Thr399Ile Polymorphism of Toll-Like Receptor 4 Gene and COVID -19 Severity in Samples of Iraqi Patients: Baghdad Province

Abstract

Background:    Toll-like receptor 4 (TLR4) is a pattern recognition receptor involved in the innate immune response, capable of recognizing certain molecular patterns found in bacteria and viruses, including the severe acute respiratory syndrome coronavirus 2 (SARS–CoV2) virus responsible for Corona virus disease 2019 (COVID-19).
Objective:    To investigate the potential relationship between the severity of COVID-19 and a specific genetic variation in the TLR4 gene known as Thr399Ile. 
Methods:    A cross-sectional study conducted on 90 patients with COVID-19 in Baghdad. The researchers genotyping of Thr399Ile polymorphism in DNA extracted from blood samples of patients was done using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analyses.
Results:    Two genotypes were found CC and CT, and no patients exhibiting the TT genotype. The CC genotype was associated with a DNA fragment size of 407 base pairs, while the CT genotype showed a size of 378 + 29 base pairs. In the non-severe infection group, the CC genotype frequency was 95.55%, while the CT genotype frequency was 4.44%. In the severe infection group, the CC genotype frequency was 93.33%, and the CT genotype frequency was 6.66%. This indicates no significant association between Thr399Ile polymorphism and COVID-19 severity. Thr399Ile mutant allele frequency among the 90 COVID-19 patients was found to be 5.5% (5 out of 90).
Conclusion:    Functionally effective Thr399Ile polymorphism of TLR4 gene have apparently no influence on the individual susceptibility for COVID-19 severity infection.
Keywords:    COVID-19, TLR4, Thr399Ile polymorphism, mutant allele frequency.
Citation:    Jaber MF, Khudhair AM. Thr399Ile Polymorphism of toll-like receptor 4 gene and COVID -19 severity in samples of Iraqi patients: Baghdad province. Iraqi JMS. 2025; 23(2): 264-271. doi: 10.22578/IJMS.23.2.9