Frederic Clayton

Elemental diet induces histologic response in adult eosinophilic esophagitis.

OBJECTIVES:Elemental diets have not been studied in adults with eosinophilic esophagitis (EoE). The goal of this trial was to assess the efficacy of an elemental diet in adults with EoE.METHODS:A total of 18 adults with EoE were given an elemental diet for 4 weeks, or just 2 weeks if their response was complete. Symptoms and histologic findings, based on biweekly biopsies, were monitored. Six subjects were rebiopsied 2–7 days after resuming a normal diet.RESULTS:After therapy, esophageal tissue eosinophil content decreased from 54 to 10 per maximal high power field (P=0.0006). There was complete or nearly complete response (≤10 eosinophils) in 72% of subjects. Mast cell content, parabasal layer thickness, and endoscopic furrows and exudates also significantly decreased. Of the 29 qualified subjects, 11 (38%) failed to adhere to the diet. Several subjects had significant weight loss. Symptoms and endoscopic fixed strictures did not improve. After the subjects resumed a normal diet, the eosinophil content increased substantially in 3–7 days.CONCLUSIONS:While symptoms did not improve and dietary compliance was problematic, there was substantial histologic improvement after 4 weeks on the elemental diet. EoE in adults is substantially triggered by foods.

Selective depletion of rectal lamina propria rather than lymphoid aggregate CD4 lymphocytes in HIV infection

The goal of this study was to examine the changes in lymphocyte populations in rectal mucosa during HIV infection and to study their relationship to mucosal immunity and to systemic depletion of CD4 lymphocytes. Rectal biopsies from 58 HIV‐infected subjects and eight controls were studied. Frozen rectal tissue sections were stained with antibodies to CD4, CD3, CD8, and markers for macrophages. HIV‐infected subjects were divided into early stage (no opportunistic infections) and AIDS groups. There was profound depletion of rectal lamina propria CD4 lymphocytes (16% and 6% of normal content in early and AIDS groups, respectively). However, lymphoid aggregate CD4 lymphocytes were far less severely depleted (69% and 40% of normal content, respectively). The extent of lymphoid aggregate CD4 lymphocyte depletion generally parallelled the CD4 lymphocyte depletion in the blood. CD8 lymphocyte content in both the lamina propria and lymphoid aggregates usually were increased, particularly in early‐stage patients. Macrophage contents were usually normal in the HIV‐infected groups. We conclude that rectal lamina propria and lymphoid aggregates are distinct compartments differing markedly in their CD4 lymphocyte content during HIV infection. In light of this and an increased number of apoptotic cells which were noted in rectal lamina propria in HIV‐infected subjects, we hypothesize that intestinal lamina propria could be a site of rapid CD4 lymphocyte destruction during HIV infection.

Effect of combination antiretroviral therapy upon rectal mucosal HIV RNA burden and mononuclear cell apoptosis.

Background:Pathogen-negative diarrhea is common in HIV infection and has been associated with clinical symptoms, histopathology, HIV expression, CD4+ lymphocyte depletion, cytokine mRNA expression, and apoptosis of lamina propria mononuclear cells. Objectives and methods:To examine the short-term (7-day) effects of treatment with combination antiretroviral therapies upon gastrointestinal symptoms and rectal mucosa in 15 HIV-infected subjects. Results:Treatment was associated with significant decreases in the perception of abdominal bloating and cramps. Similar declines in RNA burden and rises in CD4+ lymphocyte counts were found in blood and mucosa. Treatment was also associated with a fall in the number of lamina propria mononuclear cells undergoing apoptosis by in situ labeling, a change that correlated with the change in mucosal viral burden. Conclusions:Peripheral blood and mucosal compartments are equally responsive to effective antiretroviral therapies. The detection of significant changes within 7 days of starting antiviral therapy implies that intestinal dysfunction may be a direct result of local HIV infection.

