Immunostimulatory effects of dimerized lysozyme (KLP-602) on the nonspecific defense mechanisms and protection against furunculosis in salmonids.

Utilization of natural immunostimulants in fish culture offers a wide range of attractive methods for inducing and building protection against diseases. Lysozyme is an enzyme with bacteriolytic properties and is ubiquitous in its distribution among living organisms. This enzyme has antiviral, antibacterial and anti-inflammatory properties. In nature, lysozyme is found as a monomer. Lysozyme dimer is significantly less toxic than its monomer, and its high biological activity has been ascertained in cases of both viral and bacterial infections. In our study, we examined the influence of dimerized lysozyme (KLP-602) on the nonspecific cellular and humoral defense mechanisms and protection against furunculosis in rainbow trout (Oncorhynchus mykiss). We have analyzed the immunomodulatory effects of KLP-602 after experimental infection by Aeromonas salmonicida. Application of dimerized lysozyme (KLP-602) by injection stimulated the cellular and humoral defense mechanisms and provided protection against furunculosis. By contrast, mortality rate was reduced to 45% (one injection) and 25% (three injections) using 10 or 100 microg/kg KLP-602. Mortality in the untreated control group was 85%.