Fracture faces of zonulae occludentes from "tight" and "leaky" epithelia

Epithelia vary with respect to transepithelial permeability. In those that are considered "leaky", a large fraction of the passive transepithelial flux appears to follow the paracellular route, passing across the zonulae occludentes and moving down the intercellular clefts. In "tight" epithelia, the resistance of the paracellular pathway to passive flux is greatly increased. To see whether differences in the morphology of the zonula occludens could contribute to this variability in leakiness among epithelia, replicas of zonulae occludentes in freeze-fractured material from a variety of tight and leaky epithelia were examined. The junctions appear as a branching and anastomosing network of strands or grooves on the A and B membrane fracture faces, respectively. It was found that the zonula occludens from a "very leaky" epithelium, the proximal convoluted tubule of the mouse kidney, is extremely shallow in the apical-basal direction, consisting in most places of only one junctional strand. In contrast, the "very tight" frog urinary bladder exhibits a zonula occludens that is relatively deep (>0.5 microm) in the apical-basal direction, and consists of five or more interconnected junctional strands interposed between luminal and lateral membrane surfaces. Epithelia of intermediate permeabilities exhibited junctions with intermediate or variable morphology. Toad urinary bladder, mouse stomach, jejunum, and distal tubule, rabbit gallbladder, and Necturus kidney and gallbladder were also examined, and the morphological data from these epithelia were compared to physiological data from the literature.

Intestinal mucosal mast cells in normal and nematode-infected rat intestines are in intimate contact with peptidergic nerves

Inflammatory or allergic conditions, as well as situations where healing and repair processes occur, are characterized by the presence of increased numbers of mast cells. Previous work on the effect of neuropeptides on mast cell mediator release showed that only substance P caused such release from intestinal mucosal mast cells [Shanahan, F., Denburg, J. A., Fox, J., Bienenstock, J. & Befus, A. D. (1985) J. Immunol. 135, 1331-1337]. Accordingly, we investigated the microanatomical relationship between mast cells and enteric nerves in normal rat intestine and parasite-infected rat intestine, in which mucosal mast cell hyperplasia occurs. Combined immunohistochemistry for neuron-specific enolase and staining with alcian blue at pH 0.5 was employed on paraffin-embedded sections of normal and Nippostrongylus brasiliensis-infected rat jejunum. Sixty-seven percent of intestinal mucosal mast cells were touching subepithelial nerves, and an additional 20% were within 2 micron of nerves. Assessment of the proportion of the lamina propria occupied by mast cells (12.5%), the average mast cell area (121 +/- 28 microns 2), and the density of enteric nerves (one per 788 +/- 151 microns 2) suggested that the association was 5 times greater than would be expected by chance alone (P less than 0.0001). In consecutive sections, the nerves in contact with mast cells were also shown to contain substance P and/or calcitonin-gene-related peptide. Electron microscopy confirmed this association: 8% of the mast cells in infected rats exhibited membrane-membrane contact with unmyelinated axons containing 70- to 170-nm dense-core vesicles, and an additional 31% were situated less than 250 nm from nerves. Other mast cells appeared to embrace nerve bundles through the projection of lamellopodia. These data provide systematic quantitative evidence that a structural foundation for communication between the immune and nervous systems exists in the rat gastrointestinal tract.

Growth-hormone release-inhibiting hormone in gastrointestinal and pancreatic D cells

The normal pancreatic D cell has been well recognised since 1931, but its secretory product has not been identified with certainty. Combined immunocytochemical methods, and histological methods for endocrine granules, have demonstrated that it contains a product with G.H.-R.I.H.-like immunoreactivity. G.H.-R.I.H. has also been localised in the upper gastrointestinal tract, tentatively in the morphologically similar D cell of the Wiesbaden classification. The potent actions of this peptide on pancreatic and gastrointestinal function suggest that it may play an important role in digestive physiology.

