| White spot syndrome is a common explosive epidemic disease in shrimp.The Virus has three characteristics including wide spread hosts,high lethal speed and high mortality.Since first outbreak in China in the early 1990 s,it has caused great economic losses to the shrimp farming industry in the world.So,it has arisen the attention from the world.However,up to now,there is no effective method to defeat the virus.It is generally believed that the viral envelope proteins play a very important role in the process of virus infection due to their direct effects on the receptor related cells.Therefore,the study of WSSV envelope proteins has become a hot topic in the field of WSSV researchVP53B and VP110 are two WSSV membrane proteins with molecular weights of108 k Da and 110 k Da,and their functions are not fully understood.But the relevant research shows that VP53 B and VP110 can be combine to chitin binding protein in the prawn.VP110 also has a certain effect combined with arginine kinase and actin.In addition,some studies have indicated that VP110,VP53 B,respectively,have different degrees of sequence similarities to P74 and PIF2,which are the key factors for the oral infection of baculovirus in insects.This suggests that VP53 B and VP110 may be important in WSSV oral infection.Crayfish(Procambarus clarkia),commonly known as freshwater crayfish,is one of the most important hosts of WSSV.Compared with shrimp,the crayfish has a lot of advantages,such as easily laboratory domestication and easy accessible in four seasons.So,this crayfish is often used as an important research object of WSSV.In order to explore the roles of VP53 B and VP110 in oral infection of WSSV,we take the polyclonal antibody of VP110 and VP53 B protein fragment to combine with WSSV particles.And then inject virus-antibody complexes to crayfish body by oral and muscle.The dose of virus in crayfish was observed through the q PCR result.Take the mortality and the dose of virus into consideration,to confirm the protectiveeffect of polyclonal antibody protein in crayfish.The results showed that the protective effect of VP110 polyclonal antibody was 53%,and the protective rate of polyclonal antibody against VP53 B was up to 85%.QPCR results showed that the WSSV dose of survival crayfish in experimental group is much lower than the crayfish in negative positive group.The virus replication in crayfish is inhibited by VP110 and VP53 B polyclonal antibody.VP53 B and VP110 in WSSV oral infection show the different protective effects,especially VP53 B.VP53B is the key protein in WSSV oral infection.Take VP53 B and VP110 polyclonal antibody to incubated with WSSV,the protection rate can reach 90%,infection can be almost completely inhibited by WSSV in crayfish orally.In order to further study the role of VP53 B infection in WSSV,we predicted VP53 B protein structure by Fugue program.We found that the N terminal of 75-150 amino acid in VP53 B is quit similar to soybean trypsin inhibitor 1BBI(Bowman-Brick inhibitor).Comparing with VP53 B and 1BBI,the results show that1 BBI has a similar function of the active center,the center can inhibit chymotrypsin activity in 1BBI.That means VP53 B may inhibit protease.The protease inhibitors,on the one hand,can protect the virus protein from the shrimp intestinal digest enzyme.On the other hand it will influence the immune system in shrimp.Based on the above conjecture,using azocasein hydrolysis method to detect VP53 B of crayfish and Macrobrachium rosenbergi with protease inhibition.The results showed that VP53 B of crayfish gut protease has inhibitory effect in a certain,the inhibition efficiency was about 11%,While,in the Macrobrachium rosenbergi gut protease,it was no effect.And the related research indicates that WSSV is not effective by oral infection of shrimp,suggesting that VP53 B may have a certain role in protease inhibitors,the effect may be one of the key factor of WSSV oral infection.In addition,in another oral infection of baculovirus,there are also proteins that inhibit protease function,which also provides evidence for the existence of protease inhibition function of WSSV protein.Besides that,we also find a host receptor in shrimp may interact with VP53 B in WSSV by PIPE prediction tool.We found ERK(extracellular regulated protein kinases)in shrimp may interact with VP53 B.Through the study of WSSV envelope protein VP53 B,not only further proved this protein to be the key factor in WSSV oral infection in crayfish,but also take the aseries analysis for prediction and verification:VP53B,as the key factor in WSSV oral infection,may have the functions to influence the host and virus.This research provide experimental foundation and basis for further research on the prevention and treatment of WSSV. |
