IFNL3 (IL28B) Genotyping

The IFNL3 (IL28B) gene encodes for the protein interferon lambda 3, a cytokine, which has antiviral, antiproliferative, and immune-modulatory properties. Cytokines are released in the presence of viruses, bacteria, or tumor cells. IFNL3 polymorphisms may indicate either a favorable or unfavorable response to treatment of Hepatitis C Virus (HCV) Genotype 1, the most common type of HCV in the U.S., with pegylated interferon-alfa2a (Pegasys®) and ribavirin (Rebetol®)  containing regimens.[56] While IFNL3 genotyping is a strong predictor of treatment response, it does not determine whether or not to treat HCV infection. Genetic variant tested for IFNL3 is rs12979860C>T.

Indications for IFNL3 Testing

IFNL3 testing may be beneficial for HCV Genotype 1 patients to help predict response to pegylated interferon-alfa and ribavirin containing treatment regimens. However, while IFNL3 genetic testing may be prognostically useful, the clinical utility of testing is still unclear because results alone do not change current HCV treatment recommendations. There may be a limited role for IFNL3 testing in decreasing treatment duration or selecting double versus triple therapy regimens, but more research in this area is needed.