Immune responses to pneumococcal pilus RrgA and RrgB antigens and their relationship with pneumococcal carriage in humans

J Infect. 2014 Jun;68(6):562-71. doi: 10.1016/j.jinf.2014.01.013. Epub 2014 Feb 6.

Abstract

Objectives: Pneumococcal pilus antigens are shown to be important in pneumococcal pathogenesis and induce protective immunity in animal studies, but data in humans are limited. We aimed to investigate serum and mucosal immune responses to pilus-1 proteins (RrgA and RrgB) and their relationship with pneumococcal carriage in humans.

Methods: Serum and salivary antibodies to RrgA and RrgB in children and adults were analysed by ELISA and immunoblotting. Induction of B cell antibody responses to RrgA and RrgB in nasopharynx-associated lymphoid tissue was studied by ELISpot assay following stimulation with pneumococcal culture supernatants containing pilus proteins.

Results: Significant levels of serum anti-RrgA and -RrgB antibodies were observed, and anti-RrgA antibody appeared to develop earlier in childhood. Importantly, anti-RrgA IgG titres in both serum and saliva were shown to be higher in culture-negative children than in those who were culture-positive for Streptococcus pneumoniae. Stimulation of adenotonsillar cells with pneumococcal culture supernatant induced significant RrgA- and RrgB-specific antibody secreting cells and antibody production.

Conclusions: Pneumococcal pilus antigens, particularly RrgA, seem to induce significant serum and mucosal antibody responses that may contribute to natural immunity against pneumococcal carriage in children.

Keywords: B cell response; Nasopharynx-associated lymphoid tissue (NALT); Pilus proteins; Pneumococcal carriage; Serum antibody; Streptococcus pneumoniae.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Animals
  • Antibodies, Bacterial / analysis
  • Antibodies, Bacterial / blood
  • Antigens, Bacterial / immunology*
  • B-Lymphocytes / immunology
  • Carrier State / immunology*
  • Carrier State / microbiology
  • Child
  • Child, Preschool
  • Enzyme-Linked Immunosorbent Assay
  • Enzyme-Linked Immunospot Assay
  • Female
  • Fimbriae Proteins / immunology*
  • Fimbriae, Bacterial / immunology*
  • Humans
  • Immunoblotting
  • Infant
  • Male
  • Pneumococcal Infections / immunology*
  • Pneumococcal Infections / microbiology
  • Saliva / immunology
  • Serum / immunology
  • Streptococcus pneumoniae / immunology*
  • Streptococcus pneumoniae / isolation & purification*
  • Virulence Factors / immunology*
  • Young Adult

Substances

  • Antibodies, Bacterial
  • Antigens, Bacterial
  • RrgA protein, Streptococcus pneumoniae
  • Virulence Factors
  • Fimbriae Proteins