乙型肝炎病毒在宿主内不受核苷类药物影响的机理探讨

Noneffective Mechanism of Nucleoside Analogues on Hepatitis B Virus in Tissues of Infected Ducklings

[目的]探讨乙型肝炎病毒在宿主中不受药物影响而得以长期与宿主共存的机理。[方法]以核苷类药物拉米夫定(3TC)和无环鸟苷(ACV)对鸭乙肝病毒(DHBV)感染一日龄广州麻鸭模型进行治疗,以斑点杂交法检测治疗前后和停药后鸭血清中鸭乙型肝炎病毒脱氧核糖核酸(DHBV—DNA)的变化;并提取鸭的肝、肾、脾、肺、心组织中的DNA,用聚合酶链反应(PCR)方法检测DHBV—DNA在各脏器组织中存在的情况。[结果]以斑点杂交法检测鸭血清DHBV—DNA,3TC和ACV两个治疗组在治疗后5～10 d内血清DHBV—DNA含量持续下降(与模型组比较均P<0.05),但停药后均有回升倾向;用PCR方法检测各组的肝、肾、脾、肺、心组织,显示治疗后DHBV—DNA在各脏器组织中存在的情况与模型组比无显著性差异(P>0.05)。进一步比较了斑点杂交法和PCR法检测的结果,显示斑点杂交法检测组织中病毒远不如PCR法敏感,并提示可能组织中病毒复制量很低,以致用斑点杂交法检测出现很多假阴性。[结论]乙型肝炎病毒感染宿主后,药物治疗只对宿主血清DHBV—DNA含量有影响,但未发现对肝和肝外脏器组织中的DHBV—DNA有影响,乙肝病毒不受药物影响而长期在宿主中存在并低水平持续复制,可导致宿主机体对其无法识别和清除而形成慢性感染。

[Objective] To explore the mechanism that drugs are noneffective on duck hepatitis B virus (DHBV). [Methods] Ducklings infected with DHBV for one day were treated with lamivudine (3TC) and acyclovir (ACV) . Serum DHBV deoxyribonucleic acid (DNA) level was detected by dot-blot hybridization before and after medication and after suspension of medication; DHBV-DNA level in the tissues of liver, kidney, spleen, heart and lung was examined by polymerase chain reaction (PCR) method. [Results] Serum level of DHBV-DNA in 3TC group and ACV group was decreased continuously in 5-10 days of treatment (P < 0.05 as compared with model group) and then rebounded after suspension of medication; DHBV-DNA level in the tissues did not differ from that in the model group (P > 0.05). Comparison of the two methods of dot-blot hybridization and PCR showed that the latter was more sensitive than the former, which indicated the replication of DHBV was low in the tissues. This led to more false negatives by dot-blot hybridization [Conclusion] Drugs have action on serum level of DHBV-DNA in the host but have no influence on DHBV-DNA level in the liver and extrahepatic tissues. HBV can exist in the host and keep persistent replication , therefore the host is unable to recognize it and chronic infection ensures. It is suggested that the monitor of DHBV-DNA level in the tissues by PCR be used as one of the parameters of evaluating long-lasting effect of drugs for HBV.