Mucin O-glycans protect host cells by tempering pneumolysin expression in Streptococcus pneumoniae

The ability of mucosal epithelia to sustain asymptomatic colonization by pathogens, such as Streptococcus pneumoniae (Spn), remains a significant and unresolved scientific question. This study reveals that mucins—the main gel-forming elements of mucus—and their associated glycans, suppress the expression of pneumolysin, a Spn toxin that causes tissue injury and triggers inflammatory responses. These findings highlight a unique protective function of mucins, offering insights into potential therapeutic strategies. Overall design: Examination of differential gene expression in Streptococcus pneumoniae TIGR4 in response to MUC5AC mucins and MUC5AC glycans in THY medium