Experimental Pneumococcal Vaccine Successfully Prevents Disease in Animal Models

A novel pneumococcal vaccine has been successfully developed by investigators from Osaka Metropolitan University, using mucosal vaccine technology with pneumococcal surface proteins. In a press release, investigators indicate that the novel vaccine could cover a range of pneumococcal serotypes.¹

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The study investigators aimed to find a substitution for incomplete Freund adjuvant, which is not suitable for use in humans but shown to illicit a strong response to antigen-specific systemic immune responses, according to the study.²

"This research has succeeded in developing a vaccine formulation that can potentially be used in humans, which will advance the development of this vaccine for clinical applications," Kosuke Fujimoto, an associate professor in the department of immunology and genomics at the Graduate School of Medicine at Osaka Metropolitan University, said in a statement. "This next-generation vaccine technology is expected to contribute to the treatment of infectious diseases in the future."¹

In the study, investigators used the experimental vaccine on mice and macaques, finding that pneumonia caused by pneumococcal infections was suppressed with the vaccine.¹ The study authors said that the water-in-oil-in-water-emulsified prime-boost mucosal vaccine did protect against Streptococcus pneumoniae in both animal models used.²

The investigators used previous data regarding inducing antigen-specific mucosal immune responses from the potential vaccine in 2019. The responses elicited were mainly immunoglobulin A, according to the press release. To further develop the novel vaccine further, investigators combined the mucosal vaccine technology with surface proteins from pneumococcal.¹

Study investigators injected the vaccine intramuscularly in mice with fusion pneumococcal surface protein A (PspA), which was combined with cytosine-phosphate-guanosine (CpG) oligodeoxynucleotide and/or curdlan, according to the study. After 6 weeks, the PspA was administered intranasally. Investigators measured antigen specific immunoglobulin G (IgG) and immunoglobulin A (IgA) titers using blood and bronchoalveolar lavage fluid.²

Further, the study investigators gave mice intranasal S. pneumoniae so they could measure the severity of infection. The macaques were also intramuscularly injected with fusion PspA and CpG oligodeoxynucleotide and/or the curdlan at weeks 0 and 4, according to the study authors. At 13 or 41 weeks, PspA was intratracheally administered. The same specimen collection and measures were used for the macaques. Some were also intranasally administered S. pneumoniae and analyzed for severity, according to the study.²

The study authors reported that the immunization regimen did prevent S. pneumoniae infection, evident from the serum sample from bot animal models that were injected with the combination antigens.² The macaque models were used for proof-of-concept for the use of the potential vaccine in humans, according to the study authors.²

They reported that there were no adverse effects on body weight change during the study time. Investigators added that identifying the optimal formulation for the vaccine for use in humans is critical for future work.²

The study authors stated, “compared with [pneumococcal conjugate vaccine 13] and [pneumococcal polysaccharide vaccine 23], boosting respiratory mucosa, including nasal mucosa, rather than intramuscular injection, might be particularly beneficial for increasing the titers of antigen-specific IgG and IgA.”²

Furthermore, they concluded that future clinical application of this vaccine strategy should be explored.²

References

1. Macaque trials offer hope in pneumonia vaccine development. News release. Science Daily. November 28, 2023. Accessed December 13, 2023. https://www.sciencedaily.com/releases/2023/11/231128132429.htm
2. Yokota C, Fujimoto K, Yamakawa N, Kono M, et al. Prime-boost-type PspA3 + 2 mucosal vaccine protects cynomolgus macaques from intratracheal challenge with pneumococci. Inflamm Regen. 2023;43(1):55. doi:10.1186/s41232-023-00305-2