New SARS-CoV-2 Variants Escape Immune Responses

Aug, 2021 - By WMR

A team of researchers from the Kumamoto University and Weizmann Institute of Science revealed that mutations of the SARS-CoV-2 spike protein or S protein have the potential to escape cellular immunity.

The COVID-19 pandemic continues to be a challenge for the global public health and continues to spread globally despite vaccination efforts. According to the World Health Organization’s report, approximately 192 million confirmed cases of COVID-19 including 4 million deaths were reported globally as of July 21, 2021. Although, vaccination drives have been prioritized by most of the countries with 3.71 billion doses already been administered across the globe; the emerging variants of concern pose new threat to public health globally as new emerging mutants may escape immune responses induced by vaccination or natural infection. It is alarming that the mutations have the potential to affect the viral properties such as infectivity and transmissibility rate, and escaping immune responses as well. The researchers found that the L452R mutation, common to both Epsilon and Delta variants, have the potential to escape cellular immunity through the human leukocyte (HLA) A24 and is responsible for increasing the viral infectivity. The Delta variant (B.1.617.2) which emerged in India and presently circulating in many countries globally has been connected to increased transmissibility, severity of illness, infectivity, and death. Interestingly, mutations are primarily due to error-prone replication of virus. It is alarming that several SARS-CoV-2 mutants may show resistance to neutralizing antibodies which is either naturally induced or vaccine induced. Moreover, these mutants may evade cellular immunity which is caused by cytotoxic T lymphocytes. In this study, researchers studied new emerging variants of SARS-CoV-2 that have the potential to escape HLA-restricted cellular immunity. They used immunological experiments and found that an antigen derived from the SARS-CoV-2 S protein is identified by the HLA- A24 restricted cellular immunity.

In a nutshell, the team found that HLA-A24 could recognize mutations in the S protein region after conducting a large scale sequence analysis of SARS-CoV-2 strains. The team suggested that the L452R mutation should be investigated further as this mutation increases the stability of the S-protein, thereby, enhancing the replication of the virus.