Clonal diversity of the <i>Streptococcus mitis</i> biovar 1 population in the human oral cavity and pharynx

Hohwy, J.; Kilian, Mogens

doi:10.1111/j.1399-302x.1995.tb00113.x

Cited by 58 publications

(77 citation statements)

References 30 publications

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“…The identity of the ribotype and age (months) of the infant at which the saliva was collected are indicated at the bottom of each column. and replacement of S. mitis (Hohwy and Kilian, 1995;Fitzsimmons et al, 1996;Hohwy et al, 2001;Kirchherr et al, 2005), we hypothesized that the concentration of S. mitis-specific SIgA antibody in saliva is limited because the mucosal immune system has a very short exposure to the individual clones of S. mitis that appear and rapidly disappear from the mouth. Under these conditions, it might be expected that the secretory immune system would respond to those antigens that are common to every clone of S. mitis because these provide a 'stationary target'.…”

Section: Discussionmentioning

confidence: 99%

“…In parallel with our studies on the salivary mucosal immune response to commensal oral bacteria, we and others have examined the population dynamics of S. mitis biovar 1 in the mouth and have shown that, while this bacterium is stable at the species level, it exhibits significant clonal turnover and replacement (Hohwy and Kilian, 1995;Fitzsimmons et al, 1996;Hohwy et al, 2001;Kirchherr et al, 2005). Indeed, most of the clones in the current study were isolated at a single sampling visit and could not be re-isolated at the successive visit, 2 months later.…”

Section: Introductionmentioning

confidence: 99%

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Humoral immunity to commensal oral bacteria in human infants: evidence that Streptococcus mitis biovar 1 colonization induces strain-specific salivary immunoglobulin A antibodies

et al. 2008

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To define the relationship between salivary SIgA antibodies and commensal oral bacteria, we examined the reactivity of SIgA antibodies from the saliva of four infants with their own colonizing Streptococcus mitis biovar 1 (S. mitis bv 1) clones (ribotypes). Immunoblot analysis was used to examine reactivity of these antibodies with persistent ribotypes isolated from the mouths of the infants over the first year postpartum. Results showed that the pattern of SIgA antibody reactivity with the majority of clones increased in complexity after colonization but that most additional bands were common to other clones, indicating that they represented shared antigens. However, unique bands were identified in 75% of the selected persistent clones. We hypothesized that if strainspecific SIgA antibody was induced in response to colonization of a particular clone and contributed to its elimination from the mouth, then the appearance of unique bands would immediately precede the disappearance of the strain. Seventy-three percent of all unique bands identified in the study fulfilled this criterion. Because the mouth is an open, dynamic environment and multiple factors are believed to play a role in the immune response at mucosal surfaces, it may not be possible to conclusively define the relationship between SIgA antibody and commensal bacteria. However, our data provide evidence that SIgA antibody, reactive with unique antigens of their own colonizing strains, is produced in infants and may point to a role of this antibody in regulating colonization by S. mitis bv 1.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Humoral immunity to commensal oral bacteria in human infants: evidence that Streptococcus mitis biovar 1 colonization induces strain-specific salivary immunoglobulin A antibodies

et al. 2008

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“…Whole-cell DNA was purified as described by Hohwy & Kilian (1995). Approximately 10 mg DNA was digested with EcoRI and treated with RNase.…”

Section: Methodsmentioning

confidence: 99%

Horizontal transfer of the immunoglobulin A1 protease gene (iga) from Streptococcus to Gemella haemolysans

et al. 2006

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Bacterial IgA1 proteases share the ability to cleave human IgA1 at the hinge region. Nature has developed this trait along at least five independent evolutionary lineages. To obtain further insight into the phylogeny and function of IgA1 proteases, the nucleotide sequence of the iga gene that encodes the IgA1 protease was determined from two Streptococcus mitis strains and one Gemella haemolysans strain. Heterologous expression in Escherichia coli confirmed that the genes encode human IgA1-cleaving activity. IgA1 proteases from Streptococcus and G. haemolysans shared structural features, including a motif typical for zinc-dependent metalloproteases of clan MA(E) family M26 and an N-terminal signal sequence followed by an LPXTG cell-wall-anchor motif and two putative membrane-spanning domains. In addition, they all harboured a repeat region preceding the active site of the protease. In the streptococcal IgA1 proteases, a G5 domain, which has been suggested to bind N-acetylglucosamine, was identified. Conservation of these structures in otherwise diverse proteases suggests that they are essential to the biological function of the enzyme. The phylogenetic distribution of homologous iga genes and conservation of gene order in the iga gene region in different Streptococcus species, combined with the sequence homologies, strongly suggest that the iga gene is more ancient in Streptococcus than in G. haemolysans, and therefore that the IgA1 protease gene was transferred from Streptococcus to G. haemolysans.

