Immune response of the Pacific white shrimp, Litopenaeus vannamei, previously reared in biofloc and after an infection assay with Vibrio harveyi

Abstract

The effectiveness of the immune defense of Litopenaeus vannamei previously reared in biofloc or in a traditional clear seawater rearing system was assessed after a bacterial challenge with a pathogenic strain of Vibrio harveyi. The changes caused by its previous rearing system condition or the challenge were assessed in terms of metabolites (glucose, cholesterol, acylglycerides, protein), hemocyanin, the antioxidant defense system (superoxide dismutase, and catalase), and gene expression related to immune response (superoxide dismutase, alpha2 macroglobulin, prophenoloxidase, hemocyanin, and penaeidin‐3a). The biofloc rearing system was associated with a significant increase in protein, the antioxidant defense system, and the superoxide dismutase, alpha2 macroglobulin, and prophenoloxidase genes. For shrimp previously reared in biofloc, a positive interaction with the presence or absence (control) of V. harveyi significantly affected the hemocyanin concentration, and the interaction between the two rearing systems in shrimp challenged with the bacteria produced a higher transcription of the hemocyanin gene. Likewise, biofloc and clear seawater maintained a higher transcription of prophenoloxidase gene after the bacterial challenge. In the absence of the bacteria, shrimp of the biofloc group produced a higher transcription of the penaeidin‐3a gene. V. harveyi caused hepatopancreatic lesions and mortalities only in shrimp previously reared in clear seawater. These results suggest that biofloc helps to prevent the development of disease by improving the shrimp immune response.

Differential expression of immune‐related genes in Pacific white shrimp, Litopenaeus vannamei, previously reared in biofloc and challenged with Vibrio harveyi

“…This acclimation consisted of gradually diluting the biofloc water to obtain clear seawater without particulate matter and microbiota characteristic of this environment, discarding the effect of this microbiota during the challenge test and determining only the performance of the shrimp that respond to the infection. For experimental units, the conditions previously described by Aguilera‐Rivera et al () were used. Briefly, plastic aquaria (3 L capacity per aquarium), aeration (6.29–6.54 mg/L), heating systems (27 ± 1°C), nitrite (NO 2 = 0.04–0.06 mg/L), total ammonia nitrogen (TAN = 0.36–0.38 mg/L) and a 12‐hr light/dark photoperiod were maintained.…”

“…As previously reported by the authors (Aguilera‐Rivera et al, ), 100 µl of the V. harveyi CAIM1792 strain (CAIM‐CIAD; Mazatlan, Sinaloa, Mexico) (Soto‐Rodríguez et al, ) was prepared at different bacterial densities (10 3 , 10 4 , 10 5 , 10 6 , 10 7 and 10 8 CFU per ml) and injected intramuscularly into the third abdominal segment (Noble et al, ). The control group was injected with 100 µl of sterile TSB + 2.5% NaCl.…”

“…The protocols used for these analyses were performed according to the methods described by Aguilera‐Rivera et al (). Briefly, total RNA was extracted with TRIzol protocols (TRIzol © ; Life Technologies) and quantified at 260 and 280 nm with a NanoDrop spectrophotometer (Thermo Scientific).…”

“…The reaction was conducted at 37°C for 80 min. Subsequently, specific primers for the haemocyanin ( Hc ), alpha2 macroglobulin (a2M), prophenoloxidase (proFO) and penaeidin3a (pen3a) genes (Aguilera‐Rivera et al, ) were used for qPCR (Table ), which was carried out in a fluorometric iQ5 thermocycler (Bio‐Rad ® ) using a protocol described in a previous study (Aguilera‐Rivera et al, ) and using the gene β‐actin as the internal control (Wang, Chang, & Chen, ).…”

“…Because of the minimum water exchange, it has been suggested that biofloc prevents pathogen entry ponds and disease outbreak expansion between farms (Crab, Lambert, Defoirdt, Bossier, & Verstraete, ). In an attempt to demonstrate the benefits of biofloc on shrimp health status, recent studies have evaluated its probiotic effect and its role in mechanisms related to the immune response (Aguilera‐Rivera et al, , ; Cardona, Saulnier, Lorgeoux, Chim, & Gueguen, ; Ekasari et al, ; Ji, Yao, & Wang, ; Kim et al, ), suggesting that it is possible to prevent disease in shrimp using this sustainable rearing system. It is still unknown if there is a possible decrease in disease tolerance in shrimp reared in biofloc during an infection challenge.…”