New insight into sensing and function of the bacterial lysate OM-85

Bacterial lysates are widely used in the clinic to minimize the pathologic consequences of respiratory infections. Our new study shows how one such lysate, OM-85, works on human myeloid cells to trigger an immunomodulatory gene circuit.

OM-85 is a bacterial lysate commonly used in clinical practice to reduce duration and frequency of recurrent respiratory tract infections. Whereas some studies have addressed its regulatory effects in vivo, the mechanisms of OM-85 sensing remain inadequately investigated. In a new study recently published in Mucosal Immunology, led by prof. Greta Guarda at the Institute for Research in Biomedicine (IRB, affiliated to the Università della Svizzera italiana), in collaboration with OM-Pharma (Meyrin, Switzerland), Dr. med. Maurizio Bernasconi at Ente Ospedalierio Cantonale (EOC), and Oncolines (Netherlands), the researchers investigated the mechanisms of OM-85 sensing and function in the immune cells.

Dr. Hanif Khameneh and colleagues showed that, in human immune cells, TLR2 and TLR4 orchestrate the response to OM-85. RNA-sequencing on human monocyte-derived dendritic cells as well as single cell RNAseq on human bronchoalveolar lavage cells revealed a largely overlapping TLR2/4-dependent proinflammatory gene signature induced by OM-85, including a unique immunomodulatory gene set. The findings of this study reveal how a standardized bacterial lysate fine-tunes the immune response through TLR2 and TLR4, which are crucial for immunity and tolerance.