Journal Article

DNA vaccination against viral hemorrhagic septicemia virus (VHSV) affects the capacity of kidney leukocytes to respond to a posterior viral encounter

Nogales-Mérida, Silvia, Arrogante, Aitor, Simón, Rocío, Díaz-Rosales, Patricia, Tafalla, Carolina

2026

Overview

Given the lack of antiviral prophylactic measures authorized in aquaculture, vaccination is the most effective method to prevent and control diseases provoked by viral agents. Viral hemorrhagic septicemia virus (VHSV) is an important fish pathogen, known to induce high mortality rates and large economic losses worldwide in many aquaculture fish species, including rainbow trout (Oncorhynchus mykiss). DNA vaccination against VHSV has been proven a very effective method to induce a long-term protection against the virus, yet the mechanisms through which this vaccine induces protection are still unclear. To provide further insight on this matter, in the current study, we have studied the transcriptional response of leukocytes obtained from vaccinated fish when they were exposed in vitro to the virus. For this, fish were intramuscularly (i.m.) injected with the VHSV vaccine or mock-vaccinated with either the empty plasmid or saline solution and 30 days post-vaccination sacrificed to isolate kidney and spleen leukocytes. Isolated leukocytes were then exposed or not to inactivated VHSV and the transcription of a range of genes related to the antiviral response analyzed. Supernatants were also taken from these cultures and tested for antiviral activity. Our results revealed that leukocytes obtained from vaccinated fish, especially those derived from kidney, transcribed some specific antiviral genes and specially MDA5 at higher levels when exposed to the virus, correlating with an increased secretion of antiviral factors to the supernatants. The results obtained provide important insights on how leukocytes from fish effectively vaccinated respond to a posterior viral encounter, information of value to optimize this and other antiviral vaccines for use in aquaculture and establish correlates of protection. •Kidney leukocytes from VHSV DNA vaccinated fish, when exposed to VHSV, transcribe higher levels of ifn1, ifn2 and irf7.•Kidney leukocytes from vaccinated fish, when exposed to VHSV, transcribe higher levels of mda5 than those of mock-vaccinated fish.•The differential response of DNA vaccinated fish to VHSV is more pronounced in kidney than in spleen.•Supernatants from leukocytes obtained from DNA vaccinated fish have a basal antiviral activity.

• Publisher: Elsevier Ltd,Elsevier Limited
• Subject: Animals / Antiviral activity / Aquaculture / Deoxyribonucleic acid / Disease / DNA / DNA vaccine / DNA vaccines / Economic impact / Exposure / Fish / Fish Diseases - immunology / Fish Diseases - prevention & control / Fish Diseases - virology / Genes / Glycoproteins / Hemorrhagic septicemia / Hemorrhagic Septicemia, Viral - immunology / Hemorrhagic Septicemia, Viral - prevention & control / Interferon / Kidney / Kidney - cytology / Kidney - immunology / Kidneys / Laboratory animals / Leukocytes / Leukocytes - immunology / MDA5 / Mortality / Novirhabdovirus - immunology / Oncorhynchus mykiss / Oncorhynchus mykiss - immunology / Proteins / Rainbow trout / Saline solutions / Salmon / Sepsis / Spleen / Spleen - immunology / Trout / Vaccination / Vaccines / Vaccines, DNA - administration & dosage / Vaccines, DNA - immunology / Viral hemorrhagic septicemia virus (VHSV) / Viral infections / Viral Vaccines - administration & dosage / Viral Vaccines - immunology / Viruses