Conjunctival M cells selectively bind and translocate Maackia amurensis leukoagglutinin

M cell targeting engineered biomaterials for effective vaccination

Vaccines are one of the greatest medical interventions of all time and have been successful in controlling and eliminating a myriad of diseases over the past two centuries. Among several vaccination strategies, mucosal vaccines have wide clinical applications and attract considerable interest in research, showing potential as innovative and novel therapeutics. In mucosal vaccination, targeting (microfold) M cells is a frontline prerequisite for inducing effective antigen-specific immunostimulatory effects. In this review, we primarily focus on materials engineered for use as vaccine delivery platforms to target M cells. We also describe potential M cell targeting areas, methods to overcome current challenges and limitations of the field. Furthermore, we present the potential of biomaterials engineering as well as various natural and synthetic delivery technologies to overcome the challenges of M cell targeting, all of which are absent in current literature. Finally, we briefly discuss manufacturing and regulatory processes to bring a robust perspective on the feasibility and potential of this next-generation vaccine technology.

Histological and Ultrastructural Studies on the Conjunctiva of the Barred Owl (Strix varia)

This report is the first characterization of the histology and ultrastructure of the barred owl conjunctiva. The inferior eyelid was dominated by a large disk-shaped plate covered by a non-keratinized stratified squamous or cuboidal epithelium of variable thickness. The apical surface of the plate epithelium varied from flat to long microvilli or even short cytoplasmic extensions similar to those seen in the third eyelid. All specimens had a few goblet cells filled with mucous secretory granules in the plate region. The underlying connective tissue was a dense fibroelastic stroma. Eosinophils were surprisingly common in the epithelial layer and underlying connective tissue in the plate and more distal orbital mucosal region. The orbital mucosa contained goblet cells with heterogeneous glycosylation patterns. The leading edge and marginal plait of the third eyelid are designed to collect fluid and particulate matter as they sweep across the surface of the eye. The palpebral conjunctival surface of the third eyelid was covered by an approximately five-cell-deep stratified squamous epithelium without goblet cells. The bulbar surface of the third eyelid was a bilayer of epithelial cells whose superficial cells have elaborate cytoplasmic tapering extensions reaching out 25 μm. Narrow cytofilia radiated outwards up to an additional 15–20 μm from the cytoplasmic extensions. Lectin labeling demonstrated heterogeneous glycosylation of the apical membrane specializations but only small amounts of glycoprotein-filled secretory granules in the third eyelid.

Development, alteration and real time dynamics of conjunctiva-associated lymphoid tissue

Purpose

Conjunctiva-associated lymphoid tissue (CALT) is thought to play a key role in initiating ocular surface related immune responses. This study was planned to get first profound insights into the function of CALT related to development, cellular dynamics and morphological alteration using a novel mouse model.

Methods

Expression and morphology of CALT were investigated using BALB/c mice kept under different housing conditions, after topical antigen-stimulation and following lymphadenectomy and splenectomy. Particles and bacteria were applied topically to study antigen-transport. Intravital visualization was performed using two-photon microscopy.

Results

Postnatal development and ultrastructure of CALT in the mouse is similar to humans. Topical antigen-challenge significantly alters CALT expression. Bacterial translocation is demonstrated via lymphoepithelium whereas cellular velocities within follicles were approximately 8 µm/min.

Conclusions

CALT in the mouse is an immunological interface of the ocular surface, featuring dynamic processes such as morphological plasticity, particle/bacteria transport and cellular migration.

