Antigen I/II (AgI/II) has been widely studied as a candidate vaccine antigen against human dental caries. upstream of the alanine-rich repeat domain. Adherence inhibiting antibodies could be induced against two discrete domains of the protein one corresponding to the central portion of the molecule and the other corresponding to the C-terminus. have been studied as vaccine candidates [2-6]. One such protein is the cell-surface localized Antigen I/II adhesin  also called P1  Antigen B  or PAc . AgI/II family members mediate interactions with host salivary constituents cell CBLC matrix proteins and other bacteria (reviewed in ). Until recently a lack of high-resolution structural information hindered the design and interpretation of immunological studies. As deduced from the primary sequence AgI/II has discontinuous alanine (A)- and proline (P)-rich tandem repeats that flank a variable (V) region where strain differences are clustered [10 12 13 Recently an unusual tertiary structure was discovered in which the A-repeats form an α-helix that intertwines using the polyproline II (PPII) P-region helix to create a long slim stalk . The intervening portion like the V-region comprises a β sandwich organized in two bed linens . The crystal structure from the C-terminus also revealed β sheet structure with three consecutive domains implementing a DE-variant IgG fold . Therefore two globular locations rest on either last end of a protracted stalk. A higher affinity intra-molecular relationship between the N-terminus which has not been crystalized and the C-terminus increases stability of AgI/II and enhances adhesive function . The primary and modeled tertiary structures of AgI/II are illustrated (Physique 1). Physique UNC0321 1 Schematic representations of Antigen I/II illustrating location of putative T cell UNC0321 epitopes and approximate antibody binding sites. (A) A representation of the primary structure of AgI/II and the recombinant polypeptides used in this study. … AgI/II’s conversation with salivary components is complex and involves two distinct adherence sites [16 18 The conversation differs depending on whether the major physiologic receptor salivary agglutinin (SAG) is usually immobilized or is in fluid-phase. Monoclonal antibodies differ in their ability to inhibit adherence to SAG compared to SAG-mediated bacterial UNC0321 aggregation indicating that the determinants that mediate these two processes are not identical . SAG is an oligomeric protein complex consisting primarily of the scavenger receptor glycoprotein gp340 and also made up of amylase sIgA and an 80 kDa protein [20 21 Different regions of both gp340  and AgI/II  contribute to the different interactions. adherence involves binding of AgI/II to immobilized SAG within the salivary pellicle coating the tooth surface . Disruption of this conversation by antibodies is the focus of preventative therapeutic protocols. In contrast conversation of fluid-phase SAG with cell surface AgI/II represents an innate host defense mechanism [24 25 whereby aggregated are removed by swallowing. Hence it is desirable to elicit antibodies that disrupt SAG-mediated adherence but not aggregation. Numerous studies have exhibited the relevance of an antibody response against AgI/II in protection against colonization and cariogenicity (reviewed in [3 11 26 27 Both salivary and serum antibodies that enter the oral cavity via transudation through UNC0321 the gingival crevice have been reported to be protective [6 28 or in some instances non-protective [34-36]. Subtle and potentially unapparent differences among immune responses can be crucial in determining UNC0321 the outcome of a host pathogen interaction. Naturally dominant epitopes are often not optimal for protection and pathogens can persist in the face of an immune response . Therefore it is fine specificity and functional activity way more than total antibody quantity which most likely determines whether colonization and cariogenicity is certainly sufficiently inhibited to avoid disease by NG8 was expanded aerobically for 16 hr in Todd-Hewitt broth with 0.3 % fungus remove (BBL Cockeysville MD). strains had been harvested aerobically at 37°C in Luria-Bertani broth (1 % [wt/vol] tryptone 0.5 % [wt/vol] yeast extract 1 % [wt/vol] NaCl) UNC0321 supplemented with ampicillin (50-100 μg/mL) or kanamycin (25-50 μg/mL). Structure from the RR2 and CK1  NA1 P3C and NR7  and NR21  polypeptides continues to be described. Recombinant proteins were purified in nickel or amylose.