Conditional deletion of β1 integrins in the intestinal epithelium causes a loss of Hedgehog expression, intestinal hyperplasia, and early postnatal lethality

Conditional deletion of β1 integrins in the intestinal epithelium, unlike in epidermal and mammary epithelia, of mice does not result in decreased cell adhesion and proliferation, but instead causes a profound increase in epithelial proliferation with dysplasia and polypoid structures. The increased epithelial proliferation inhibited epithelial differentiation that caused severe malnutrition and early postnatal lethality. The striking similarities between β1 integrin–deleted mice and neonatal mice with defective Hedgehog signaling led to the discovery that Hedgehog expression was markedly reduced in the former mice. β1 integrins were found to drive the expression of Hedgehogs in intestinal epithelial cells in an HNF-3β (Foxa2)–dependent fashion. The expression of Tcf-4, a transcription factor known to be required for intestinal epithelial stem cell proliferation, was increased and mislocalized in the intestinal epithelia of the β1 integrin–deleted mice and in newborn mice treated with the Hedgehog signaling inhibitor cyclopamine. This study shows that β1 integrins are key regulators of proliferation and homeostasis in the intestine and achieve this not through anchorage-dependent effects but by generating Hh expression and signaling.

Analysis of microvascular changes in frostbite injury

Reported here is the characterization of the hairless mouse ear as a model system for defining the microvascular effects of minimal frostbite injury by means of gross, in vivo microscopic, histologic, and electron microscopic analysis. Initial efforts, using controlled temperatures and time of freezing, defined the minimum conditions necessary to produce consistent tissue necrosis to be -4 degrees C for 3 min. In vivo observation, after rapid thaw, showed a return of blood flow to apparent normal prefreeze rates, followed by a gradual sludging of blood 15 to 20 min post-thaw and eventually in cessation of blood flow. No vascular spasm was observed. Histologic and electron microscopic examination, unexpectedly, did not reveal evidence of early platelet or fibrin thrombi. However, marked vasodilatation and circulatory congestion began 2-3 hr after thawing. Subsequently, prominent discontinuities between damaged endothelial cells and breaks in the microvascular basement membranes were found at the light and ultrastructural level. Interstitial edema and extravasated erythrocytes occurred shortly thereafter, preceding gross tissue necrosis evident at post-freeze Day 3. We conclude that in this animal system thrombus formation is not an initial event, but rather that vascular injury in the form of endothelial cell damage predominates in early frostbite injury.

Gp120-induced Bob/GPR15 activation: A possible cause of human immunodeficiency virus enteropathy

Human immunodeficiency virus (HIV)-infected patients often develop malabsorption and increased intestinal permeability with diarrhea, called HIV enteropathy, even without enteric opportunistic infections. HIV gp120-induced calcium signaling, microtubule loss, and physiological changes resembling HIV enteropathy were previously found in the HT-29 intestinal cell line. How gp120 caused these changes was unclear. We show that the HIV co-receptor Bob/GPR15, unlike CCR5 and CXCR4, is abundant at the basal surface of small intestinal epithelium. The gp120-induced effects on HT-29 cells were inhibited by anti-Bob neutralizing antibodies, the selective G protein inhibitor pertussis toxin, and the phospholipase inhibitor U73122, but not neutralizing antibodies to CXCR4. Gp120 strains that induced signaling in HT-29 cells also induced calcium fluxes in Bob-transfected Ghost (3) cells, whereas gp120 strains not activating HT-29 cells also did not activate Bob-transfected cells. Bob is the first HIV co-receptor shown to be abundantly expressed on the basolateral surface of intestinal epithelium. Although Bob is an inefficient infection-inducing co-receptor, it mediates viral strain-specific gp120-induced calcium signaling at low, physiologically reasonable gp120 concentrations, up to 10,000-fold lower gp120 concentrations than the principal co-receptors. Gp120-induced Bob activation is a plausible cause of HIV enteropathy.

