Tucker T J, Smuts H, Eickhaus P, Robson S C, Kirsch R E
MRC/UCT Liver Research Center, Department of Medicine, University of Cape Town, South Africa.
J Med Virol. 1999 Sep;59(1):52-9.
GB virus C/hepatitis G virus (GBV-C/HGV) has been characterised as a novel flavivirus, and to date three known genotypes have been cloned. Greater genetic variation of GBV-C/HGV has been demonstrated in West African isolates, but no major deletions have been shown in the 5' non-coding region (NCR). The 5'NCR regulates protein translation via an internal ribosomal entry site (IRES). We cloned, sequenced, and analysed a 344-bp polymerase chain reaction (PCR) product, representing >60% of the 5'NCR, from 32 GBV-C/HGV PCR-positive volunteers. Wild-type virus amplicons were detected in all samples. However, 5/32 (15.6%) also amplified another fragment of between 205 and 231 bp. Sequence analysis showed all cloned PCR fragments to be GBV-C/HGV-specific. A typical deletion of 113-131 bp with minor variation was detected in isolates generating the smaller bands. RNA secondary structure analysis showed the deletions to be over domains II and III. This finding suggests that nucleotides 303-444 may be non-essential for 5'NCR functioning. Phylogenetic analysis demonstrated a novel fourth South African genotype, distinct from genotypes 1-3 with DNA distances of >0.1000. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) values for the wild-type and mutant samples were normal. This study documents the first major deletion in the 5'NCR of GBV-C/HGV, and suggests that bases 303-444 may not be essential for viral replication and ribosomal entry. A fourth GBV-C/HGV genotype appears to predominate in South Africa.
GB病毒C/庚型肝炎病毒（GBV-C/HGV）已被鉴定为一种新型黄病毒，迄今为止已克隆出三种已知基因型。在西非分离株中已证明GBV-C/HGV具有更大的遗传变异，但在5'非编码区（NCR）未发现重大缺失。5'NCR通过内部核糖体进入位点（IRES）调节蛋白质翻译。我们从32名GBV-C/HGV PCR阳性志愿者中克隆、测序并分析了一个344 bp的聚合酶链反应（PCR）产物，该产物占5'NCR的60%以上。在所有样本中均检测到野生型病毒扩增子。然而，5/32（15.6%）还扩增出了另一个205至231 bp之间的片段。序列分析表明，所有克隆的PCR片段均为GBV-C/HGV特异性。在产生较小条带的分离株中检测到一个典型的113 - 131 bp缺失，且有微小变异。RNA二级结构分析表明，缺失发生在结构域II和III上。这一发现表明，核苷酸303 - 444对于5'NCR的功能可能并非必需。系统发育分析显示，南非存在一种新的第四基因型，与基因型1 - 3不同，DNA距离>0.1000。野生型和突变型样本的丙氨酸转氨酶（ALT）和天冬氨酸转氨酶（AST）值均正常。本研究记录了GBV-C/HGV 5'NCR中的首次重大缺失，并表明碱基303 - 444对于病毒复制和核糖体进入可能并非必需。在南非，第四种GBV-C/HGV基因型似乎占主导地位。
