A live attenuated vaccine to combat against KHVD
Since the late 1990th, KHV is a major threat for carp and koi industry worldwide. Because of its high fatalities and live-long persistence, eradication of the agent is hard but necessary. Many attempts were undertaken to develop a protective vaccine to combat KHVD. Unfortunately, none is approved until now in the EU or elsewhere. Therefore, a safe and reliable vaccine is needed.
In this talk we will present data on a newly established live vaccine, based on KHV from Taiwan (KHV-T). A live attenuated KHV was generated by serial passages onto CCB cells at 20°C. This vaccine virus is applicable either orally, by immersion or in a combination of both and leads to a 100% survival rate after wild-type virus challenge. It did not induce any clinical signs. Serological data revealed a successful, humoral immune response after immunization but also after challenge. Whole genome sequencing revealed some major differences to the wild type virus, and a differentiation of infected from vaccinated animals (DIVA) is possible by PCR. Moreover, a deletion in ORF150 was discovered, probably associated to the attenuation. Tested in carp model, ORF150 was demonstrated to cause attenuation if deleted. Additionally, a deletion of ORF150 converts KHV-T to an attenuated virus.