Dietary chitosan nanoparticles protect crayfish Procambarus clarkii against white spot syndrome virus (WSSV) infection.

Chitosan nanoparticles have exhibited potential antibacterial activity or anticancer activity as their unique character. In this study, we investigated the effect of chitosan nanoparticles protect crayfish Procambarus clarkii against WSSV. Chitosan (from crab shell) nanoparticles were prepared by ultrafine milling. The physicochemical properties of the nanoparticles were determined by particle size measure, zeta potential analysis and scanning electron microscope observation. The total hemocyte count (THC), phenoloxidase (PO) and superoxide dismutase (SOD) activity were measured at days 1, 4, 9 and 12, and the survival rate was also recorded after WSSV challenge. The results showed that chitosan nanoparticles could enhance the survival rate of WSSV-challenged crayfish. And crayfish fed diets supplemented with 10 mg/g chitosan nanoparticles (65% mortality) showed a significantly higher survival rate when compared to the control group (100% mortality). The analysis of immunological parameters revealed that 10 mg/g chitosan nanoparticles showed significantly higher level of prophenoloxidase (proPO), superoxide dismutase (SOD) and total hemocyte count (THC) when compared to the control group. It was found that chitosan nanoparticles could inhibit WSSV replication in crayfish. Our results demonstrated that dietary chitosan nanoparticles effectively improve innate immunity and survival of P. clarkii challenged with WSSV.

Protection of Procambarus clarkii against white spot syndrome virus using inactivated WSSV.

White spot syndrome virus (WSSV) is a highly pathogenic and prevalent virus infecting shrimp and other crustaceans. The potentiality of binary ethylenimine (BEI)-inactivated WSSV against WSSV in crayfish, Procambarus clarkii, was investigated in this study. Efficacy of BEI-inactivated WSSV was tested by vaccination trials followed by challenge of crayfish with WSSV. The crayfish injected with BEI-inactivated WSSV showed a better survival (P<0.05) to WSSV on the 7th and 21st day post-vaccination (dpv) compared to the control. Calculated relative percent survival (RPS) values were 77% and 60% on the 7th and 21st dpv for 2mM BEI-inactivated WSSV, and 63%, 30% on 7th and 21st dpv for 3mM BEI-inactivated WSSV. However, heat-inactivated WSSV did not provide protection from WSSV even on 7th dpv. In the inactivation process WSSV especially their envelope proteins maybe changed as happened to 3mM BEI and heat-inactivated WSSV particles. These results indicate the protective efficacy of BEI-inactivated WSSV lies on the integrity of envelope proteins of WSSV and the possibility of BEI-inactivated WSSV to protect P. clarkii from WSSV.

A new method for quantifying white spot syndrome virus: Experimental challenge dose using TaqMan real-time PCR assay.

White spot syndrome virus (WSSV) is an important pathogen in shrimp aquaculture. The susceptibility of crayfish (Procambarus clarkii) was assessed by means of serial dilutions of a solution containing WSSV. A TaqMan real-time PCR was used to quantify the WSSV challenge dose in P. clarkii. The results showed that WSSV copies could be detected at concentrations from 1.365×10(4) to 1.129×10(9) copies/µl. The viral infectivity (LD(50)), measured as the mortality of infected crayfish, indicated 60% mortality in the 10(5) dilution group (1.524×10(5) copies/µl). TaqMan real-time PCR represents a novel standard method, based on the by quantitation of WSSV copies, for determining the appropriate concentration of WSSV for use in infection experiments.

Mechanism of anti-angiogenic activities of chitooligosaccharides may be through inhibiting heparanase activity.

Metastatic disease is the primary cause of death for most cancer patients. Angiogenesis is the formation of a new capillary network from pre-existing vessels and required for tumor vasculature. Heparanase, a beta-endoglucuronidase, assistants tumor invasion, metastasis and angiogenesis. Chitooligosaccharides (COS) is obtained by hydrolysis of chitosan. COS has been proved to be anti-angiogenesis activity. The mechanism of COS inhibits angiogenesis is not very clear, COS is hypothesized by author to be an inhibitor of heparanase.