Anti-shiftless antiviral inhibitor of ribosomal frameshifting antibodies are used for the immunodetection of the protein encoded by the SHFL gene. In humans, the canonical protein has a reported length of 291 amino acid residues and a mass of 33.1 kDa. Its subcellular localization is in the nucleus and cytoplasm. Alternative splicing is reported to yield 4 different isoforms for this protein. A member of the SHFL protein family, it is reported to inhibit programmed -1 ribosomal frameshifting (-1PRF) of a variety of mRNAs from viruses, such as HIV1, and cellular genes, such as PEG10. Other names for this target antigen include IRAV, RyDEN, SFL, shiftless antiviral inhibitor of ribosomal frameshifting protein, Repressor of yield of Dengue virus, and C19orf66. Gene orthologs have been identified in the mouse, rat, bovine, frog, zebrafish and chimpanzee species.