SUMMARYIntranasal (i.n.) immunization is an effective route for inducing mucosal immune responses especially in the upper respiratory tract and mouth. To characterize the cells involved in these responses, nasal lymphoid tissue (NALT; considered to be the equivalent of Waldeyer's ring in humans) of normal mice, and of mice immunized intranasally with a bacterial protein antigen conjugated to cholera toxin B subunit, was isolated and the lymphoid cells analysed according to surface phenotype, immunoglobulin and antibody secretion, and cytokine profile. Compared with cells obtained from Peyer's patches (PP), NALT cells contained a higher proportion of T cells, especially naive (CD45RB hi ) T-helper cells, and fewer surface (s)IgA cells. Both tissues contained high proportions of sIgM IgD unswitched B cells. After i.n. immunization, IgA antibody-secreting cells were increased, indicating that isotype switching and differentiation of B cells to IgA-secreting cells occurred in NALT, whereas smaller numbers of antibody-secreting cells were found in PP after intragastric (i.g.) immunization. Antigen-specific memory cells persisted in NALT for at least 8 months after initial immunization. The cytokine expression profiles of antigen-stimulated NALT and PP cells of immunized mice, revealed by reverse transcription polymerase chain reaction analysis of mRNA, were similar. Both NALT and PP cells tended to express type 2 earlier or for longer than type 1 cytokine mRNA, but NALT cells tended to express interleukin-4 (IL-4) earlier, and IL-5 for a longer period, than PP cells. Thus NALT shares with PP cell populations typical of a mucosal inductive site, including unswitched B cells and naive T-helper (Th) cells. After i.n. immunization, NALT has the capacity to provide help for B-cell maturation and differentiation, as well as to maintain immune memory.

The effect of human secretory immunoglobulin A (S-IgA) and serum antibodies to surface protein antigen (Ag) 1I/ on the adherence of Ag VII-bearing Streptococcus mutans and of free Ag VII to saliva-coated hydroxyapatite (SHA) was investigated. The inhibition by S-IgA of binding of both S. mutans and free Ag IJI to SHA was dependent on antibody to Ag VII. Essentially no difference was found between S-IgAl and S-IgA2 with respect to antibody-dependent inhibition of Ag I/II binding to SHA, but S-IgAl inhibited S. mutans adherence more effectively than did either serum immunoglobulin Al (IgAl) or IgG antibodies. The antiadherence effect of S-IgA was abrogated after cleavage by IgAl protease. Purified Faba fragments containing Ag I/I-binding activity enhanced the binding of free Ag I/I to SHA and showed greater binding to SHA than did intact S-IgAl. Despite its relative inability to interact with precoated SHA, S-IgAl containing antibody to Ag I/I was readily incorporated into the salivary pellicle during coating, but this did not promote Ag I/I binding. These data suggest that S-IgA antibodies can inhibit the initial adherence of S. mutans to salivary pellicle-coated tooth surfaces in an adhesin-specific fashion, but the presence in the oral cavity of bacterial IgAl proteases would potentially interfere with this antiadherence mechanism.

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Background: On the analogy of the non-pathogenic microbiota found in oral cavity, skin and gastrointestinal tract, existence of blood microbiota was confirmed by DNA sequencing, but never deeply characterized. Hypothesis for the existence of dormant blood microbiota in healthy humans have been arisen and single species have been isolated. The aim of our study was to resuscitate and investigate the biodiversity of bacterial and fungal dormant blood microbiota in healthy individuals by blood culturing and NGS DNA sequencing. Results: Twenty eight blood samples of healthy individuals, seven for each blood type, were studied. Several culture media were tested. Blood microbiota resuscitation was performed in BHI broth supplemented with vitamin K 1 mg/ml, 2% sucrose, 0.25% sodium citrate and 0.2% yeastolate at 43˚C for 72 h. All tested blood samples were culture positive, as confirmed by Gram staining and TEM. TEM images demonstrated well defined cell structures. Analysis for bacterial and eukaryotic species was performed by 16S rRNA and ITS2 targeted sequencing. The obtained sequences were clustered (≥97% identity) in Operational Taxonomic Units (OTUs). Among cultured and uncultured samples we identified OTUs similarity with 47 bacterial orders belonging to 15 phyla and 39 fungi orders blonging to 2 phyla. For the first time we demonstrated isolation and sequencing identification of fungal blood microbiota in healthy individuals. Blood-group differences were identified among the bacterial microbiome compositions. Conclusion: The dormant blood microbiome is innate of the healthy individuals. Interventional strategies to bind the host blood microbiome with the states of health and disease remain an unmet research goal.

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