A Brief Review on the Overview on Immunology of COVID-19: Current State of the Research

After the attack of Influenza (Flu) in1918 which later turned pandemic, the world is again facing a similar situation. Although, the advancement in medical science has made it possible to identify that the novel infectious agent is from the coronaviridae family. Rapid genome sequencing by various groups helped in identifying the structure and function of the virus, its immunogenicity in diverse populations, and potential preventive measures. Coronavirus attacks the respiratory system to be more specific it attacks ACE2 receptors, causing pneumonia and lymphopenia in maximum infected individuals. Viral subunits like spike and nucleocapsid proteins trigger an immune response in the host which eliminate the virus. These viral antigens can be either recognized by the B cells or by MHC complexes to the T-cells, resulting in antibody production, increased in cytokine secretion, and cytolytic activity in the acute phase of infection. Genetic polymorphism in MHC enables it to present some of the T-cell surface very well over the other MHC alleles. The association of MHC alleles and its downregulated expression has been correlated with disease severity against influenza and coronaviruses. Studies have reported that infected individuals can, after recovery, induce strong protective responses by generating a memory T-cell pool against SARS-CoV and MERS-CoV. These memory T-cells were not persistent in the long term and, upon reactivation, caused local damage due to cross-reactivity. So far, the reports suggest that SARS-CoV-2, which is highly contagious, shows related symptoms in three different stages and develops an exhaustive T-cell pool at higher loads of viral infection. As there are no specific treatments available for this novel coronavirus, numerous small molecular drugs that are being used for the treatment of diseases like SARS, MERS, HIV, ebola, malaria, and tuberculosis are being given to COVID-19 patients, and clinical trials for many such drugs have already begun.