Rs12252

rs12252 is a SNP in the IFITM3 gene, which encodes the interferon-inducible transmembrane protein. The rs12252(C) allele encodes an IFITM3 isoform (known as Δ21 IFITM3) which is lacking 21 amino acids at the amino terminus of the protein.

In a 2012 study of ~100 hospitalized Caucasian patients with H1N1/09 influenza (flu) virus in 2009, there was a significant enrichment in individuals with rs12252(C;C) genotypes. Specifically, although 1 in 300 uninfected people were reported to carry the (C;C) genotype, in the hospitalized patients the frequency was 1 in 17.; see also MedPage

However, in subsequent studies of more than 5000 subjects in two separate cohorts the association between the rs12252(C) polymorphism and the severity of H1N1 influenza could not be established, although there was a susceptibility to mild infection.

The frequency of the rs12252(C) allele varies very widely between Caucasian and Asian patients; while very low in Caucasians, up to 25 - 50% of all Japanese or Chinese individuals may have the rs12252(C;C) genotype. A study of Han Chinese concluded that the rs12252(C;C) genotype was estimated to confer a sixfold greater risk for severe infection than the CT and TT genotypes.