Heparin is essential for the storage of specific granule proteases in mast cells

All mammals produce heparin, a negatively charged glycosaminoglycan that is a major constituent of the secretory granules of mast cells which are found in the peritoneal cavity and most connective tissues. Although heparin is one of the most studied molecules in the body, its physiological function has yet to be determined. Here we describe transgenic mice, generated by disrupting the N-deacetylase/N-sulphotransferase-2 gene, that cannot express fully sulphated heparin. The mast cells in the skeletal muscle that normally contain heparin lacked metachromatic granules and failed to store appreciable amounts of mouse mast-cell protease (mMCP)-4, mMCP-5 and carboxypeptidase A (mMC-CPA), even though they contained substantial amounts of mMCP-7. We developed mast cells from the bone marrow of the transgenic mice. Although these cultured cells contained high levels of various protease transcripts and had substantial amounts of mMCP-6 protein in their granules, they also failed to express mMCP-5 and mMC-CPA. Our data show that heparin controls, through a post-translational mechanism, the levels of specific cassettes of positively charged proteases inside mast cells.

Sweet taste receptors in rat small intestine stimulate glucose absorption through apical GLUT2

Natural sugars and artificial sweeteners are sensed by receptors in taste buds. T2R bitter and T1R sweet taste receptors are coupled through G-proteins, alpha-gustducin and transducin, to activate phospholipase C beta2 and increase intracellular calcium concentration. Intestinal brush cells or solitary chemosensory cells (SCCs) have a structure similar to lingual taste cells and strongly express alpha-gustducin. It has therefore been suggested over the last decade that brush cells may participate in sugar sensing by a mechanism analogous to that in taste buds. We provide here functional evidence for an intestinal sensing system based on lingual taste receptors. Western blotting and immunocytochemistry revealed that all T1R members are expressed in rat jejunum at strategic locations including Paneth cells, SCCs or the apical membrane of enterocytes; T1Rs are colocalized with each other and with alpha-gustducin, transducin or phospholipase C beta2 to different extents. Intestinal glucose absorption consists of two components: one is classical active Na+-glucose cotransport, the other is the diffusive apical GLUT2 pathway. Artificial sweeteners increase glucose absorption in the order acesulfame potassium approximately sucralose > saccharin, in parallel with their ability to increase intracellular calcium concentration. Stimulation occurs within minutes by an increase in apical GLUT2, which correlates with reciprocal regulation of T1R2, T1R3 and alpha-gustducin versus T1R1, transducin and phospholipase C beta2. Our observation that artificial sweeteners are nutritionally active, because they can signal to a functional taste reception system to increase sugar absorption during a meal, has wide implications for nutrient sensing and nutrition in the treatment of obesity and diabetes.

Identification of novel lymphoid tissues in murine intestinal mucosa where clusters of c-kit+ IL-7R+ Thy1+ lympho-hemopoietic progenitors develop

We have revealed that about one and a half thousand tiny clusters, filled with one thousand closely packed lymphocytes, can be found throughout the murine small and large intestinal mucosa. They are located in crypt lamina propria (cryptopatches; CP) and can be first detected at 14-17 d after birth. A large fraction of lymphocytes in CP expresses c-kit, IL-7R, Thy1 and a lymphocyte function-associated antigen, LFA-1, whereas most of them remain CD3-, TCR alpha beta-, TCR gamma delta-, sIgM-, and B220-. The population size of IL-2R alpha+, HSA+ and Pgp-1+ subsets is variable (20-50%) and the composition of CD8+, Ly-1+, and CD4+ subsets is smaller but also variable (3-20%). In the small intestine, CP do not contain cells undergoing apoptosis nor cells bearing RAG-1 molecules, but do contain dendritic stromal cells bearing CD11c/CD18 molecules. The frequency of DNA replicating cells in CP is higher than that in Peyer's patches (PP), is lower than that in the thymic cortex and is almost comparable with that in the thymic medulla. The numbers of CP remain the same in aged mice (> 114 wk) but double after estrogen treatment even though the thymi are attenuated sharply in both conditions. Thus, with respect to histogenesis, lymphocyte composition and tissue level of cellular behavior, neither PP, isolated lymphoid follicles, peripheral LNs, nor thymus are identical with CP. Finally, CP are virtually absent in lamina propria of IL-7R-deficient mice that display a profound reduction in thymic and peripheral lymphoid cellularity. By contrast, CP are present in germ-free mice and in athymic (nu/nu), SCID, TCR beta x delta-/-, RAG-2-/-, PP-deficient (aly/aly), stem cell factor (Sl/Sld) and c-kit (W/Wv) mutant mice. Taking all of these results together, CP are the first identification of gut-associated murine lymphoid tissues where the generation of IL-7-dependent lympho-hematopoietic progenitors for T and/or B cell descendants may start to take place at the age of commencement of weaning.

