Characterization of proteases in the skin mucus of Atlantic salmon (Salmo salar) infected with the salmon louse (Lepeophtheirus salmonis) and in whole-body louse homogenate

AS part of an investigation of the biochemical interactions between the sal mon louse Lepeophtheirus salmonis and Atlantic salmon Salmo salar, we chara cterized protease activity in the skin mucus of noninfected Atlantic salmon and Atlantic salmon infected with L. salmonis and in an L, salmonis whole- body homogenate. Zymography revealed that mucus from infected salmon contai ned a series of low-molecular-mass (17-22 kDa) serine proteases that were n ot present in the mucus of noninfected salmon. Based on molecular mass, inh ibition studies, and affinity chromatography, the series of proteases was i dentified as being trypsin-like. Similar proteases were observed in the L. salmonis homogenate and in mucus from noninfected Atlantic salmon following a 1-hr incubation with live L. salmonis. An antibody raised against Atlant ic salmon trypsin failed to recognize any proteases in the mucus of noninfe cted salmon or infected salmon or in the L. salmonis homogenate. Collective ly, these findings suggest that the trypsin-like proteases present in the m ucus of infected Atlantic salmon were produced by L. salmonis, possibly to aid in feeding and evasion of host immune responses.As part of an investiga tion of the biochemical interactions between the salmon louse Lepeophtheiru s salmonis and Atlantic salmon Salmo salar, we characterized protease activ ity in the skin mucus of noninfected Atlantic salmon and Atlantic salmon in fected with L. salmonis and in an L, salmonis whole-body homogenate. Zymogr aphy revealed that mucus from infected salmon contained a series of low-mol ecular-mass (17-22 kDa) serine proteases that were not present in the mucus of noninfected salmon. Based on molecular mass, inhibition studies, and af finity chromatography, the series of proteases was identified as being tryp sin-like. Similar proteases were observed in the L. salmonis homogenate and in mucus from noninfected Atlantic salmon following a 1-hr incubation with live L. salmonis. An antibody raised against Atlantic salmon trypsin faile d to recognize any proteases in the mucus of noninfected salmon or infected salmon or in the L. salmonis homogenate. Collectively, these findings sugg est that the trypsin-like proteases present in the mucus of infected Atlant ic salmon were produced by L. salmonis, possibly to aid in feeding and evas ion of host immune responses.