Pneumolysin with Low Hemolytic Activity Confers an Early Growth Advantage to Streptococcus pneumoniae in the Blood

Abstract

Streptococcus pneumoniae is a leading cause of human diseases such as pneumonia, bacteremia, meningitis, and otitis media. Pneumolysin (Ply) is an important virulence factor of S. pneumoniae and a promising future vaccine target. However, the expansion of clones carrying ply alleles with reduced hemolytic activity has been observed in serotypes associated with outbreaks of invasive disease and includes an allele identified in a highly virulent serotype 1 isolate (ply4496). The virulence of Ply-deficient and ply allelic-replacement derivatives of S. pneumoniae D39 was compared with that of wild-type D39. In addition, the protective immunogenicity of Ply against pneumococci with low versus high hemolytic activity was also investigated. Replacement of D39 ply with ply4496 resulted in a small but statistically significant reduction of virulence. However, both native Ply-and Ply4496-expressing strains were significantly more virulent than a Ply-deficient mutant. While the numbers of both Ply-and Ply4496-expressing isolate cells were higher in the blood than the numbers of Ply-deficient mutant cells, the growth of the Ply4496-expressing strain was superior to that of the wild type in the first 15 h postchallenge. Ply immunization provided protection regardless of the hemolytic activity of the challenge strain. In summary, we show that low-hemolyticactivity Ply alleles contribute to systemic virulence and may provide a survival advantage in the blood. Moreover, pneumococci expressing such alleles remain vulnerable to Ply-based vaccines.

The cholesterol-dependent cytolysins pneumolysin and streptolysin O require binding to red blood cell glycans for hemolytic activity

“…These truncated proteins consisted of domains 1-3 of Ply (PlyL) and domains 1-3 of Ply306 (PlyL306), as well as domain 4 of Ply (PlyS) and domain 4 of PlyL460D (PlySL460D). PlyS and domain 4 of Ply306 share 100% amino acid sequence identity, and PlyL and domains 1-3 of PlyL460D share 100% amino acid sequence identity (21). It was found that PlyS bound to both LeX and sLeX, whereas the PlySL460D mutant, PlyL, and PlyL306 showed no binding to LeX or sLeX.…”

Multivalent Pneumococcal Protein Vaccines Comprising Pneumolysoid with Epitopes/Fragments of CbpA and/or PspA Elicit Strong and Broad Protection

“…S. pneumoniae serotype 4 bioluminescent strain TIGR4X was grown in chemically defined medium (CϩY) without aeration at 37°C in 5% CO 2 to an optical density at 620 nm (OD 620 ) of 0.4 to 0.5 (54). S. pneumoniae strains D39, 1861, and P9 were grown in serum broth to an OD 600 of 0.18, as previously described (55). S. pneumoniae strains DBL6A, A66.1, and EF3030 were grown in Todd-Hewitt broth to an OD 600 of 0.4, as previously described (42).…”

FMS-Like Tyrosine Kinase 3 Ligand Treatment of Mice Aggravates Acute Lung Injury in Response to Streptococcus pneumoniae: Role of Pneumolysin

“…We used a PLY-producing clinical isolate of capsular group 19 S. pneumoniae strain EF3030 (6). In selected experiments, an otherwise isogenic PLY-deficient derivate of serotype 19 S. pneumoniae strain EF3030 (EF3030⌬PLY) (19,51) was employed. Bacteria were grown in Todd-Hewitt broth (Oxoid, Basingstoke, United Kingdom) supplemented with 20% fetal calf serum (FCS) (PAA Laboratories, Pasching, Austria) to mid-log phase.…”