adrialop

• Guslund, Naomi Croft; Jonsson, Alexandra; Krabberød, Anders Kristian; Porras, Adrian Lopez; Nørstebø, Simen Foyn & Sørum, Henning [Show all 9 contributors for this article] (2026). IgM-mediated protection drives early B-cell activation and mucosal containment of Vibrio anguillarum in Atlantic cod (Gadus morhua). Frontiers in Immunology. 17. doi: 10.3389/fimmu.2026.1771403. Full text in Research Archive Show summary

  Background: Atlantic cod lack functional MHC class II and CD4, raising fundamental questions about how vaccination generates protection in this species. Methods: We combined single-cell transcriptomic profiling of splenic cells with qRT-PCR across complementary active vaccination and passive serum-transfer experiments to define cellular and transcriptional correlates of immunity to Vibrio anguillarum. Results: Bath-vaccinated fish and recipients of immune serum showed effective containment of infection, with bacterial signals largely restricted to gills and minimal detection in spleen or head kidney, whereas naïve fish frequently developed high systemic bacterial loads by day 3 post-infection. All groups exhibited increased splenic macrophage abundance following challenge, but only naïve fish showed strong and sustained inflammatory activation, consistent with their higher pathogen burden. Vaccinated fish and immune-serum recipients displayed only transient or weak myeloid responses despite similar early neutrophil activation. Across both experimental models, a transcriptionally distinct B-cell subset expanded at the peak of infection. This population showed increased immunoglobulin and MHC class I expression together with innate sensing features, consistent with an activated B-cell state. Although this B-cell subset increased in all groups, the largest expansions were observed in vaccinated fish and immune-serum recipients. Overall, these findings are consistent with antigen-specific IgM enhancing early B-cell activation and contributing to protection against V. anguillarum through coordinated humoral and innate-like B-cell responses. Discussion: These findings identify an antibody-driven mode of immune coordination that operates independently of classical CD4+ T-cell help and provide insight into how effective vaccination can be achieved in vertebrates with divergent adaptive immune architectures.

• Jonsson, Alexandra; Porras, Adrian Lopez; Nørstebø, Simen Foyn; Guslund, Naomi Croft; Sørum, Henning & Qiao, Shuo-Wang [Show all 7 contributors for this article] (2025). Protective IgM-mediated immunity against Vibrio anguillarum in Atlantic cod with evolutionary losses of mhc class II and cd4. Frontiers in Immunology. 16. doi: 10.3389/fimmu.2025.1579541. Full text in Research Archive Show summary

  The unique adaptive immune system of the Atlantic cod ( Gadus morhua ), with genetic loss of the mhc class II and cd4 , poses questions about the protective role of specific antibodies in this species. We investigate the IgM response against Vibrio anguillarum , a common pathogen in aquaculture. Juvenile Atlantic cod were bath-immunized with formalin-fixed V. anguillarum serotype O2a. Vaccinated cod were fully protected against lethal vibriosis when challenged by immersion with serotype O2a and partially protected against challenge with serotype O2b. Serum IgM from immunized cod reacted specifically with V. anguillarum O2a in ELISA, with some crossreactivity towards the O2b serotype. Bath-immunized cod were also protected against intracelomic challenge with V. anguillarum O2a, supporting the induction of systemic immunity by bath vaccination. Passive transfer experiments were conducted to evaluate the protective efficacy of IgM. Naive cod that received total serum or purified IgM from immunized donors were protected against lethal vibriosis; whereas, naive cod that received naive serum were not protected. Western blotting revealed that these protective antibodies recognized a proteinase K-sensitive antigen rather than lipopolysaccharides. These insights enhance our understanding of cod immunity and provide guidance for developing future vaccination strategies in aquaculture.

• Porras, Adrian Lopez; Jonsson, Alexandra; Qiao, Shuo-Wang & Johansen, Finn-Eirik (2025). Sustained T cell-independent type 2 antibody response in a naturally MHC II-deficient teleost fish. Developmental and Comparative Immunology. ISSN 0145-305X. 164. doi: 10.1016/j.dci.2025.105330. Full text in Research Archive Show summary

  Atlantic cod (Gadus morhua) is well-known to show poor specific antibody responses after immunization, despite having high natural IgM levels. Unlike mammals and nearly all examined other vertebrates, cod lack the MHC II-CD4 axis required for T cell-dependent (TD) antibody responses. We evaluated the cod's antibody response to hapten carriers inducing T cell-independent (TI) and TD responses in mammals. Remarkably, cod generated strong hapten-specific IgM levels against hapten linked to the TI-2 antigens ficoll or dextran. Specific IgM levels plateaued 6–9 weeks after a single immunization and remained stable for six months. The serum half-life of IgM was 4 days, indicating continuous IgM production during this period. These findings reveal unique immune mechanisms in Atlantic cod, enhancing our understanding of vertebrate immunology and aiding the development of novel vaccination strategies in aquaculture.

