Rationals: Infection with the Respiratory Syncytial Virus (RSV) is one of the most common causes of respiratory tract diseases. However, treatment for pediatric RSV infection remains supportive to prevent co-infection bacteria and respiratory failure. In recent years, preventive and supportive probiotic therapies for respiratory tract infections (RTIs) have been increasingly strengthened, however, the use of oral administrative probiotics as functional foods is effective only for mild symptoms and not applicable for Acute RTIs (ARTIs). Here, we propose that direct spraying of probiotics into the nose can be a fast and effective symptomatic treatment for ARTIs.

Objectives: Investigate symptomatic treatment effects of probiotic product LiveSpo Navax, as liquid-suspension form containing Bacillus spores of safe B. subtilis ANA4 and B. clausii ANA39 strains, in children having acute respiratory diseases caused by RSV:

• Primary Objective: Evaluation of improved efficacy and reduced treatment time of LiveSpo Navax in children infected with RSV.
• Secondary Objectives: Measurement of changes in RSV viral load, co-infectious bacterial concentrations, and major cytokine indicators in the nasopharyngeal mucosa before and after 3 days using LiveSpo Navax.

Endpoints:

Primary endpoint: 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.

Secondary endpoint: Patients in Navax group had more significant reductions in RSV load (>10 fold) than patients in Control group at day 3 of intervention.

Study Population: Sample size is 100. Description of Sites: The study is carried out at Vietnam National Children's Hospital.

Description of Study Intervention: Totally 100 eligible patients are divided randomly into 2 groups (n = 50/group each): Patients in Control group received the routine treatment and three times per day 0.9% NaCl physiological saline while the and patients in Navax group received three times per day LiveSpo Navax in addition to the same standard of care treatment. The standard treatment regimen is 3-6 days but can be extended further depending on the severity of the patients' respiratory failure.

Study Duration: 12 months

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.

Inclusion Criteria:

• Children (male/female) aged from 4 to 60 months.
• Admitted hospital due to lower respiratory infection.
• RSV is positive by rapid test.
• Parents of the pediatric patient agree to participate in the study, explain and sign the research consent form.

Exclusion Criteria:

• Newborn babies.
• Have a history of drug allergy.
• Need oxygen therapy.
• Discharged before day 3.
• Lost to follow-up.
• Withdrawn from the trial.
• Continuing in the trial but missing data.
• Meeting the criteria for psychiatric disorders other than depression and/or anxiety.

Data or samples share that will be coded, with no PHI include. Approval of the request and execution of all applicable agreements (i.e. a material transfer agreement) are prerequisites to the sharing of data with the requesting party.

Data requests can be submitted starting 9 months after article publication and the data will be made accessible for up to 24 months. Extensions will be considered on a case-by-case basis.

Access to trial IPD can be requested by qualified researchers engaging in independent scientific research and will be provided following review and approval of a study protocol, informed consent form (ICF), clinical study peport (CSR). For more information or to submit a request, please contact clinicaltrial.probiotics@gmail.com

LiveSpo Navax and placebo 0.9% NaCl physiological saline are indistinguishable regarding taste and smell. The color and turbidity of LiveSpo Navax suspension is unrecognizable to investigators except the PI and analyzer, nurses, patient's parents, and patients due to opaque plastic container.