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Multicenter Study
. 2025 May 27;45(1):100.
doi: 10.1007/s10875-025-01892-0.

From Rare to Common: Genetic Insights into TLR7 Variants in a Multicentric Spanish Study on COVID-19 Severity

Arnau Antolí  1   2   3   4 , Gardenia Vargas-Parra #  5   6   7 , Angels Sierra-Fortuny #  1   3 , Jose Luis Gomez-Vazquez  1   3   4 , Paula Rofes  5   6   7 , Elisabet Munté  5   6   7 , Julen Viana-Errasti  6 , Raúl Marín-Montes  6   8 , Adriana López-Doriga  8   9 , Lidia Feliubadaló  5   6   7 , Jesús Del Valle  5   6   7 , Alexandre Pérez-González  10   11 , Eva Poveda  11 , Xavier Solanich #  1   2   3   4 , Conxi Lázaro #  12   13   14   15
Affiliations
Multicenter Study

From Rare to Common: Genetic Insights into TLR7 Variants in a Multicentric Spanish Study on COVID-19 Severity

Arnau Antolí et al. J Clin Immunol. .

Abstract

TLR7, which encodes a key receptor for single-stranded RNA (ssRNA) virus of the innate immune system, was recently associated with X-linked immunodeficiency and COVID-19 susceptibility. This study investigates the association between TLR7 variants and susceptibility to severe COVID-19 in a multicentric Spanish cohort. The TLR7 gene was sequenced in a cohort of 365 COVID-19 patients, stratified into two groups: one comprising mild and asymptomatic patients, considered as controls (n = 87), and the other consisting of moderate to severely affected patients hospitalized due to COVID-19 pneumonia, considered as cases (n = 278). A total of 152 unique TLR7 variants were identified, of note, six rare variants were identified in 11 cases (3.96%), all of whom belonged to the case group. The functional impact of rare TLR7 variants was assessed using a luciferase reporter assay and revealed that N215S is a loss-of-function (LOF) variant, while D332G exhibits an hypomorphic behavior. Conversely, H90Y, V219I, A448V, and R902K maintained normal signaling. No skewed X-inactivation was observed in female carriers of N215S or D332G. In addition, the common variants Q11L (rs179008), c.4-151A>G (rs179009) and c.*881C>G (rs3853839) were associated with severe pneumonia, while c.4-151A>G (rs179009) was specifically linked to Intensive Care Unit (ICU) admission. These findings highlight the role of TLR7 in antiviral immune response and its association with severe COVID-19 in men. The luciferase assay proves to be a reliable tool for evaluating TLR7 signaling, effectively distinguishing between neutral, LOF, and gain-of-function (GOF) variants. Further research is needed to better understand TLR7 variants and its implications in immunodeficiency and immune dysregulation.

Keywords: COVID-19; TLR7; X-linked; immunodeficiency; innate immunity.

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Conflict of interest statement

Declarations. Ethics Approval: The study involving human participants was reviewed and approved by Bellvitge University Hospital Research Ethics Committee (approval number PR040/21). The patients/participants provided their written informed consent to participate in this study, and for the publication of any data included in this article. Competing interests: The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Functional evaluation of the 6 rare TLR7 variants. Previous known TLR7 LOF variants N75H, Q710Rfs*18 and V795F (References 12,22), GOF variant: R28G (Reference 71), and common variants Q11L and V222D were included in the functional evaluation as controls. A Immunobloting of TLR7 (140kD) WT and variants using N-terminal and C-terminal primary antibodies. B HEK293T were or not stimulated with R848 1 μg/mL, CL264 5 μg/mL, R837 5 μg/mL for 24 h. NFκB response was measured using a Dual-Luciferase Reporter, Luciferase/Renilla ratios were normalized against the stimulated WT variant values. Mean ± SEM of n = 3 experiments. Two-way ANOVA with Dunnett’s post hoc test. Variants with less than 25% of the activity of the stimulated WT variant were considered LOF. EV: Empty vector; WT: Wild Type; LOF: Loss of function; GOF: Gain of function; NS: non-stimulated; *p < 0.0332; **p < 0.0021; ***p < 0.0002; ****p < 0.0001
Fig. 2
Fig. 2
Pedigree of the family harbouring D332G variant. X+ indicates D332G allele. X− indicates WT allele. The proband is indicated with an arrow. Black color indicates COVID-19 moderate (WHO-OS 4) to severe phenotype (WHO-OS 5), while grey indicates patients with a mild to asymptomatic (WHO-OS 1–2) disease presentation
See this image and copyright information in PMC

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