Studies on the restriction of herpes simplex virus type 1 multiplication in neuroblastoma cells

在37 ℃下用环腺苷酸（cAMP）预处理6天并在cAMP存在下培养的神经母细胞瘤细胞系IMR-32中，单纯疱疹病毒1型（HSV-1）的增殖受到限制。在0.5至1.0 mM的浓度下获得最大效应。该效应对cAMP和神经母细胞瘤细胞类型具有特异性。当MOI大于0.01或培养基中胎牛血清浓度大于1%时，cAMP的抑制作用减弱。用于培养的血清批次影响cAMP的抑制作用。结果表明，血清中含有拮抗cAMP抑制作用的因子。本研究用选定的血清批次来降低cAMP对HSV-1增殖的抑制作用，从感染细胞培养物中去除cAMP引起病毒增殖的启动，表明cAMP的抑制作用是可逆的。当温育温度降低到34.5 ℃时，甚至在cAMP存在下也发生病毒增殖。将孵育温度从34.5 ℃升高至38.5 ℃强烈抑制病毒增殖。如果悬浮液在38.5 ℃下孵育，则游离病毒的感染性降低，而不管是否存在cAMP。另一方面，当从培养基中除去cAMP时，甚至在38.5 ℃下也观察到病毒生长。因此，cAMP诱导的病毒增殖抑制不是由于感染细胞产生的成熟病毒失活，而是由于神经母细胞瘤细胞中病毒生长受到抑制，当在去除cAMP的同时向感染的培养物中加入维拉帕米（<Ca^（2+）>拮抗剂）时，病毒增殖仍然受到抑制。佛波酯不诱导病毒增殖，如果药物被添加到cAMP处理的细胞培养物。cAMP处理的神经母细胞瘤细胞中HSV-1增殖的限制机制仍有待澄清。

Multiplication of herpes simplex virus type 1 (HSV-1) was restricted in neuroblastoma cell line IMR-32 pretreated with cyclic AMP (cAMP) at 37 C for 6 days and cultured in the presence of cAMP. Maximum effect was obtained at a concentration of 0.5 to 1.0 mM. The effect was specific to cAMP and neuroblastoma cell-type. The inhibitory effect of cAMP was reduced, if MOI was raised over 0.01 or if the concentration of fetal bovine serum in medium was increased above 1%. Serum lots used for cultivation influenced the inhibitory effect of cAMP. The finding indicated that serum contains factor(s) antagonizing the inhibitory effect of cAMP. In this study the selected lots of serum were employed to reduce a fluctuation of cAMP-induced restriction of HSV-1 multiplication.Removal of cAMP from infected cell cultures caused the initiation of viral multiplication, indicating that the inhibitory effect of cAMP was reversible. When the incubation temperature was lowered to 34.5 C, the viral multiplication occurred even in the presence of cAMP. A shift-up of incubation temperature from 34.5 to 38.5 C strongly inhibited the viral multiplication. The infectivity of free virus decreased irrespective of the presence or absence of cAMP, if the suspension was incubated at 38.5 C. On the other hand, the viral growth was observed even at 38.5 C, when cAMP was removed from the culture medium. Therefore, cAMP-induced restriction of viral multiplication was not due to inactivation of mature virus yielded from infected cells but due to inhibition of viral growth in neuroblastoma cells.Viral multiplication remained to be restricted, when verapamil, <Ca^(2+)> antagonist, was added to the infected culture at the time cAMP was removed. Phorbol ester did not induce viral multiplication, if the drug was added to cAMP-treated cell cultures. The mechanism of restriction of HSV-1 multiplication in cAMP-treated neuroblastoma cells remains to be clearified.