Why are children and many adults not affected by COVID-19? Role of the host immune response

作     者：Hélène Banoun 

作者机构：Pharmacist biologistFormer Inserm researcherMember of the Independent Scientific CouncilMarseille 13000France. 

出 版 物：《Infectious Diseases Research》 (传染病研究（英文）)

年 卷 期：2022年第3卷第3期

页      面：29-40页

学科分类：1002[医学-临床医学] 100201[医学-内科学(含：心血管病、血液病、呼吸系病、消化系病、内分泌与代谢病、肾病、风湿病、传染病)] 10[医学] 

主　　题：COVID-19 outcome children immune response inflamm-aging ACE2 cross-immunity 

摘      要：Children are less susceptible to COVID-19 than adults:they often have asymptomatic and very rarely severe *** protection is valid for all variants of the *** aim here is to compare the immune response of children with that of adults,asymptomatic adults or those with mild disease with those who develop severe *** protective factors for children have been mentioned but some of them do not seem to be ***,there is no clear difference in the quantity of virus receptors(angiotensin-converting enzyme 2(ACE2),transmembrane serine protease 2(TMPRSS2))present according to age that could explain a lesser entry of the virus into the cells of the nose,oropharynx and lungs of *** fact,children and adults generally have similar viral loads and respiratory tract *** adults,like children,have antibodies(and T cells)that cross-react with human coronavirus(HCoVs)and respiratory syndrome coronavirus 2(SARS-CoV-2),but this humoral reactivity does not correlate with disease severity in adults;the difference appears to be more qualitative(IgM and anti-S in children and IgG and IgA and anti-N in adults)than quantitative,and mildly affected adults have some of the characteristics of the cross-reactivities of *** the cellular level,the difference between children and adults lies more in the naivety of the T cells *** amount of salivary and mucosal IgA is negatively correlated with age and positively correlated with the absence of Covid infection:these IgAs are different and more effective than serum *** COVID-19 is characterized by hyperinflammation following invasion of the lower respiratory tract when the virus has not been cleared from the upper respiratory tract by innate *** is associated with an alteration of the immune system,often with a chronic hyperinflammatory state:deficient innate immunity combined with age-related dysregulation of adaptive immunity could cause severe *** innate cell