慢性 C 型肝炎為台灣肝硬化與肝癌的重要風險因子。台灣C型肝炎之盛行率約為 4.4%而大台南地區在 45 歲以上的人口更高達9%。目前C型肝炎病毒主要可分為 7 大型及 67 種亞型。正確分型的重要性對於肝臟疾病或肝外相關腎臟病變的進展以及治療的成效都有顯著的影響。在過去台灣本土的研究報告指出, 基因型 1b 約佔台灣 45-50%而 2a/2c 約佔 30-40%. 而基因型第 6 型主要分布在中國南方,香港, 越南等東南亞國家。在台灣針對第6型感染的研究報告較少。早年的報告約在整個C型肝炎族群的1-2%，且較侷限於 HIV-HCV 共同感染的靜脈毒癮患者。在最新的多中心世代研究當中顯示亞裔且肝硬化的Ｃ肝患者中，若罹患第6基因型感染者有較其他型的患者有較高的肝癌發生率。然而隨著分子診斷學的進步，我們已經了解到使用過去 line probe assay 針對 C 型肝炎病毒 5’UTR 做定序的方法並不容易將第 1 型與第 6 型病毒區分。因此有必要找尋較佳的方式將此兩種基因型區分。
本研究主要以回溯性的方式了解了本院自2014至2016年健保給付Ｃ型肝炎基因分型後本院的基因型分佈。以Abbott m2000GT II平台發現本院近三年來C型肝炎基因型分佈為：G1:49.1%, G2: 42.3% 而G6為3.9%. 但無法定型 (Indeterminate)的比例逐年升高。為了解其次亞型的分佈並瞭解目前臨床上分型方法的正確性，我們針對本院341位慢性C肝炎患者以實驗室所設計針對5’UTR_Core _E1區域的引子（primer）做進一步分析。我們發現到共有89位患者為第六型感染。這些病人某部分原來接受羅氏線性分析法(Linear Array)分型為第一行。另一部分原來接受Abbott m2000 GTII則分型為“ 無法分型”或“G1” 。我們進一步針對此89位第六型患者進行了演化樹譜分析（phylogenetic tree）發現到其次亞型分佈為6a:30位, 6w:19位以及另外40位似6g。以平均核酸變異比率發現此40位與第六行各亞型6b-6w的變異比率均<20%. 但與NCBI參考的6g變異比率最低為10.08%。
我們亟欲了解是否有病毒重組的現象產生，故應用Simplot及Bootscan兩種工具分析本院的6a, 6w及似6g三群病人。 不管是針對Core基因以及5’UTR_Core _E1較長的基因片段，6a及6w均無重組之現象。但似6g此一族群卻與6b, 6g以及某段無法分行的區域產生了重組現象。為了更加確認此一觀察，我們針對nt674至nt912以及nt184至nt674加上nt913至nt1392以ML tree證實前段與6g產生群聚(cluster)但後段則無法與任何一型產生群聚。若我們以部分NS5B片段再以Simplot及Bootscan分析8位似6g患者，發現會由6i, 6w, 6g以及無法分型片段組成。因此我們認為此一族群為一全新的次分型。若以胺基酸序列也發現此一新型在第10, 70及72位置出現特殊的變化。
回到臨床分析，此一新型與6w的病患，相較於6a患者，年紀呈現較大，較高比例具有肝癌，且不容易有靜脈藥物使用之病史。再以Abbott GT PLUS assay分析22位曾接受過Linear Array及Abbott GTII檢測之患者，發現GT PLUS assay與我們的定序法具有81.8%的一致性。這些病患當中，有9位因原來分型為第一型而接受了維建樂以及易奇瑞±雷巴威林的合併治療，有7位在第四週測不到病毒。
總結來說，我們在南台灣發現到一新的第六行亞型病毒，其具有6g與他型重組的特性。而有部分不容易被市售檢測法驗出來的第六型多為6w及新6g。以一新型病毒若以維建樂以及易奇瑞±雷巴威林的長期療效目前則未知。

Hepatitis C virus infection remains a main etiology of cirrhosis and hepatocellular carcinoma. The accurate genotyping of HCV not only impact on the disease severity but also extra-hepatic outcomes. Recent large cohort studies showed HCV genotype 6 infection is associated with higher risks of HCC development especially in cirrhotic Asian population. The current commercial methods for HCV genotyping have limitations in identifying G1 and G6. The efficacy of current all oral direct antiviral agents reimbursed in Taiwan is unknown in some G6 population that was misclassified as G1.
The aim of current study was to investigate the clinical and virological characteristics in HCV G6 virus infection in Southern Taiwan. We found the seroprevelance of G6 in Southern Taiwan is 3.9%. To evaluate the subtype distribution, we designed a specific primer targeting the 5’UTR_Core_E1 region and subsequently identified the certain groups of G6 population could not be correctly genotyped by current commercial assays. The majority of them are 6w and new 6g. The new 6g strains showed recombination with 6b, 6g and unclassified regions. HCV PLUS assay showed high concordance with our sequencing results in 22 G6 samples. 9 G6 patients received PrOD-based treatment and the SVR rate may be further evaluated.
Key words: HCV genotype, subtypes, phenogenetic analysis, PrOD

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