| Pacific oyster is an important oyster breeding species in China.It has developed rapidly in Shandong Province in recent years,and has large-scale farms in Weihai,Qingdao,Binzhou,Yantai and other places.The imbalance of the expansion of breeding scale has led to the occurrence of diseases.The Ostreid herpesvirus-1(OsHV-1)is the only known herpes virus that can infect mollusks,belonging to the Mollusk herpesviruses family.The main hosts of the OsHV-1 are bivalve mollusks and gastropod mollusks.The infection of OsHV-1 will cause the growth rate of shellfish to slow down or even die,it has caused huge losses to the shellfish farming industry and harming the healthy development of China's marine shellfish farming.This paper studies the infection of two types of Pacific oysters with OsHV-1 and the analysis of the induced host immune response.The results of the study showed that the total mortality of Pacific oysters infected with OsHV-1 was 32%,and the death peak was at 48hours.Transmission electron microscopy observations showed that OsHV-1 were found in the muscle,from inside to outside Virus core,coat core,capsule.TaqMan fluorescence quantitative PCR was used to detect a load of oyster herpes virus in tissues such as the closed muscle,digestive glands,gills and mantle membrane of OsHV-1 infected diploid and triploid Pacific oysters.The results showed that each tissue contained OsHV-1,in which the closed-shell muscle,digestive gland,gill,and mantle of diploid oyster had the highest virus content at 72,84,84,and 48 h,reaching 1.33×10~5,4.45×10~4,5.68×10~4,6.11×10~4cp/mg;the closed-shell muscle,digestive gland,gill,and mantle of triploid oyster had the highest virus content on days 2,4,3,and 2,reaching 5.25×10~4,6.3×10~3,1.86×10~4,1.55×10~5cp/mg.During the observation period,the virus content of all tissues increased first and then decreased,and then stabilized,but the oysters died after 120 hours of infection,and a certain amount of OsHV-1 still exists in the living oysters;histopathological studies found After the infection,there is tissue dissolution,cell shedding and nuclear shrinkage in the connective tissues of various organs.The qPCR method was used to study the cytokine changes of triploid Pacific oysters infected with OsHV-1.The results showed that during the infection period,the expression of SOD in the oyster closed-shell muscle,digestive gland,gill and mantle membrane of the infected group was significantly higher than that in the control group;The expression of REL in digestive gland and closed-shell muscle was significantly higher than that in the control group;the expression of IL-17 in gill and the digestive gland was significantly higher than that in the control group.The MyD88 of triploid oysters in the infected group was significantly lower than that in the control group throughout the observation period.Studies showed that expression of immune-related factors in triploid Pacific oysters has changed when OsHV-1 infection,and the expression levels of pro-inflammatory cytokines,REL transcription factors,and SOD have been significantly increased,which is the resistance of oysters to the invasion of OsHV-1 The immune response of MyD88 is decreased,which may be related to the immunosuppression caused by OsHV-1.In short,OsHV-1 can infect two kinds of Pacific oysters,survive and proliferate in their bodies and bring death to them.After infection with OsHV-1,the immune-related genes of oysters were deferentially expressed.IL-17,REL and SOD increased significantly,while MyD88 showed a downward trend.This is the interaction between oysters resisting the invasion of oyster herpes virus and oyster herpes virus infection.This study confirmed that OsHV-1 can infect two kinds of Pacific oysters,and the difference between the viral load of the diploid and triploid oysters infected with the oyster herpes virus and the genes related to the triploid oyster immunity expression.This study provides a theoretical basis for the further study of the interaction between the oyster herpes virus and the host. |
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