When administered intracerebroventricularly to mice performing various learning tasks involving either short-term or long-term memory, secreted forms of the β-amyloid precursor protein (APP ^s ₇₅₁ and APP ^s ₆₉₅ ) have potent memory-enhancing effects and block learning deficits induced by scopolamine. The memory-enhancing effects of APP ^s were observed over a wide range of extremely low doses (0.05-5,000 pg intracerebroventricularly), blocked by anti-APP ^s antisera, and observed when APP ^s was administered either after the first training session in a visual discrimination or a lever-press learning task or before the acquisition trial in an object recognition task. APP ^s had no effect on motor performance or exploratory activity. APP ^s ₆₉₅ and APP ^s ₇₅₁ were equally effective in the object recognition task, suggesting that the memory-enhancing effect of APP ^s does not require the Kunitz protease inhibitor domain. These data suggest an important role for APP ^s s on memory processes.

Data on the value of therapeutic drug monitoring of infliximab (IFX) to predict mucosal healing (MH) in inflammatory bowel diseases (IBD) are scarce. All consecutive patients with IBD receiving ongoing IFX (5 mg/kg) treatment and developing secondary failure to IFX were enrolled in a prospective study between June 2010 and May 2011. IFX trough levels, antibodies to IFX concentrations, C-reactive protein levels, and fecal calprotectin were measured before IFX optimization and at week 8. A proctosigmoidoscopy was performed on the day of first IFX optimization and at week 8 in all patients with ulcerative colitis (UC). MH was defined by fecal calprotectin 0.5 μg/mL was associated with MH (sensitivity [se], 0.88; specificity [sp], 0.77; P = 0.0001, area under the receiver operating characteristic curve, 0.89). On multivariate analysis, the only factor associated with MH after IFX optimization was a delta IFX >0.5 µg/mL (likelihood ratio = 2.02; 95% confidence interval, 1.01-4.08; P = 0.048) in patients with IBD. Therapeutic drug monitoring of IFX strongly predicts the likelihood of achieving MH following IFX dose intensification in both CD and UC.

Intestinal microfold (M) cells possess a high transcytosis capacity and are able to transport a broad range of materials including particulate antigens, soluble macromolecules, and pathogens from the intestinal lumen to inductive sites of the mucosal immune system. M cells are also the primary pathway for delivery of secretory IgA (SIgA) to the gut-associated lymphoid tissue. However, although the consequences of SIgA uptake by M cells are now well known and described, the mechanisms whereby SIgA is selectively bound and taken up remain poorly understood. Here we first demonstrate that both the Cα1 region and glycosylation, more particularly sialic acid residues, are involved in M cell–mediated reverse transcytosis. Second, we found that SIgA is taken up by M cells via the Dectin-1 receptor, with the possible involvement of Siglec-5 acting as a co-receptor. Third, we establish that transcytosed SIgA is taken up by mucosal CX3CR1⁺ dendritic cells (DCs) via the DC-SIGN receptor. Fourth, we show that mucosal and systemic antibody responses against the HIV p24-SIgA complexes administered orally is strictly dependent on the expression of Dectin-1. Having deciphered the mechanisms leading to specific targeting of SIgA-based Ag complexes paves the way to the use of such a vehicle for mucosal vaccination against various infectious diseases. Secretory IgA (SIgA) antibodies are secreted into the gut lumen and are considered to be a first line of defense in protecting the intestinal epithelium from gut pathogens. SIgA patrol the mucus and are usually known to help immune tolerance via entrapping dietary antigens and microorganisms and other mechanisms. SIgA, in complex with its antigens, can also be taken back up by the intestinal epithelium in a process known as reverse transcytosis. SIgA can thereby promote the uptake and delivery of antigens from the intestinal lumen to the Gut-Associated Lymphoid Tissues (GALT), influencing inflammatory responses. This reverse transcytosis of SIgA is mediated by specialized epithelial M cells. Because M cells possess the ability to take up antigens and are therefore important to the local immune system, they are a key target for the specific delivery of novel mucosal vaccines against various diseases. M cell receptors that take up the SIgA-antigen complexes, which serve as mucosal vaccine vehicles, represent an important aspect of this vaccine strategy. The identification of SIgA receptor(s) on the surface of M cells has, however, remained elusive for more than a decade. In this study, we now identify Dectin-1 and Siglec-5 as the key receptors for M cell–mediated reverse transcytosis of SIgA complexes. We further find that the glycosylation modification, and particularly sialylation, of SIgA is required for its uptake by M cells. We show that, when administered orally in complex with SIgA, the HIV p24 antigen is taken up in a strictly Dectin-1-dependent manner to stimulate a mucosal and systemic antibody response. These findings are considered important for understanding gut immunity.

Several decision algorithms based on the measurement of infliximab (IFX) trough levels and antibodies to IFX have been proposed. Whether such algorithms can be extrapolated to the pharmacokinetics of adalimumab (ADA) has yet to be determined. A prospective study included all consecutive patients with inflammatory bowel disease (IBD) having a disease flare while being on ADA 40 mg every 2 weeks were included. All patients were primary responders to ADA therapy and were anti-tumor necrosis factor (TNF) naive. ADA trough levels and antibodies against ADA (AAA) were measured blinded to clinical data (Elisa LISA-Tracker, Theradiag). All patients were optimized with ADA 40 mg weekly. Four months later, in the absence of clinical remission (CR; Crohn's disease activity index <150 for Crohn's disease (CD), and Mayo score 4.9 μg/ml; group B, ADA<4.9 μg/ml and undetectable levels of AAA (<10 ng/ml); and group C, ADA10 ng/ml. A total of 82 patients were included (55% CD; mean age=43 years, disease duration=7.4 years, duration of ADA therapy=17 months). After optimization of ADA treatment, 29.2% of patients achieved CR in group A (N=41), 67% in group B (N=24), and 12% in group C (N=17; P<0.01 between groups A/B and B/C). C-reactive protein level at the time of relapse, disease duration, duration of ADA therapy, and IBD type was not predictive of CR after ADA optimization by univariate analysis. The response to ADA optimization was significantly more durable in group B (15 months) than in groups A and C (4 and 5 months, respectively). Fifty-two patients who failed following ADA optimization (63%) were treated with IFX, and 30.6% of them achieved CR. CR rates following IFX initiation were 6.9%, 25%, and 80% in groups A, B, and C, respectively (P<0.01 between groups C/A and between groups C/B). Duration of response to IFX was significantly higher in group C than in groups A and B (14 vs. 3 and 5 months, respectively, P4.9 μg/ml are associated with failure of two anti-TNF agents (ADA and IFX) in 90% of cases, and switching to another drug class should be considered.