Nanomedicines for back of the eye drug delivery, gene delivery, and imaging

Treatment and management of diseases of the posterior segment of the eye such as diabetic retinopathy, retinoblastoma, retinitis pigmentosa, and choroidal neovascularization is a challenging task due to the anatomy and physiology of ocular barriers. For instance, traditional routes of drug delivery for therapeutic treatment are hindered by poor intraocular penetration and/or rapid ocular elimination. One possible approach to improve ocular therapy is to employ nanotechnology. Nanomedicines, products of nanotechnology, having at least one dimension in the nanoscale include nanoparticles, micelles, nanotubes, and dendrimers, with and without targeting ligands. Nanomedicines are making a significant impact in the fields of ocular drug delivery, gene delivery, and imaging, the focus of this review. Key applications of nanotechnology discussed in this review include a) bioadhesive nanomedicines; b) functionalized nanomedicines that enhance target recognition and/or cell entry; c) nanomedicines capable of controlled release of the payload; d) nanomedicines capable of enhancing gene transfection and duration of transfection; f) nanomedicines responsive to stimuli including light, heat, ultrasound, electrical signals, pH, and oxidative stress; g) diversely sized and colored nanoparticles for imaging, and h) nanowires for retinal prostheses. Additionally, nanofabricated delivery systems including implants, films, microparticles, and nanoparticles are described. Although the above nanomedicines may be administered by various routes including topical, intravitreal, intravenous, transscleral, suprachoroidal, and subretinal routes, each nanomedicine should be tailored for the disease, drug, and site of administration. In addition to the nature of materials used in nanomedicine design, depending on the site of nanomedicine administration, clearance and toxicity are expected to differ.

A novel immunofluorescent computed tomography (ICT) method to localise and quantify multiple antigens in large tissue volumes at high resolution

Current immunofluorescence protocols are limited as they do not provide reliable antibody staining within large tissue volumes (mm³) and cannot localise and quantify multiple antigens or cell populations in the same tissue at high resolution. To address this limitation, we have developed an approach to three-dimensionally visualise large tissue volumes (mm³) at high resolution (<1 µm) and with multiple antigen labelling, for volumetric and quantitative analysis. This is made possible through computer reconstruction of serial sectioned and sequentially immunostained butyl-methyl methacrylate (BMMA) embedded tissue. Using this novel immunofluorescent computed tomography (ICT) approach, we have three-dimensionally reconstructed part of the murine lower eyelid that contains the meibomian gland and localised cell nuclei (DAPI), Ki67 and cytokeratin 1 (CK1), as well as performing non-linear optical (NLO) microscopy imaging of collagen, to assess cell density, cell proliferation, gland keratinisation and gland volume respectively. Antigenicity was maintained after four iterative stains on the same tissue, suggesting that there is no defined limit to the number of antigens that can be immunostained for reconstruction, as long as the sections remain intact and the previous antibody has been successfully eluted. BMMA resin embedding also preserved fluorescence of transgenic proteins. We propose that ICT may provide valuable high resolution, three-dimensional biological maps of multiple biomolecules within a single tissue or organ to better characterise and quantify tissue structure and function.

M cell-targeted ocular immunization: effect on immunoglobulins in tears, feces, and serum

PURPOSE

This study investigates whether antigen-sampling M cells, present in the follicle-associated epithelium (FAE) above organized conjunctiva-associated lymphoid tissue in rabbits, bind and retro-transport secretory IgA (sIgA) from the tear film. The hypothesis that IgA-mediated uptake of antigens promotes local and systemic production of immunoglobulins was tested.

METHODS

sIgA binding and retro-translocation by M cells was characterized by immunocytochemistry. Immunoglobulin concentrations in tears, feces and serum were measured using enzyme-linked immunoassays (ELISA) after topical and systemic immunization with either goat IgG anti-rabbit IgA or nonspecific goat IgG.

RESULTS

Endogenous sIgA was found associated with the apical membrane of conjunctival M cells. Exogenous anti-IgA immunoglobulins were translocated across M cells. Significant levels of sIgA against goat IgG were present in tears of pre-immune animals. Topical application of either goat IgG specific for rabbit IgA or nonspecific goat IgG led to similar increases in antigen-specific IgA in tear, feces, and serum. The antigen-specific IgG response in tears mirrored the serum response for both immunogens consistent with transudation of this immunoglobulin. The IgM response in tears and serum was weak for both immunogens. Systemic immunization did not sustain or enhance the local mucosal IgA responses.

