Sars-cov-2 Specific Immune Response in Patients Recovering from COVID-19

By collecting the blood of convalescent patients with COVID-19, the sars-cov -2 specific humoral immunity and cellular immunity of these discharged patients were studied. In the fourth 11 months after the onset, follow-up analysis of 171 patients showed high levels of IgG antibodies. A total of 78.1% (164/210) of the specimens tested positive for neutralizing antibody (NAb). The il-2 and -IFN-γ responses stimulated by the SARS-CoV-2 antigen peptide pool can distinguish individuals in the recovery period of COVID-19 from healthy donors. Interestingly, the IL-2 response, IL-8 response and -IFN-γ response stimulated by the antigen peptide pool significantly affect the survival of NAb. The count of CD8+ T cells activated by the antigen peptide pool is correlated with NAb. The counts of activated natural killer (NK) cells in the antigen peptide pool of individuals in the recovery period are correlated with NAb and the severity of the disease. The data indicate that the development of NAb is related to the activation of T cells and NK cells. This research provides a basis for further analysis of the protective immunity of SARS-CoV-2 and understanding of the pathogenesis of COVID-19. This also has significance for the development of effective vaccines for SARS-CoV-2 infection.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)-related Coronavirus Disease (COVID-19) is a respiratory tract-borne disease that can lead to serious illness and death. SARS-CoV-2 has the same receptor and host cells as SARS-CoV. A variety of disease models have been established to study the infection, immunogenicity and pathogenesis of SARS-CoV-2. Based on previous understanding of other coronaviruses, a variety of factors and pathways have been identified and discovered, and these factors and pathways are promising potential therapeutic targets. However, the development of effective treatments requires a more comprehensive understanding, which requires better molecular details at different stages of virus propagation and disease progression in host cells. In the early and mild stages of infection, the virus is still confined to the upper respiratory tract, resulting in a low level of innate immune response. This asymptomatic state lasts for several days, and then the virus spreads to the catheter and terminal respiratory tract.

At this stage of the disease, an optimal but controlled adaptive and innate immune response will help fight the infection. The successful removal of the virus from recovered patients indicates the presence of sufficient adaptive immune cells, immunomodulatory molecules and neutralizing antibodies. However, at this stage, damage to the adaptive immune response and excessive activation of the innate immune system can cause severe disease symptoms in COVID-19 patients. Histopathological data from deceased patients showed adaptive immune dysfunction and enhanced pro-inflammatory response, with inflammatory cells infiltrating the lungs. In addition, the severity of the disease has been found to be positively correlated with the increase in pro-inflammatory interleukin-6 (IL-6) levels and the proportion of neutrophil lymphocytes. Patients with COVID-19 may suffer from acute respiratory distress syndrome (ARDS) with excessive inflammation and lymphocytosis. These changes lead to cell death and tissue destruction, leading to airway collapse, multiple organ failure, and death of 67 85% of intensive care unit (ICU) patients.

Clinically, the host immune system is involved in the pathogenesis of this disease. The protective and sustained immune response to viral infection usually comes from the combined action of lymphocytes: B cells (responsible for humoral antibody immunity) and T cells (responsible for cellular immunity and helper B cell response). IgM, IgG and IgA antibodies, a small amount of IgD and IgE can be detected in the serum. For SARS-CoV-2, the focus is on IgM, IgG, and IgA antibodies, which can neutralize the virus by binding to spikes and other membrane proteins, thereby preventing infection. Some studies have focused on the immune response to SARS-CoV-2 infection, especially the characteristics of the adaptive immune response.

Eight newly discharged patients had high IgG antibody titers, and 6 patients had high antibody titers 2 weeks after discharge. Neutralizing antibody (NAb) is also related to the number of specific T cells. However, this study did not distinguish between CD4+ and CD8+ T cell responses. Based on these reports, it can be inferred that the antibody response of some COVID-19 patients may not last long, which brings challenges to antibody-based therapy and vaccine research. These data suggest the possibility of re-infection. However, longitudinal studies with larger cohort sizes and longer time frames are needed to discover the persistence of sars-cov -2 specific antibody responses.

In this study, blood was collected from COVID-19 patients in the virus-free recovery period to study the immune response of host cells, and analyze their SARS-CoV-2 specific antibodies and CD4+, CD8+ and natural killer (NK) cells against SARS-CoV-2 antigen peptide pools ’S response. The virus-specific lymphocytes of COVID19 patients and their correlation with NAB were also detected. The author established the immune trajectory of patients with new coronary pneumonia who successfully cleared the virus, as well as the time effect of the innate and acquired immune systems.

Reference:

1. Yunbao Pan et al. SARS-CoV-2-specific immune response in COVID-19 convalescent individuals. Signal Transduction and Targeted Therapy (2021) 6:256