Immunological map in COVID-19

Abstract

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by SARS-CoV-2, a newly discovered coronavirus that exhibits many similarities with the severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) coronaviruses (SARS-CoV and MERS-CoV, respectively). The definite pathogenesis and immunological influences of SARS-CoV-2 have not been fully elucidated. Therefore, we constructed a brief summary comparison of SARS-CoV-2, SARS-CoV, and MERS-CoV infections regarding their immunological changes. In addition, we further investigated the immunological differences between severe and nonsevere COVID-19 cases, and we searched for possible immunological predictors of the patient outcome by reviewing case series studies to date. Possible immunological predictors of a poor outcome are leukocytosis, neutrophilia, lymphopenia (both CD4 and CD8 T cells), an increased neutrophil-to-lymphocyte ratio (NLR), and increased levels of pro-inflammatory cytokines (IL-6 and TNF-α), Th1 cytokines (IL-2 and IFN-γ), regulatory T cell cytokines (IL-10) and Th17 cytokines (IL-17). A more precise immunological map needs to be established, which may assist in diagnosing this disease and facilitate immunological precision medicine treatment.

Keywords: COVID-19; Immune; Pandemic; Pneumonia; SARS-CoV-2.

Figure 1

Summary of the immunologic map in MERS-CoV, SARS-CoV, and SARS-CoV-2 infections. A: MERS-CoV, SARS-CoV, and SARS-CoV-2 invade human cells via different cell surface receptors. SARS-CoV and SARS-CoV-2 invade via angiotensin-converting enzyme 2 (ACE2), and MERS-CoV invades via dipeptidyl peptidase 4 (DPP4). B: The viral influences of MERS-CoV, SARS-CoV, and SARS-CoV-2 on immune cells and cytokines. The upward arrow means increased level and the downward arrow means decreased level. The length of each color bar is correlated with the influence degree of each infection. C: The viral influences of MERS-CoV, SARS-CoV, and SARS-CoV-2 on organ system. The length of each color bar is correlated with the influence degree of each infection. D: The mortality rate of MERS-CoV, SARS-CoV, and SARS-CoV-2 infection (SARS-CoV-2 mortality rate data were obtained at the world health organization website on March 15, 2021).