Human immunodeficiency virus infection of enterocytes and mononuclear cells in human jejunal mucosa

Treating From the Inside Out: Relevance of Fecal Microbiota Transplantation to Counteract Gut Damage in GVHD and HIV Infection

The gastrointestinal (GI) tract is a complex and well-balanced milieu of anatomic and immunological barriers. The epithelial surface of the GI tract is colonized by trillions of microorganisms, known as the gut microbiota, which is considered an “organ” with distinctive endocrine and immunoregulatory functions. Dysregulation of the gut microbiota composition, termed dysbiosis, has been associated with epithelial damage and translocation of microbial products into the circulating blood. Dysbiosis, increased gut permeability and chronic inflammation play a major role on the clinical outcome of inflammatory bowel diseases, graft-vs.-host disease (GVHD) and HIV infection. In this review, we focus on GVHD and HIV infection, conditions sharing gut immune damage leading to dysbiosis. The degree of dysbiosis and level of epithelial gut damage predict poor clinical outcome in both conditions. Emerging interventions are therefore warranted to promote gut microbiota homeostasis and improve intestinal barrier function. Interventions such as anti-inflammatory medications, and probiotics have toxicity and/or limited transitory effects, justifying innovative approaches. Fecal microbiota transplantation (FMT) is one such approach where fecal microorganisms are transferred from healthy donors into the GI tract of the recipient to restore microbiota composition in patients with Clostridium difficile-induced colitis or inflammatory bowel diseases. Preliminary findings point toward a beneficial effect of FMT to improve GVHD and HIV-related outcomes through the engraftment of beneficial donor bacteria, notably those producing anti-inflammatory metabolites. Herein, we critically review the potential for FMT in alleviating dysbiosis and gut damage in patients with GVHD or HIV-infection. Understanding the underlying mechanism by which FMT restores gut function will pave the way toward novel scalable and targeted interventions.

Plasma Levels of C-Type Lectin REG3α and Gut Damage in People With Human Immunodeficiency Virus

BACKGROUND

Regenerating islet-derived protein 3α (REG3α) is an antimicrobial peptide secreted by intestinal Paneth cells. Circulating REG3α has been identified as a gut damage marker in inflammatory bowel diseases. People living with human immunodeficiency virus (PWH) on antiretroviral therapy (ART) present with an abnormal intestinal landscape leading to microbial translocation, persistent inflammation, and development of non-AIDS comorbidities. Herein, we assessed REG3α as a marker of gut damage in PWH.

METHODS

Plasma from 169 adult PWH, including 30 elite controllers (ECs), and 30 human immunodeficiency virus (HIV)-uninfected controls were assessed. REG3α plasma levels were compared with HIV disease progression, epithelial gut damage, microbial translocation, and immune activation markers.

RESULTS

Cross-sectionally, REG3α levels were elevated in untreated and ART-treated PWH compared with controls. ECs also had elevated REG3α levels compared to controls. Longitudinally, REG3α levels increased in PWH without ART and decreased in those who initiated ART. REG3α levels were inversely associated with CD4 T-cell count and CD4:CD8 ratio, while positively correlated with HIV viral load in untreated participants, and with fungal product translocation and inflammatory markers in all PWH.

CONCLUSIONS

Plasma REG3α levels were elevated in PWH, including ECs. The gut inflammatory marker REG3α may be used to evaluate therapeutic interventions and predict non-AIDS comorbidity risks in PWH.

The Spontaneous Control of HIV Replication is Characterized by Decreased Pathological Changes in the Gut-associated Lymphoid Tissue

BACKGROUND

HIV infection induces alterations in the gut-associated lymphoid tissue (GALT) that constitutes the most important site for viral replication due to the extensive presence of effector memory T-cells. In the case of HIV-controllers, several studies have reported fewer peripheral alterations and conserved immune responses that correlate with viral control; however, the histopathological characterization of GALT in those patients is still missing. In this study, we evaluated pathological alterations in GALT, trying to associate them with clinical parameters of HIV infected patients with or without evidence of viral control.

METHODS

This study included eight HIV-controllers (antiretroviral treatment-naïve patients, with viral loads below 2.000 copies/mL for at least 1 year); 14 Noncontrollers (antiretroviral treatmentnaïve patients, with viral loads > 2.000 copies/mL and CD4+ T cells count > 250 cells/μL), and 12 uninfected donors. Biopsy fragments were obtained by rectosigmoidoscopy and stained with hematoxylin and eosin, silver methenamine, Ziehl Neelsen, and modified Ziehl Neelsen.

RESULTS

Histopathological findings in HIV-controllers were similar to those observed in the uninfected group. In contrast, noncontrollers exhibited several alterations including condyloma acuminate, squamous metaplasia and acute colitis. These alterations were associated with disease progression.

CONCLUSION

HIV-controllers exhibit lower pathological alterations in the gut tissue, associated with higher CD4 T cell count, and lower viral load.

Circulating LPS and (1→3)-β-D-Glucan: A Folie à Deux Contributing to HIV-Associated Immune Activation

Immune activation is the driving force behind the occurrence of AIDS and non-AIDS events, and is only partially reduced by antiretroviral therapy (ART). Soon after HIV infection, intestinal CD4+ T cells are depleted leading to epithelial gut damage and subsequent translocation of microbes and/or their products into systemic circulation. Bacteria and fungi are the two most abundant populations of the gut microbiome. Circulating lipopolysaccharide (LPS) and (1→3)-β-D-Glucan (βDG), major components of bacterial and fungal cell walls respectively, are measured as markers of microbial translocation in the context of compromised gut barriers. While LPS is a well-known inducer of innate immune activation, βDG is emerging as a significant source of monocyte and NK cell activation that contributes to immune dysfunction. Herein, we critically evaluated recent literature to untangle the respective roles of LPS and βDG in HIV-associated immune dysfunction. Furthermore, we appraised the relevance of LPS and βDG as biomarkers of disease progression and immune activation on ART. Understanding the consequences of elevated LPS and βDG on immune activation will provide insight into novel therapeutic strategies against the occurrence of AIDS and non-AIDS events.

