Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
PLoS One. 2012;7(5):e36318. doi: 10.1371/journal.pone.0036318. Epub 2012 May 1.
In this study, the effect of innate serum inhibitors on influenza virus infection was addressed. Seasonal influenza A(H1N1) and A(H3N2), 2009 pandemic A(H1N1) (H1N1pdm) and highly pathogenic avian influenza (HPAI) A(H5N1) viruses were tested with guinea pig sera negative for antibodies against all of these viruses as evaluated by hemagglutination-inhibition and microneutralization assays. In the presence of serum inhibitors, the infection by each virus was inhibited differently as measured by the amount of viral nucleoprotein produced in Madin-Darby canine kidney cells. The serum inhibitors inhibited seasonal influenza A(H3N2) virus the most, while the effect was less in seasonal influenza A(H1N1) and H1N1pdm viruses. The suppression by serum inhibitors could be reduced by heat inactivation or treatment with receptor destroying enzyme. In contrast, all H5N1 strains tested were resistant to serum inhibitors. To determine which structure (hemagglutinin (HA) and/or neuraminidase (NA)) on the virus particles that provided the resistance, reverse genetics (rg) was applied to construct chimeric recombinant viruses from A/Puerto Rico/8/1934(H1N1) (PR8) plasmid vectors. rgPR8-H5 HA and rgPR8-H5 HANA were resistant to serum inhibitors while rgPR8-H5 NA and PR8 A(H1N1) parental viruses were sensitive, suggesting that HA of HPAI H5N1 viruses bestowed viral resistance to serum inhibition. These results suggested that the ability to resist serum inhibition might enable the viremic H5N1 viruses to disseminate to distal end organs. The present study also analyzed for correlation between susceptibility to serum inhibitors and number of glycosylation sites present on the globular heads of HA and NA. H3N2 viruses, the subtype with highest susceptibility to serum inhibitors, harbored the highest number of glycosylation sites on the HA globular head. However, this positive correlation cannot be drawn for the other influenza subtypes.
本研究旨在探讨先天血清抑制剂对流感病毒感染的影响。通过血凝抑制和微量中和试验评估，用未检出针对所有这些病毒抗体的豚鼠血清对季节性流感 A(H1N1)、A(H3N2)、2009 年大流行 A(H1N1)(H1N1pdm)和高致病性禽流感(HPAI)A(H5N1)病毒进行了检测。在存在血清抑制剂的情况下，通过在马-达二氏犬肾细胞中产生的病毒核蛋白的量来衡量每种病毒的感染情况，结果显示，血清抑制剂对季节性流感 A(H3N2)病毒的抑制作用最大，而对季节性流感 A(H1N1)和 H1N1pdm 病毒的抑制作用则较小。血清抑制剂的抑制作用可以通过热失活或用受体破坏酶处理来降低。相比之下，所有测试的 H5N1 株均对血清抑制剂具有抗性。为了确定病毒颗粒上的哪种结构（血凝素(HA)和/或神经氨酸酶(NA)）提供了这种抗性，应用反向遗传学(rg)技术从 A/Puerto Rico/8/1934(H1N1)(PR8)质粒载体构建嵌合重组病毒。rgPR8-H5 HA 和 rgPR8-H5 HANA 对血清抑制剂具有抗性，而 rgPR8-H5 NA 和 PR8 A(H1N1)亲本病毒则敏感，表明高致病性禽流感 H5N1 病毒的 HA 赋予了病毒对血清抑制的抗性。这些结果表明，抵抗血清抑制的能力可能使具有血液传染性的 H5N1 病毒能够传播到远端终末器官。本研究还分析了对血清抑制剂的敏感性与 HA 和 NA 球形头部上存在的糖基化位点数量之间的相关性。对血清抑制剂敏感性最高的 H3N2 病毒在 HA 球形头部上具有最高数量的糖基化位点。然而，对于其他流感亚型，这种正相关性无法得出。
