Pilus of Streptococcus pneumoniae: structure, function and vaccine potential

The pilus is an extracellular structural part that can be detected in some Streptococcus pneumoniae ( S. ) isolates (type I pili are found approximately 30% of strains, while type II 20%). It anchored to the cell wall by LPXTG-like motifs on peptidoglycan. Two kinds have been discovered, namely, pilus-1 and pilus-2. former encoded islet 1 (PI-1) a polymer formed protein subunits RrgA, RrgB RrgC. latter 2 (PI-2) composed mainly PitB. Although not necessary for survival , they serve as basis virulence factors mediate adhesion bacteria host cells play direct role promoting adhesion, colonization pathogenesis . In addition, candidate antigens vaccines, promising potential use vaccines with combined immunization strategies. Given current understanding regarding genes, proteins, structure, biological function epidemiological relationship serotypes, immunoprotective efficacy pilins candidates we here systematically describe research status prospects provide new ideas subsequent vaccine development.