Sex differences influence intestinal epithelial stem cell proliferation independent of obesity

The intestinal epithelium is continuously regenerated by cell renewal of intestinal epithelial stem cells (IESCs) located in the intestinal crypts. Obesity affects this process and results in changes in the size and cellular make-up of the tissue, but it remains unknown if there are sex differences in obesity-induced alterations in IESC proliferation and differentiation. We fed male and female mice a 60% high-fat diet (HFD) or a 10% low-fat diet (LFD) for 3 months and investigated the differences in (1) the expression of markers of different intestinal epithelial cell types in vivo, and (2) lasting effects on IESC growth in vitro. We found that the growth of IESCs in vitro were enhanced in females compared with males. HFD induced similar in vivo changes and in vitro early growth of IESCs in males and females. The IESCs isolated and grown in vitro from females, though, showed an enhanced growth that was independent of obesity. To determine whether this effect was driven by sex steroid hormones, we used primary intestinal crypts isolated from male and female mice and investigated the differences in (1) the expression of steroid hormone receptors, and (2) cell proliferation in response to steroid hormones. We found that estrogen receptor α was expressed in crypts from both sexes, but estrogen had no effect on proliferation in either sex. These results suggest that obesity similarly effects IESCs in males and females, but IESCs in females have greater proliferation ability than males, but this is not driven by a direct effect of sex steroid hormones on IESCs or other crypt cells that provide essential niche support for IESCs.

Dysbiotic bacteria translocate in progressive SIV infection

Infection of gut-resident CD4(+) memory T cells during acute human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infection is associated with rapid loss of these cells and damage to the epithelial barrier. Damage to the epithelial barrier allows translocation of microbial products from the intestinal lumen into the body. Immune activation caused by these microbial products has been associated with disease progression. Although microbial translocation has been demonstrated in SIV-infected nonhuman primates, the identity of translocating bacteria has not been determined. In this study we examined the communities of bacteria both within the gastrointestinal (GI) tract and systemic tissues of both healthy and experimentally SIV-infected Asian macaques. Although there were only modest changes in the GI tract-associated microbiome resulting from infection, there is substantial dysbiosis after administration of antiretrovirals. Analysis of bacterial DNA isolated from tissues of infected animals revealed a preference for the phylum Proteobacteria, suggesting that they preferentially translocate. Consistent with this finding, we observed increased metabolic activity of Proteobacterial species within the colonic lumen of SIV-infected animals. Overall, these data provide insights into disease progression and suggest that therapies aimed at altering the composition and metabolic activity of the GI tract microbiome could benefit chronically HIV-infected individuals, particularly those on antiretroviral therapies.

The role of serum I-FABP concentration in assessment of small intestine mucosa among HIV-infected patients

Objectives:

The intestinal fatty acid binding protein (I-FABP) is a useful marker in the assessment of damages and inflammation to the small intestinal mucosa. We have investigated the influence of HIV infections and antiretroviral treatment on the small intestine mucosa aided by the evaluation of I-FABP concentration levels.

Methods:

We included in the study: 31 HIV-infected patients with antiretroviral therapy (ART) treatment (T), 32 HIV-infected patients not treated with ART (NT), and 18 healthy volunteers as a control group. The concentrations of I-FABP were measured in serum using a sandwich enzyme immunoassay kit: Human I-FABP.

Results:

The median level of I-FABP in the serum of HIV-infected patients was 2.10 ± 2.56 ng/mL and did not significantly differ between T and NT (2.32 ± 2.69 ng/mL vs. 1.89 ± 2.45 ng/mL). However, the I-FABP serum level was significantly higher in HIV-infected patients when compared to the group control (2.10 ± 2.56 ng/mL vs. 1.26 ± 1.18 ng/mL; P = 0.048). We recorded a correlation for treated HIV-infected patients between Viral load and I-FABP serum level (r = −0.66; P <0.05).

Conclusions:

Elevated serum I-FABP level in HIV-infected patients confirm that HIV causes damage to the intestinal mucosa. I-FAB is a useful marker in the assessment of intestinal damage in HIV-infected patients.

Development of HIV reservoir targeted long acting nanoformulated antiretroviral therapies

Human immunodeficiency virus (HIV) infection commonly results in a myriad of comorbid conditions secondary to immune deficiency. Infection also affects broad organ system function. Although current antiretroviral therapy (ART) reduces disease morbidity and mortality through effective control of peripheral viral load, restricted infection in HIV reservoirs including gut, lymphoid and central nervous system tissues, is not eliminated. What underlies these events is, in part, poor ART penetrance into each organ across tissue barriers, viral mutation and the longevity of infected cells. We posit that one means to improve these disease outcomes is through nanotechnology. To this end, this review discusses a broad range of cutting-edge nanomedicines and nanomedicine platforms that are or can be used to improve ART delivery. Discussion points include how polymer-drug conjugates, dendrimers, micelles, liposomes, solid lipid nanoparticles and polymeric nanoparticles can be harnessed to best yield cell-based delivery systems. When completely developed, such nanomedicine platforms have the potential to clear reservoirs of viral infection.

Unexplained diarrhoea in HIV-1 infected individuals

BACKGROUND

Gastrointestinal symptoms, in particular diarrhoea, are common in non-treated HIV-1 infected individuals. Although various enteric pathogens have been implicated, the aetiology of diarrhoea remains unexplained in a large proportion of HIV-1 infected patients. Our aim is to identify the cause of diarrhoea for patients that remain negative in routine diagnostics.

