A multi-epitope vaccine targeting Mycoplasma pneumoniae adhesin and toxin elicits dual protective immunity in mice

Mycoplasma pneumoniae (Mp), a significant cause of pediatric respiratory infections, urgently requires vaccines due to its high infection rates and increasing antibiotic resistance. This study designed and tested a multi-epitope vaccine (MEV), P1Tx, targeting the Mp adhesin P1 and the unique exotoxin, community-acquired respiratory distress syndrome (CARDS) toxin. Bioinformatics was used to identify the dominant T- and B-cell epitopes for constructing the chimeric protein P1Tx. In vitro, the recombinant P1Tx expressed in bacteria reacted with sera from patients infected with Mp. P1Tx-specific antibodies prevented Mp from adhering to human bronchial epithelial cells (BEAS-2B) and neutralized the vacuolating effects of CARDS toxin. In BALB/c mouse models, P1Tx immunization produced high levels of IgG, stimulated the proliferation of splenic germinal center (GC) B cells and memory B cells (MBCs), and elicited a Th2-skewed immune response. The vaccine significantly reduced lung bacterial counts, mitigated inflammatory damage, and lowered pro-inflammatory cytokine levels in the lungs of mice infected with Mp, demonstrating strong protection. Overall, our results indicate that the MEV P1Tx provides therapeutic effects similar to those of P1 subunit vaccines in alleviating pneumonia caused by Mp infection. These findings establish MEV P1Tx as a promising new vaccine candidate against Mp infection.