Study On Induced Immune Response To Microbial Infection Of Chrysomya Megacephala Lavrae

Insect immunity include prevent foreign body infection physical barriers(integument, digestive tract,etc.),cavity cellular immunity in body cavity,and humoral immunity which is composed of a variety of antimicrobial peptides with immune function.The insect antibacterial peptides are kinds of insect humoral immunity.They has broad antibacterial spectrum,stable for the heat and not easy to have drug fastness.They have resistibility to both Gram+ bacteria and Gram- bacteria.Some of them even can resist virus and the tumor cells.They can be applied in the medicine and the agricultural domain. This paper takes the Chrysomya megacephala larvae as the object of study,has studied the larvae immune response which infected by microorganism.There found a method of inducing the antimicrobial peptides of C.megacephala larvae and instituted the best conditions for the induction.This paper has isolated,purified and tested bioactivity for the antimicrobial peptides of C.megacephala larvae,and made the following findings.1.By the experiment of using different microorganisms to infect different instar larvae of C.megacephala,The results showed that the mortality decreased as the dose increased,but the pupation rate increased.The larvae showed different types of immune response to the infection of different microorganisms.2.By antibacterial activity test of C.megacephala larvae hemolymph extracts that without induced,we found that it has weak antibacterial activity,which suggested that there has antibacterial activity materials in the body of C.megacephala larvae. This active materials has good heat resistance,but antimicrobial peptides are low content.3.Larvae of C.megacephala were induced by five invasion methods,including immersion,puncture by bacterial-carried needle,UV light and ultrasound,and the effect of different induction source to the antibacterial activity of antibacterial peptide of C.megacephala larvae was studied.The results showed that puncture by bacterial-carried needle was the best inducement method,its inhibitory effect was superior than other methods.To deal with different induction time,24h after the induction of antimicrobial peptides was found in the best inhibition. 4.The extract of induced antimicrobial peptides was purified by Sephadex G50,and the antibacterial activity,ability of heat resistance and cold resistance was also tested for each component that has a peak.The results showed that at 280nm,the absorption peak value of 0.6-0.7 has the better antibacterial activity.The antimicrobial peptides after purification have the higher antibacterial activity,by the heat resistance and freeze-thaw resistance measurement is also found to have good stability.