与墨西哥第二波疫情中患者严重程度和死亡率相关的 A（H1N1）pdm09 HA D222 变异株。

BACKGROUND

Pandemic type A (H1N1) influenza arose in early 2009, probably in Mexico and the United States, and reappeared in North America in September for seven more months. An amino acid substitution in the hemagglutinin (HA), D222G, has been reported in a significant proportion of patients with a severe and fatal outcome. We studied the prevalence of HA222 substitutions in patients in Mexico during the second wave and its association with clinical outcome and pathogenicity in a mouse model.

METHODS

The nucleotide sequences of hemagglutinin (HA) from viruses collected from 77 patients were determined including 50 severe and fatal cases and 27 ambulatory cases. Deep sequencing was done on 5 samples from severe or fatal cases in order to determine the quasispecies proportion. Weight loss and mortality due to infection with cultured influenza viruses were analyzed in a mouse model.

RESULTS

Viruses from 14 out of 50 hospitalized patients (28%) had a non aspartic acid residue at the HA 222 position (nD222), while all 27 ambulatory patients had D222 (p=0.0014). G222 was detected as sole species or in coexistence with N222 and D222 in 12 patients with severe disease including 8 who died. N222 in coexistence with D222 was detected in 1 patient who died and co-occurrence of A222 and V222, together with D222, was detected in another patient who died. The patients with a nD222 residue had higher mortality (71.4%), compared to the group with only D222 (22.2%, p=0.0008). Four of the 14 viruses from hospitalized patients were cultured and intranasally infected into mice. Two viruses with G222 were lethal while a third virus, with G222, caused only mild illness in mice similar to the fourth virus that contained D222.

CONCLUSIONS

We confirm the elevated incidence of HA222 (H1N1)pdm09 variants in severe disease and mortality. Both clinical and mouse infection data support the idea that nD222 mutations contribute to increased severity of disease but additional determinants in disease outcome may be present.

背景

甲型（H1N1）流感大流行于 2009 年初在墨西哥和美国爆发，9 月再次出现在北美，并持续了七个月。在相当一部分重症和致死患者中发现了血凝素（HA）的一个氨基酸替代，即 D222G。我们研究了第二波疫情中墨西哥患者中 HA222 替代的流行情况及其与临床结果和小鼠模型中致病性的关系。

方法

从 77 例患者采集的病毒血凝素（HA）核苷酸序列进行了测定，包括 50 例重症和致死病例和 27 例门诊病例。对 5 例重症或致死病例的样本进行深度测序，以确定准种比例。用培养的流感病毒在小鼠模型中分析体重减轻和死亡率。

结果

50 例住院患者中有 14 例（28%）HA222 位置的非天冬氨酸残基（nD222），而 27 例门诊患者均为 D222（p=0.0014）。12 例重症患者中仅检测到 G222 或与 N222 和 D222 共存，其中 8 例死亡。1 例死亡患者中检测到 N222 与 D222 共存，另 1 例死亡患者中检测到 A222 和 V222 与 D222 共存。nD222 残基的患者死亡率（71.4%）高于仅 D222 组（22.2%，p=0.0008）。从住院患者中分离出的 14 株病毒中的 4 株进行培养，然后通过鼻腔感染小鼠。2 株含有 G222 的病毒是致命的，而第 3 株含有 G222 的病毒在小鼠中仅引起轻度疾病，类似于第 4 株含有 D222 的病毒。