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

单纯疱疹病毒1型（HSV-1）在神经母细胞瘤细胞系IMR-32中增殖受到抑制，该细胞系经环AMP （cAMP）在37℃下预处理6天，并在cAMP存在下培养。浓度为0.5 ~ 1.0 mM时效果最大，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。血清培养对cAMP的抑制作用有影响。结果表明，血清中含有拮抗cAMP抑制作用的因子。在本研究中，选取大量血清用于降低camp诱导的HSV-1增殖限制的波动。从受感染的细胞培养物中去除cAMP引起病毒增殖的启动，表明cAMP的抑制作用是可逆的。当孵育温度降至34.5℃时，即使存在cAMP，病毒也能增殖。孵育温度从34.5℃升高到38.5℃，强烈抑制病毒增殖。在38.5℃孵育时，无论cAMP的存在与否，游离病毒的感染性均下降。而在38.5℃孵育时，除去cAMP后，病毒仍能生长。因此，camp诱导的病毒增殖限制不是由于感染细胞产生的成熟病毒失活，而是由于抑制了成神经细胞瘤细胞中的病毒生长。在去除cAMP的同时，在感染培养物中加入<Ca^(2+)>拮抗剂维拉帕米，病毒增殖仍然受到限制。如果将phobol酯添加到camp处理的细胞培养物中，则不会诱导病毒增殖。在camp处理的神经母细胞瘤细胞中，限制HSV-1增殖的机制尚不清楚。

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.