Antigen presentation and processing in the intestinal mucosa and lymphocyte homing

Development of polypeptide-based materials toward messenger RNA delivery

Messenger RNA (mRNA)-based therapeutic agents have demonstrated significant potential in recent times, particularly in the context of the COVID-19 pandemic outbreak. As a promising prophylactic and therapeutic strategy, polypeptide-based mRNA delivery systems attract significant interest because of their low cost, simple preparation, tuneable sizes and morphology, convenient large-scale production, biocompatibility, and biodegradability. In this review, we begin with a brief discussion of the synthesis of polypeptides, followed by a review of commonly used polypeptides in mRNA delivery, including classical polypeptides and cell-penetrating peptides. Then, the challenges against mRNA delivery, including extracellular, intracellular, and clinical barriers, are discussed in detail. Finally, we highlight a range of strategies for polypeptide-based mRNA delivery, offering valuable insights into the advancement of polypeptide-based mRNA carrier development.

Function and dysfunction of plasma cells in intestine

As the main player in humoral immunity, antibodies play indispensable roles in the body's immune system. Plasma cells (PCs), as antibody factories, are important contributors to humoral immunity. PCs, recognized by their unique marker CD138, are always discovered in the medullary cords of spleen and lymph nodes and in bone marrow and mucosal lymphoid tissue. This article will review the origin and differentiation of PCs, characteristics of short- and long-lived PCs, and the secretion of antibodies, such as IgA, IgM, and IgG. PCs play a crucial role in the maintenance of intestinal homeostasis using immunomodulation though complex mechanisms. Clearly, PCs play functional roles in maintaining intestinal health, but more details are needed to fully understand all the other effects of intestinal PCs.

Protein transport across the small intestine in food allergy

In view of the imminent deficiency of protein sources for human consumption in the near future, new protein sources need to be identified. However, safety issues such as the risk of allergenicity are often a bottleneck, due to the absence of predictive, validated and accepted methods for risk assessment. The current strategy to assess the allergenic potential of proteins focuses mainly on homology, stability and cross-reactivity, although other factors such as intestinal transport might be of added value too. In this review, we present an overview of the knowledge of protein transport across the intestinal wall and the methods currently being used to measure this. A literature study reveals that protein transport in sensitised persons occurs para-cellularly with the involvement of mast cells, and trans-cellularly via enterocytes, while in non-sensitised persons micro-fold cells and enterocytes are considered most important. However, there is a lack of comparable systematic studies on transport of allergenic proteins. Knowledge of the multiple protein transport pathways and which model system can be useful to study these processes may be of added value in the risk assessment of food allergenicity.

Contribution of gut bacteria to liver pathobiology

Emerging evidence suggests a strong interaction between the gut microbiota and health and disease. The interactions of the gut microbiota and the liver have only recently been investigated in detail. Receiving approximately 70% of its blood supply from the intestinal venous outflow, the liver represents the first line of defense against gut-derived antigens and is equipped with a broad array of immune cells (i.e., macrophages, lymphocytes, natural killer cells, and dendritic cells) to accomplish this function. In the setting of tissue injury, whereby the liver is otherwise damaged (e.g., viral infection, toxin exposure, ischemic tissue damage, etc.), these same immune cell populations and their interactions with the infiltrating gut bacteria likely contribute to and promote these pathologies. The following paper will highlight recent studies investigating the relationship between the gut microbiota, liver biology, and pathobiology. Defining these connections will likely provide new targets for therapy or prevention of a wide variety of acute and chronic liver pathologies.

Enhanced antigen uptake by dendritic cells induced by the B pentamer of the type II heat-labile enterotoxin LT-IIa requires engagement of TLR2

