The safety and longevity of DNA vaccines for fish

Abstract

A plasmid that contained the cytomegalovirus (CMV)-promoter-driven lacZ reporter gene (pCMV-lacZ) remained in the epaxial muscle of five of eight goldfish as covalently closed circles, the most functional form of plasmid, for at least 70 days at 22 degrees. It was not present in the gills or elsewhere by polymerase chain reaction and was not integrated. Its expressed protein, Escherichia coli beta-galactosidase (beta-gal), which was in the injected myofibres, was detected in all the fish at 4-21 days and in about half the fish from 28 days until the end of the experiment at 70 days. The numbers of cells that secreted antibody to beta-gal in the kidney peaked at 14 days. Serum antibody and proliferating kidney cells to beta-gal were in all fish from 14 days with a plateau of the responses from 21 days onwards. The plasmid did not induce autoimmune-like antibodies to itself or to single- or double-stranded salmon testis DNA. Plasmids can therefore induce long-term foreign protein expression whilst inducing humoral and cell-mediated immunity without autoimmunity or integration in goldfish.

Luciferase expression 2 years after DNA injection in glass catfish (Kryptopterus bicirrhus)

“…1c-e). Histological analysis using glass catfish injected with a -galactosidase expressing DNA construct and examined 1 week after injection demonstrated expression in the myofibres (data not shown), which agrees with studies of Heppel et al (1998), Prenzen et al (1998) and Kanellos et al (1999). Depending on the experimental system, Anderson et al (1996b) and Heppel et al (1998) could also detect some luciferase expression after intramuscular DNA injection in other organs, namely, gills, heart, kidney, liver and spleen.…”

DNA vaccines as a tool for analysing the protective immune response against rhabdoviruses in rainbow trout

“…Usually, a specific antibody response to inoculation with virus in rainbow trout kept at 10-15 C is not detectable until several weeks post-inoculation [24,26]. Possibly, administration of the antigen in the form of a DNA vaccine can induce a more rapid response.…”

“…cytokines and natural killer cells) [17,18]. In fish, genetic immunization has been demonstrated to induce a specific antibody response, both in the case of reporter gene constructs [26] and the rhabdovirus G gene constructs [6,7,21,30]. Passive immunisation trials further indicated that neutralising antibodies in serum from genetically immunised donor fish, like sera from convalescent fish [24,25], were able to confer protection to recipient fingerlings against virus challenge [30,31].…”

Preclinical and Clinical Safety Studies on DNA Vaccines

“…36,37 Also in other studies no auto-immune mediated pathology, 13,38 or development of systemic auto-immune responses 39 were observed in normal animals after DNA vaccination. No anti-DNA antibodies were observed in sera after DNA vaccination of mice, 13,39,40 rat, 15 rabbits, 13 fish, 33 and non-human primates. 41 Certain transgenes may increase the risk of anti-DNA antibodies.…”

“…Aluminium phosphate adjuvant had no effect on the tissue distribution and integration frequency. 17 Studies in rat 31,32 or fish 33 have also not been able to demonstrate any integration event.…”