Needle-free uptake across mucosal barriers is a preferred route for delivery of biologics, but the efficiency of unassisted transmucosal transport is poor. To make administration and therapy efficient and convenient, strategies for the delivery of biologics must enhance both transcellular delivery and plasma half-life. We found that human albumin was transcytosed efficiently across polarized human epithelial cells by a mechanism that depends on the neonatal Fc receptor (FcRn). FcRn also transported immunoglobulin G, but twofold less than albumin. We therefore designed a human albumin variant, E505Q/T527M/K573P (QMP), with improved FcRn binding, resulting in enhanced transcellular transport upon intranasal delivery and extended plasma half-life of albumin in transgenic mice expressing human FcRn. When QMP was fused to recombinant activated coagulation factor VII, the half-life of the fusion molecule increased 3.6-fold compared with the wild-type human albumin fusion, without compromising the therapeutic properties of activated factor VII. Our findings highlight QMP as a suitable carrier of protein-based biologics that may enhance plasma half-life and delivery across mucosal barriers.
Background & aims: The pathogenesis of celiac disease (CD) is thought to be driven by a transglutaminase 2 (TG2)-dependent inflammatory CD4 + T-cell response in the gut towards deamidated gluten peptides in the context of disease-associated HLA-DQ molecules. We aimed to gain insight into the antigen presentation process underlying this mucosal immune response. Methods: We generated monoclonal antibodies (mAbs) specific for the peptide-MHC (pMHC) complex HLA-DQ2.5 and the immunodominant gluten epitope DQ2.5-glia-α1a using phage display. Using these mAbs we assessed gluten peptide presentation in freshly prepared single-cell suspensions of patient intestinal biopsies. Results: The mAbs allowed specific detection of in vivo generated pMHC complexes on the cells of gut biopsies from CD patients consuming gluten. Surprisingly, we identified B cells and plasma cells (PCs) as the most abundant cells presenting DQ2.5-glia-α1a in the inflamed mucosa. Further, we demonstrate that a group of these PCs expresses B-cell receptors (BCRs) specific for either gluten peptides or the autoantigen TG2. MHC class II (MHCII) expression was not restricted to these specific PCs associated with CD, but was observed at an average of 30% of the gut PCs both in CD patients as well as in non-inflamed tissue. Conclusions: A population of PCs in the gut expresses MHCII and is the most abundant cell type presenting the immunodominant gluten peptide DQ2.5-glia-α1a. These results suggest an important and previously unappreciated role of PCs in the gut as antigen presenting cells (APCs). PCs may thus be responsible for promoting and sustaining intestinal inflammation such as in CD.
Ab-coated viruses can be detected in the cytosol by the FcR tripartite motif-containing 21 (TRIM21), which rapidly recruits the proteasomal machinery and triggers induction of immune signaling. As such, TRIM21 plays a key role in intracellular protection by targeting invading viruses for destruction and alerting the immune system. A hallmark of immunity is elicitation of a balanced response that is proportionate to the threat, to avoid unnecessary inflammation. In this article, we show how Ab affinity modulates TRIM21 immune function. We constructed a humanized monoclonal IgG1 against human adenovirus type 5 (AdV5) and a panel of Fc-engineered variants with a wide range of affinities for TRIM21. We found that IgG1-coated viral particles were neutralized via TRIM21, even when affinity was reduced by as much as 100-fold. In contrast, induction of NF-κB signaling was more sensitive to reduced affinity between TRIM21 and the Ab variants. Thus, TRIM21 mediates neutralization under suboptimal conditions, whereas induction of immune signaling is balanced according to the functional affinity for the incoming immune stimuli. Our findings have implications for engineering of antiviral IgG therapeutics with tailored effector functions.
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