen, Even; Gjessing, Mona Cecilie; Dahle, MariaAbstract
Salmon Gill Poxvirus Disease (SGPVD) has emerged as a cause of acute mortality in
Atlantic salmon (Salmo salar L.) presmolts in Norwegian aquaculture. The clinical phase of
the disease is associated with apoptotic cell death in the gill epithelium causing acute
respiratory distress, followed by proliferative changes in the regenerating gill in the period
after the disease outbreak. In an experimental SGPV challenge trial published in 2020,
acute disease was only seen in fish injected with hydrocortisone 24 h prior to infection.
SGPV-mediated mortality in the hydrocortisone-injected group was associated with more
extensive gill pathology and higher SGPV levels compared to the group infected with
SGPV only. In this study based on the same trial, SGPV gene expression and the innate
and adaptive antiviral immune response was monitored in gills and spleen in the presence
and absence of hydrocortisone. Whereas most SGPV genes were induced from day 3
along with the interferon-regulated innate immune response in gills, the putative SGPV
virulence genes of the B22R family were expressed already one day after SGPV exposure,
indicating a potential role as early markers of SGPV infection. In gills of the hydrocortisoneinjected fish infected with SGPV, MX expression was delayed until day 10, and then
expression skyrocketed along with the viral peak, gill pathology and mortality occurring
from day 14. A similar expression pattern was observed for Interferon gamma (IFNg) and
granzyme A (GzmA) in the gills, indicating a role of acute cytotoxic cell activity in SGPVD.
Duplex in situ hybridization demonstrated effects of hydrocortisone on the number and
localization of GzmA-containing cells, and colocalization with SGPV infected cells in the
gill. SGPV was generally not detected in spleen, and gill infection did not induce any
corresponding systemic immune activity in the absence of stress hormone injection.
However, in fish injected with hydrocortisone, IFNg and GzmA gene expression was induced in spleen in the days prior to acute mortality. These data indicate that suppressed
mucosal immune response in the gills and the late triggered systemic immune response in
the spleen following hormonal stress induction may be the key to the onset of
clinical SGPVD.
Publisher
Frontiers MediaCitation
Amundsen MM, Tartor HM, Andersen K, Sveinsson KO, Thoen E, Gjessing MCG, Dahle MK. Mucosal and Systemic Immune Responses to Salmon Gill Poxvirus Infection in Atlantic Salmon Are Modulated Upon Hydrocortisone Injection. Frontiers in Immunology. 2021;12Metadata
Show full item recordCollections
Copyright 2021 The Author(s)