Burns D P, Collignon C, Desrosiers R C
New England Regional Primate Research Center, Harvard Medical School, Southborough, Massachusetts 01772-9102.
J Virol. 1993 Jul;67(7):4104-13. doi: 10.1128/JVI.67.7.4104-4113.1993.
We previously described the pattern of sequence variation in gp120 following persistent infection of rhesus monkeys with the pathogenic simian immunodeficiency virus SIVmac239 molecular clone (D.P.W. Burns and R.C. Desrosiers, J. Virol. 65:1843, 1991). Sequence changes were confined largely to five variable regions (V1 to V5), four of which correspond to human immunodeficiency virus type 1 (HIV-1) gp120 variable regions. Remarkably, 182 of 186 nucleotide substitutions that were documented in these variable regions resulted in amino acid changes. This is an extremely nonrandom pattern, which suggests selective pressure driving amino acid changes in discrete variable domains. In the present study, we investigated whether neutralizing-antibody responses are one selective force responsible at least in part for the observed pattern of sequence variation. Variant env sequences called 1-12 and 8-22 obtained 69 and 93 weeks after infection of a rhesus monkey with cloned SIVmac239 were recombined into the parental SIVmac239 genome, and variant viruses were generated by transfection of cultured cells with cloned DNA. The 1-12 and 8-22 recombinants differ from the parental SIVmac239 at 18 amino acid positions in gp120 and at 5 and 10 amino acid positions, respectively, in gp41. Sequential sera from the monkey infected with cloned SIVmac239 from which the 1-12 and 8-22 variants were isolated showed much higher neutralizing antibody titers to cloned SIVmac239 than to the cloned 1-12 and 8-22 variants. For example, at 55 weeks postinfection the neutralizing antibody titer against SIVmac239 was 640 while those to the variant viruses were 40 and less than 20. Two other rhesus monkeys infected with cloned SIVmac239 showed a similar pattern. Rhesus monkeys were also experimentally infected with the cloned variants so that the type-specific nature of the neutralizing antibody responses could be verified. Indeed, each of these monkeys showed neutralizing-antibody responses of much higher titer to the homologous variant used for infection. These experiments unambiguously demonstrate that SIV mutants resistant to serum neutralization arise during the course of persistent infection of rhesus monkeys.
我们之前描述了恒河猴被致病性猿猴免疫缺陷病毒SIVmac239分子克隆持续感染后，gp120基因的序列变异模式（D.P.W.伯恩斯和R.C.德罗西耶，《病毒学杂志》65:1843，1991年）。序列变化主要局限于五个可变区（V1至V5），其中四个与1型人类免疫缺陷病毒（HIV-1）的gp120可变区相对应。值得注意的是，在这些可变区记录的186个核苷酸替换中，有182个导致了氨基酸变化。这是一种极其非随机的模式，表明在离散的可变结构域中存在驱动氨基酸变化的选择压力。在本研究中，我们调查了中和抗体反应是否是至少部分导致所观察到的序列变异模式的一种选择力量。在一只恒河猴感染克隆的SIVmac239后69周和93周获得的名为1-12和8-22的变异env序列，被重组到亲本SIVmac239基因组中，通过用克隆DNA转染培养细胞产生变异病毒。1-12和8-22重组体在gp120的18个氨基酸位置以及gp41的5个和10个氨基酸位置分别与亲本SIVmac239不同。从感染克隆的SIVmac239并从中分离出1-12和8-22变异体的猴子中获取的连续血清，对克隆的SIVmac239的中和抗体滴度比对克隆的1-12和8-22变异体的中和抗体滴度高得多。例如，在感染后55周，针对SIVmac239的中和抗体滴度为640，而针对变异病毒的中和抗体滴度分别为40和小于20。另外两只感染克隆的SIVmac239的恒河猴也表现出类似的模式。恒河猴也通过实验感染了克隆的变异体，以便验证中和抗体反应的型特异性。事实上，这些猴子中的每一只对用于感染的同源变异体都表现出更高滴度的中和抗体反应。这些实验明确证明，在恒河猴持续感染过程中会产生对血清中和具有抗性的SIV突变体。