METHODS

In this study stool samples of 196 HIV-1 infected persons, including 29 persons with diarrhoea, were examined for enteropathogens and HIV-1. A search for unknown and unexpected viruses was performed using virus discovery cDNA-AFLP combined with Roche-454 sequencing (VIDISCA-454).

RESULTS

HIV-1 RNA was detected in stool of 19 patients with diarrhoea (66%) compared to 75 patients (45%) without diarrhoea. In 19 of the 29 diarrhoea cases a known enteropathogen could be identified (66%). Next to these known causative agents, a range of recently identified viruses was identified via VIDISCA-454: cosavirus, Aichi virus, human gyrovirus, and non-A non-B hepatitis virus. Moreover, a novel virus was detected which was named immunodeficiency-associated stool virus (IASvirus). However, PCR based screening for these viruses showed that none of these novel viruses was associated with diarrhoea. Notably, among the 34% enteropathogen-negative cases, HIV-1 RNA shedding in stool was more frequently observed (80%) compared to enteropathogen-positive cases (47%), indicating that HIV-1 itself is the most likely candidate to be involved in diarrhoea.

CONCLUSION

Unexplained diarrhoea in HIV-1 infected patients is probably not caused by recently described or previously unknown pathogens, but it is more likely that HIV-1 itself plays a role in intestinal mucosal abnormalities which leads to diarrhoea.

Microbial translocation in HIV infection: causes, consequences and treatment opportunities

Systemic immune activation is increased in HIV-infected individuals, even in the setting of virus suppression with antiretroviral therapy. Although numerous factors may contribute, microbial products have recently emerged as potential drivers of this immune activation. In this Review, we describe the intestinal damage that occurs in HIV infection, the evidence for translocation of microbial products into the systemic circulation and the pathways by which these products activate the immune system. We also discuss novel therapies that disrupt the translocation of microbial products and the downstream effects of microbial translocation.

HIV infection and the gastrointestinal immune system

There has recently been a resurgence of interest in the gastrointestinal pathology observed in patients infected with HIV. The gastrointestinal tract is a major site of HIV replication, which results in massive depletion of lamina propria CD4 T cells during acute infection. Highly active antiretroviral therapy leads to incomplete suppression of viral replication and substantially delayed and only partial restoration of gastrointestinal CD4 T cells. The gastrointestinal pathology associated with HIV infection comprises significant enteropathy with increased levels of inflammation and decreased levels of mucosal repair and regeneration. Assessment of gut mucosal immune system has provided novel directions for therapeutic interventions that modify the consequences of acute HIV infection.

HIV enteropathy: crypt stem and transit cell hyperproliferation induces villous atrophy in HIV/Microsporidia-infected jejunal mucosa

OBJECTIVES

The study aim was to analyse the kinetics of stem and transit cells in the crypts of jejunal mucosa infected with HIV and Microsporidia.

DESIGN

The size of villi, depth of crypts and proliferative activity of transit and stem cells in jejunal mucosa were measured using morphometric techniques.

METHODS

The surface area/volume ratio (S/V) of jejunal biopsies was estimated under light microscopy using a Weibel graticule. Crypt length was measured by counting enterocytes along the crypt side from the base to the villus junction, and the mean crypt length was calculated. The S/V and crypt lengths of the jejunal mucosa of 21 HIV and Microsporidia-infected test cases were compared with 14 control cases. The labelling index in relation to the crypt cell position of 10 of the test cases was analysed compared with 13 control cases.

RESULTS

Differences were found in the S/V and crypt length, and there was a negative correlation between S/V and crypt length in test and control cases combined. Cell labelling indices fell into low and high proliferation groups. There were significant differences in labelling indices between low proliferation test cases and controls, between high proliferation test cases and controls, and between high and low proliferation test cases.

CONCLUSION

Villous atrophy induced by HIV and Microsporidia is attributed to crypt cell hyperplasia and the encroachment of crypt cells onto villi. These infections induce crypt hypertrophy by stimulating cell mitosis predominantly in transit cells but also in stem cells. Increased stem cell proliferation occurs only in high proliferation cases.

CD4/CXCR4 co-expression allows productive HIV-1 infection in canine kidney MDCK cells

The Madin-Darby canine kidney (MDCK) cell line has become the prototypic cell type for studying the mechanisms involved in viral glycoproteins transport and viral assembly in polarized cells. This cell line has been used in our laboratories for studying human immunodeficiency virus (HIV-1), despite the fact that MDCK cells cannot be infected by HIV. In transfected MDCK cells, HIV-1 glycoproteins are specifically transported to the basolateral cell surface where viral budding also mostly occurs. However, this model is of limited use when viral propagation, infection of most cells, or larger production of virions, is needed. The initial objective of this work was thus to establish an MDCK-derived cell line that could be productively infected by HIV-1, in order to pursue our studies on the polarization of viral budding. Expression of both receptor and co-receptor for T-tropic strains of the virus showed that canine cells are rendered permissive once virus binding and entry is allowed. In addition, a reduced infectivity of the viral particles released from the basolateral surface was observed. This observation most likely reflects the interference mediated by CD4 molecules that accumulate at the basolateral domain. Accordingly, this effect was largely prevented when using viruses that down-regulate cell surface CD4 by expression of both viral accessory proteins Vpu and Nef. This is a further evidence that the function of different viral proteins depends of the site of viral budding, which is itself determined by the presence of targeting signal(s) harbored by viral envelope glycoproteins.

Perils at mucosal front lines for HIV and SIV and their hosts

HIV-1 and simian immunodeficiency virus (SIV), as well as their hosts, face perils at mucosal front lines in early infection. At these sites, 'resting' CD4+ memory T cells fuel infection (because they are hosts for virus), depleting CD4+ memory T cells throughout the lymphoid tissues, particularly in the gut, and eliciting an immunosuppressive regulatory T-cell response that impairs host defence. But HIV-1 and SIV also risk elimination at the earliest stage of infection, at the mucosal point of entry, if founder populations of infected cells do not expand sufficiently to establish a self-propagating infection. Microbicides and vaccines could increase these viral vulnerabilities at mucosal front lines.

