The production of toxins is critical to the success of bacteria, with their targets and outcomes varying widely. Pneumolysin (Ply), produced by the major human pathogen Streptococcus pneumoniae, is a ...

The production of toxins is critical to the success of bacteria, with their targets and outcomes varying widely. Pneumolysin (Ply), produced by the major human pathogen Streptococcus pneumoniae, is a cytolytic pore forming toxin that plays many diverse roles including inducing tissue damage and inflammation, evasion of many aspects of the human immune system, invasion of the bacteria into deeper tissue, and transmission to new hosts. Despite its importance, many aspects of the biology of this toxin have to date remained unknown, in particular, what role of the three other genes that form part of the ply operon play in Ply production. Here we demonstrate that these genes encode a complex regulatory system, that includes a putative membrane destabilising protein (PlyA) and a MazEF-like toxin-antitoxin system (PlyB and PlyC), the toxin of which (PlyC) destabilises the Ply transcript. We propose a tripartite model whereby when the operon reaches relatively high levels of expression PlyA destabilises the S. pneumoniae membrane creating a stress that triggers a necessary negative feedback loop which results in the degradation of the PlyB antitoxin, release of the PlyC toxin and degradation of the ply transcript, thereby providing a means by which Ply production can be tightly regulated. Given the importance of Ply to the ability of S. pneumoniae to cause infection, identifying the factors that result in the shutdown of Ply production and release by the bacteria would seem promising target for future therapeutic strategies.   ### Competing Interest Statement The authors have declared no competing interest. Taighde Éireann - Research Ireland, 21/FFP-A/9704 Wellcome Trust, 227883/23/Z, 323576/Z/24/Z Medical Research Council, MR/Y012070/1

A new study by scientists at the Rajiv Gandhi Centre for Biotechnology (RGCB) in Thiruvananthapuram has revealed an unexpected mechanism by which pneumolysin, a toxin from the pneumonia-causing…

Researchers in Sweden have developed tiny vesicles that reduced damage to brain cells in mice infected with bacteria that cause meningitis.  Bacterial meningitis affects the protective lining of the…

Bacterial meningitis can cause severe brain damage even when patients receive antibiotic treatment promptly. Researchers at Karolinska Institutet have developed tiny biological vesicles that, in animal studies, were able to capture bacterial toxins, protect neurons, reduce inflammation and delay disease progression.

Profiling of pneumococcal population structure during infection reveals an unappreciated role of bacteriocins in driving the development of pneumonia by facilitating the release of inflammatory mediat...

Severe illness and even death are likely to result if you develop another respiratory infection after catching the flu. Now, however, a team of researchers has determined that if you reverse the order of infection, pneumococcus bacteria may actually protect against a bad case of the flu. The bacterial protein pneumolysin, a bacterial virulence factor, might protect certain immune system cells (macrophages) in the alveoli of the lungs, preventing inflammation and, thus, pneumonia.

Background: Streptococcus pneumonia is the primary etiological agent of community-acquired pneumonia (CAP).

Author summary Streptococcus pneumoniae, the Gram-positiv...

Author Summary Cardiac complications frequently accompany...

Author Summary The pore-forming cholesterol-dependent cyt...

Traditional polysaccharide vaccines are constrained by streptococcus pneumoniae diversity. We propose a protein-based pneumococcal vaccine (PBPV) — formulated with conserved surface proteins P3296, P5668, PRx1, and pneumolysin (Ply) — that could potentially offer superior immune breadth independent of capsular polysaccharide serotypes. Here, we evaluated the multifunctional antibody responses induced by PBPV, including immunogenicity, Ply neutralization, opsonophagocytic activity (OPA), and such nonopsonic functions as NK cell activation (ADNKA), antibody-dependent cellular phagocytosis, and neutrophil phagocytosis (ADNP) in a cohort of 50- to 69-year-olds. While PBPV showed shorter-lasting immune responses, including reduced Ply-neutralizing capacity, it provided broader cross-serotype protection than 23-valent pneumococcal polysaccharide vaccine. Correlation analysis identified distinct PspA-specific IgG subclass roles: P3296-IgG1 correlated with OPA, and IgG3 correlated with ADNKA/ADNP; P5668-IgG2 correlated with ADNKA/ADNP, and IgG3 correlated with OPA; and PRx1-IgG2 correlated with OPA, and IgG3 correlated with ADNKA. Critically, while no efficacy data have yet confirmed the protective effect of PBPV, its targeting of conserved proteins rather than capsular polysaccharides enables simplified manufacturing and expanded coverage, positioning it as a promising alternative to traditional multipolysaccharide vaccines.