Sockeye salmon immunoglobulin V_H usage and pathogen loads differ between spawning sites.

Area of Science:

• Immunology
• Ichthyology
• Genetics

Background:

• The Immunological Imprinting Hypothesis suggests juvenile fish develop pathogen-specific immunity at natal sites.
• Long-lived plasma cells (LLPCs) produce antibodies, conferring protection upon return to native waters.

Purpose of the Study:

• To test the Immunological Imprinting Hypothesis in Alaskan sockeye salmon populations.
• To investigate the relationship between antibody gene usage, pathogen exposure, and site-specific immunity.

Main Methods:

• Analysis of Immunoglobulin V_H gene family usage via RT-qPCR in spleen and anterior kidney samples.
• Quantification of pathogen loads and infection prevalence for Renibacterium salmoninarum, Flavobacterium psychrophilum, and Infectious Hematopoietic Necrosis Virus.
• Comparison of immunological and pathological data across six distinct spawning sites.

Main Results:

• Significant differences in V_H gene usage, pathogen prevalence, and loads were observed between spawning sites.
• Infection probability varied by location for each pathogen.
• Negative correlations were found between specific V_H gene usage patterns and pathogen loads.

Conclusions:

• Findings support the Immunological Imprinting Hypothesis, demonstrating site-dependent V_H gene usage in sockeye salmon.
• This suggests a mechanism for natural immunization, potentially protecting wild and farmed fish populations from endemic pathogens.