A Review Article on Immunological Effects of Bacterial Lysate in Upper Respiratory Tract Infection

Bacterial lysates are immunostimulants clinically used to prevent respiratory tract infections (RTIs). They enhance both innate and adaptive immune responses, demonstrating efficacy in restoring epithelial barrier integrity, activating ILC3 and dendritic cells, and promoting a Th1 response. Additionally, they stimulate the production of specific serum IgG and salivary IgA, providing cross-protection against other pathogens via trained immunity. Clinical studies report a reduction in RTI frequency and severity in patients pretreated with bacterial lysates, alongside a potential protective effect against disease progression in conditions like COPD, without significant side effects. Bacterial lysates (BLs), composed of bacterial antigens, have been utilized for decades to reduce the risk of recurrent respiratory tract infections in both pediatric and adult populations. Recent research has explored their application in allergology, particularly for allergic rhinitis (AR). The findings indicate that incorporating BLs into standard therapy for seasonal or perennial AR alleviates nasal symptoms and reduces the need for antiallergic medications in both children and adults. Furthermore, BLs demonstrate a favorable safety profile. The analysis reveals that therapeutic effects emerge within 2–6 weeks of treatment initiation and persist for at least three months post-treatment.