Immune evasion of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2); molecular approaches.

In December 2019, a new betacoronavirus, known as severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), caused an outbreak at the Wuhan seafood market in China. The disease was further named coronavirus disease 2019 (COVID-19). In March 2020, the World Health Organization (WHO) announced the disease to be a pandemic, as more cases were reported globally. SARS-CoV-2, like many other viruses, employs diverse strategies to elude the host immune response and/or counter immune responses. The infection outcome mainly depends on interactions between the virus and the host immune system. Inhibiting IFN production, blocking IFN signaling, enhancing IFN resistance, and hijacking the host's translation machinery to expedite the production of viral proteins are among the main immune evasion mechanisms of SARS-CoV-2. SARS-CoV-2 also downregulates the expression of MHC-I on infected cells, which is an additional immune-evasion mechanism of this virus. Moreover, antigenic modifications to the spike (S) protein, such as deletions, insertions, and also substitutions are essential for resistance to SARS-CoV-2 neutralizing antibodies. This review assesses the interaction between SARS-CoV-2 and host immune response and cellular and molecular approaches used by SARS-CoV-2 for immune evasion. Understanding the mechanisms of SARS-CoV-2 immune evasion is essential since it can improve the development of novel antiviral treatment options as well as vaccination methods.

OMICRON: Virology, immunopathogenesis, and laboratory diagnosis.

Since its emersion, coronavirus disease 2019 (COVID-19) has been a significant global dilemma. Several mutations in the severe acute respiratory virus (SARS-Co-2) genome has given rise to different variants with various levels of transmissibility, severity and mortality. Up until November 2021, the variants of concern declared by the World Health Organization were Alpha, Beta, Delta and Gamma. Since then, a novel variant named Omicron (B.1.1.529) has been developed. BA.1, BA.1.1, BA.2 and BA.3 are four known subvariants of Omicron. The Omicron variant involves new mutations in its spike protein, most of which are in its receptor binding site, and increase its transmissibility and decrease its antibody and vaccine response. Understanding the virology and mutations of Omicron is necessary for developing diagnostic and therapeutic methods. Moreover, important issues, such as the risk of re-infection, the response to different kinds of vaccines, the need for a booster vaccine dose and the increased risk of Omicron infection in pediatrics, need to be addressed. In this article, we provide an overview of the biological and immunopathological properties of Omicron and its subvariants, its clinical signs and symptoms, Omicron and pediatrics, vaccines against Omicron, re-infection with Omicron, diagnostic approaches and specific challenges of Omicron in the successful control and management of the rapid global spread of this variant.