Department of Biochemistry, University of Shizuoka, School of Pharmaceutical Sciences and Global COE Program for Innovation in Human Health Sciences, Shizuoka, Japan.
PLoS One. 2010 Dec 9;5(12):e15556. doi: 10.1371/journal.pone.0015556.
The "Spanish" pandemic influenza A virus, which killed more than 20 million worldwide in 1918-19, is one of the serious pathogens in recorded history. Characterization of the 1918 pandemic virus reconstructed by reverse genetics showed that PB1, hemagglutinin (HA), and neuraminidase (NA) genes contributed to the viral replication and virulence of the 1918 pandemic influenza virus. However, the function of the NA gene has remained unknown. Here we show that the avian-like low-pH stability of sialidase activity discovered in the 1918 pandemic virus NA contributes to the viral replication efficiency. We found that deletion of Thr at position 435 or deletion of Gly at position 455 in the 1918 pandemic virus NA was related to the low-pH stability of the sialidase activity in the 1918 pandemic virus NA by comparison with the sequences of other human N1 NAs and sialidase activity of chimeric constructs. Both amino acids were located in or near the amino acid resides that were important for stabilization of the native tetramer structure in a low-pH condition like the N2 NAs of pandemic viruses that emerged in 1957 and 1968. Two reverse-genetic viruses were generated from a genetic background of A/WSN/33 (H1N1) that included low-pH-unstable N1 NA from A/USSR/92/77 (H1N1) and its counterpart N1 NA in which sialidase activity was converted to a low-pH-stable property by a deletion and substitutions of two amino acid residues at position 435 and 455 related to the low-pH stability of the sialidase activity in 1918 NA. The mutant virus that included "Spanish Flu"-like low-pH-stable NA showed remarkable replication in comparison with the mutant virus that included low-pH-unstable N1 NA. Our results suggest that the avian-like low-pH stability of sialidase activity in the 1918 pandemic virus NA contributes to the viral replication efficiency.
1918-19 年在全球范围内导致超过 2000 万人死亡的“西班牙”流感 A 病毒是有记录以来的严重病原体之一。通过反向遗传学对 1918 年大流行病毒进行的重建特征表明，PB1、血凝素 (HA) 和神经氨酸酶 (NA) 基因有助于 1918 年大流行流感病毒的复制和毒力。然而，NA 基因的功能仍然未知。在这里，我们发现 1918 年大流行病毒 NA 中发现的唾液酸酶活性的类似禽类的低 pH 稳定性有助于病毒复制效率。我们发现，与其他人类 N1 NAs 的序列相比，在 1918 年大流行病毒 NA 中的位置 435 处的 Thr 缺失或位置 455 处的 Gly 缺失与 1918 年大流行病毒 NA 中唾液酸酶活性的低 pH 稳定性有关，通过比较嵌合构建体的唾液酸酶活性。这两个氨基酸都位于或靠近在低 pH 条件下稳定天然四聚体结构的氨基酸残基附近，类似于 1957 年和 1968 年出现的大流行病毒的 N2 NAs。从 A/WSN/33（H1N1）的遗传背景中生成了两种反向遗传病毒，该病毒包括来自 A/USSR/92/77（H1N1）的低 pH 不稳定 N1 NA 和其对应的 N1 NA，其唾液酸酶活性通过在位置 435 和 455 的两个氨基酸残基的缺失和取代转换为低 pH 稳定的性质与 1918 NA 中唾液酸酶活性的低 pH 稳定性有关。与包括低 pH 不稳定 N1 NA 的突变病毒相比，包括“西班牙流感”样低 pH 稳定 NA 的突变病毒显示出显著的复制能力。我们的结果表明，1918 年大流行病毒 NA 中类似禽类的低 pH 稳定性唾液酸酶活性有助于病毒复制效率。
