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

Abstract

As part of an investigation of the biochemical interactions between the salmon louse Lepeophtheirus salmonis and Atlantic salmon Salmo salar, we characterized 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 contained a series of low-molecular-mass (17-22 kDa) serine proteases that were not present in the mucus of noninfected salmon. Based on molecular mass, inhibition studies, and affinity chromatography, the series of proteases was identified 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 Atlantic salmon trypsin failed to recognize any proteases in the mucus of noninfected salmon or infected salmon or in the L. salmonis homogenate. Collectively, these findings suggest that the trypsin-like proteases present in the mucus of infected Atlantic salmon were produced by L. salmonis, possibly to aid in feeding and evasion of host immune responses.

The effects of Lepeophtheirus salmonis infections on the stress response and immunological status of Atlantic salmon (Salmo salar)

“…high levels of cortisol) is responsible for the lack of response of Atlantic salmon to L. salmonis [8,9]. The identification of trypsin and PGE 2 in the secretions of L. salmonis has given validity to this hypothesis [8,10,11]. Prostaglandin E 2 is a vasodilatory compound that inhibits several salmonid immune-related genes including interleukin-1b (IL-1b), cyclooxygenase-2 (COX-2), and major histocompatibility (MH) class I and II [12].…”

Sexual maturation and administration of 17β-estradiol and testosterone induce complex gene expression changes in skin and increase resistance of Atlantic salmon to ectoparasite salmon louse

“…It is noteworthy that LMPs include domains with properties of trypsin and proteinase inhibitors. Lice release proteases that may be required for nutrition or immunomodulation and inactivation of protective proteins (Firth et al, 2000), and their neutralization can be beneficial for the host. Possible importance of mucus in the salmon-louse interaction is commonly recognized.…”

Proteome reference map of the skin mucus of Atlantic cod (Gadus morhua) revealing immune competent molecules

“…The information available on a hostemucosalepathogen paradigm with respect to infection and disease susceptibility has been compelling enough to further characterize these components, primarily from the host mucus. Characterization of the mucus from fish skin has been approached from different angles, which includes the focus on the different proteases present in the skin mucus [7,8]. A study on cod skin mucus proteases has revealed that serine proteases are more predominant than metalloproteases and that overall protease activity was less compared to some fresh water fish and hag fish [9].…”