The potent mucosal adjuvant properties of the type II heat-labile enterotoxin LT-IIa of Escherichia coli are dependent upon binding of the B pentamer of the enterotoxin (LT-IIa-B(5)) to ganglioside receptors on immunocompetent cells. To evaluate the immunomodulatory activities of LT-IIa-B(5), in vitro experiments employing bone marrow-derived dendritic cells (BMDC) were performed. Uptake of OVA-FITC, a model antigen (Ag), was enhanced by treatment of BMDC with LT-IIa-B5, but not by treatment of cells with the B pentamer of cholera toxin (CTB). Expression of co-stimulatory molecules (CD40, CD80, CD86, and MHC-II) and cytokines (IL-12p40, TNF-alpha, and IFN-gamma) was increased in BMDC treated with LT-IIa-B(5). The capacity of LT-IIa-B(5) to enhance Ag uptake and to induce expression of co-stimulatory receptors and cytokines by BMDC was dependent upon expression of TLR2 by the cell. Increased Ag uptake induced by LT-IIa-B(5) was correlated with increased Ag-specific proliferation of CD4(+) T cells in an in vitro syngeneic DO11.10 CD4(+) T cell proliferation assay. These experiments confirm that LT-IIa-B(5) exhibits potent immunomodulatory properties which may be exploitable as a non-toxic mucosal adjuvant.

Sublingual and oral immunotherapy

Sublingual immunotherapy (SLIT) is a viable alternative to the subcutaneous route for the treatment of respiratory allergy, whereas the pure oral route has been abandoned because of its lack of efficacy. The main distinctive feature of SLIT is its optimal safety profile, which has been demonstrated in adults and children. The indications for SLIT are similar to those for the subcutaneous route. A long-lasting effect has been demonstrated for the sublingual route, but data are needed to determine the optimal dose and the preventive effect in asthma.

Gastrointestinal immunopathology and food allergy

OBJECTIVE

To review the current data that support the pivotal function of the gastrointestinal immune system in health and disease and its critical role in the pathogenesis of a wide variety of clinical disorders associated with food allergy (FA).

DATA SOURCES

Internet-based literature search and our own data.

STUDY SELECTION

The studies included in this review were selected based on the expert opinion of the authors.

RESULTS

In contrast to the beneficial expressions of gastrointestinal-associated lymphoid tissue, which are seen with relevance to newer methods of delivery of vaccines directly applied to the gastrointestinal mucosal surfaces (eg, oral poliovirus, rotavirus, Salmonella typhi vaccines), the adverse consequences of a mucosal immune response gone astray are evidenced in many diseases such as FA. A classification of clinical disorders associated with FA based on classic mechanisms of immunologic injury is presented, which includes the following: (1) IgE-mediated, (2) non-IgE-mediated, and (3) mixed IgE- and non-IgE-mediated disorders. Our study of immunologic disturbance in patients with non-IgE FA revealed a pattern of increased CD4+ and decreased TH1 cell counts in peripheral blood mononuclear cells in contrast to patients with celiac disease, where a pattern of increased CD8+ and TH1 cell counts in peripheral blood mononuclear cells and increased CD8+ cell counts was seen.

CONCLUSIONS

The gastrointestinal immune response thus plays a pivotal role in maintaining protective immunity in health and a critical role in the pathogenesis of a wide variety of clinical disorders associated with FA.

Birth weight predicts response to vaccination in adults born in an urban slum in Lahore, Pakistan

BACKGROUND

Substantial evidence exists linking small size at birth to later-life susceptibility to chronic disease. Evidence is also emerging that some components of immune function may be programmed in early life. However, this evidence is limited and requires confirmation.

OBJECTIVE

We investigated the association between size at birth and response to vaccination in a cohort of 257 adults (mean age: 29.4 y; 146 men) born in an urban slum in Lahore, Pakistan, during 1964-1978.

DESIGN

A single dose of Vi polysaccharide vaccine for Salmonella typhi and 2 doses of rabies vaccine were given to each subject. Antibody titers were measured in prevaccination serum samples (Vi) and in postvaccination samples (Vi and rabies).

RESULTS

The mean birth weight of the subjects was 3.24 kg; 14% of the subjects had low birth weights (<2.5 kg). Vaccine responses were not consistently associated with contemporary variables (month of study, sex, current age, or indicators of wealth). Response to typhoid vaccination was positively related to birth weight (anti-Vi immunoglobulin G: r = 0.138, P = 0.031; anti-Vi immunoglobulin M: r = 0.197, P = 0.034). Response to the rabies vaccine was not significantly associated with birth weight.

CONCLUSIONS

These findings add to a growing body of evidence suggesting that components of the immune system may be permanently programmed by events in early life. The contrasting effects on typhoid and rabies responses suggest that antibody generation to polysaccharide antigens, which have greater B cell involvement, is compromised by fetal growth retardation.