Preliminary Study On The Effects And Mechanisms Of Immunoreactive Substances Of Shrimps

Recent years, shrimp culture suffered great damage from diseases. Recognizing the negative effect of antibiotic, emphasis was transfered to stimulate the immune system of shrimp. Immunological capability and health of shrimp is highly correlated to each other, fortunately, immunostimulants can enhance the immunocompetence of animal, which can contribute to health of animal, making them more immune to many kinds of diseases.This study mainly included three contents, the purpose is to evaluate the effectiveness of dietary Ig-Guard (shrimp), as an immunostimulants, in modulating the non-specific immunity and the resistance to WSSV for Penaeus chinensis and Litopenaeus vannamei, and impacting the LD50 of Procambarus clarkia.The first study is the effect of Ig-Guard (shrimp) on impacting the resistance to WSSV of Penaeus chinensis. Penaeus chinensis were continuously fed by basic diets containing three levels (1%, 0.5%, 0.1%)(M/M) Ig-Guard(shrimp) respectively for 21 days, and the basic diets as blank control and P280 Premix as positive control. Phenoloxidase (PO), acid phosphatase (ACP), lysozyme (UL) activity and superoxide dismutase (SOD) of the serum, and protein concentration of the serum was detected in the 7, 14, 21 day. The results suggested that these immune parameters could be improved by Ig-Guard(shrimp). At the end of the immune test, the PO, UL, SOD activity of 1% Ig-Guard (shrimp) were not higher (P>0.05) than the blank control group, ACP activity was higher (P<0.05) than the blank control group; PO, UL, ACP, SOD activity were higher significantly (P<0.01) or higher(P<0.05) than the positive control group. PO, ACP, SOD activity of 0.5% Ig-Guard (shrimp) and 0.1% Ig-Guard (shrimp) were higher significantly (P<0.01) or higher(P<0.05) than the blank control group, UL activity of 0.5% Ig-Guard (shrimp) was not higher (P>0.05) than the blank control group, UL activity of 0.1% Ig-Guard (shrimp) was higher significantly (P<0.01) than the blank control group; UL, ACP, SOD activity of 0.5% Ig-Guard (shrimp) were higher significantly (P<0.01) or higher(P<0.05) than the positive control group, PO activity was not higher (P>0.05) than the positive control group, and the activity of the four immune factors of 0.1% Ig-Guard (shrimp) were not higher (P>0.05) than the positive control group. After 21 days, they were challenged by white spot syndrome virus (WSSV). All of the immune groups and the control groups were died within 11 days, but we can find that Ig-Guard (shrimp) can delay the death of the shrimps, especially the lower dose infection group dietary of 0.1% Ig-Guard (shrimp). But when the dose of infection was higher, Ig-Guard (shrimp) can not play the role of prevention effective.The second study is the effect of Ig-Guard (shrimp) on impacting the activity of enzyme about non-special immunity and the resistance to WSSV of Litopenaeus vannamei. Litopenaeus vannamei were continuously fed by basic diets containing three levels (1%, 0.5%, 0.1%)(M/M) Ig-Guard (shrimp) respectively for 20 days, and the basic diets as blank control. Phenoloxidase (PO), acid phosphatase (ACP), alkaline phosphatase (AKP), lysozyme(UL) activity of the serum and superoxide dismutase (SOD), catalase (CAT) activity of the muscle, and protein concentration of the serum and the muscle were detected in the 5, 10, 15, 20 day. All the immune parameters of the test groups measured were higher (P<0.05) than the control group. At the end of the immune test, the phenoloxidase (PO) activity of 1% Ig-Guard (shrimp) and 0.5% Ig-Guard (shrimp) group were not higher (P>0.05) than the control group, and 0.1% Ig-Guard (shrimp) group was higher (P<0.05) than the control group; the lysozyme (UL) activity of 0.5% Ig-Guard (shrimp) group was higher (P<0.05) than the control group, and 1% Ig-Guard (shrimp) and 0.1% Ig-Guard (shrimp) group were not higher (P>0.05) than the control group; acid phosphatase (ACP) activity of 1% Ig-Guard (shrimp) was not higher (P>0.05) than the control group, while 0.5% Ig-Guard (shrimp) group and 0.1% Ig-Guard (shrimp) group were higher (P<0.05) or higher significantly (P<0.01) than the control group; alkaline phosphatase (AKP) activity of 1% Ig-Guard (shrimp), 0.5% Ig-Guard (shrimp) group and 0.1% Ig-Guard (shrimp) were higher significantly (P<0.01) than the control group; superoxide dismutase (SOD) and catalase (CAT) activity were not higher (P>0.05) than the control group. After 20 days, they were challenged by white spot syndrome virus (WSSV). The mortalities of challenging test were recorded in seven days. The relative percent survival (RPS) value of the test groups was 17.95%, 23.08%, 35.90%. This experiment indicates that Ig-Guard (shrimp) can effectively enhance the shrimps'activity of enzyme about non-special immunity, and it can also promote shrimps'resistance to WSSV.The third study is the effect of Ig-Guard (shrimp) on impacting the resistance to WSSV of Procambarus clarkia. As the animal model, Procambarus clarkii were continuously fed by basic diets containing three levels (1%, 0.5%, 0.1%)(M/M) Ig-Guard (shrimp) respectively for twenty-one days, and the basic diets as blank control. After twenty-one days, they were challenged by white spot syndrome virus (WSSV). The mortalities of crawfishes after challenged with WSSV of the same dilutions were negatively correlated with the the dose of Ig-Guard (shrimp), that is, along with the increase of the dose of Ig-Guard (shrimp), their mortalities were decline; The LD50 of the immune group was higher than the control group, further more, along with the increase of the dose of Ig-Guard (shrimp), the effectes were obvious. This experiment indicates that Ig-Guard (shrimp) can delay the time of death of crawfish, and inhibit the infectivity of WSSV to some extent.Specific immune system of shrimps is unclear, so the effects of the signal recognition proteins to defense pathogenic microorganisms are very important. To the present,β-1, 3-glucan binding proteins (βGBP) and lipolysaccharide binding proteins (LBP) were isolated successfully from shrimps, but no research of peptidoglycan recognition proteins (PGRP) of shrimps was reported. We found peptidoglycan can activate the prophondoxidase-activating system (proPO-AS) and other non-specific immunity factors of the shrimp, and can promote the resistance to WSSV. These means PGRP might exist in shrimps. To prove this conjecture, we took the methods of RT-PCR and PCR to clone PGRP of shrimps, and want to do some preliminary studies on the PGRP of shrimps. But no PGRP gene was cloned up to now, this paper will also carry out a preliminary analysis of the reasons.