A genetic variant found among Japanese individuals may help explain lower COVID-19 case and death rates in Japan, the Japan Times reports.
It notes that the lower case and death rates in Japan as well as in neighboring countries had been thought to be due to higher rates of mask-wearing, but that a genetic or immunological factor might also be at play. As they report in Communication Biology, researchers from the Riken Center for Integrative Medical Science and elsewhere screened peripheral blood mononuclear cells from blood samples obtained from people in early 2020 without any exposure to SARS-CoV-2 or, previously, to SARS-CoV-1 or MERS. They found that when samples from individuals with a particular HLA allele — HLA-A24 — were exposed to the QYI peptide from the SARS-CoV-2 spike protein, it sparked killer T cells to multiply. The researchers further found that the samples have similar reactions to such epitopes from other, seasonal coronaviruses, suggesting that there is cross-immunity between seasonal coronavirus infections and SARS-CoV-2, Nikkei Asia adds.
The HLA-A24, it notes, is found among 60 percent of ethnic Japanese individuals, but is less common among Western populations.
"It could be considered an 'X-factor,'" senior author Shin-ichiro Fujii, a team leader at Riken's immunotherapy laboratory, tells Nikkei Asia.