Bacterial lysates as add-on therapy in obstructive lung diseases: a systematic review and meta-analysis
Immunological mechanisms (English)Background
Exacerbations are the main cause of morbidity in obstructive lung diseases such as asthma and COPD. In a substantial number of exacerbations, respiratory viruses are involved. Bacterial lysates (BL), might prevent recurrent respiratory tract infections and therefore reduce exacerbations. BL mainly consist of inactive bacterial extracts from pathogenic respiratory bacteria and have been used from the early 50’s. Moreover, immunomodulatory effects have been observed in human and animal studies. In this meta-analysis we aim to assess the effect of add-on bacterial lysate therapy on exacerbation frequency in obstructive lung diseases and discuss the underlying immunological mechanisms.
We performed a systematic literature review based on the PRISMA statement and a meta-analysis using Revman_5.3. Data was estimated using mean differences (MD) and relative risks (RR). Out of 98 screened articles 24 studies were included, of which 6 provided sufficient data for a meta-analysis and 18 were suitable for systematic review; 15 clinical trials and 10 laboratory studies.
Twelve articles were used for a meta-analysis. After sensitivity analysis to resolve heterogeneity, omitting 6 articles, for asthma a MD of -0.86 exacerbations (95%CI -1.21;-0.50;p<0.00001) and for COPD a 23% exacerbation reduction (RR 0.77; 95%CI -0.68;-0.88;p=0.0002) was calculated (table 1). In animal studies a significant reduction of eosinophils was described combined with a reduction of several serum cytokines such as IL-4, IL1β, IL-5, IL-13 and TGFβ and an increase of IL-10 and IFNγ. (1)
Bacterial lysates can be considered as add-on therapy in adults with obstructive lung diseases such as asthma and COPD to prevent recurrent exacerbations, most likely through Treg differentiation and Th2-cytokine downregulation.
Registered with Prospero: CRD42017078141
Hypothesized working mechanism of Broncho-Vaxom