Highly pathogenic H5N1 influenza viruses carry virulence determinants beyond the polybasic hemagglutinin cleavage site.
Highly pathogenic H5N1 influenza viruses carry virulence determinants beyond the polybasic hemagglutinin cleavage site.
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DOI：
10.1371/journal.pone.0011826
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发表时间：
2010-07-27
期刊：
影响因子：
3.7
通讯作者：
Stech J
中科院分区：
文献类型：
--
作者：
Bogs J;Veits J;Gohrbandt S;Hundt J;Stech O;Breithaupt A;Teifke JP;Mettenleiter TC;Stech J
高致病性禽流感病毒 (HPAIV) 起源于无毒力前体，但与所有其他流感病毒的不同之处在于其 H5 或 H7 亚型血凝素 (HA) 中存在多碱基切割位点。在这项研究中，我们研究了低致病性禽 H5N1 毒株转化为 HPAIV 的能力。利用反向遗传学，我们用 HPAIV 的多碱基基序 (TG05poly) 替换了低致病性菌株 A/Teal/Germany/Wv632/2005 (H5N1) (TG05) 的一元 HA 裂解位点。为了阐明 HPAIV 所有病毒基因的毒力潜力，我们生成了两个重配体，其携带来自 HPAIV A/Swan/Germany/R65/06 (H5N1) (R65) 的 HA 加上 TG05 的其余基因 (TG05-HAR65) 或反向组合的突变 TG05 HA 加上 R65 基因 (R65-HATG05poly)。在体外，TG05poly 和两种重配体无需添加胰蛋白酶即可复制，这是 HPAIV 的特征。此外，与无毒力的TG05相比，变体TG05poly、TG05-HAR65和R65-HATG05poly对鸡的致病性程度越来越高。 HA 裂解位点突变体 TG05poly 会导致所有动物出现暂时性非致死性疾病，而重配 TG05-HAR65 会导致 10 只动物中有 3 只死亡。此外，重配 R65-HATG05poly 表现出最高的致死率，每 10 只鸡中有 8 只死亡，类似于“天然”HPAIV 菌株。总而言之，获得多碱基HA切割位点只是低致病性H5N1毒株进化为HPAIV的必要步骤之一。然而，这些低致病性菌株可能已经具有隐秘的毒力潜力。此外，除了多碱基切割位点外，H5N1 HPAIV 的其他毒力决定簇位于 HA 本身和其他病毒蛋白中。
Highly pathogenic avian influenza viruses (HPAIV) originate from avirulent precursors but differ from all other influenza viruses by the presence of a polybasic cleavage site in their hemagglutinins (HA) of subtype H5 or H7. In this study, we investigated the ability of a low-pathogenic avian H5N1 strain to transform into an HPAIV. Using reverse genetics, we replaced the monobasic HA cleavage site of the low-pathogenic strain A/Teal/Germany/Wv632/2005 (H5N1) (TG05) by a polybasic motif from an HPAIV (TG05poly). To elucidate the virulence potential of all viral genes of HPAIV, we generated two reassortants carrying the HA from the HPAIV A/Swan/Germany/R65/06 (H5N1) (R65) plus the remaining genes from TG05 (TG05-HAR65) or in reversed composition the mutated TG05 HA plus the R65 genes (R65-HATG05poly). In vitro, TG05poly and both reassortants were able to replicate without the addition of trypsin, which is characteristic for HPAIV. Moreover, in contrast to avirulent TG05, the variants TG05poly, TG05-HAR65, and R65-HATG05poly are pathogenic in chicken to an increasing degree. Whereas the HA cleavage site mutant TG05poly led to temporary non-lethal disease in all animals, the reassortant TG05-HAR65 caused death in 3 of 10 animals. Furthermore, the reassortant R65-HATG05poly displayed the highest lethality as 8 of 10 chickens died, resembling “natural” HPAIV strains. Taken together, acquisition of a polybasic HA cleavage site is only one necessary step for evolution of low-pathogenic H5N1 strains into HPAIV. However, these low-pathogenic strains may already have cryptic virulence potential. Moreover, besides the polybasic cleavage site, the additional virulence determinants of H5N1 HPAIV are located within the HA itself and in other viral proteins.