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The tyrosine-based YXXØ targeting motif of murine leukemia virus envelope glycoprotein affects pathogenesis

Retroviruses, such as human and simian immunodeficiency viruses (HIV and SIV), and murine leukemia viruses (MuLV), harbor a tyrosine-based motif in the intracytoplasmic domain of their envelope glycoprotein. This motif can act as an endocytosis signal or as a targeting signal, restricting viral budding at specific cell surface membrane domains. In the present study, proviral DNA of the ecotropic Cas-Br-E strain of MuLV was modified by substitution or deletion of the critical tyrosine residue. Mutant viruses lost basolateral targeting in polarized MDCK epithelial cells while expression level of the glycoprotein at the cell surface was not affected. This suggests that the tyrosine-based motif in MuLV does not act as an endocytosis signal. Only a small delay in the appearance of disease was observed in inoculated mice. In contrast, a striking change in the pathology was observed with enlarged thymus and lymph nodes in animals inoculated with mutant viruses.

Viral load in tissues during the early and chronic phase of non-pathogenic SIVagm infection

African green monkeys (AGMs) persistently infected with SIVagm do not develop AIDS, although their plasma viremia levels can reach those reported for pathogenic HIV-1 and SIVmac infections. In contrast, the viral burden in lymph nodes in SIVagm-infected AGMs is generally lower in comparison with HIV/SIVmac pathogenic infections, at least during the chronic phase of SIVagm infection. We searched for the primary targets of viral replication, which might account for the high viremias in SIVagm-infected AGMs. We evaluated for the first time during primary infection SIVagm dissemination in various lymphoid and non-lymphoid tissues. Sixteen distinct organs at a time point corresponding to maximal virus production were analyzed for viral RNA and DNA load. At days 8 and 9 p.i., viral RNA could be detected in a wide range of tissues, such as jejunum, spleen, mesenteric lymph nodes, thymus and lung. Quantification of viral DNA and RNA as well as of productively infected cells revealed that viral replication during this early phase takes place mainly in secondary lymphoid organs and in the gut (5 x 10(4)-5 x 10(8) RNA copies/10(6) cells). By 4 years p.i., RNA copy numbers were below detection level in thymus and lung. Secondary lymphoid organs displayed 6 x 10(2)-2 x 10(6) RNA copies/10(6) cells, while some tissue fragments of ileum and jejunum still showed high viral loads (up to 10(9) copies/10(6) cells). Altogether, these results indicate a rapid dissemination of SIVagm into lymphoid tissues, including the small intestine. The latter, despite showing marked regional variations, most likely contributes significantly to the high levels of viremia observed during SIVagm infection.

Comparison of SIVmac239(352-382) and SIVsmmPBj41(360-390) enterotoxic synthetic peptides

To characterize the active domain of the simian immunodeficiency virus (SIV) surface unit (SU) enterotoxin, peptides corresponding to the V3 loop of SIVmac239 (SIVmac) and SIVsmmPBj41 (SIVpbj) were synthesized and examined for enterotoxic activity, alpha-helical structure, and interaction(s) with model membranes. SIVmac and SIVpbj induced a dose-dependent diarrhea in 6-8-day-old mouse pups similar to full-length SU. The peptides mobilized [Ca(2+)](i) in HT-29 cells with distinct oscillations and elevated inositol triphosphate levels. Circular dichroism analyses showed the peptides were predominantly random coil in buffer, but increased in alpha-helical content when placed in a hydrophobic environment or with cholesterol-containing membrane vesicles that are rich in anionic phospholipids. None of the peptides underwent significant secondary structural changes in the presence of neutral vesicles indicating ionic interactions were important. These data show that the SIV SU enterotoxic domain localizes in part to the V3 loop region and interacts with anionic membrane domains on the host cell surface.

Infectious agent and immune response characteristics of chronic enterocolitis in captive rhesus macaques

Chronic enterocolitis is the leading cause of morbidity in colonies of captive rhesus macaques (Macaca mulatta). This study's aim was to identify the common enteric pathogens frequently associated with chronic enterocolitis in normal, immunocompetent rhesus monkeys and to elucidate the influence of this clinical syndrome on the host immune system. We analyzed the fecal specimens from 100 rhesus macaques with or without clinical symptoms of chronic diarrhea. Retrospective analysis revealed an increased incidence of Campylobacter spp. (Campylobacter coli and Campylobacter jejuni), Shigella flexneri, Yersinia enterocolitica, adenovirus, and Strongyloides fulleborni in samples collected from animals with chronic diarrhea (P < 0.05). The presence of additional enteric pathogens, such as Escherichia coli, carrying the eaeA intimin or Stx2c Shiga toxin virulence genes, Balantidium coli, Giardia lamblia, Enterocytozoon bieneusi, and Trichuris trichiura was found in all animals regardless of whether diarrhea was present. In addition, the upregulation of interleukin-1 alpha (IL-1 alpha), IL-3, and tumor necrosis factor alpha cytokine genes, accompanied by an increased presence of activated (CD4(+) CD69(+)) T lymphocytes was found in gut-associated lymphoid tissues collected from animals with chronic enterocolitis and diarrhea in comparison with clinically healthy controls (P < 0.05). These data indicate that chronic enterocolitis and diarrhea are associated, in part, with a variety of enteric pathogens and highlight the importance of defining the microbiological status of nonhuman primates used for infectious disease studies. The data also suggest that chronic colitis in rhesus macaques may have potential as a model of inflammatory bowel disease in humans.

