title: Variation of pneumococcal Pilus-1 expression results in vaccine escape during Experimental Otitis Media [EOM].
abstract: The pneumococcal Pilus-1 enhances attachment to epithelial cells in the respiratory tract and subsequent invasion. Pilus-1 expression is bi-stable and positively regulated by the RlrA transcriptional regulator. To delineate the role of pilus-1 in Experimental Otitis Media (EOM), we evaluated colonization and disease due to a Streptococcus pneumoniae (SP) wild type strain (Taiwan19F-14 wt) and its otherwise isogenic pilus-1 and pilus-2 deficient mutant (Taiwan19F-14 ΔPI-1/PI-2-) as well as potential for a chimeric protein (RrgB321) vaccine candidate for prevention of middle ear (ME) disease.
  
  
  METHODS
  Chinchillas were challenged intranasally with either Taiwan19F-14 wt or Taiwan19F-14PI-1/PI-2 deficient mutant. ME status was assessed and direct cultures performed. New cohorts of animals were immunized with RrgB321 or alum. Intranasal challenge with Taiwan19F-14 wt [erythromycin susceptible E(S)] was performed. Subsequently, a second cohort of animals was immunized and challenged with either Taiwan19F-14 wt or a Pilus-1 over-expressing mutant [Taiwan19F-14+pMU1328_Pc-rlrA mutant; E resistant (R)] strain. Pilus-1 expression was analyzed in SP isolated from nasopharynx (NP) and ME fluids by flow cytometry.
  
  
  RESULTS
  Culture positive EOM developed following challenge with either wild type SP (Taiwan19F-14) or its pilus-1 deficient mutant. Culture positive EOM developed following challenge with wild type in both RrgB321 immunized and control animals. Pilus-1 expression in ME fluids was significantly higher in controls compared to immunized chinchillas. In second cohort of immunized and control animals challenged with the over-expressing Pilus-1 mutant, delayed development of EOM in the immunized animals was observed. Pneumococci recovered from ME fluid of immunized animals were no longer E(R) signifying the loss of the pMU1328_Pc-rlrA plasmid.
  
  
  CONCLUSIONS
  Pneumococcal pilus-1 was not essential for EOM. Regulation of Pilus-1 expression in ME fluids in the presence of anti RrgB321 antibody was essential for survival of S. pneumoniae. Pneumococci have evolved mechanisms of regulation of non-essential surface proteins to evade host defenses.
authors.affiliation: Section of Pediatric Infectious Diseases, Maxwell Finland Laboratory for Infectious Diseases, Boston Medical Center, Boston, Massachusetts, United States of America.
authors.forename: Marisol
authors.initials: M
authors.lastname: Figueira
authors.affiliation: Novartis Vaccines and Diagnostics, Siena, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Moschioni
authors.affiliation: Novartis Vaccines and Diagnostics, Siena, Italy.
authors.forename: Gabriella
authors.initials: G
authors.lastname: De Angelis
authors.affiliation: Novartis Vaccines and Diagnostics, Siena, Italy.
authors.forename: Michèle
authors.initials: M
authors.lastname: Barocchi
authors.affiliation: Section of Pediatric Infectious Diseases, Maxwell Finland Laboratory for Infectious Diseases, Boston Medical Center, Boston, Massachusetts, United States of America.
authors.forename: Vishakha
authors.initials: V
authors.lastname: Sabharwal
authors.affiliation: Novartis Vaccines and Diagnostics, Siena, Italy.
authors.forename: Vega
authors.initials: V
authors.lastname: Masignani
authors.affiliation: Section of Pediatric Infectious Diseases, Maxwell Finland Laboratory for Infectious Diseases, Boston Medical Center, Boston, Massachusetts, United States of America.
authors.forename: Stephen I
authors.initials: SI
authors.lastname: Pelton
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000276:immunology*; D002682:Chinchilla / Q000276:immunology / Q000382:microbiology; D015169:Colony Count, Microbial; D004432:Ear, Middle / Q000276:immunology / Q000382:microbiology; D010861:Fimbriae, Bacterial / Q000276:immunology*; D007114:Immunization; D009154:Mutation / Q000235:genetics; D009305:Nasopharynx / Q000276:immunology / Q000382:microbiology; D010033:Otitis Media / Q000139:chemically induced / Q000276:immunology* / Q000382:microbiology*; D022242:Pneumococcal Vaccines / Q000276:immunology*; D013296:Streptococcus pneumoniae / Q000276:immunology*; D016896:Treatment Outcome
chemical_list: D001426:Bacterial Proteins; D022242:Pneumococcal Vaccines