In addition to its antiviral and immunomodulatory properties, the zebrafish β-defensin 2 (zfBD2) is a potent viral DNA vaccine molecular adjuvant

•The zebrafish beta defensin 2 (zfBD2) possesses antiviral properties against the spring viraemia of carp (SVC) virus.•The immunomodulatory properties of the zfBD2 result in protection of adult zebrafish against SVCV in vivo.•Adjuvant-like properties of zfBD2 improve the efficacy of a DNA vaccine against SVCV.•Most likely, zfBD2 modulates the zebrafish immune system through an initial activation of the master regulator NF-κB.

It is well known that β-defensins are key components of the host innate immune response against pathogens and potentially provide a link between innate and adaptive immunity. In zebrafish (Danio rerio), a vertebrate model species in numerous biomedical fields, three β-defensin isoforms were recently identified. To our knowledge, however, studies describing antimicrobial or immunomodulatory properties of any of the zebrafish β-defensins isoforms are absent today. Since it is indubitable that deepening the study of zebrafish β-defensins would be of interest in this work we investigated whether or not the zebrafish β-defensin 2 (zfBD2) has the antiviral properties described for their vertebrate counterparts. Our in vitro and in vivo studies showed that zfBD2 has antiviral activity, immunomodulatory properties and, most importantly, is a potent viral DNA vaccine molecular adjuvant. In addition, a potential relationship between zfBD2 activity and the NF-κB signaling pathway is suggested. Altogether these results show that the zebrafish could be a suitable in vivo animal model to study the roles played by β-defensin 2 in viral diseases, vaccinology and even in clinical dermatology. To note that psoriasis can be induced in zebrafish and the over-expression of β-defensin 2 is implicated in the inflammatory response associated with this human skin disorder.