Abstract
Both SARS-CoV-2 infections and vaccines induce robust immune responses. Current data suggested that high neutralizing antibody titers with sustained Th1 responses might correlate with protection against viral transmission and disease development and severity. In addition, genetic and innate immune factors, including higher levels of type I interferons, as well as the induction of trained immunity and local mucosal immunity also contribute to lower risk of infection and amelioration of disease severity. The identification of immune correlates of protection will facilitate the development of effective vaccines and therapeutics strategies.
Highlights
After crossing the species barrier, most likely from bats, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has recently emerged to infect humans and cause severe public health problems
Several studies found that virus-specific CD4+ T cell responses were correlated with the magnitude of the anti-SARS-CoV-2 IgG and IgA against spike protein and nucleocapsid protein, live virus neutralizing antibody titers, and SARS-CoV-2 pseudovirus neutralization titers in COVID-19 patients [13,22,23,26]
We summarize the data from non-human primate (NHP) studies that had both immunogenicity and SARS-CoV-2 viral challenge outcomes presented (Table 1), in the hope to glean some clues on the immune correlates of protections
Summary
After crossing the species barrier, most likely from bats, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has recently emerged to infect humans and cause severe public health problems. Several studies found that virus-specific CD4+ T cell responses were correlated with the magnitude of the anti-SARS-CoV-2 IgG and IgA against spike protein and nucleocapsid protein, live virus neutralizing antibody titers, and SARS-CoV-2 pseudovirus neutralization titers in COVID-19 patients [13,22,23,26]. Patients with severe disease have high viral loads, which lead to high innate, and humoral/cellular immune responses, while the asymptomatic patients with lower viral loads induce lower immune responses This is true for SARS-Cov-2 infected patients. In the early convalescent phase, IgG and neutralizing antibody levels in asymptomatic individuals declined much more quickly than those in the symptomatic patients [34] These inverse correlations between disease severity and the magnitude of immune responses most likely indicate that severe disease, with high viral burden, leads to more robust immune responses, rather than the other way around
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