rs12980275 — IFNL3

IFNL3 rs12980275 — The Asian HCV Pharmacogenomics Marker

When Tanaka and colleagues performed a genome-wide association study in Japanese hepatitis C patients in 2009, two variants near the IL28B gene emerged with striking statistical force: rs8099917 and rs12980275. The latter — a simple A-to-G change on chromosome 19 — reached P=1.93×10⁻¹³ for null virological response and P=3.99×10⁻²⁴ for sustained virologic response, making it one of the most significant host genetic associations in hepatitis C pharmacogenomics. While rs12979860 later became the standard marker in European clinical practice, rs12980275 remains the preferred tag in Asian populations and HCV genotype-4 testing panels.

The variant sits approximately 1 kilobase downstream of the IFNL3 (formerly IL28B) gene on chromosome 19q13.13, in a regulatory region that influences expression of interferon lambda-3¹¹ interferon lambda-3
one of four type III interferons that restrict viral replication at mucosal and hepatic surfaces by activating the JAK-STAT pathway in epithelial cells and hepatocytes. The G allele at rs12980275 is in strong linkage disequilibrium²² linkage disequilibrium
non-random co-inheritance of nearby genetic variants with the T allele of rs12979860 (r²=0.68–1.0 depending on population) — meaning both tag the same underlying IFNL3/IFNL4 haplotype that impairs antiviral immunity.

The Mechanism

rs12980275 does not alter any protein sequence; its effect is regulatory. The G allele tags the same unfavourable haplotype across the IFNL3/IFNL4 region as rs12979860 T and rs8099917 G. On this haplotype, the functional causal variant is the ss469415590 frameshift (rs368234815)³³ ss469415590 frameshift (rs368234815)
a dinucleotide variant in IFNL4 intron 1 that either creates or destroys functional interferon lambda-4 protein. The ΔG allele at rs368234815 — tagged by rs12980275 G — produces functional IFN-λ4 protein, which paradoxically impairs hepatitis C clearance by inducing endoplasmic reticulum stress in hepatocytes, pre-activating interferon-stimulated genes in ways that desensitise cells to exogenous interferon treatment, and dampening HCV-specific CD8+ T-cell responses.

The rs12980275 G allele also tags regulatory elements controlling IFNL3 transcription itself. In a haemodialysis cohort, the AG genotype was associated with elevated plasma IFN-λ3 levels, suggesting the variant influences IFNL3 expression in a complex dosage-dependent manner that differs between heterozygotes and GG homozygotes.

The Evidence

The Tanaka et al. 2009 GWAS⁴⁴ Tanaka et al. 2009 GWAS in Japanese HCV genotype-1 patients was the discovery study for this marker. SVR rates declined sharply across genotypes: AA patients achieved approximately 76.9% SVR, while GG patients achieved only 12.5% — a striking gradient that established the clinical importance of this locus in Asian populations.

A meta-analysis of 16 studies comprising 2,786 patients⁵⁵ meta-analysis of 16 studies comprising 2,786 patients found the AA genotype predicts significantly higher SVR than AG/GG genotypes with peginterferon/ribavirin. The overall odds ratio was approximately 2.88; in the Asian subgroup it was OR 3.08 (95% CI 1.45–6.54) and in Caucasians it was OR 2.74 (95% CI 1.53–4.92). The association held specifically for HCV genotypes 1 and 4.

In a Chinese Han cohort of 238 patients, rs12980275 AA was the only IL28B marker independently associated with rapid viral response⁶⁶ rs12980275 AA was the only IL28B marker independently associated with rapid viral response. Carriers of AG/GG genotypes had an adjusted OR of 0.43 (95% CI 0.24–0.75) for achieving rapid viral response, confirming the G allele's predictive value specifically in this population.

Notably, in Korean patients where the AA genotype frequency reaches 87.2% and the GG genotype is essentially absent, IL28B testing including rs12980275 was found to have limited clinical utility precisely because the favourable genotype predominates. This mirrors the broader pattern across East Asia: the G allele frequency is only ~10% in East Asians compared to ~31% in Europeans and ~51% in Africans, making rs12980275 most clinically relevant in mixed or non-East-Asian populations.

Beyond hepatitis C, the G allele has been linked to impaired antiviral responses more broadly. In a Spanish surgical cohort, GG homozygotes had a 2.15-fold higher adjusted hazard of 28-day mortality during septic shock⁷⁷ GG homozygotes had a 2.15-fold higher adjusted hazard of 28-day mortality during septic shock compared to AA carriers, consistent with impaired innate immune defence. In COVID-19 patients, the AA genotype was significantly enriched in survivors versus non-survivors⁸⁸ the AA genotype was significantly enriched in survivors versus non-survivors, with GG genotype independently associated with severe disease in multivariate analysis.

Practical Actions

For hepatitis C management, rs12980275 provides essentially the same clinical information as rs12979860 in most populations. With modern pangenotypic direct-acting antivirals (DAAs), overall SVR rates exceed 95% regardless of IFNL3 genotype. The variant's main clinical relevance today lies in treatment duration decisions: GG carriers are not candidates for abbreviated 8-week protocols and should receive full 12-week courses. The variant also retains value for predicting the likelihood of spontaneous clearance in acute HCV infection.

For non-HCV health contexts, the G allele signal across septic shock and COVID-19 mortality suggests GG carriers have a broadly attenuated innate antiviral and antibacterial response, making vaccination and early treatment adherence particularly important.

Interactions

rs12980275 is in strong linkage disequilibrium with rs12979860⁹⁹ linkage disequilibrium with rs12979860
r²=0.68–1.0 depending on population; both tag the same IFNL4/3 haplotype but with varying predictive weights across ancestries, and with rs8099917¹⁰¹⁰ rs8099917
also in LD across the IFNL3/4 locus; the two were co-identified in the original Japanese GWAS, and with rs368234815¹¹¹¹ rs368234815
the true causal frameshift in IFNL4 that determines whether functional IFN-λ4 protein is produced. Commercial HCV pharmacogenomics panels often include rs12980275 alongside rs12979860 and rs8099917 because no single marker provides complete predictive information across all ancestries. The variants should not be treated as independent effects — they all tag the same underlying functional haplotype.