Organ culture of mucosal biopsies of human small intestine

In vitro experiments of small intestinal mucosal function and metabolism utilizing excised tissue have been limited to a few hours by rapid epithelial cell necrosis which occurs with current incubation methods. We describe a method for culturing human mucosal biopsies for up to 24 hr employing organ culture methodology and demonstrate its potential application to studies of mucosal function. Peroral biopsies were placed in organ culture plates and maintained with modified Trowell's medium in 95% O(2)-5% CO(2) at 37 degrees C for 6-24 hr. To study cell proliferation, 2 muc of thymidine-(3)H was added per ml of medium. To study fat absorption, biopsies were exposed to micellar solutions of linolenic acid, monoolein, and taurodeoxycholate in Krebs-Ringer buffer for 15 min after culture in vitro for 24 hr. After 24 hr of culture, villi were shorter and wider. Cells in the lamina were reduced in number. Light and electron microscopic morphology of epithelial cells compared favorably to those of control biopsies except in occasional areas of partial necrosis. Some absorptive cells were more cuboidal and contained more lysosomes; many appeared entirely normal. Most crypt cells appeared normal; some contained increased glycogen and lysosomes. Mitoses were present, and labeled cells were abundant in crypts of biopsies after 6 hr of incubation with thymidine-(3)H-containing medium. By 24 hr. labeled cells migrated to the base of the villi. When biopsies cultured in vitro were subsequently exposed to micellar lipid, numerous lipid droplets were identified in the cytoplasm of absorptive cells. Thus, after 24 hr in vitro under these culture conditions, many human small intestinal epithelial cells maintain near normal morphology, epithelial cell proliferation proceeds, and fat absorption occurs.

Intestinal macrophages lack CD14 and CD89 and consequently are down-regulated for LPS- and IgA-mediated activities

The intestinal mucosa normally displays minimal inflammation despite the close proximity between mucosal macrophages and lumenal bacteria. Macrophages interact with bacteria and their products through CD14, a surface receptor involved in the response to LPS, and CD89, the receptor for IgA (FcalphaR). Here we show that resident macrophages isolated from normal human intestine lack CD14 and CD89. The absence of CD14 and CD89 was not due to the isolation procedure or mucosal cell products, but was evident at the transcriptional level, as the macrophages expressed neither CD14- nor CD89-specific mRNAs, but did express Toll-like receptor 2 and 4 transcripts. Consistent with their CD14(-) phenotype, lamina propria macrophages displayed markedly reduced LPS-induced cytokine production and LPS-enhanced phagocytosis. In addition, IgA-enhanced phagocytosis was sharply reduced in lamina propria macrophages. Thus, the absence of CD14 and CD89 on resident intestinal macrophages, due to down-regulated gene transcription, causes down-modulated LPS- and IgA-mediated functions and probably contributes to the low level of inflammation in normal human intestinal mucosa.

Regulation of intestinal epithelial cell growth by transforming growth factor type beta

