Abstract
This study investigated the specific role played by conserved membrane eukaryotic-like Ser/Thr protein kinases (StkP) during infection, particularly pneumonia, in order to get deep insights about Ser/Thr protein kinases signaling during infection and pathogenesis. The wild type and mutated Ser/Thr protein kinases (Spr1577) strains were tested on different cell lines to understand their virulence based on gentamicin protection assay, gene expression analysis and the expression of various interleukins. Though there was no uptake of bacterial CFU at the beginning, after 24 h it was 50% less for the mutated in comparison to wild-type strain, thus indicating a possible role of Spr1577 gene in the phagosomal survival of S pneumoniae. The complemented, strain-restored bacterial survival to the similar extent alike wild-type strains suggest that the Spr1577 kinase activity is not critical for the intracellular survival of S. pneumoniae within macrophages. Peak expression of spr1577 post infection indicating that the virulent genes seemed persuaded within the macrophages. Higher induction of pro-inflammatory cytokines by the wild type and complemented strains, but not by mutated strain, suggest its role in the induction of macrophages functions. S. pneumoniae and S. pyogenes are closely-related pathogens having 97% similarity in their gene sequences suggesting that the virulence mechanisms greatly varies and remain poorly understood for S. pneumoniae.
•The present study characterizes a putative spr 1577 of S. pneumoniae and establishes it as a novel virulence factor.•Spr1577 protein kinase activity is not critical for intracellular survival of S pneumoniae within macrophages.•Spr1577 functions here through a different mechanism which is a novel virulence factor of S. pneumonia.•Virulence mechanisms of S. pneumoniae remain poorly understood despite 97% similarity to S. pyogenes..