马传染性贫血病毒弱毒疫苗株与亲本强毒株的体内病毒载量与诱导保护性免疫关系的研究

Study of the Correlation between the Plasma Viral Load and Protective Immunity Induced by the Equine Infectious Anemia Attenuated Vaccine and Its Parental Virulent Strain

慢病毒免疫应答的载量阈值学说认为病毒载量决定了机体对病毒反应的类型。为了探讨马传染性贫血病毒(EIAV)血浆病毒载量与马体免疫保护的相关性,本研究利用Real-time RT-PCR方法对EIAV弱毒疫苗株(EIA-VDLV125)免疫马和EIAV强毒株(EIAVLN40)非致死剂量接种马血浆中病毒载量进行了动态比较。结果显示两组马在监测过程中皆可检测到相似水平的病毒载量(103～105copies/mL),且两者之间差异不显著(P>0.05)。以上毒株接种23周后,对马匹进行了强毒株(EIAVLN40)的致死剂量攻毒,根据攻毒后典型马传贫急性发病与否确定接种保护率。结果显示,疫苗组的保护率为67%而非致死剂量强毒组的保护率为0。以上结果提示,病毒血浆载量不是决定EIAV弱毒疫苗诱导免疫保护能力的主要或单一因素。

The threshold hypothesis of attenuated lentiviral vaccine considers that the type of host response to infections of lentiviruses depends on the viral load. To evaluate the correlation between viral loads of the attenuated vaccine strain of equine infectious anemia virus （EIAV） and their effects to induce protective immunity,longitudinal plasma viral loads in groups of horses inoculated with either an attenuated EIAV vaccine strain （EIAVDLV125） or sub-lethal dose of an EIAV virulent strain （EIAVLN40） were compared. Similar levels of plasma viral loads ranging from 10^3-10^5 copies/mL were detected from samples of these two groups of animals（P〉0.05） during 23 weeks post the inoculation. However,different responses to the challenge performed thereafter with lethal dose of the EIAV virulent strain were observed from the groups of horses inoculated with either EIAVDLV125 or sub-lethal dose of EIAVLN40. The protective efficiency was 67% （3 of 4 cases） and 0 （none of 2 cases）,respectively. Our results implicate that the viral load of EIAV attenuated vaccine is not the primary factor,or at least not the solo primary factor,to determine the establishment of immune protection.