About Streptococcus pneumoniae

Streptococcus pneumoniae is a major pathogen found largely in the respiratory tract. Humans are the only known host and anywhere from 5 to 95% of the population may be asymptomatically colonized at any one time. Such carriers are the principal reservoir for transmission of the bacterium in the community. Nasopharyngeal carriage is a dynamic process, with the number of bacteria usually kept under control by the innate and acquired immune defences of the host. If this delicate balance is disturbed, however, the bacteria can invade deeper tissues and result in a spectrum of diseases including pneumonia, bacteraemia, meningitis, otitis media and sinusitis.


Streptococcus pneumoniae exists as 100 different serotypes distinguishable by the capsular polysaccharides expressed on the bacterial surface. Each serotype is immunologically different, such that most of the vaccines under development need to be targeted to each specific serotype. While polysaccharide conjugate vaccines (PCVs) have been highly effective against the serotypes that they cover, serotypes not covered by these vaccines often increase in prevalence (a phenomenon called serotype replacement), thereby offsetting reductions in disease burden and resulting in these vaccines becoming less effective over time.


While Streptococcus pneumoniae is sensitive to penicillin, resistance to penicillin and many other antibiotics has increased such that there is now a high rate of resistance. This leaves vaccination as a critical tool in disease control.


The Science






Development Progress


We have developed a reproducible and scaled-up manufacturing process to GMP standard using state-of-the-art microbial fermentation and irradiation facilities in Australia. Our manufacturing process is vastly simpler and more cost-effective compared to the manufacture of polysaccharide conjugate vaccines, which require hundreds of process steps and over two years to complete a single batch. A GLP toxicology study commenced in Q2 2022 and we are planning a randomised, placebo-controlled, double-blind, sequential ascending-dose study to evaluate the acute safety, tolerability, and immunogenicity of Gamma-PN™ in comparison to Prevnar 13® and Pneumovax 23® in healthy adults aged 50-64 years of age. This clinical study will be conducted in Australia commencing in 2023.





David et al. 2022 A Nonadjuvanted Whole-Inactivated Pneumococcal Vaccine Induces Multiserotype Opsonophagocytic Responses Mediated by Noncapsule-Specific Antibodies. mBio. Click here for Japanese translation (日本語訳はこちら).


David et al. 2019 Enhanced safety and immunogenicity of a psaA mutant whole-cell inactivated pneumococcal vaccine. Immunol. Cell Biol. 97: 726-739.

David et al. 2017 The effect of gamma-irradiation conditions on the immunogenicity of whole inactivated influenza A virus. Vaccine 35: 1071-1079.

Babb et al. 2016 Enhanced protective responses to a serotype-independent pneumococcal vaccine when combined with an inactivated influenza vaccine. Clinical Science 131: 169-180.

Babb et al. 2016. Intranasal vaccination with γ–irradiated Streptococcus pneumoniae whole-cell vaccine provides serotype-independent protection mediated by B-cells and innate IL-17 responses. Clinical Science 130: 697-710.

Protecting children and adults from the world’s foremost bacterial pathogen