Protein extract from red seaweed Gracilaria fisheri prevents acute hepatopancreatic necrosis disease (AHPND) infection in shrimp

Abstract

Outbreaks of acute hepatopancreatic necrosis disease (AHPND) have caused a decrease in shrimp production in Thailand for years. Previous studies revealed that seaweed proteins, particularly lectins, have antibacterial property. Therefore, this study aimed at evaluating the antibacterial activity of a protein extract from the red seaweed Gracilaria fisheri against Vibrio parahaemolyticus, the causative agent of AHPND. The crude protein extract from G. fisheri (GPE) was evaluated for lectin-like activities. GPE showed hemagglutination activity towards rabbit, sheep, and goose erythrocytes and required Mn2+ for the hemagglutination. GPE agglutinating activity could be inhibited by glycoproteins such as fetuin and porcine stomach mucin. The activity was stable within the temperature range 0–50 °C. GPE caused agglutination of V. parahaemolyticus in a dose dependent manner and inhibited the growth rates of the virulent bacterial strains (MIC50 = 30–38 μg mL−1). LC-MS/MS and BLAST analyses revealed that GPE contained proteins with similar amino acid sequences to lectins and phycobiliproteins from other red seaweeds. Penaeus vannamei fed with GPE showed improved survival rates and more normalized histological features of the hepatopancreas and less AP3 toxin gene expression following AHPND infection. In summary, this study demonstrates that GPE has antibacterial activity against V. parahaemolyticus, and that G. fisheri is a viable source of antibacterial substance that could be used as a feed supplement in shrimp culture to protect against or prevent AHPND.