A nontransformed rat jejunal crypt cell line (IEC-6) expresses transforming growth factor type beta 1 (TGF-beta 1) mRNA, secretes latent 125I-labeled TGF-beta 1 competing activity into culture medium, and binds 125I-labeled TGF-beta 1 to specific, high-affinity (Kd = 3.7 pM) cell surface receptors. IEC-6 cell growth is markedly inhibited by TGF-beta 1 and TGF-beta 2 with half-maximal inhibition occurring between 0.1 and 1.0 ng of TGF-beta 1 per ml. TGF-beta 1-mediated growth inhibition is not associated with the appearance of biochemical markers of enterocyte differentiation such as alkaline phosphatase expression and sucrase activity. TGF-beta 1 (10 ng/ml) increases steady-state levels of its own mRNA expression within 8 hr of treatment of rapidly growing IEC-6 cells. In freshly isolated rat jejunal enterocytes that are sequentially eluted from the crypt villus axis, TGF-beta 1 mRNA expression is most abundant in terminally differentiated villus tip cells and least abundant in the less differentiated, mitotically active crypt cells. We conclude that TGF-beta 1 is an autoregulated growth inhibitor in IEC-6 cells that potentially functions in an autocrine manner. In the rat jejunal epithelium, TGF-beta 1 expression is most prominently localized to the villus tip--i.e., the region of the crypt villus unit that is characterized by the terminally differentiated phenotype. These data suggest that TGF-beta 1 may function in coordination of the rapid cell turnover typical for the intestinal epithelium.

Permeability of intestinal capillaries. Pathway followed by dextrans and glycogens

The pathway followed by macromolecules across the wall of visceral capillaries has been studied by using a set of tracers of graded sizes, ranging in diameter from 100 A (ferritin) to 300 A (glycogen). Polysaccharide particles, i.e. dextran 75 (mol wt approximately 75,000; diam approximately 125 A), dextran 250 (mol wt 250,000; diam approximately 225 A), shellfish glycogen (diam approximately 200 A) and rabbit liver glycogen (diam approximately 300 A), are well tolerated by Wistar-Furth rats and give no vascular reactions ascribable to histamine release. Good definition and high contrast of the tracer particles were obtained in a one-step fixation-in block staining of the tissues by a mixture containing aldehydes, OsO(4) and lead citrate in phosphate or arsenate buffer, pH 7.4, followed by lead staining of sections. The glycogens and dextrans used move out of the plasma through the fenestrae and channels of the endothelium relatively fast (3-7 min) and create in the pericapillary spaces transient (2-5 min) concentration gradients centered on the fenestrated sectors of the capillary walls. The tracers also gained access to the plasmalemmal vesicles, first on the blood front and subsequently on the tissue front of the endothelium. The particles are temporarily retained by the basement membrane. No probe moved through the intercellular junctions. It is concluded that, in visceral capillaries, the fenestrae, channels, and plasmalemmal vesicles, viewed as related parts in a system of dynamic structures, are the structural equivalent of the large pore system.

The mechanism whereby bile acid micelles increase the rate of fatty acid and cholesterol uptake into the intestinal mucosal cell

Studies were undertaken to define the mechanism whereby bile acid facilitates fatty acid and cholesterol uptake into the intestinal mucosal cell. Initial studies showed that the rate of uptake (Jd) of several fatty acids and cholesterol was a linear function of the concentration of these molecules in the bulk phase if the concentration of bile acid was kept constant. In contrast, Jd decreased markedly when the concentration of bile acid was increased relative to that of the probe molecule but remained essentially constant when the concentration of both the bile acid and probe molecule was increased in parallel. In other studies Jd for lauric acid measured from solutions containing either 0 or 20 mM taurodeoxycholate and saturated with the fatty acid equaled 79.8+/-5.2 and 120.8+/-9.4 nmol.min(-1).100 mg(-1), respectively: after correction for unstirred layer resistance, however, the former value equaled 113.5+/-7.1 nmol.min(-1).100 mg(-1). Maximum values of Jd for the saturated fatty acids with 12, 16, and 18 carbons equaled 120.8+/-9.4, 24.1+/-3.2, and 13.6+/-1.1 nmol.min(-1).100 mg(-1), respectively. These values essentially equaled those derived by multiplying the maximum solubility times the passive permeability coefficients appropriate for each of these compounds. The theoretical equations were then derived that define the expected behavior of Jd for the various lipids under these different experimental circumstances where the mechanism of absorption was assumed to occur either by uptake of the whole micelle, during interaction of the micelle with an infinite number of sites on the microvillus membrane or through a monomer phase of lipid molecules in equilibrium with the micelle. The experimental results were consistent both qualitatively and quantitatively with the third model indicating that the principle role of the micelle in facilitating lipid absorption is to overcome unstirred layer resistance while the actual process of fatty acid and cholesterol absorption occurs through a monomer phase in equilibrium with the micelle.

