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Lectins are important pattern recognition receptors (PRRs) and their immunological action is related to the recognition of glycans present in the pathogen cells surface. The lectins described for Litopenaeus vannamei are divided into C-type, L-type and galectin, which are mainly expressed in hepatopancreas and hemocytes. They are involved in several immune response pathways, such as phagocytosis, hemocytes recruitment, prophenoloxidase activation, and gene regulation. Although lectins have multiple immune functions, most experimental challenges focus only on WSSV and Vibrio sp. This article is a detailed review on the role of lectins in L. vannamei immune system, bringing together information on molecular structure, temporal and special expression and immune function, highlighting the wide participation of these molecules in shrimp innate immune system. • All known Litopenaeus vannamei lectins can be classified into three categories. • L. vannamei lectins are mainly expressed in hepatopancreas, gills and hemolymph. • Many L. vannamei lectins are upregulated after pathogen challenges. • L. vannamei lectins are involved in several immune pathways. • L. vannamei lectins are involved in response against bacteria and viruses. [ABSTRACT FROM AUTHOR]

The shrimp nursery is an important tool to improve the shrimp zootechnical and health performances. However, diseases and high mortality rates are the main limitations of the nursery system. Therefore, this work aimed to evaluate the influence of stocking density in the synbiotic nursery system, through growth, microbial composition, and water quality. The experiment lasted 30 days and used Penaeus vannamei postlarvae (PL10, 0.003 ± 0.001 g), fed with commercial feed (40–45% crude protein) and treatments were completely randomized with 2000, 4000, and 6000 PL‧m−3, with three replicates. Before and after stocking the postlarvae, in the experimental units (10 m3), were added a mixture of rice bran, brown sugar, commercial probiotic, and sterilized water (Synbiotic). The bottom water of tanks was drained twice a week, totaling a total 5% water exchange during the total experiment and alkalinity was corrected with calcium hydroxide (Ca(OH)2) when the alkalinity values were < 100 mg CaCO3‧L−1. Weekly, the total ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, and total alkalinity were monitored and microbiological analyses were conducted at the beginning and end. After the trial (30 days), the influence of the different stocking densities on the final weight, survival, feed conversion ratio, weekly growth rate, and productivity, with higher values for 2000 PL‧m−3. Also observed. Vibrio spp., Lactobacillus spp., total heterotrophic bacteria, and yeast count values increased by the end of the period in all shrimp stocking densities, however, with only significant differences in yeast count. In relation to ammonia, nitrite, and nitrate, no significant differences were observed in the influence of the different stocking densities. Based on the data obtained, we recommend using a density of 2000 PL‧m−3 in the nursery phase, with better zootechnical performance, water quality, and microbial composition. [ABSTRACT FROM AUTHOR]

Lectins are proteins capable of recognizing and binding to glycan in a specific way. In invertebrates, lectins are a crucial group of Pattern Recognition Proteins (PRRs), activating cellular and humoral responses in the innate immune system. The shrimp Penaeus vannamei is the main crustacean cultivated worldwide, however, the productivity of cultures is strongly affected by diseases, mainly viral ones, such as Infectious Myonecrosis (IMN). Thus, we investigated the participation of five lectins (LvAV , LvCTL4 , LvCTL5 , LvCTLU , and LvLdlrCTL) in IMNV-challenged shrimp. We verified upregulation gene profiles of lectins after IMNV-challenge, especially in hepatopancreas and gills, in addition to an increase in total hemocytes count (THC) after to 12 h post-infection (hpi). The bioinformatics characterization also revealed several sites of post-translational modification (PTM), such as phosphorylation and glycosylation, which possibly influence the action and stabilization of these lectins. We conclude that LvLdlrCTL and LvCTL5 are the lectins with greater participation in the activation of the immune system against IMNV, showing the greatest potential for PTM, higher upregulation levels, and overlapping with the THC and IMNV viral load. • The lectins of P. vannamei are able to act against IMNV. • LvLdlrCTL and LvCTL5 are the most expressed lectins after IMNV-challenge. • Post-translational modifications influence the action of lectins. • Upregulation of lectins influences hemocytes recruitment. [ABSTRACT FROM AUTHOR]

The phenomenon of viral interference during co-infections has already been reported for several aquatic species. Understanding the relationship established between different viruses and the host's immune system is necessary to understand the forms of progression and/or remediation of a disease. In the present study, we investigated viral interference in healthy shrimp naturally co-infected by the two main viruses that affect Brazilian shrimp farming, IMNV and WSSV. Through quantitative real-time PCR we have observed a reduction in IMNV viral load after overexposure to WSSV, reaching the lowest point four days post infection (dpi). That trend was similar among all tissues analyzed (gills, muscle, intestine, pleopods, hepatopancreas and hemolymph). At 13 dpi, viral loads reset to baseline levels of natural co-infection. We hypothesize that WSSV and IMNV compete for cellular receptors to promote the initiation of infection. Viral competition would explain the lower load of IMNV after challenge with WSSV, which was evident from the viral load results obtained by qPCR. The re-establishment of viral loads at 13 dpi is likely due to the shrimp's immune responses mainly to WSSV, reaching what appears to be a double viral accommodation point for these shrimp. • Evidence of viral interference between WSSV and IMNV is described. • Healthy shrimp naturally co-infected by WSSV and IMNV did not show signs of disease. • Experimental infection with a high WSSV dose induced reduction in IMNV viral load. [ABSTRACT FROM AUTHOR]

Abstract A new mucin-binding lectin (AFL) was isolated from the marine sponge Aplysina fulva. AFL was purified by affinity chromatography on Sepharose™ matrix. Its hemagglutinating activity was independent of divalent ions, and it was weakly inhibited by simple sugars. However, porcine stomach mucin was a powerful inhibitor. In SDS PAGE, piridylethylated AFL showed one band of approximately 16 kDa, whereas in the non-reducing conditions, AFL showed at least two bands of 30 and 70 kDa. Mass spectrometry MALDI-ToF analysis showed one major ion of 31,652 ± 5 Da, which corresponded to a dimer formed by subunits linked by disulfide bonds. The first fifteen amino acids of AFL were determined, and no sequence similarity was observed with any known protein. Internal sequences were obtained by mass spectrometry analysis of tryptic digestion of AFL spots. These peptides showed similarity with a lectin from marine sponge Aplysina lactuca. Secondary structure of AFL was predominantly formed by β-conformations, which were stable at variations of pH and temperature. AFL did not inhibit planktonic growth of Gram-positive and Gram-negative bacteria tested. However, the lectin did significantly reduce the biomass biofilm of the bacteria Staphylococcus aureus , S. epidermidis , and Escherichia coli. [ABSTRACT FROM AUTHOR]