Respiratory syncytial virus (RSV) is the most common virus that causes Acute Respiratory Tract Infections (ARTIs) in young children, with a high risk of serious bronchiolitis. RSV infection symptoms range from mild fever, cough, runny nose, and wheezing to severe symptoms such as difficulty breathing and respiratory failure. Cytokines in the airways of children with bronchiolitis, such as tumor necrosis factor (TNF-alpha), Interleukin-6 (IL-6) and IL-8, have been shown to increase at a very high level in primary RSV infection, and extreme elevation of IL-6 is associated with sudden death in children with RSV infection. The World Health Organization (WHO) estimates that 160,000-600,000 children under the age of five die or hospitalize each year as a result of RSV infection. There is currently no vaccine or specific treatment for RSV-infected children because monoclonal antibody palivizumab therapy and antiviral nucleotide drug ribavirin are either too expensive or too dangerous for children and are only recommended for high-risk patients.
In recent years, preventive and supportive therapies for respiratory tract infection have grown in popularity, with probiotics emerging as promising safe candidates for therapeutic support and antibiotic reduction. It is suggested that probiotics can capture viruses through direct interactions, or produce secondary growths that inhibit virus growth or stimulate the immune system to capture virus intrusion. However, the efficacy of oral digested probiotics on children's respiratory tracts has been slow to develop (normally it takes about 3-12 months) and is primarily used for prevention rather than supportive treatment of ARITs. As a result, alternative delivery routes for probiotics in the treatment of ARTIs are required.
The aim of the study about to evaluate the effectiveness of nasal-spraying probiotics containing two bacterial strains, Bacillus subtilis and Bacillus clausii in preventing and in supporting the treatment of children having acute respiratory symptoms due to RSV infection.
Methods: A randomized, blind, and controlled clinical trial are conducted. The patient's parents are required to provide the following information of their children: full name, sex, age, obstetric history, vaccination history, antibiotic use history… After informed consent, 100 patients with ARTIs due to RSV will be randomized into 2 groups (n = 50/group): the control group (named "Control" group) use 0.9% NaCl physiological saline and an experimental group (named the "Navax" group) use the probiotics LiveSpo Navax. The patient is given a coded spray in the form of a blind sample to ensure the objectivity of the study. The clinical follow-up will be 6 days, nasopharyngeal samples will be collected at day 0 and day 3 to evaluate potential reductions in viral load and co-infection bacteria, as well as modulation of overreacted cytokine release and the presence of probiotic spores in the patient's nasal mucosa.
Real-time PCR for detection of microorganism in nasopharyngeal samples: semi-quantitative assays for measuring changes in RSV load and co-infection bacterial concentrations is conducted by the real-time RT-PCR/PCR routine protocol which has been standardized under ISO 15189:2012 criteria and used in Vietnam National Children's Hospital. Detection of B. subtilis ANA4 and B. clausii ANA39 are also conducted by real-time PCR SYBR Green that has been standardized under ISO 17025: 2017 standard and routinely in the Key Laboratory of Enzyme and Protein Technology, VNU University of Science.
ELISA assays for cytokine levels: pro-inflammatory cytokines levels (pg/mL) including interleukin (IL-6, IL-8) and TNF-alpha are quantified using an enzyme-linked immunosorbent assay kit (ELISA) according to the manufacturer's instructions.
During treatment, patients are monitored daily for typical clinical symptoms of RSV-induced respiratory tract infections, including runny nose, chest depression, difficulty breathing, dry rales, moist rales, body temperature (oC), oxymetry (SpO2) (%), pulse (beats/min), and breath (beats/min) until discharged. The patients' health conditions are observed by doctors and nurses, and their pieces of information are filled in medical records. During this study, parents' patients are asked to abstain from consumption for their children of other probiotics, either via nasal spray or oral administration and refrain from cleaning nose for their children with other 0.9% NaCl physiological saline sprayers.
Data collection and statistical analysis: individual medical records are collected, and the patient's information is then gathered and systematized in a data set. The efficacy of LiveSpo Navax is evaluated and compared to 0.9% NaCl physiological saline based on the following clinical and sub-clinical criteria obtained in Navax and Control groups: (i) the symptomatic-relieving day; (ii) the reduction levels (2\^△Ct) of RSV load and co-infection bacteria concentrations. △Ct for target genes is calculated as Ct (threshold cycle) at day 3 - Ct at day 0 while Ct of internal control is adjusted to be equal among all samples; (iii) the reduction levels of IL-6, IL-8, and TNF-alpha cytokines. The tabular analysis is performed on dichotomous variables using the χ2 test or Fisher's exact test when the expected value of any cell is below five. Continuous variables are compared using either the Wilcoxon test, t-test, or the Mann-Whitney test when data are not normally distributed. The correlations among the variables are assessed by Spearman's correlation analysis. Statistical and graphical analyses are performed on GraphPad Prism v8.4.3 software (GraphPad Software, CA, USA). The significance level of all analyzes is set at p \< 0.05. P-values.
Expected outcomes: (i) LiveSpo Navax alleviates RSV-infection symptoms about 25% more effectively, as indicated by 90% of patients using LiveSpo Navax (Navax group) are symptom-free at day 3-6 of intervention depending on symptoms, compared to 65% of patients in Control group; (ii) Patients in Navax group has more significant reductions in RSV load (\>10 fold) than patients in Control group at day 3 of intervention.
