The Effect of Oral Immune Therapy on Salivary Secretory Immunoglobulin A ( SIgA ) Levels in Sick Premature Infants

Abstract

Background and aim of the work: Preterm infants have an immature mucosal immune system characterized by low endogenous production of secretory immunoglobulin A (sIgA), increasing their susceptibility to infections. Oral Immune Therapy (OIT), defined as the oropharyngeal administration of mother's own milk, may enhance mucosal immunity through direct exposure of immunological components. This study aimed to evaluate the effect of OIT on salivary sIgA levels in ill preterm infants.

Research design and methods: This study was a randomized controlled trial with a non-blinded design conducted in the Neonatal Intensive Care Unit (NICU) from February to August 2025. A total of 42 ill preterm infants were randomly allocated into an intervention group (n = 21) and a control group (n = 21). The intervention group received oropharyngeal administration of breast milk (0.1–0.2 mL every 3 hours) for 7 consecutive days, while the control group received standard care. Salivary sIgA levels were measured before (day 1) and after intervention (day 8) using an indirect enzyme immunoassay (ELISA). Statistical analysis included paired and independent tests, as well as multiple linear regression.

Results: In the intervention group, mean salivary sIgA levels significantly increased from 0.86 ± 0.12 to 1.89 ± 0.18 µg/mL (p = 0.001). In contrast, no significant change was observed in the control group (0.87 ± 0.11 to 0.89 ± 0.12 µg/mL; p = 0.321). The increase in ΔsIgA was significantly higher in the intervention group compared to the control group (p = 0.001). Multiple linear regression analysis showed that enteral nutrition (p = 0.104) and timing of gut priming initiation (p = 0.340) were not significantly associated with changes in sIgA levels.

Conclusions: Oral Immune Therapy significantly increases salivary sIgA levels in ill preterm infants, suggesting its beneficial role in enhancing early mucosal immunity. OIT may serve as a simple, safe, and non-invasive immunological intervention in neonatal care.