# The role of soluble toll-like receptor-2 and 4 in children with pneumonia: a combined analysis of saliva and serum samples

## TL;DR

This study explores the use of saliva and serum samples to identify biomarkers for diagnosing and assessing the severity of pneumonia in children.

## Contribution

The study introduces salivary TLR-2 and TLR-4 as potential non-invasive biomarkers for pediatric pneumonia diagnosis and severity stratification.

## Key findings

- Salivary TLR-2 and TLR-4 showed high sensitivity for detecting pneumonia in children.
- Serum levels of TLR-2, TLR-4, and several cytokines were significantly lower in children with COVID-19 compared to other viral pneumonias.
- Soluble TLR-2 and TLR-4 in saliva may serve as promising non-invasive biomarkers for pediatric pneumonia.

## Abstract

Since rapid and accurate diagnosis of pneumonia and determination of its severity remain challenging, particularly in childhood, we aimed to evaluate the role of toll-like receptors (TLR) in pneumonia, which has been limited in animal and adult studies.

In this study, TLR-2, TLR-4, interleukin (IL)-1β, IL-4, IL-6, IL-10, interferon (IFN)-α, and tumor necrosis factor (TNF)-α levels were measured in serum samples of n = 67 pediatric patients with community acquired pneumonia (CAP) (43 inpatients and 24 outpatients) and 22 healthy pediatric controls. Saliva samples of n = 30 pediatric patients with CAP (19 inpatients and 11 outpatients) and 19 healthy pediatric controls were also investigated to analyze the expression of these cytokines and TLRs.

In saliva samples taken at the time of diagnosis, threshold levels of TLR-2 were 1.16 2-ΔΔCt and of TLR-4 1.28 2-ΔΔCt differentiating patients with and without pneumonia. The sensitivity of salivary TLR-2 and TLR-4 tests were found to be 0.80 and 0.86, respectively. In serum samples, soluble TLR-2 and TLR-4, IL-1β, IL-4, IL-6, Il-10, IFN-α, and TNF-α levels were significantly decreased in patients with coronavirus disease-19 (COVID-19) as compared with other viruses (p < 0.05 in each). Only one mortal case was present in the inpatient group during the study period.

This study demonstrates that salivary TNF-α, soluble TLR-2 and TLR-4 may serve as promising non-invasive biomarkers for diagnosing and stratifying pediatric pneumonia.