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“…Other observations add to our skepticism. First, nonpathogenic bacteria show extensive diversity at their rfb loci (33,34), abrogating extensive, direct exposure to the immune system as a necessity for extreme variability; in addition, loci not encoding surface antigens show high diversity (e.g., the hsd locus; see refs. 5 and 35).…”

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confidence: 99%

Protozoan predation, diversifying selection, and the evolution of antigenic diversity in Salmonella

Wildschutte

Wolfe

Tamewitz

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

147

142

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Extensive population-level genetic variability at the Salmonella rfb locus, which encodes enzymes responsible for synthesis of the O-antigen polysaccharide, is thought to have arisen through frequency-dependent selection (FDS) by means of exposure of this pathogen to host immune systems. The FDS hypothesis works well for pathogens such as Haemophilus influenzae and Neisseria meningitis, which alter the composition of their O-antigens during the course of bloodborne infections. In contrast, Salmonella remains resident in epithelial cells or macrophages during infection and does not have phase variability in its O-antigen. More importantly, Salmonella shows host-serovar specificity, whereby strains bearing certain O-antigens cause disease primarily in specific hosts; this behavior is inconsistent with FDS providing selection for the origin or maintenance of extensive polymorphism at the rfb locus. Alternatively, selective pressure may originate from the host intestinal environment itself, wherein diversifying selection mediated by protozoan predation allows for the continued existence of Salmonella able to avoid consumption by host-specific protozoa. This selective pressure would result in high population-level diversity at the Salmonella rfb locus without phase variation. We show here that intestinal protozoa recognize antigenically diverse Salmonella with different efficiencies and demonstrate that differences solely in the O-antigen are sufficient to allow for prey discrimination. Combined with observations of the differential distributions of both serotypes of bacterial species and their protozoan predators among environments, our data provides a framework for the evolution of high genetic diversity at the rfb locus and host-specific pathogenicity in Salmonella.T he enteric pathogen Salmonella enterica presents at least 70 different O-antigens [the outermost structure of the Gramnegative lipopolysaccharide (LPS)] to mammalian immune systems (1); this polysaccharide decorates the outer surface of the cell. Historically, extensive genetic diversity at the rfb locus, which encodes enzymes directing O-antigen synthesis (2-6), has been attributed to frequency-dependent selection (FDS) (7,8) imposed by the host immune system (5, 9, 10). Novel rfb loci would have an advantage because their cognate O-antigens would be unrecognized by immune systems (Fig. 1A); strains carrying rare loci would have higher fitness and would avoid rapid stochastic loss, rising to higher frequency. Yet selective advantages decrease with abundance; as a result, strains with common rfb loci cannot dominate the population or elicit a selective sweep (7) because their fitnesses become lower as they become more abundant. In concert, FDS prevents the loss of rare alleles or the dominance of common alleles, thus maintaining diversity (8).According to the FDS model, expression of different LPS molecules through gene regulation allows invading bacteria to escape host immunity, survive, and proceed throughout its life cycle; this hypothesis explains...

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Clonal diversity of the Streptococcus mitis biovar 1 population in the human oral cavity and pharynx

Cited by 58 publications

References 30 publications

Humoral immunity to commensal oral bacteria in human infants: evidence that Streptococcus mitis biovar 1 colonization induces strain-specific salivary immunoglobulin A antibodies

Humoral immunity to commensal oral bacteria in human infants: evidence that Streptococcus mitis biovar 1 colonization induces strain-specific salivary immunoglobulin A antibodies

Horizontal transfer of the immunoglobulin A1 protease gene (iga) from Streptococcus to Gemella haemolysans

Protozoan predation, diversifying selection, and the evolution of antigenic diversity in Salmonella

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