In vitro and in vivo evaluation of humanized monoclonal antibodies targeting pneumolysin

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Streptococcus pneumoniae is a gram-positive bacterium that causes a variety of diseases, including otitis media, sinusitis, pneumonia, bacteremia, and meningitis. While pneumococcal conjugate vaccines have reduced disease burden globally, serotype replacement affects the effectiveness of the vaccine, and S. pneumoniae has become resistant to a variety of antibiotics. Infections caused by antibiotic-resistant strains can interfere with the treatment of associated diseases. Monoclonal antibody therapy has emerged as a promising solution to the clinical problems caused by refractory S. pneumoniae . Enzyme-linked immunosorbent assay was used to detect antigen-antibody affinity. The anti-hemolytic activity of the antibody was comprehensively evaluated by in vitro anti-hemolytic assay and in vivo mouse assay. The blood concentration-time change of the antibody was evaluated by pharmacokinetic assay. Humanized monoclonal antibody (2E5zumab) was found to have high affinity for pneumolysin (PLY). In vitro anti-hemolysis experiments demonstrated that the antibody could effectively neutralize PLY. In vivo experiments indicated that the survival rate of S. pneumoniae -infected mice was significantly improved by the antibody ( P < 0.01). Pharmacokinetic studies revealed that the antibody possessed a long half-life and high bioavailability, which were essential for sustained resistance to the toxin. In summary, the humanized antibody (2E5zumab) was successfully prepared, and the monoclonal antibody showed significant pharmacodynamic effects within in vivo mouse models and in vitro experiments. IMPORTANCE Streptococcus pneumoniae is a leading bacterial cause of a wide range of infections, including otitis media, community-acquired pneumonia, sepsis, and meningitis. Pneumococcal disease has become a major public health problem worldwide. In this study, we developed a humanized monoclonal antibody (2E5zumab). In vitro functional assays demonstrated that the antibody was effective in neutralizing PLY, and in vivo studies showed that the antibody had a strong effect against pneumococcal infections. Therefore, the present study provides a new humanized anti-PLY antibody that is important for the development of therapeutic interventions against pneumococcal infections.