United States channel catfish (Ictalurus punctatus) production has declined by nearly 50% since its peak of approximately 300 million kg in 2003, largely due to low-cost imports and recurrent infectious diseases. Channel Catfish Virus (CCV) is particularly destructive to fry and fingerlings, causing rapid and severe mortality. Current control strategies rely primarily on biosecurity and environmental management, while antibiotics and medicated feeds are ineffective against CCV. Here, we evaluated a long-term, sustainable genetic approach to enhance antiviral resistance using antimicrobial peptide (AMP) transgenesis in channel catfish. Cathelicidin (Cath), derived from alligator, was integrated into the catfish genome using CRISPR/Cas9-assisted microinjection. First-generation (F₁) fingerlings derived from cathelicidin-positive (Cath⁺) parents were used in a controlled, blinded CCV challenge.
Three replicate genetic groups were evaluated: (1) cathelicidin-transgenic families (All Cath⁺; inheritance rate 90%), (2) cathelicidin-hybrid families (Cath⁺ female × blue catfish (Ictalurus furcatus) control male; inheritance rate 45%), and (3) non-cathelicidin families (inheritance rate 0%) expressing the Fat1/Fat2 desaturase transgene (Cath⁻ female × Fat1_Fat2⁺ transgenic male; Fat1_Fat2 inheritance rate 100%). Ten fish per replicate were randomly selected, housed in mesh cages within a recirculating system, and challenged with 2.32 × 10⁶ CFU mL⁻¹ of CCV by 1 h of static immersion. Cumulative percent mortality (CPM) differed significantly among groups (one-way ANOVA: p = 0.0014, F = 23.74, R² = 0.8878). All Cath⁺ families exhibited significantly lower (p = 0.0024) mortality, 76.7%, than both hybrid and Cath⁻ × desaturase families, as both of these genetic groups experienced 100% mortality. Transgene inheritance was confirmed post-challenge by polymerase chain reaction (PCR), and all surviving fish in the All Cath⁺ families carried the cathelicidin transgene.
These findings demonstrate that cathelicidin AMP transgenesis enhances CCV resistance in channel catfish and represents a promising long-term strategy for increased sustainability in catfish aquaculture.