title: The two variants of the Streptococcus pneumoniae pilus 1 RrgA adhesin retain the same function and elicit cross-protection in vivo.
abstract: Thirty percent of Streptococcus pneumoniae isolates contain pilus islet 1, coding for a pilus composed of the backbone subunit RrgB and two ancillary proteins, RrgA and RrgC. RrgA is the major determinant of in vitro adhesion associated with pilus 1, is protective in vivo in mouse models, and exists in two variants (clades I and II). Mapping of the sequence variability onto the RrgA structure predicted from X-ray data showed that the diversity was restricted to the "head" of the protein, which contains the putative binding domains, whereas the elongated "stalk" was mostly conserved. To investigate whether this variability could influence the adhesive capacity of RrgA and to map the regions important for binding, two full-length protein variants and three recombinant RrgA portions were tested for adhesion to lung epithelial cells and to purified extracellular matrix (ECM) components. The two RrgA variants displayed similar binding abilities, whereas none of the recombinant fragments adhered at levels comparable to those of the full-length protein, suggesting that proper folding and structural arrangement are crucial to retain protein functionality. Furthermore, the two RrgA variants were shown to be cross-reactive in vitro and cross-protective in vivo in a murine model of passive immunization. Taken together, these data indicate that the region implicated in adhesion and the functional epitopes responsible for the protective ability of RrgA may be conserved and that the considerable level of variation found within the "head" domain of RrgA may have been generated by immunologic pressure without impairing the functional integrity of the pilus.
authors.affiliation: Novartis Vaccines and Diagnostics, Via Fiorentina, Siena 53100, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Moschioni
authors.forename: Carla
authors.initials: C
authors.lastname: Emolo
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Biagini
authors.forename: Silvia
authors.initials: S
authors.lastname: Maccari
authors.forename: Werner
authors.initials: W
authors.lastname: Pansegrau
authors.forename: Claudio
authors.initials: C
authors.lastname: Donati
authors.forename: Markus
authors.initials: M
authors.lastname: Hilleringmann
authors.forename: Ilaria
authors.initials: I
authors.lastname: Ferlenghi
authors.forename: Paolo
authors.initials: P
authors.lastname: Ruggiero
authors.forename: Antonia
authors.initials: A
authors.lastname: Sinisi
authors.forename: Mariagrazia
authors.initials: M
authors.lastname: Pizza
authors.forename: Nathalie
authors.initials: N
authors.lastname: Norais
authors.forename: Michèle A
authors.initials: MA
authors.lastname: Barocchi
authors.forename: Vega
authors.initials: V
authors.lastname: Masignani
mesh_terms: D018829:Adhesins, Bacterial / Q000235:genetics / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D056738:Cross Protection / Q000235:genetics / Q000502:physiology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000502:physiology*; D005434:Flow Cytometry; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics / Q000502:physiology; D007116:Immunization, Passive; D051379:Mice; D008807:Mice, Inbred BALB C; D011008:Pneumococcal Infections / Q000382:microbiology; D017434:Protein Structure, Tertiary / Q000235:genetics / Q000502:physiology; D011994:Recombinant Proteins / Q000235:genetics; D013296:Streptococcus pneumoniae / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology
chemical_list: D018829:Adhesins, Bacterial; D011994:Recombinant Proteins
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