Human intestinal mucosal mast cells: evaluation of fixation and staining techniques

The staining properties of tissue mast cells are influenced by the method of fixation. Differences in fixation and staining techniques may explain the contradictory results in the published reports on the number of human mucosal mast cells (MMC) in the gastrointestinal mucosa in health and disease. We have examined the influence of fixatives on the staining properties of human MMC in operative biopsy specimens of human jejunum. Specimens were divided into pieces, each of which was fixed in one of the following fixatives: Carnoy's, basic lead acetate (BLA), Baker's, Bouin's, isotonic formol-acetic-acid (IFAA), 10% neutral buffered formalin, formol sublimate, and formol saline. Thereafter, tissues were paraffin-embedded and 5 micron sections were cut and stained with either astra-blue/safranin pH 0.3, or toluidine blue pH 0.5. Counts of the number of MMC/mm2 were obtained for each fixation method. The results show a critical influence of the fixative on the number of mast cells identified after staining. For example with astra-blue/safranin the mean MMC/mm2 count was 40 in formol-saline-fixed specimens, and 268 in Carnoy's-fixed specimens. In biopsies fixed with formalin-based fixatives, mast cells were more readily stained with toluidine blue. It is recommended that Carnoy's or BLA be used as the fixative for any light microscopic study of human MMC.

Eotaxin is required for the baseline level of tissue eosinophils

Eotaxin is an eosinophil-selective chemokine that is constitutively expressed in a variety of organs such as the intestine. Previous studies have demonstrated that the recruitment of eosinophils during inflammation is partially dependent on eotaxin, but the function of constitutive eotaxin during homeostasis has not been examined. To elucidate the biological role of this molecule, we now examine tissue levels of eosinophils in healthy states in wild-type and eotaxin-deficient mice. The lamina propria of the jejunum of wild-type mice is demonstrated to express eotaxin mRNA, but not mRNA for the related monocyte chemoattractant proteins. Wild-type mice contained readily detectable eosinophils in the lamina propria of the jejunum. In contrast, mice genetically deficient in eotaxin had a large selective reduction in the number of eosinophils residing in the jejunum. The reduction of tissue eosinophils was not limited to the jejunum, because a loss of thymic eosinophils was also observed in eotaxin-deficient mice. These studies demonstrate that eotaxin is a fundamental regulator of the physiological trafficking of eosinophils during healthy states. Because a variety of chemokines are constitutively expressed, their involvement in the baseline trafficking of leukocytes into nonhematopoietic tissue should now be considered.

Peroxisomes in absorptive cells of mammalian small intestine

Huge numbers of peroxisomes are present in guinea pig duodenum, jejunum, and ileum, and in rat duodenum. The peroxisomes have been studied by light and electron microscopy, including visualization by incubation in a newly-developed alkaline 3,3' diaminobenzidine (DAB) medium. Electron micrographs of more than 3700 guinea pig peroxisomes have been studied. The diameter of most peroxisomes ranges from 0.15 micro. to 0.25 micro. They often appear in clusters, surrounded by and continuous, in numerous places, with smooth endoplasmic reticulum (ER). The ER is extremely tortuous in these regions. Serial sectioning is valuable for studying the ER-peroxisome relationships but viewing sections at different angles, tilted with a goniometer stage, is more informative. The intimate relations of the two organelles appear the same in tissue fixed in four different fixatives. The peroxisomes may be interpreted as localized dilatations of smooth ER retaining multiple membranous continuities. This interpretation is discussed in light of the turnover data on peroxisomal proteins of rat hepatocytes reported by Poole and colleagues. The very large numbers of peroxisomes in intestinal epithelium lead to speculations concerning their functional significance. They resemble the small peroxisomes described in many other cell types. Although the distinctive relationship of these peroxisomes to the ER is probably more significant than their small size, for practical purposes we propose the term "microperoxisomes" to distinguish these peroxisomes from the better-known larger peroxisomes of liver and kidney.

