TLR7 polymorphisms are associated with COVID-19 susceptibility and severity
Edyta Paradowska1, Katarzyna D Kania1, Dariusz Jarych1
1Laboratory of Virology, Institute of Medical Biology of the Polish Academy of Sciences, Lodz, Poland.
Frontiers in Immunology
|June 15, 2026
Summary
Genetic variations in Toll-like receptor 7 (TLR7) influence COVID-19 severity. The TLR7 rs3853839 SNP is linked to increased hospitalization risk, while TLR7 rs179008 may reduce symptom severity.
Area of Science:
- Immunology
- Genetics
- Infectious Diseases
Background:
- Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) triggers innate immune responses via pattern-recognition receptors (PRRs).
- PRRs like Toll-like receptors (TLRs) and RIG-I-like receptors (RLRs) detect viral RNA, initiating signaling pathways for interferon and cytokine production.
- Host genetic variations in PRRs may impact SARS-CoV-2 infection susceptibility and COVID-19 disease severity, but their precise roles are not fully understood.
Purpose of the Study:
- To investigate the association between specific polymorphisms in PRR genes and the severity of COVID-19.
- To analyze the frequency of PRR gene polymorphisms in hospitalized COVID-19 patients and correlate them with clinical outcomes and cytokine profiles.
Main Methods:
- Genotyping of ten PRR polymorphisms (including TLR3, TLR7, TLR8, IFIH1, and DDX58) in 261 individuals (166 COVID-19 patients).
- Quantitative PCR (qPCR) and PCR-RFLP techniques were used for SNP genotyping.
- Serum cytokine levels were measured using MILLIPLEX Magnetic Bead Panels and Luminex xMAP technology.
Main Results:
- The recessive G/G genotype of TLR7 rs3853839 SNP was associated with an increased risk of hospitalization.
- The presence of at least one recessive T allele for TLR7 rs179008 SNP correlated with lower levels of cytokines (IP-10, IL-10, TNF-α).
- TLR7 rs179008 SNP was linked to a decreased risk of severe symptoms in hospitalized patients.
Conclusions:
- The TLR7 rs3853839 SNP may serve as a genetic risk factor for severe COVID-19.
- The missense TLR7 rs179008 SNP (Q11L) appears to contribute to milder COVID-19 symptoms.
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