Other viruses causing gastroenteritis

Besides the viruses producing the majority of human viral gastroenteritis, other viruses infect more rarely but are sometimes able to cause epidemics. In particular, they cause chronic infection in the immunocompromised. Some of these viruses discussed in this chapter are toroviruses, picobirnaviruses, enteroviruses, human immunodeficiency virus (HIV), herpesviruses, and coronaviruses. Toroviruses make up a genus of the Coronaviridae family. They are a well-described cause of diarrhea in calves and horses but may also infect sheep, goats, and pigs. Picobirnaviruses are related to members of the Birnaviridae family. They are found in the feces of HIV-infected patients with diarrhea more frequently than in HIV-infected patients without diarrhea, but a virus-specific immune response was not measurable. The genus Enterovirus is of the Picornaviridae family. All enteroviruses infect man via the gastrointestinal tract where they have their first site of replication, probably in lymphoid tissues of the pharynx and gut. HIV, the causative agent of the acquired immunodeficiency syndrome (AIDS), is a member of the Lentivirus genus of the Retroviridae family. Cytomegalovirus (CMV) and herpes simplex viruses, members of the Herpesviridae family, are found as the cause of colitis and esophagitis, mainly in HIV-infected patients. Coronavirus is another genus of the Coronaviridae family. Coronaviruses infect the respiratory and gastrointestinal tracts. They are a recognized cause of the common cold in man.

Early pathogenesis of transmucosal feline immunodeficiency virus infection

To identify the early target cells and tissues in transmucosal feline immunodeficiency virus (FIV) infection, cats were exposed to a clade C FIV isolate via the oral-nasal or vaginal mucosa and multiple tissues were examined by virus isolation coculture (VI), DNA PCR, catalyzed tyramide signal-amplified in situ hybridization (TSA-ISH), and immunohistochemistry between days 1 and 12 postinoculation (p.i.). FIV RNA was detected in tonsil and oral or vaginal mucosa as early as 1 day p.i. by TSA-ISH and in retropharyngeal, tracheobronchial, or external iliac lymph nodes and sometimes in spleen or blood mononuclear cells by day 2, indicating that regional and distant spread of virus-infected cells occurred rapidly after mucosal exposure. By day 8, viral RNA, DNA, and culturable virus were uniformly detected in regional and distant tissues, connoting systemic infection. TSA-ISH proved more sensitive than DNA PCR in detecting early FIV-infected cells. In mucosal tissues, the earliest demonstrable FIV-bearing cells were either within or subjacent to the mucosal epithelium or were in germinal centers of regional lymph nodes. The FIV(+) cells were of either of two morphological types, large stellate or small round. Those FIV RNA(+) cells which could be colabeled for a phenotype marker, were labeled for either dendritic-cell-associated protein p55 or T-lymphocyte receptor antigen CD3. These studies indicate that FIV crosses mucous membranes within hours after exposure and rapidly traffics via dendritic and T cells to systemic lymphoid tissues, a pathway similar to that thought to occur in the initial phase of infection by the human and simian immunodeficiency viruses.

Simian immunodeficiency virus (SIV)-specific cytotoxic T lymphocytes in gastrointestinal tissues of chronically SIV-infected rhesus monkeys

Although systemic virus-specific cytotoxic T lymphocyte (CTL) responses are of critical importance in controlling virus replication in individuals infected with human immunodeficiency virus 1 (HIV-1), little is known about this immune response in the gastrointestinal (GI) tract. This study investigated the GI tract CTL response in a nonhuman primate model for HIV-1 infection, simian immunodeficiency virus (SIV)-infected rhesus monkeys. Lymphocytes from duodenal pinch biopsy specimens were obtained from 9 chronically SIVmac-infected rhesus monkeys and GI tract lymphocytes were harvested from the jejunum and ileum of 4 euthanized SIVmac-infected rhesus monkeys. Lymphocytes were also assessed in GI mucosal tissues by in situ staining in histologic specimens. SIVmac Gag-specific CTLs were assessed in the monkeys using the tetramer technology. These GI mucosal tissues of chronically SIVmac-infected rhesus monkeys contained levels of CTLs comparable to those found in the peripheral blood and lymph nodes. The present studies suggest that the CD8(+) CTL response in GI mucosal sites is comparable to that seen systemically in SIVmac-infected rhesus monkeys.

Targeting of 3'-azido 3'-deoxythymidine (AZT)-loaded poly(isohexylcyanoacrylate) nanospheres to the gastrointestinal mucosa and associated lymphoid tissues

PURPOSE

The aim of the studv was to evaluate the capacity of poly(isohexylcyanoacrylate) nanospheres to concentrate 3'-azido 3'-deoxythymidine (AZT) in the intestinal epithelium and associated immunocompetent cells, which are known to be one of the major reservoirs of the human immunodeficiency virus (HIV).

METHODS

The tissue concentration of 3H-radiolabeled AZT in the gastrointestinal (GI) tract was obtained 30 and 9() minutes after intragastric administration to rats at a dose of 0.25 mg AZT/100 g of body weight. The distribution along the intestine was determined. AZT concentrations in the lymph were obtained by lymphatic duct cannulation.

RESULTS

Unlike the solution. nanoparticles did concentrate AZT very cfficiently in the intestinal mucosa, as well as in the Peyer's patches, and could simultaneously control the release of free AZT. Concentration in Peyer's patches was 4 times higher for nanoparticles, compared with the control solution. The tissue concentration was 30-45 microM, which was much higher than the reported IC50 of AZT (0.06-1.36 microM) and was regularly distributed along the gastrointestinal tract.

CONCLUSIONS

Nanoparticles have been shown to be efficient in concentrating AZT in the intestinal epithelium and gut-associated lymphoid tissues, supporting the view that these particles may represent a promising carrier to treat specifically the GI reservoir of HIV.