pH-dependent binding of immunoglobulins to intestinal cells of the neonatal rat

Rat and rabbit IgG immunoglobulins conjugated to horseradiah peroxidase as a histochemical marker bind at 0 degrees C to the luminal surface of absorptive cells in isolated segments of jejunum from 10-12-day old rats. Binding is observed at pH 6.0, near the normal luminal pH of the duodenum and jejunum at this age, but not at pH 7.4. Furthermore, no binding occurs when cells are exposed at pH 6.0 to either free peroxidase or peroxidase conjugated to chicken or sheep IgG immunoglobulins or bovine serum albumin. The sensitivity of binding to pH suggests a means whereby immunoglobulins which are selectively absorbed by the cells can be released efficiently at the abluminal surface.

The evolution and involution of Peyer's patches in fetal and postnatal sheep

The Peyer's patches (PP) of sheep have a number of important anatomical features and functional characteristics which are similar to tissues that have been classified as primary lymphoid organs. The prenatal maturation of PP occurs in the absence of any antigenic stimulus as immunogenic molecules are not normally encountered by the sheep fetus. Primordial PP were first detected in the small intestine of fetal sheep at about 60-days gestation; lymphoid follicles were present by 75-days gestation and vigorous lymphopoiesis was occurring in these follicles by 100 days. From 120-days gestation until birth, at about 150 days, the PP follicles were histologically mature and they had the greatest density of proliferating lymphoid cells found anywhere in the body. The total number of PP and their constituent follicles had developed before birth when there were 25-40 discrete PP in the jejunum and proximal ileum and one single continuous PP in the terminal ileum. There was no evidence of any change in the rate of growth of the PP follicles at birth which could be related to the advent of the first antigens in the gut. The total weight of PP tissue was greater than any other single lymphoid tissue by about 6 weeks after birth weighing around 120 g or about 1.2% of the body weight; about 50-60 g of the PP tissue was calculated to be lymphoid tissue. At this time the ileocecal PP (IPP) extended 2.5 m along the terminal ileum and accounted for about 90% of the total mass of PP. From about 12 weeks after birth the IPP began to involute and only a few PP follicles remained in this region of the intestine by 18 months of age. Follicles in PP in other parts of the small intestine remained and continued to produce lymphocytes throughout the life of the animal. PP contain a number of anatomically and functionally distinct lymphoid compartments that could play different roles in the body's immune defense. Explicit in most theories on the function of PP is the notion that antigenic stimulation is the cause of the lymphopoiesis in the follicles; our results do not support this view. Instead they suggest that the follicles in the PP of sheep may play a role similar to that played by the bursa of Fabricius in birds.

The stem-cell zone of the small intestinal epithelium. I. Evidence from Paneth cells in the adult mouse

Stem cells in the small intestinal epithelium are known to differentiate into columnar, mucous, enteroendocrine, and Paneth cells. However, the site of initiation of stem-cell differentiation has been unknown. To approach this problem we determined the site of stem-cell differentiation along the Paneth cell line, using light microscopic morphometry and radioautography. The smallest Paneth cells containing the smallest granules were in positions 6 and 7, while the largest ones containing the largest granules were in positions 1 and 2 at the base of the crypt. Paneth cell death was less prevalent above position 3 than it was in position 1. Since cell size, granule size, and cell death are indicators of Paneth cell age, it was deduced that there is a gradient of Paneth cell age in the crypt base, with the oldest Paneth cells at the bottom, and the youngest at the top. After single injection or continuous infusion of 3H-thymidine, the first labeled Paneth cells to appear were the highest Paneth cells in their crypt column. Later, labeled Paneth cells became more prevalent in lower positions, and, eventually, appeared in position 1. The size of granules in labeled Paneth cells increased with time. It was concluded that Paneth cells originate in position 5 or above and then migrate downward. These results are consistent with a stem-cell zone hypothesis, which proposes that stem cells in positions 1-4 receive no inducement to differentiate. Only those stem cells that migrate up out of the stem-cell zone into position 5 will be induced and then begin to differentiate.