• Porras, Adrian Lopez; Berg, Ragnhild Stenberg; Burgerhout, Erik; Hansen, Øyvind J; Györkei, Ádám & Qiao, Shuo-Wang [Show all 7 contributors for this article] (2024). CRISPR-Cas9/Cas12a-based genome editing in Atlantic cod (Gadus morhua). Aquaculture. ISSN 0044-8486. 581, p. 1–9. doi: 10.1016/j.aquaculture.2023.740440. Full text in Research Archive Show summary

  Aquaculture is the fastest-growing food sector worldwide but faces sustainability challenges that need to be addressed in many ways, including genetic enhancement. Atlantic cod has re-emerged as an aquaculture species and tools for genetic manipulation are needed. Thus, we compared five formats of CRISPR to determine which was most efficient to generate knock outs in Atlantic cod. Cas9 protein was presented in preformed ribonucleoprotein (RNP) complexes with single guide or with duplex guide RNAs or an mRNA encoding Cas9 was used with the same two formats of guide RNAs. Cas12a was tested as RNP complexes with single guide RNAs. We found Cas9 mRNA with single guide RNA to be the most efficient format to knock out both alleles of the slc45a2 gene, which resulted in an albino-like phenotype in up to 75% of surviving larvae. DNA analysis of individual larvae revealed mosaic genotypes with variable indel mutations. The mortality of injected eggs was high, resulting in low overall efficiency. Nevertheless, this study lays the foundation for further genetic and functional research using the CRISPR/Cas9 genome editing system in Atlantic cod.

• Dalum, Alf Seljenes; Kraus, Aurora; Khan, Shanawaz; Davydova, Erna; Rigaudeau, Dimitri & Bjørgen, Håvard [Show all 13 contributors for this article] (2021). High-Resolution, 3D Imaging of the Zebrafish Gill-Associated Lymphoid Tissue (GIALT) Reveals a Novel Lymphoid Structure, the Amphibranchial Lymphoid Tissue. Frontiers in Immunology. 12. doi: 10.3389/fimmu.2021.769901. Full text in Research Archive Show summary

  The zebrafish is extensively used as an animal model for human and fish diseases. However, our understanding of the structural organization of its immune system remains incomplete, especially the mucosa-associated lymphoid tissues (MALTs). Teleost MALTs are commonly perceived as diffuse and scattered populations of immune cells throughout the mucosa. Yet, structured MALTs have been recently discovered in Atlantic salmon (Salmo salar L.), including the interbranchial lymphoid tissue (ILT) in the gills. The existence of the ILT was only recently identified in zebrafish and other fish species, highlighting the need for in-depth characterizations of the gill-associated lymphoid tissue (GIALT) in teleosts. Here, using 3-D high-resolution microscopy, we analyze the GIALT of adult zebrafish with an immuno-histology approach that reveals the organization of lymphoid tissues via the labeling of T/NK cells with an antibody directed to a highly conserved epitope on the kinase ZAP70. We show that the GIALT in zebrafish is distributed over at least five distinct sub-regions, an organization found in all pairs of gill arches. The GIALT is diffuse in the pharyngeal part of the gill arch, the interbranchial septum and the filaments/ lamellae, and structured in two sub-regions: the ILT, and a newly discovered lymphoid structure located along each side of the gill arch, which we named the Amphibranchial Lymphoid Tissue (ALT). Based on RAG2 expression, neither the ILT nor the ALT constitute additional thymi. The ALT shares several features with the ILT such as presence of abundant lymphoid cells and myeloid cells embedded in a network of reticulated epithelial cells. Further, the ILT and the ALT are also a site for T/NK cell proliferation. Both ILT and ALT show structural changes after infection with Spring Viraemia of Carp Virus (SVCV). Together, these data suggest that ALT and ILT play an active role in immune responses. Comparative studies show that whereas the ILT seems absent in most neoteleosts (“Percomorphs”), the ALT is widely present in cyprinids, salmonids and neoteleosts, suggesting that it constitutes a conserved tissue involved in the protection of teleosts via the gills.

• Hawke, John P.; Daniel, Ryan; Strother, Keith; Sokolova, Yuliya; Elliott, Jacqueline & Carossino, Mariano [Show all 12 contributors for this article] (2021). Streptococcus dysgalactiae: A Pathogen of Feral Populations of Silver Carp from a Fish Kill Event. Journal of Aquatic Animal Health. ISSN 0899-7659. 33(4), p. 231–242. doi: 10.1002/aah.10138. Full text in Research Archive

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