In vitro exposure to highly cytopathic HIV-1 X4 strains increases expression of mucosa-associated integrins on CD4(+) T cells

To determine whether infection with HIV-1 strains of different tropisms would influence expression of the mucosa-associated integrins alpha 4 beta 7 and alpha E beta 7 or the lymph node homing receptor L-selectin on peripheral T lymphocytes, cells were infected with the CXCR4-tropic (X4)/syncytium-inducing (SI) HIV-1(IIIB) strain or with X4/SI or CCR5-tropic (R5)/non-SI (NSI) primary human isolates. Flow cytometric analyses of CD4(+) T cells from cultures infected with HIV-1(IIIB) and one X4/SI primary HIV-1 isolate revealed a significant increase in surface expression of alpha 4 beta 7 and alpha E beta 7 12 days after infection. L-selectin expression was not significantly affected on CD4(+) T cells. However, infection with another X4/SI and two R5/NSI primary HIV-1 isolates did not significantly alter homing receptor expression on CD4(+) T cells. Since a higher degree of CD4 cytopathicity occurred in those cultures having increased integrin expression, these data suggest that significantly altered mucosal homing receptor expression on CD4(+) T cells may result as a "bystander" effect after infection with some cytopathic isolates of HIV-1.

The envelope glycoprotein of simian immunodeficiency virus contains an enterotoxin domain

By the use of a mouse model, the enteropathic effects of the simian immunodeficiency virus (SIV) surface unit (SU) envelope glycoprotein were explored. Purified SU (0.01-0.45 nmol) was administered intraperitoneally to 6- to 8-day-old mouse pups and induced a dose-dependent diarrheal response. Surgical introduction of SU into adult mouse intestinal loops revealed fluid accumulation without histological alterations and SU-treated unstripped intestinal mucosa induced chloride (Cl(-)) secretory currents in Ussing chambers. Similarly to rotavirus NSP4, the first described viral enterotoxin, SU induced a transient increase in intracellular calcium levels and increased inositol 1,4,5-triphosphate (IP(3)) levels in HT-29 cells. These data indicate the calcium response is mediated by IP(3). The presence of diarrhea and fluid accumulation within intestinal loops in the absence of histological alterations and induction of Cl(-) secretory currents demonstrate that SIV contains an enterotoxic domain localized within SU and is the second viral enterotoxin described.

Fat malabsorption assessed by 14C-triolein breath test in HIV-positive patients in different stages of infection: is it an early event?

The aim of this study was to evaluate fat absorption in HIV-positive (HIV+) patients in different phases of HIV infection using a 14C-triolein breath test. We distributed 47 HIV+ patients according to the 1993 Centers for Disease Control Revised Classification: 20 in Group 2 (A1 or A2) and 27 in Group 3 (B1, B2, A3, B3, or C). Ten HIV-negative healthy subjects comprised the control group (Group 1). All individuals underwent a 14C-triolein breath test. Parasitic infection was evaluated through three stool exams, including Cryptosporidium and Isospora investigation. The median value of cumulative 6 hours' 14C excretion expressed as percentage of the 14C given as triolein was significantly higher in Group 1 (8.4%) than Group 2 (5.5%) or Group 3 (3.4%), p = 0.04 and p << 0.01, respectively. Fat malabsorption was found in 25% of Group 2 individuals, 52.6% of those without diarrhea in Group 3, and was correlated with CD4+ lymphocyte counts (p << 0.01). Fat malabsorption is a common feature in advanced stages of HIV infection, even in the absence of diarrhea and is also present in asymptomatic HIV+ patients. These findings suggest that malabsorption is an early event in HIV-infected individuals and is correlated with the degree of immunosuppression.

Alterations in RANTES gene expression and T-cell prevalence in intestinal mucosa during pathogenic or nonpathogenic simian immunodeficiency virus infection

RANTES, a beta-chemokine, can suppress human immunodeficiency virus (HIV) as well as simian immunodeficiency virus (SIV) infections in T-lymphocyte cultures in vitro. However, the association of RANTES levels in peripheral blood with viral loads and disease outcome in HIV infection has been inconclusive. SIV-infected rhesus macaques were evaluated to determine whether RANTES gene expression correlated with suppression of viral infection in intestinal lymphoid tissues. Intestinal tissues were obtained from rhesus macaques infected with either pathogenic or nonpathogenic SIVmac variants at various stages of infection (primary acute, asymptomatic, and terminal). We examined the level of SIV infection (in situ hybridization), RANTES expression (quantitative competitive RT-PCR), and T-cell counts (immunohistochemistry). The most pronounced increase in RANTES gene expression in intestinal tissues was observed in primary SIV infection, which correlated with the pathogenicity of the infecting virus and not the tissue viral loads. Our results demonstrated that in contrast to the occurrence of viral suppression by RANTES in vitro, there was no direct correlation between high RANTES gene expression and suppression of viral loads in intestinal lymphoid tissues. Thus RANTES expression in the gut lymphoid tissue may not be a correlate for viral suppression. However, RANTES gene expression in primary SIV infection may be part of early host immune response to viral infection.

Interactions of viruses and microparticles with apical plasma membranes of M cells: implications for human immunodeficiency virus transmission

In the rectal mucosa, specialized M cells of the lymphoid follicle-associated epithelium conduct vesicular transport of antigens from the mucosal surface into organized mucosal lymphoid tissues, where immune responses are induced. Bacteria and viruses may exploit this mechanism to initiate mucosal or systemic infection. Viral pathogens, including reovirus, poliovirus, and possibly human immunodeficiency virus (HIV), can enter the intestinal or rectal mucosa by adhering to apical membranes of M cells, but the membrane components involved in these interactions are unknown. Glycoprotein coats on the apical surfaces of epithelial cells act as diffusion barriers that limit access of particles and microorganisms to membrane glycolipids and to certain oligosaccharide epitopes of enterocytes but allow selective adherence to M cells. The accessibility of membrane glycolipids of M cells, along with their active endocytic activity, could promote entry of HIV into the rectal mucosa.

