Immune Efficacy of a Genetically Engineered Vaccine against Lymphocystis Disease Virus: Analysis of Different Immunization Strategies

Fish Iridoviridae: infection, vaccination and immune response

Each year, due to climate change, an increasing number of new pathogens are being discovered and studied, leading to an increase in the number of known diseases affecting various fish species in different regions of the world. Viruses from the family Iridoviridae, which consist of the genera Megalocytivirus, Lymphocystivirus, and Ranavirus, cause epizootic outbreaks in farmed and wild, marine, and freshwater fish species (including ornamental fish). Diseases caused by fish viruses of the family Iridoviridae have a significant economic impact, especially in the aquaculture sector. Consequently, vaccines have been developed in recent decades, and their administration methods have improved. To date, various types of vaccines are available to control and prevent Iridoviridae infections in fish populations. Notably, two vaccines, specifically targeting Red Sea bream iridoviral disease and iridoviruses (formalin-killed vaccine and AQUAVAC® IridoV, respectively), are commercially available. In addition to exploring these themes, this review examines the immune responses in fish following viral infections or vaccination procedures. In general, the evasion mechanisms observed in iridovirus infections are characterised by a systemic absence of inflammatory responses and a reduction in the expression of genes associated with the adaptive immune response. Finally, this review also explores prophylactic procedure trends in fish vaccination strategies, focusing on future advances in the field.

Antiviral activity of phosvitin from zebrafish Danio rerio

Lymphocystis disease virus (LCDV), a virus of Iridoviridae, can infect numerous teleost species, causing serious losses of aquaculture industry, and thus effective ways of prophylaxis and treatment are demanded. Previous studies have shown that phosvitin (Pv) is an antimicrobial agent in zebrafish, and vitellogenin, the precursor of yolk proteins including Pv, is able to neutralize virus, we thus hypothesize that Pv may have an antiviral activity. Here we clearly demonstrated that recombinant Pv (rPv) purified was capable of inhibiting the cytopathic effect in LCDV-infected cells and reducing the virus quantities in the infected cells as well as in the infected zebrafish. These data indicate that Pv possesses an antiviral activity and participates in immune defense of host against the infection by viruses like LCDV.