Protection and antibody response induced by intramuscular DNA vaccine encoding for viral haemorrhagic septicaemia virus (VHSV) G glycoprotein in turbot (Scophthalmus maximus)

Transcriptome Profiles Associated to VHSV Infection or DNA Vaccination in Turbot (Scophthalmus maximus)

“…Thus, matrix protein and RNA-directed RNA polymerase L were not significantly increased in vaccinated fish at any of the tested time points, whereas the other three genes were only detected after 72 hours post-infection and in a lower level in comparison with the other two groups of non-vaccinated fish. This reduction in the number of viral transcripts in the host cells and, as consequence, the high survival rates obtained after vaccination, might be directly related to the presence of specific neutralizing antibodies against VHSV (strain UK-860/94) one month after immunization as was previously reported [13]. However, we cannot rule out that some non-specific immune responses could also be contributing to the reduction of viral replication because it is known that the specific protection provided by VHSV and IHNV G gene DNA vaccines in fish is preceded by a protective nonspecific antiviral response, possibly related to interferon-induced mechanisms [25].…”

“…Indeed, some experiments have shown that the early immune response induced shortly after DNA vaccination against VHSV in trout is non-specific and cross-protective against other rhabdoviruses [33], [34] and even against nodavirus in turbot [35]. Although in our turbot vaccination trials we did not observe any significant difference in final mortalities between PBS and empty plasmid-injected fish groups, only a slight reduction and delay in the mortality [13], our results suggest the importance of the intrinsic adjuvant properties of the plasmids used in DNA vaccination [28] and the persistence of the non-specific immune response.…”

“…The expression vector pMCV1.4 (Ready-Vector, Madrid, Spain) was used for the construction of the vaccine containing the G glycoprotein cDNA sequence from VHSV strain UK-860/04 (GeneBank accession number AY546628) as was previously described by Pereiro et al [13]. High amounts of DNA vaccine (pMCV1.4-G 860 ) and the corresponding empty plasmid (pMCV1.4) were obtained by transformation in One Shot TOP10F’ chemically competent E. coli (Invitrogen) for its cloning following the protocol instructions.…”

“…Equal amounts of tissue from three fish belonging to the same tank and sampling point were pooled, obtaining 4 biological replicates for treatment and time point (3 turbot/replicate). The whole experimental procedure was conducted in parallel to the previously published work in which the high protective effect induced by the pMCV 1.4-G 860 vaccine was demonstrated, obtaining a relative percent survival (RPS) higher than 80% [13]. Mortality events were not recorded in the absolute control groups (non-immunized and non-infected fish) during the experiment.…”

“…Rhabdoviruses possess a surface glycoprotein G that acts as the target of virus neutralizing antibodies [12] and therefore, the most successful DNA vaccines against these viruses are based on the G glycoprotein gene under the control of the cytomegalovirus promoter (CMV). We have recently constructed a DNA vaccine encoding the G glycoprotein from VHSV strain UK-860/94 (isolated from infected turbot) and have demonstrated the high degree of protection provided against this virus as well as the production of specific neutralizing antibodies one month after vaccination [13]. However, the early immune mechanisms implicated in the success of that vaccination remain still unclear.…”