Replication and budding of simian immunodeficiency virus in polarized epithelial cells

Simian immunodeficiency virus (SIV) infection of primates provides an important model for infection of humans by HIV. Since mucosal epithelium is likely to be an important portal of entry, we decided to study aspects of the interaction of SIV with epithelial cells. SIV was shown to produce virus efficiently in polarized epithelial cells (Vero C1008) transfected with SIVmac239 proviral DNA. The virus titer in the epithelial cell culture fluid reached 10(3) TCID50/ml at day 3 posttransfection. Initially after transfected epithelial cells were plated on a permeable membrane, virus budded at both the apical and the basolateral domains. However, after the cells formed a tight monolayer, 95-100% of the virus particles budded basolaterally, as assessed by release of p27 antigen into the fluid above and below the monolayer. This finding was confirmed by electron microscopy, which showed that the mature virus budded basolaterally in polarized cells. After introduction of the CD4 gene into Vero cells by a retrovirus vector, polarizable cells were able to be infected by cell-free SIVmac239 virus. The virus titer reached 10(4) TCID50/ml in culture fluid and virions also budded basolaterally, the same as the virus from transfected cells. Two viruses (SIVmac1A11 and SIVmac251) that contain truncated TMgp28 instead of TMgp41 also budded basolaterally. Furthermore, we found that HIV-1 with full-length or truncated TMgp41 also budded basolaterally.

Intestinal absorption and permeability in human immunodeficiency virus-infected patients

BACKGROUND

Impaired intestinal function could account for diarrhoea and weight loss, which are common features of advanced human immunodeficiency virus (HIV) infection.

METHODS

We assessed intestinal permeability to lactulose and mannitol and absorption of D-xylose in 96 HIV-infected patients (group I: asymptomatic subjects (CDC-A); group II: symptomatic subjects (CDC-B or C) without body weight loss and/or diarrhoea; group III: 25 acquired immunodeficiency syndrome (AIDS) patients (CDC-C) with severe body weight loss and/or diarrhoea) and 10 healthy subjects as controls.

RESULTS

An incremental decrease in urinary D-xylose recoveries was observed, with all groups statistically different from each other. Impaired intestinal permeability was only found in patients of group III (statistically different from all other groups).

CONCLUSIONS

These findings suggest a loss of intestinal functional absorptive surface as HIV disease progresses. This process may be present at the early stage of infection. Impaired intestinal permeability is observed later in AIDS patients when digestive signs are present, particularly diarrhoea.

Primary intestinal epithelial cells can be infected with laboratory-adapted strain HIV type 1 NDK but not with clinical primary isolates

Infectivities of HIV-1 primary isolates and laboratory-adapted strains were compared in primary fetal enterocytes and the colonic epithelial cell line HT29. Infection by two laboratory strains, HIV-1 NDK and HIV-1 NDK(A4), which were adapted on CEM and HT29 cells, respectively, produced significant amounts of virus in both target cell systems. Intestinal cells were resistant to infection with HIV-1 primary isolates regardless of their genetic subtype or SI/NSI phenotype. Biological properties of analyzed viruses rather than differences in cultivation system seem to be responsible for differences between these in vitro and ex vivo results.

Intestinal intraepithelial lymphocytes are primed for gamma interferon and MIP-1beta expression and display antiviral cytotoxic activity despite severe CD4(+) T-cell depletion in primary simian immunodeficiency virus infection

Intraepithelial lymphocytes (IEL) are a critical effector component of the gut-associated lymphoid tissue (GALT) and play an important role in mucosal immunity as well as in the maintenance of the epithelial cell integrity and barrier function. The objective of this study was to determine whether simian immunodeficiency virus (SIV) infection of rhesus macaques would cause alterations in the immunophenotypic profiles of IEL and their mitogen-specific cytokine (gamma interferon [IFN-gamma] and MIP-1beta) responses (by flow cytometry) and virus-specific cytotoxic T-cell (CTL) activity (by the chromium release assay). Virally infected IEL were detected through the entire course of SIV infection by in situ hybridization. Severe depletion of CD4(+) single-positive and CD4(+)CD8(+) double-positive T cells occurred early in primary SIV infection, which was coincident with an increased prevalence of CD8(+) T cells. This was in contrast to a gradual depletion of CD4(+) T cells in peripheral blood. The CD8(+) IEL were the primary producers of IFN-gamma and MIP-1beta and were found to retain their potential to produce both IFN-gamma and MIP-1beta through the entire course of SIV infection. SIV-specific CTL activity was detected in primary IEL at 1, 2, and 4 weeks post-SIV infection. These results demonstrated that IEL may be involved in generating antiviral immune responses early in SIV infection and in suppressing viral infection thereafter. Alterations in homeostasis in epithelia due to severe CD4(+) T-cell depletion accompanied by changes in the cytokine and chemokine production by IEL may play a role in the enteropathogenesis of SIV infection.

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.

Intracellular cytokine expression in the CD4+ and CD8+ T cells from intestinal mucosa of simian immunodeficiency virus infected macaques

Isolated intraepithelial lymphocytes (IEL) and lamina propria lymphocytes (LPL) from jejunum of SIV infected animals were examined for alterations in basal cytokine expression by RT-PCR. Remarkable changes in IFNgamma and IL-10 RNA levels were observed in IEL and LPL in SIV infection while IL-4 and IL-2 RNA levels remained unaltered. In addition, the CD4+ and CD8+ LPL were examined for intracellular cytokine production following mitogenic activation by flowcytometry. Both CD4+ and CD8+ T lymphocytes in intestinal mucosa retained the potential to produce IFNgamma in response to mitogenic stimulation in vitro, without a remarkable change in IL-4 production. The dominant IFNgamma cytokine response could be one of the major contributing factors in SIV associated enteropathy.

