Study On Security And Immune-enhancing Activity Of Lentinan

Animal diseases are doing more and more serious harm to live stock breeding.When the original disease has not been controlled a new disease is followed,in modern farming,mainly to control the development of the disease through vaccination.Most vaccines and immune enhancer need to use in order to play better results together.Many chemicals of immune enhancer have drug residues,causing the body discomfort and other shortcomings.Chinese herbal medicine can enhance immunity and non-harmful residue in animal products as immunopotentiators.In this study,safety of lentinan was observed through acute toxicity and sub chronic toxicity tests.Through a series of experiments in vitro and in vivo immune-enhancing action and mechanism were investigated.The purpose is to give the theory basis to develop lentinan as immunopotentiators.The details are divided into three parts as follows:Test 1.The determination of safety of lentinan Firstly the acute toxicity of lentinan was determined.In acute toxicity test,because the median lethal dose LD50 of LNT for mice could not be measured out,its maximum administration dosage was determined.The results showed that the mice had a transient discomfort after each dose,but returned to normal soon,no mice died within 7 days,the maximum dosage was 6000 mg/kg.The results indicated that LNT was nontoxic in fact.In long-term toxicity test,80 ICR mice which were divided into four groups,the effect of LNT on average weight,morbidity and mortality condition,hematological and serum biochemical index,organ growth and their pathological change with the autopsy and biopsy of mice were observed after the mice were intragastrically administrated with LNT at high,middle and low dosage for 14 days.The results showed that the incidence and mortality did not appear during the trial,mice in the high dosage group had the transient stress response after administration;There was no significant difference in body weight increase,and serum biochemical index,organ growth of mice in each group in the first day and 14th day after stopping administration;After 14-days continuous intragastric administra-tion,the WBS of 3 dosage groups were higher than the control group and the ALT in high-dose group presented slightly higher than the control group;Liver cells and renal tubular epithelial cells were slightly swollen,with mild granular degeneration in the first day after stopping administration,all recovered to normal in the 14th day after stopping administration.These indicated that the LNT has no obvious sub chronic toxicity.Test 2.Determination of immune-enhancing activity in vitro of lentinan Firstly the safe concentration of lentinan on peripheral blood lymphocyte in chicken was meatured,then the lentinan at 5 concentrations within safe concentration were added into cultivate system of the lymphocytes singly or together with PHA,and the changes of lymphocyte proliferation were measured by MTT assay.The study showed that when lentinans were singly added,the A570 values in lentinan at 37.5-9.375 ?g·mL-1 groups were significantly greater than that in cells control group,when lentinans were added together with PHA,the A570 values in lentinan at 37.5-9.375 ?g·mL-1 groups were significantly greater than that in PHA control group.These results indicated that lentinan at suitable concentration could significantly promote the lymphocytes proliferation alone or synergistically with PHA,thereby enhancing cell immunity.Test 3.Determination of immune-enhancing activity in vivo of lentinan Firstly the optimal dosage of LNT was determined.270 roman roosters were divided into nine groups,all with Newcastle disease vaccine iv intranasal and eye immunization except the control group at 14 day-old,second immunization at 28 days age.At the same time as first vaccination,seven dosage groups mixed drink with different concentrations of LNT for 3 days,the immune control group and blank control group without administration.On days 7,14,21 and 28 after the first vaccination,serum antibody titers and T lymphocyte proliferation were measured.The results showed that the antibody titers and the A570 value of lentinan in each dosage group at each time point were both higher than the immunized control group and the blank control group.This indicated that the enhanced immune effect of lentinan mixed drink in the 10?20 mg/kg concentrations was most significant.In clinical trials,180 14-day-old roman roosters were randomly divided into 6 groups and all chikens were immunized firstly with Newcastle disease vaccine iv intranasal and eye immunization except the control group,second immunization at 28 days of age.At the same time as first vaccination,drug groups mixed drink with lentinan respectively according 40,20,10 mg/kg concentrations and hypericin for 3 consecutive days,the immune control group and blank control group with no administration.On days 7,14,21 and 28 after the first vaccination,serum antibody titers and T lymphocyte proliferation were determined.On days 14 and 28 after the first immunization,chicken's weights of whole body,spleen,thymus and bursa were weighted for calculation of the average weight and immune organ index.The results showed that high dosage and the middle dosage of LNT at all time points,the low dosage group in some certain time points can significantly increasing serum antibody titers,stimulating lymphocyte proliferation and immune organs,promoting the chicks growth.These indicated that LNT had better immune enhancing function,the role of high-dosage and middle dosage were better.Given to little significant differences between the high and middle dosages,middle dosage(20mg/kg mixed drink)are recommended for clinical application dose.