SARS-CoV-2 infection have caused global pandemic and claimed over 5,000,000 tolls[1][1]–[4][2]. Although the genetic sequences of their etiologic viruses are of high homology, the clinical and pathological characteristics of COVID-19 significantly differ from SARS[5][3],[6][4]. Especially, it seems that SARS-CoV-2 undergoes vast replication in vivo without being effectively monitored by anti-viral immunity[7][5]. Here, we show that the viral protein encoded from open reading frame 8 (ORF8) of SARS-CoV-2, which shares the least homology with SARS-CoV among all the viral proteins, can directly interact with MHC-I molecules and significantly down-regulates their surface expression on various cell types. In contrast, ORF8a and ORF8b of SARS-CoV do not exert this function. In the ORF8-expressing cells, MHC-I molecules are selectively target for lysosomal degradation by an autophagy-dependent mechanism. As a result, CTLs inefficiently eliminate the ORF8-expressing cells. Our results demonstrate that ORF8 protein disrupts antigen presentation and reduces the recognition and the elimination of virus-infected cells by CTLs[8][6]. Therefore, we suggest that the inhibition of ORF8 function could be a strategy to improve the special immune surveillance and accelerate the eradication of SARS-CoV-2 in vivo.

### Competing Interest Statement

The authors have declared no competing interest.

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The COVID-19 outbreak caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a global major concern. In this review, we addressed a theoretical model on immunopathogenesis associated with severe COVID-19, based on the current literature of SARS-CoV-2 and other epidemic pathogenic coronaviruses, such as SARS and MERS. Several studies have suggested that immune dysregulation and hyperinflammatory response induced by SARS-CoV-2 are more involved in disease severity than the virus itself. Immune dysregulation due to COVID-19 is characterized by delayed and impaired interferon response, lymphocyte exhaustion and cytokine storm that ultimately lead to diffuse lung tissue damage and posterior thrombotic phenomena. Considering there is a lack of clinical evidence provided by randomized clinical trials, the knowledge about SARS-CoV-2 disease pathogenesis and immune response is a cornerstone to develop rationale-based clinical therapeutic strategies. In this narrative review, the authors aimed to describe the immunopathogenesis of severe forms of COVID-19.

Infection caused by SARS-CoV-2 can result in severe respiratory complications and death. Patients with a compromised immune system are expected to be more susceptible to a severe disease course. In this report we suggest that patients with systemic lupus erythematous might be especially prone to severe COVID-19 independent of their immunosuppressed state from lupus treatment. Specially, we provide evidence in lupus to suggest hypomethylation and overexpression of ACE2 , which is located on the X chromosome and encodes a functional receptor for the SARS-CoV-2 spike glycoprotein. Oxidative stress induced by viral infections exacerbates the DNA methylation defect in lupus, possibly resulting in further ACE2 hypomethylation and enhanced viremia. In addition, demethylation of interferon-regulated genes, NF?B, and key cytokine genes in lupus patients might exacerbate the immune response to SARS-CoV-2 and increase the likelihood of cytokine storm. These arguments suggest that inherent epigenetic dysregulation in lupus might facilitate viral entry, viremia, and an excessive immune response to SARS-CoV-2. Further, maintaining disease remission in lupus patients is critical to prevent a vicious cycle of demethylation and increased oxidative stress, which will exacerbate susceptibility to SARS-CoV-2 infection during the current pandemic. Epigenetic control of the ACE2 gene might be a target for prevention and therapy in COVID-19.

### Competing Interest Statement

The authors have declared no competing interest.

### Funding Statement

This work was supported by the Lupus Research Alliance and the National Institute of Allergy and Infectious Diseases of the National Institutes of Health grants number U19AI110502 and R01AI097134 to Dr. Sawalha; and the National Natural Science Foundation of China (No. 81830097), the innovation project of Chinese academy of medical sciences (Research Unit, No. 2019-I2M-5-033) and an urgent grant of Hunan Province for fighting against coronavirus disease- 2019 epidemic (2020SK3005 ) to Dr. Lu.

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SARS-CoV-2 variants of concern (VOCs) possess mutations that confer resistance to neutralizing antibodies within the Spike protein and are associated with breakthrough infection and reinfection. By contrast, less is known about the escape from CD8+ T cell-mediated immunity by VOC. Here, we demonstrated that VOCs retain similar MHC-I downregulation capacity compared to the ancestral virus. However, VOCs exhibit a greater ability to suppress type I IFN than the ancestral virus. Although VOCs possess unique mutations within the ORF8 gene, which suppresses MHC-I expression, none of these mutations enhanced the ability of ORF8 to suppress MHC-I expression. Notably, MHC-I upregulation was strongly inhibited after the ancestral SARS-CoV-2 infection in vivo . Collectively, our data suggest that the ancestral SARS-CoV-2 already possesses an intrinsically potent MHC-I evasion capacity, and that further adaptation by the variants was not observed.

### Competing Interest Statement

The authors have declared no competing interest.