Protective Effects of Laser-Irradiated Streptococcus pneumoniae: A Novel Vaccine Candidate

Streptococcus pneumoniae (S. pneumoniae) is a significant cause of community-acquired pneumonia worldwide. Pneumococcal vaccines can prevent severe disease; however, their high cost, limited serotype coverage, and variable effectiveness across populations underscore the need for alternative vaccine strategies. Laser irradiation has been proposed as a novel approach to attenuate bacterial virulence while preserving immunogenicity. Clinical isolates of S. pneumoniae were irradiated using low‑energy laser irradiation at wavelengths of ۶۶۰ nm, ۸۲۰ nm, and ۹۱۵ nm to prepare an inactivated bacterial vaccine. Sterility testing confirmed complete bacterial inactivation. BALB/c mice were immunized three times at two-week intervals and were then challenged with wild-type S. pneumoniae. A commercial pneumococcal vaccine served as a positive control. Antibody responses (immunoglobulin M [IgM], IgG, and IgA) were measured, and survival was monitored for ۲۱ days post-challenge. Irradiation at ۹۱۵ nm was the most effective for bacterial inactivation. Mice immunized with the ۹۱۵ nm-inactivated vaccine showed significantly higher levels of IgM, IgG, and IgA compared to the unvaccinated group. Following bacterial challenge, all mice in this group survived, whereas ۴۰% of mice immunized with the commercial vaccine died within ۲۱ days after challenge. Low-energy laser irradiation at ۹۱۵ nm effectively inactivated S. pneumoniae while retaining its immunogenic properties. Immunization with this preparation elicited robust antibody responses and provided complete protection in mice, suggesting that it may serve as a novel pneumococcal vaccine candidate.

کلیدواژه ها:

Pneumococcal vaccine ، Laser ، Immunization ، Antibody.