British Columbia Centre for Disease Control, Vancouver, British Columbia, Canada ; University of British Columbia, Vancouver, British Columbia, Canada.
Centre Hospitalier Universitaire de Québec [University Hospital Centre of Québec], Québec, Canada ; Laval University, Québec, Canada.
PLoS One. 2014 Jan 27;9(1):e86555. doi: 10.1371/journal.pone.0086555. eCollection 2014.
During spring-summer 2009, several observational studies from Canada showed increased risk of medically-attended, laboratory-confirmed A(H1N1)pdm09 illness among prior recipients of 2008-09 trivalent inactivated influenza vaccine (TIV). Explanatory hypotheses included direct and indirect vaccine effects. In a randomized placebo-controlled ferret study, we tested whether prior receipt of 2008-09 TIV may have directly influenced A(H1N1)pdm09 illness. Thirty-two ferrets (16/group) received 0.5 mL intra-muscular injections of the Canadian-manufactured, commercially-available, non-adjuvanted, split 2008-09 Fluviral or PBS placebo on days 0 and 28. On day 49 all animals were challenged (Ch0) with A(H1N1)pdm09. Four ferrets per group were randomly selected for sacrifice at day 5 post-challenge (Ch+5) and the rest followed until Ch+14. Sera were tested for antibody to vaccine antigens and A(H1N1)pdm09 by hemagglutination inhibition (HI), microneutralization (MN), nucleoprotein-based ELISA and HA1-based microarray assays. Clinical characteristics and nasal virus titers were recorded pre-challenge then post-challenge until sacrifice when lung virus titers, cytokines and inflammatory scores were determined. Baseline characteristics were similar between the two groups of influenza-naïve animals. Antibody rise to vaccine antigens was evident by ELISA and HA1-based microarray but not by HI or MN assays; virus challenge raised antibody to A(H1N1)pdm09 by all assays in both groups. Beginning at Ch+2, vaccinated animals experienced greater loss of appetite and weight than placebo animals, reaching the greatest between-group difference in weight loss relative to baseline at Ch+5 (7.4% vs. 5.2%; p = 0.01). At Ch+5 vaccinated animals had higher lung virus titers (log-mean 4.96 vs. 4.23pfu/mL, respectively; p = 0.01), lung inflammatory scores (5.8 vs. 2.1, respectively; p = 0.051) and cytokine levels (p>0.05). At Ch+14, both groups had recovered. Findings in influenza-naïve, systematically-infected ferrets may not replicate the human experience. While they cannot be considered conclusive to explain human observations, these ferret findings are consistent with direct, adverse effect of prior 2008-09 TIV receipt on A(H1N1)pdm09 illness. As such, they warrant further in-depth investigation and search for possible mechanistic explanations.
2009 年春夏期间，来自加拿大的几项观察性研究表明，在接种过 2008-09 年三价灭活流感疫苗（TIV）的人群中，实验室确诊的甲型 H1N1pdm09 疾病的风险增加。解释性假说包括直接和间接的疫苗效应。在一项随机安慰剂对照雪貂研究中，我们测试了先前接种 2008-09 年 TIV 是否可能直接影响甲型 H1N1pdm09 疾病。32 只雪貂（每组 16 只）在第 0 天和第 28 天分别接受 0.5 毫升肌内注射加拿大制造的市售、非佐剂、分裂的 2008-09 年 Fluviral 或 PBS 安慰剂。第 49 天，所有动物均接受甲型 H1N1pdm09 攻击（Ch0）。每组 4 只雪貂随机选择在攻毒后第 5 天（Ch+5）处死，其余动物继续观察至第 14 天。用血凝抑制（HI）、微量中和（MN）、核蛋白 ELISA 和 HA1 微阵列检测血清中针对疫苗抗原和甲型 H1N1pdm09 的抗体。在攻毒前和攻毒后记录临床特征和鼻病毒滴度，直至攻毒后处死时测定肺病毒滴度、细胞因子和炎症评分。两组流感未感染动物的基线特征相似。ELISA 和基于 HA1 的微阵列检测到针对疫苗抗原的抗体升高，但 HI 或 MN 检测不到；两组动物在攻毒后均通过所有检测方法检测到针对甲型 H1N1pdm09 的抗体升高。从 Ch+2 开始，接种疫苗的动物比安慰剂动物的食欲和体重下降更明显，在 Ch+5 时与基线相比体重下降的组间差异最大（7.4%比 5.2%；p=0.01）。在 Ch+5 时，接种疫苗的动物肺病毒滴度更高（log-均值分别为 4.96 和 4.23pfu/mL，p=0.01），肺炎症评分（5.8 比 2.1，p=0.051）和细胞因子水平（p>0.05）更高。在 Ch+14 时，两组动物均已康复。在未感染流感的系统性感染雪貂中的发现可能无法复制人类的经验。虽然它们不能被认为是解释人类观察结果的结论性证据，但这些雪貂的发现与先前接种 2008-09 年 TIV 对甲型 H1N1pdm09 疾病的直接、不良影响一致。因此，它们需要进一步深入研究，并寻找可能的机制解释。