CONCLUSIONS

Conjunctival M cells bind and translocate sIgA from the tear film. Topical conjunctival immunization leads to generation of antigen-specific immunoglobulins from both local and distant mucosae and in serum. Natural antibodies, present in the tear film before immunization, may have contributed to similar immune responses to goat anti-rabbit IgA and nonspecific goat IgG.

Giant papillary conjunctivitis

PURPOSE OF REVIEW

Despite shorter replacement intervals and new lens materials, giant papillary conjunctivitis still limits the ability of some patients to wear contact lenses.

RECENT FINDINGS

Recent research has elucidated many new mediators of inflammation. The presence of chemokines and cytokines such as IL-8, IL-6, IL-11, macrophage inflammatory protein-delta, tissue inhibitor of metalloproteinases-2 macrophage-colony stimulating factor and monokine-induced gamma interferon, eotaxin, pulmonary and activation-regulated CC chemokines have been shown to be elevated in patients with giant papillary conjunctivitis. In addition, M cells and B lymphocytes have been hypothesized to play a role in the pathogenesis of giant papillary conjunctivitis.

SUMMARY

The pathophysiology of giant papillary conjunctivitis is complicated with both immune and mechanical mechanisms playing a role in the development of this condition; understanding these mechanisms is important in both treatment and prevention of giant papillary conjunctivitis.

Histochemical demonstration of two subtypes of O-linked oligosaccharides in the rat gastric glands

The gastric glands synthesize glycoproteins whose oligosaccharides are linked to the peptide core mainly by the O-glycosidic bond, specifically removed by beta-elimination procedure. Our aim was to research the possibility of the existence of two subtypes of O-linked oligosaccharides with a different behavior to the removal procedure. The lectins from peanut (PNA) and Maackia amurensis (MAA-I) were histochemically used as markers of the O-linked oligosaccharides. Sections were also pretreated with beta-elimination and/or peptide N-Glycosidase F (PNGase-F) for the specific removal of O- and N-linked oligosaccharides, respectively. The lectin GNA, which mainly labels to N-linked oligosaccharides, was used to test the correct working of PNGase-F. To test the possibility that the beta-elimination treatment could remove the terminal sialic acid residues, the lectin LFA was used. The surface epithelium was negative to PNA, while it became strongly positive when beta-elimination was performed for 1 day. This staining was resistant to PNGase-F, suggesting that PNA was labeling to O-linked oligosaccharides. However, after beta-elimination for 5 days this staining is not observed. A similar pattern appeared with MAA-I. We propose the existence of two subtypes of O-linked oligosaccharides: labile and resistant. The labile O-linked oligosaccharides are removed with beta-elimination for 1 day, unmasking the PNA-positive oligosaccharides. These oligosaccharides are resistant O-linked oligosaccharides because staining is abolished with longer treatment of beta-elimination. The results with MAA-I also support this suggestion. In summary, the labile O-linked oligosaccharides are removed with short treatment, while the resistant O-linked oligosaccharides need a stronger procedure (for 5 days).

M cells are involved in pathogenesis of human contact lens-associated giant papillary conjunctivitis

Introduction:

The objective was to study the pathogenesis of contact lens-associated giant papillary conjunctivitis (CL-GPC).

Materials and Methods:

Twenty-one biopsies of conjunctival giant papillae were obtained from soft contact lens wearers. The tissues were fixed in 4% paraformaldehyde and embedded in paraffin. Sections of 5 µm thickness were used for studies of histology and immunohistochemistry of pan-B and pan-T cell distributions.

Results:

Conjunctival epitheliums on the top of conjunctiva-associated lymphoid tissue typically lacked goblet cells. Lymphocytes from underlying lymphoid follicle were pressed into intra-epithelial “pockets” formed through epithelial invagination. Under the follicle-associated epithelium, pan-B cells were mostly gathered in the central folliclar area and intraepithelial pockets, while CD3-positive T cells were predominantly distributed in parafolliclar region, but only a few in the intraepithelial pockets.

Conclusions:

Membranous epithelial cells (M cells) play a key role in the pathogenesis of CL-GPC for the binding and translocation of antigen and pathogen.