HLA A24 linked cellular immune response cross reactive to SARS CoV2 and its variants.

 A very interesting paper regarding cross reactivity of the SARS-CoV2 with the other species of Corona viruses has been published in Communications Biology in Nature dated Dec 2nd from a Japanese laboratory of Riken. What attracted my attention most was that the cross reactivity was through an allele HLA A24, which 60% of Japanese posses. It could, at least partially, explain why COVID-19 cases have not been so numerous nor serious in Japan and the areas adjacent in the Eastern Asia.  

https://www.nature.com/articles/s42003-021-02885-6

Most people have had Corona Virus infection as upper respiratory tract infection in the past since that species are quite common in the society. They have found the epitopes with high affinity to HLA-24 in SARS-CoV2 spike region. Unexposed healthy individuals could have cytotoxic T cells reactive to that epitope. Thus, the preponderance of the allele among Japanese and the races in the Eastern Asia and ubiquitous infection of "common" species of Corona viruses may explain why COVID-19 has not devastating in our country. 

It is a clear cut example as for how specific HLA alleles could work in immune response. This finding may also be important for universal vaccine development against Corona viruses. Since I have been involved in research of relationship of HLA with diseases for a few years long time ago, this study showing the function of HLA as an immune response gene/product has made me a bit excited. The researchers have long been studying tumor immunity as their site says. The accumulated knowledges and methodologies in immunology through such a research might have made it possible for such a short period. 

Universal masking or keeping the other precautions are often told to be the reason why we Japanese have not had so many cases of COVID-19 in our country. It is sometimes hued with a kind of nuisance nationalism or strange self confidence. This finding should be a thesis against those nonsense ideas.     

 

If this finding turns out correct, it should be emphasized this HLA linked immune response might apply for the SARS-CoV2 and its variants except for the Delta variant so far. This RNA virus could undergo a lot of mutations ahead and may evade the immunity linked with HLA A24.