Morphometric data on the endothelium of blood capillaries

Local differentiations within the endothelium of both muscular (diaphragm, myocardium) and visceral (pancreas, jejunal villi) capillaries have been studied in rats on sectioned and freeze-cleaved preparations. Four distinct parts have been recognized in the endothelial cells of all these vessels on the basis of subcellular components present in each part and on the basis of variations in the local frequency of plasmalemmal vesicles: (a) the parajunctional zone, (b) the peripheral zone, (c) the organelle region, and (d) the nuclear region. Our data indicate that approximately 16, approximately 7.0, and 8.5% of the endothelial cytoplasmic volume (in the peripheral zone) is accounted for by vesicles, their content, and their membranes, respectively. The average density of vesicular openings per microm(2) is 78 in diaphragm, 89 in myocardium, 25 in pancreas, and 10 in jejunal mucosa capillaries. The frequency of fenestrae is 1.7 times as high in jejunal (26/microm(2)) as in pancreatic capillaries (15/microm(2)), the corresponding fractional areas being approximately 9.5 and approximately 6%, respectively, of the endothelial surface. Intercellular spaces occupy a relatively small area ( approximately 0.08 to 0.2%) of the inner endothelial surface.

Gastrointestinal T lymphocytes retain high potential for cytokine responses but have severe CD4(+) T-cell depletion at all stages of simian immunodeficiency virus infection compared to peripheral lymphocytes

Gastrointestinal complications in human immunodeficiency virus (HIV) infection are indicative of impaired intestinal mucosal immune system. We used simian immunodeficiency virus (SIV)-infected rhesus macaques as an animal model for HIV to determine pathogenic effects of SIV on intestinal T lymphocytes. Intestinal CD4(+) T-cell depletion and the potential for cytokine responses were examined during SIV infection and compared with results for lymphocytes from lymph nodes and blood. Flow cytometric analysis demonstrated severe depletion of CD4(+)CD8(-) single-positive T cells and CD4(+)CD8(+) double-positive T cells in intestinal lamina propria lymphocytes (LPL) and intraepithelial lymphocytes (IEL) during primary SIV infection which persisted through the entire course of SIV infection. In contrast, CD4(+) T-cell depletion was gradual in peripheral lymph nodes and blood. Flow cytometric analysis of intracellular gamma interferon (IFN-gamma) and interleukin-4 (IL-4) production following short-term mitogenic activation revealed that LPL retained same or higher capacity for IFN-gamma production in all stages of SIV infection compared to uninfected controls, whereas peripheral blood mononuclear cells displayed a gradual decline. The CD8(+) T cells were the major producers of IFN-gamma. There was no detectable change in the frequency of IL-4-producing cells in both LPL and peripheral blood mononuclear cells. Thus, severe depletion of CD4(+) LPL and IEL in primary SIV infection accompanied by altered cytokine responses may reflect altered T-cell homeostasis in intestinal mucosa. This could be a mechanism of SIV-associated enteropathy and viral pathogenesis. Dynamic changes in intestinal T lymphocytes were not adequately represented in peripheral lymph nodes or blood.

Human Norovirus Replication in Human Intestinal Enteroids as Model to Evaluate Virus Inactivation

Human noroviruses are a leading cause of epidemic and endemic acute gastroenteritis worldwide and a leading cause of foodborne illness in the United States. Recently, human intestinal enteroids (HIEs) derived from human small intestinal tissue have been shown to support human norovirus replication. We implemented the HIE system in our laboratory and tested the effect of chlorine and alcohols on human norovirus infectivity. Successful replication was observed for 6 norovirus GII genotypes and was dependent on viral load and genotype of the inoculum. GII.4 viruses had higher replication levels than other genotypes. Regardless of concentration or exposure time, alcohols slightly reduced, but did not completely inactivate, human norovirus. In contrast, complete inactivation of the 3 GII.4 viruses occurred at concentrations as low as 50 ppm of chlorine. Taken together, our data confirm the successful replication of human noroviruses in HIEs and their utility as tools to study norovirus inactivation strategies.