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Background: Vaccination with hypoallergenic recombinant Bet v 1 derivatives (Bet v 1 fragments and Bet v 1 trimer) is associated with the induction of IgG antibodies specific to natural Bet v 1., Objective: To investigate whether IgG antibodies induced following vaccination with genetically modified hypoallergenic Bet v 1 derivatives are able to inhibit IgE-facilitated binding of allergen-IgE complexes to B cells., Methods: Sera from 46 patients obtained before and after subcutaneous vaccination with Bet v 1 trimer (n=14), Bet v 1 fragments (n=11) or placebo (n=21) were incubated with recombinant (r) Bet v 1 and an indicator serum (IS) from a birch pollen-allergic patient with high CD23 binding capacity. Bet v 1 immune complexes were added to a CD23-expressing B cell line and co-operative binding of Bet v1-IgE complexes to CD23 was measured with a polyclonal anti-IgE FITC antibody using a bio-functional cellular flow cytometric assay., Results: When sera from patients vaccinated with rBet v 1 derivatives were incubated with Bet v 1 and the IS, a reduction of IgE binding to CD23 was observed. This effect was not seen when sera from placebo-treated patients were used. The decrease in CD23/IgE binding was statistically significant in the trimer group [pre- vs. post-specific immunotherapy (SIT): P=0.02; trimer vs. placebo: P<0.04] but not in the Bet v 1 fragments-treated group. Trimer-treated patients had higher levels of Bet v 1-specific IgG than fragment-treated patients. The degree of inhibitory activity of IgE-facilitated allergen binding correlated with Bet v 1-specific IgG levels following SIT (R=0.492; P=0.012)., Conclusion: Vaccination with both recombinant Bet v 1 derivatives induces Bet v 1-specific IgG antibodies, which are able to inhibit the co-operative binding of allergen-IgE complexes to CD23, and may thereby reduce allergen-specific T cell responses.

Background: The mechanisms of sublingual immunotherapy (SLIT) are less well understood than those of subcutaneous immunotherapy (SCIT)., Objectives: To determine the effects of grass-pollen SLIT on oral mucosal immune cells, local regulatory cytokines, serum allergen-specific antibody subclasses and B cell IgE-facilitated allergen binding (IgE-FAB)., Methods: Biopsies from the sublingual mucosa of up to 14 SLIT-treated atopics, nine placebo-treated atopics and eight normal controls were examined for myeloid dendritic cells (mDCs) (CD1c), plasmacytoid dendritic cells (CD303), mast cells (AA1), T cells (CD3) and Foxp3 using immunofluorescence microscopy. IL-10 and TGF-beta mRNA expression were identified by in situ hybridization. Allergen-specific IgG and IgA subclasses and serum inhibitory activity for binding of allergen-IgE complexes to B cells (IgE-FAB) were measured before, during and on the completion of SLIT., Results: Foxp3(+) cells were increased in the oral epithelium of SLIT- vs. placebo-treated atopics (P=0.04). Greater numbers of subepithelial mDCs were present in placebo-treated, but not in SLIT-treated, atopics compared with normal controls (P=0.05). There were fewer subepithelial mast cells and greater epithelial T cells in SLIT- compared with placebo-treated atopics (P=0.1 for both). IgG(1) and IgG(4) were increased following SLIT (P<0.001). Peak seasonal IgA(1) and IgA(2) were increased during SLIT (P<0.05). There was a time-dependent increase in serum inhibitory activity for IgE-FAB in SLIT-treated atopics., Conclusions: SLIT with grass pollen extract is associated with increased Foxp3(+) cells in the sublingual epithelium and systemic humoral changes as observed previously for SCIT.

Objectives: To determine if the expression of CD38 on CD8+ T-cells could be used as a marker of viral replication <50 copies/ml in peripheral blood., Methods: In a cross-sectional study of patients attending a single HIV clinic in London, an ultra-sensitive HIV RNA viral load assay, with a limit of detection of 3 copies/ml, was used to determine HIV-1 replication in plasma in 70 patients who had sustained viral suppression <50 copies/ml by bDNA assays. Immune activation using the expression of CD38 on CD8+ T-cells was also assessed in patients on antiretroviral therapy (ART) with sustained viral suppression, individuals with persistent low-level viraemia <400 copies/ml and subjects failing ART (viral load >400 copies/mi)., Results: There was no significant difference in the percentage of CD8+CD38++ T-cells between patients with <50 copies or <3 copies/ml. Immune activation was significantly increased in patients with persistent low-level viraemia and in subjects failing ART. CD4+ T-cell counts in patients on long-term successful ART are inversely associated with CD8+ T-cell activation., Conclusions: T-cell activation in patients on long-term successful ART is not due to residual low-level viral replication in the blood compartment of HIV-1. CD8+ T-cell activation in this patient group appears to be associated with poor CD4+ T-cell recovery.

The IgE-facilitated allergen binding (IgE-FAB) assay represents an in vitro model of facilitated allergen presentation. Allergen-IgE complexes are incubated with an EBV-transformed B cell line and complexes bound to CD23 on the surface of cells are detected by flow cytometry. The addition of serum from patients who have received allergen-specific immunotherapy has been shown previously to inhibit allergen-IgE complex binding to CD23 on B cells. In this study, we describe the characterisation and analytical validation of the grass pollen-specific IgE-FAB assay according to guidelines from the International Conference on Harmonisation. We established the intra- and inter-assay variability of IgE-FAB and have defined the detection limits of this assay. We have also demonstrated assay linearity and robustness. Using the results from a randomised double-blind placebo-controlled trial of grass pollen immunotherapy (n=33), we have defined the clinical sensitivity and specificity of the IgE-FAB assay using ROC curve analysis. In conclusion, the IgE-FAB assay is reproducible, robust, sensitive and a specific method suitable as a tool for monitoring inhibitory antibody function from patients receiving allergen immunotherapy.