The virotoxin model of HIV-1 enteropathy: Involvement of GPR15/Bob and galactosylceramide in the cytopathic effects induced by HIV-1 gp120 in the HT-29-D4 intestinal cell line

BACKGROUND Malabsorption and diarrhea are common, serious problems in AIDS patients, and are in part due to the incompletely understood entity HIV enteropathy. Our prior in vitro work has shown that increased transepithelial permeability and glucose malabsorption, similar to HIV enteropathy, are caused by HIV surface protein gp120, although the mechanism remains unclear. RESULTS We studied the effects of HIV surface protein gp120 on the differentiated intestinal cell line HT-29-D4, specifically the effects on microtubules, transepithelial resistance, and sodium glucose cotransport. gp120 induced extensive microtubule depolymerization, an 80% decrease in transepithelial resistance, and a 70% decrease in sodium-dependent glucose transport, changes closely paralleling those of HIV enteropathy. The effects on transepithelial resistance were used to study potential inhibitors. Neutralizing antibodies to GPR15/Bob but not to CXCR4 (the coreceptor allowing infection with these HIV strains) inhibited these effects. Antibodies to galactosylceramide (GalCer) and a synthetic analog of GalCer also inhibited the gp120-induced changes, suggesting the involvement of GalCer-enriched lipid rafts in gp120 binding to intestinal epithelial cells. CONCLUSION We conclude that direct HIV infection and gp120-induced cytopathic effects are distinct phenomena. While in vivo confirmation is needed to prove this, gp120 could be a virotoxin significantly contributing to HIV enteropathy.

Biomarkers of the involvement of mast cells, basophils and eosinophils in asthma and allergic diseases

Biomarkers of disease activity have come into wide use in the study of mechanisms of human disease and in clinical medicine to both diagnose and predict disease course; as well as to monitor response to therapeutic intervention. Here we review biomarkers of the involvement of mast cells, basophils, and eosinophils in human allergic inflammation. Included are surface markers of cell activation as well as specific products of these inflammatory cells that implicate specific cell types in the inflammatory process and are of possible value in clinical research as well as within decisions made in the practice of allergy-immunology.

Endoscopic appearance and location dictate diagnostic yield of biopsies in eosinophilic oesophagitis

Acknowledging that eosinophilic esophagitis (EoE) is a disease with variable involvement throughout the oesophagus, studies have suggested a minimum of five biopsies to diagnose EoE. Although it is accepted that furrows and exudates appear to represent areas of inflammation, no research to date has looked specifically at EoE endoscopic findings to see if eosinophilic infiltrate correlates with specific endoscopic findings.

Lipopolysaccharide upregulates renal shiga toxin receptors in a primate model of hemolytic uremic syndrome.

Background: Although Shiga toxin (Stx) mediates classical hemolytic uremic syndrome (HUS), it is not fully understood why only some subjects exposed to Stx-expressing Escherichia coli develop HUS. We have previously shown in a baboon model of Stx-mediated HUS that coadministration of lipopolysaccharide (LPS) results in an augmented host response to otherwise subtoxic Stx1 doses. We used this model to test the hypothesis that LPS upregulates renal Stx receptor (Gb3) expression. Methods: Juvenile baboons were treated with either Stx1 (100 ng/kg), LPS (1 mg/kg as two divided doses 24 h apart), or a sham injection of saline, and sacrificed and immediately autopsied at 72 h. Renal cortical tissue Gb3 content was quantitated by lipid extraction and thin-layer chromatography, and Stx1 and Gb3/CD77 immunostaining was assessed by quantitative immunofluorescent microscopy. Results: Compared to saline-in jected controls, LPS administration resulted in a 2.2-fold increase in renal cortical Gb3 by chromatography (p < 0.01), a 2.5-fold increase in Stx1 staining (p = 0.003) and a 1.7-fold increase in CD77 immunostaining (p = 0.004). Stx treatment did not significantly alter either Stx or CD77 immunostaining. Conclusion: These observations suggest that LPS primes the host for Stx-mediated renal injury by upregulating renal Gb3 expression.