Optimizing Conditions for Using Lectin as a Marker for Banana Shrimp Response against Pathogenic Challenge

Abstract

Lectin is one of pattern recognition proteins which plays an important role in crustacean innate immunity. It is capable of recognizing specific carbohydrates on the cell surfaces of invading microorganisms. In this study, in order to optimize conditions for using lectin as a marker for Banana shrimp response against pathogenic challenge, changes in hemagglutinating activity (HA) of lectin in the hemolymph of shrimp injected with pathogens were investigated. ELISA was also developed to quantify lectin contents in the hemolymph with the sensitivity as low as 12 ng per assay. Among the challenge of shrimp with various amounts of pathogenic bacterium, the injection with Vibrio harveyi (5×10⁷ cells) resulted in a significant increase in HA and specific HA of hemolymph lectin to the maximum level at 12 h post-injection of 6.8 and 10.5 folds, respectively and then decreased. It was agreed well with a change in levels of lectin contents determined by ELISA while total protein in the hemolymph was reduced from injection. The changes in hemolymph HA and lectin contents indicated the significant response of shrimp against pathogenic V. harveyi and toward the appropriate amount of the challenged bacterium since HAs were more or less the same in the hemolymph of shrimp during injection with saline, inactive V. harveyi or non-pathogenic Vibrio cholerae. When each shrimp was injected with white spot syndrome virus (WSSV) 10^-7 of stock, HA of hemolymph lectin increased to the highest level (3.8 folds) at 18 h post-injection and then declined. Altogether, it is concluded that changes in lectin levels in the hemolymph could be used as a marker for shrimp response toward invading pathogens, indicating the appropriate amount for pathogenic challenge that was V. harveyi 5×10⁷ cells or WSSV 10^-7 of stock