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Related Experiment Video

Updated: Jan 1, 2026

In Vivo Functional Study of Disease-associated Rare Human Variants Using Drosophila

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Published on: August 20, 2019

IFNL4: Notable variants and associated phenotypes.

Michelle Z Fang¹, Sarah S Jackson¹, Thomas R O'Brien¹

¹Infections and Immunoepidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, 9609 Medical Center Dr, 6E108, MSC 9767, Bethesda, MD 20892, USA.

|December 18, 2019

Summary

Interferon lambda proteins protect tissue barriers, but a specific variant (IFNL4-TT) impairs hepatitis C virus clearance. This variant shows strong evolutionary selection, yet its biological mechanisms remain unclear.

Keywords:

Hepatitis C virus IFNL3 Infectious disease Interferon lambda Liver

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Area of Science:

Immunology
Genetics
Virology

Background:

Interferon lambda proteins activate the JAK-STAT pathway, upregulating antiviral genes.
Initially considered redundant to interferon alpha, interferon lambdas uniquely protect tissue barriers.
The interferon lambda 4 (IFNL4) gene and its protein product are determined by the IFNL4-ΔG/TT variant (rs368234815).

Purpose of the Study:

To investigate the role of IFNL4 genotypes in viral infections and associated diseases.
To explore the evolutionary selection pressures acting on IFNL4 alleles.
To elucidate the biological mechanisms underlying IFNL4 genotype-phenotype associations.

Main Methods:

Analysis of IFNL4 genotype data.
Correlation studies linking IFNL4 genotype to viral clearance, viral genome variation, and disease risk.
Evolutionary genetic analysis of IFNL4 allele frequencies.

Main Results:

IFNL4-ΔG allele generates functional IFNL4 protein, while IFNL4-TT leads to premature termination.
Genotypes producing IFNL4 protein are strongly associated with impaired hepatitis C virus (HCV) clearance.
IFNL4 genotype is linked to HCV genome variation, hepatic fibrosis, cancer risk, and other infectious diseases.

Conclusions:

Despite general antiviral functions of interferons, specific IFNL4 genotypes impair HCV clearance.
Strong evolutionary selection against the ancestral IFNL4-ΔG allele, prevalent in African populations, is observed.
The biological basis for IFNL4's influence on viral infections and disease susceptibility requires further investigation.