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Covid-19 Infection: The Perspectives on Age-Dependent Difference in Immune Responses and Immunological Strategies to Reduce Viral Burden

Mounika Dwibhashyam Sai, Umesh Yadav, Monisha Joshi Kudali, Shifa Nurain, Gautam Anand and Anup Kumar Gupta

Covid-19 is caused by the novel strain of Corona virus named as SARS-CoV-2 because of its homology with
SARS infection and it is first detailed in Wuhan, China in December 2019. From that point forward, it has spread
globally, already contaminating a large number of individuals worldwide and has been proclaimed as a pandemic by
the WHO (World Health Organization) on March 2020. SARS-CoV-2 causes acute respiratory infection with
fluctuating seriousness in various age groups, wherein geriatric patents in general will have serious disease. In
children it is moderately spread till-date. A few contrasts in the pathogenesis of Covid-19 among pediatric and
geriatric patients have been proposed to clarify these differences. Severe Covid-19 disease is associated with high
and persistent viral burdens in the elderly patients. Children have strong innate immune response because of
trained immunity (secondary to live-vaccines and frequent viral infections), leading to presumably early control of
infection at the site of entry and also the risk factors associated with children were very less as compared to elderly
individuals. The expression of primary target receptor for SARS-CoV-2, i.e. angiotensin converting enzyme-2
(ACE-2), decreases with age which has lung defensive effects and the severity of the disease can be explained by
the presence of enzyme called Furin. Henceforth, this review will highlight the clinical features, disease
pathogenesis, age-dependent difference in immune responses and immunological strategies to reduce viral burden.