COVID-19 的病理生理学:儿童为何比成人预后更好?
Pathophysiology of COVID-19: Why Children Fare Better than Adults?
机构信息
Department of Pediatrics, All India Institute of Medical Sciences, New Delhi, India.
Department of Pediatrics, Kokilaben Dhirubhai Ambani Hospital and Medical Research Institute, Mumbai, India.
出版信息
Indian J Pediatr. 2020 Jul;87(7):537-546. doi: 10.1007/s12098-020-03322-y. Epub 2020 May 14.
The world is facing Coronavirus Disease-2019 (COVID-19) pandemic, which is causing a large number of deaths and burden on intensive care facilities. It is caused by Severe Acute Respiratory Syndrome coronavirus-2 (SARS-CoV-2) originating in Wuhan, China. It has been seen that fewer children contract COVID-19 and among infected, children have less severe disease. Insights in pathophysiological mechanisms of less severity in children could be important for devising therapeutics for high-risk adults and elderly. Early closing of schools and day-care centers led to less frequent exposure and hence, lower infection rate in children. The expression of primary target receptor for SARS-CoV-2, i.e. angiotensin converting enzyme-2 (ACE-2), decreases with age. ACE-2 has lung protective effects by limiting angiotensin-2 mediated pulmonary capillary leak and inflammation. Severe COVID-19 disease is associated with high and persistent viral loads in adults. Children have strong innate immune response due to trained immunity (secondary to live-vaccines and frequent viral infections), leading to probably early control of infection at the site of entry. Adult patients show suppressed adaptive immunity and dysfunctional over-active innate immune response in severe infections, which is not seen in children. These could be related to immune-senescence in elderly. Excellent regeneration capacity of pediatric alveolar epithelium may be contributing to early recovery from COVID-19. Children, less frequently, have risk factors such as co-morbidities, smoking, and obesity. But young infants and children with pre-existing illnesses could be high risk groups and need careful monitoring. Studies describing immune-pathogenesis in COVID-19 are lacking in children and need urgent attention.
世界正面临 2019 年冠状病毒病(COVID-19)大流行,这导致重症监护病房负担沉重,大量人员死亡。它是由源自中国武汉的严重急性呼吸系统综合征冠状病毒 2(SARS-CoV-2)引起的。人们已经发现,儿童感染 COVID-19 的比例较低,在感染者中,儿童的疾病较轻。了解儿童疾病严重程度较轻的病理生理机制对于为高风险成年人和老年人制定治疗方法可能很重要。学校和日托中心的早期关闭导致儿童接触减少,因此感染率降低。SARS-CoV-2 的主要靶受体,即血管紧张素转换酶 2(ACE-2)的表达随年龄增长而降低。ACE-2 通过限制血管紧张素-2 介导的肺毛细血管渗漏和炎症发挥肺保护作用。严重的 COVID-19 疾病与成年人中高且持续的病毒载量相关。由于训练有素的免疫(继发于活疫苗和频繁的病毒感染),儿童具有强大的固有免疫反应,导致感染可能在进入部位早期得到控制。成人患者在严重感染中表现出抑制的适应性免疫和功能失调的过度活跃的固有免疫反应,而儿童则没有。这可能与老年人的免疫衰老有关。儿科肺泡上皮的出色再生能力可能有助于从 COVID-19 中早期康复。儿童不太常见的危险因素包括合并症、吸烟和肥胖。但是,患有潜在疾病的婴幼儿可能是高危人群,需要密切监测。描述 COVID-19 免疫发病机制的研究在儿童中缺乏,需要紧急关注。
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