The single D380 amino acid substitution increases pneumolysin cytotoxicity towards neuronal cells

Strikingly, the switch from Aspartate to Asparagine in the D4 domain significantly enhances PLY capability of binding to cholesterol which increases the cytotoxicity of PLY towards neuronal cells due to a more acute pore-forming activity as revealed by the scanning electron microscopy analysis showing the degree of pore formation on neuronal plasma membrane. Furthermore, the higher neuronal cytotoxicity by the PLY of the clinical isolates with the single aa substitution was also observed in patch clamp electrophysiological recordings using mouse brain slices ex vivo.

In conclusion, a single aa substitution in the PLY D4 domain is sufficient to significantly alter the pore-forming activity of PLY and enhance its cytotoxicity, making pneumococcal strains more neuro-toxic, thereby increasing the risks of neurological sequelae.