Researchers have successfully generated IgM+ B cell-deficient Atlantic salmon (Salmo salar) by employing CRISPR/Cas9 technology to knockout two immunoglobulin M (IgM) genes. This breakthrough, published on January 29, 2025, addresses significant challenges posed by infectious diseases within the Norwegian aquaculture industry.
Vaccines are typically the frontline defense against these diseases, but the need for enhanced efficacy and broader pathogen coverage has driven the scientific community to deepen their insight of the immune system's mechanics. IgM plays a central role as the main antibody, facilitating systemic immune responses.
The researchers' novel approach resulted in high mutagenesis efficiency of nearly 97%, assessed through high-throughput sequencing. Their detailed analysis revealed significant reductions of IgM+ B cells within the studied salmon's peripheral blood, fostering expectations for more accurate models to investigate immune responses at the genetic level.
The authors noted, "This work presents the first application of CRISPR/Cas9 to disrupt an immune-related gene in the F0 generation of Atlantic salmon," highlighting its importance to future fish health research.
Prior to this study, existing methods for gene editing fish had not effectively targeted immune-related genes, making this research particularly groundbreaking. Through the induction of frameshift mutations, which disrupt expected gene sequences entirely, it was observed the edited salmon exhibited about 78% fewer IgM+ B cells compared to control groups.
While the research revealed clear mutations, notable compensatory mechanisms seemed to come from increased expression of IgT, another antibody type showing heightened levels of mRNA, indicating teleost fish might adapt under immune challenges. The authors concluded, "The IgM crispants show normal or higher mRNA levels of secreted IgM, implying potential compensatory features already at play. Further exploration is required to understand their full interactions."
Flow cytometry and Western blotting confirmed these findings at both cellular and protein expression levels, unraveling the complexity of immune response adaptations. The future direction envisaged includes breeding these F0 crispants to establish homozygous knockout individuals for precise elucidation of immune functions and the role of various antibodies.
Consequently, the researchers aim to leverage their CRISPR-edited fish as models to advance aquaculture practices and optimize vaccination by deepening the overall comprehension of immunity, which could have extensive applications for managing diseases affecting salmonids and other aquaculture species.