HIV-1/Simian Immunodeficiency Virus Infection of Human and Nonhuman Primate Lymphocytes Results in the Migration of CD2+ T Cells into the Intestine of Engrafted SCID Mice

Increased lymphocytic infiltration of intestinal tissues has been observed in patients infected with HIV-1 and in SIV-infected rhesus macaques. To determine whether HIV-1 and SIV infections influence the homing of human and nonhuman primate PBMC to intestinal tissues, we engrafted SCID mice with human or nonhuman primate PBMC and infected them with either cell-free or cell-associated HIV-1 or SIV. In mice that received both PBMC and virus, human or nonhuman primate CD2+ T cells were found in intestinal tissues, primarily in the intraepithelial lymphocyte compartment and lamina propria. Immunomagnetic sorting revealed that these cells were derived from the CD4+ population. Using gag-specific primers, PCR analysis of these tissues detected the presence of HIV-1 proviral DNA. However, in SCID mice that were engrafted with either human or nonhuman primate PBMC and no HIV-1 or SIV, CD2+ T cells were not detected in intestinal tissues. These results indicate that HIV-1 and SIV can modulate the migratory properties of human and nonhuman primate T cells in the SCID mouse model.

Direct effect of type 1 human immunodeficiency virus (HIV-1) on intestinal epithelial cell differentiation: relationship to HIV-1 enteropathy

Human immunodeficiency virus (HIV)-infected patients display severe impairments of gastrointestinal functions, including diarrhea and malabsorption, even in the absence of opportunistic infections. Since HIV-1 proteins and nucleic acids have been detected in several cell types of the intestinal mucosa, it has been postulated that HIV-1 itself could alter enterocytic functions. In the present study, we analyzed the effect of HIV-1 on the differentiation process of the epithelial intestinal cell clone HT-29-D4, which mimics the maturation of enterocytes along the crypt-villus axis of the small intestine. We found that HIV-1 infection impairs cellular differentiation (i) by affecting the barrier function of the epithelium, as evidenced by a decrease in the transepithelial electrical resistance, and (ii) by inhibiting the activity of one major glucose absorption function, i.e., sodium/glucose cotransport. At the morphological level, HIV-1 infection of HT-29-D4 cells was associated with the formation of lumina, which are representative of a defect in cellular organization. These morphofunctional perturbations induced by HIV-1 could be mimicked by nocodazole, a microtubule-disrupting agent. Correspondingly, HIV-1 exposure of HT-29-D4 cells evoked a massive disruption of microtubules, as revealed by alpha-tubulin indirect immunofluorescence staining. A similar effect was observed after incubation of the cells with either recombinant gp120 or a monoclonal antibody against galactosylceramide (GalCer), the intestinal receptor for HIV-1 gp120, suggesting that the effect of HIV-1 was mediated by the binding of gp120 to GalCer. Based on these data, we propose that HIV-1 may selectively alter enterocytic functions through a direct effect on the intracellular architecture of the cells. In contrast with previous theories for HIV-1 enteropathy, our data support the concept that HIV-1 may perturb intestinal functions without necessarily infecting intestinal epithelial cells.

The impact of HIV infection on lactose absorptive capacity

Forty HIV-infected adult patients at different disease stages and 44 healthy volunteers were evaluated for lactose malabsorption using the hydrogen breath test after 20 g lactose ingestion. All subjects were previously tested for breath hydrogen (H2) excretion after 12 g lactulose ingestion. The presence of intestinal superinfections, gastrointestinal symptoms and the intensity of clinical intolerance after lactose load were accurately searched in each patient. The cumulative H2 excretion after lactulose did not significantly differ between the different groups studied. The prevalence of lactose malabsorption turned out to be significantly higher (P < 0.001) in HIV-infected patients (70%) than in controls (34%). Moreover, in patients in more advanced disease stages the degree of lactose malabsorption was significantly greater than in patients at earlier disease stages, who did not differ from healthy volunteers. Furthermore the degree of lactose intolerance was significantly greater (P < 0.001) in symptomatic patients than in those without intestinal symptoms and in healthy volunteers, while no significant difference was observed between these latter groups. The results here demonstrate the negative impact of HIV infection on lactose absorptive capacity in adult patients, particularly marked in more advanced stages of the disease, suggesting that, in addition to the presence of the virus alone, other factors may contribute to determine the enterokinetic alterations responsible for lactase deficiency.

Human immunodeficiency virus-1 infection of the lymphoid tissues of Waldeyer's ring

Human immunodeficiency virus-1 (HIV-1) infection is a fatal retroviral infection that may first present clinically as enlargement of the lymphoid tissues of Waldeyer's ring. These tissues are a major site of viral replication. The presence of the virus in these tissues causes a unique constellation of diagnostic histopathologic features, including florid follicular hyperplasia, follicle lysis, and productively HIV-1-infected multinucleated giant cells of probable dendritic cell origin. Serologic evaluation is confirmatory of HIV infection. With the recent advances in antiretroviral chemotherapy, the early institution of which may significantly prolong life and disease-free interval, the recognition of the clinical and pathologic parameters of HIV-related enlargement of Waldeyer's ring tissues is essential.

Decreased fat and nitrogen losses in patients with AIDS receiving medium-chain-triglyceride-enriched formula vs those receiving long-chain-triglyceride-containing formula

OBJECTIVE

The purpose of this study was to compare two enteral formulas, differing only in fat source, for product acceptance, tolerance, and effect on fat malabsorption and nutritional status in subjects with acquired immune deficiency syndrome (AIDS).

DESIGN

The double-blind, randomized 15-day trial was divided into a 3-day period in which solid food was consumed followed by a 12-day experimental period in which liquid formulas were consumed.

SETTING/SUBJECTS

Twenty-three men and one woman with AIDS and fat malabsorption completed the study. The study was conducted in the General Clinical Research Center, University of Alabama Hospital, University of Alabama at Birmingham. Laboratory assays were performed in the Department of Nutrition Sciences.

INTERVENTIONS

After 3 days of consuming a controlled, solid food diet containing 100 g fat per day from mixed sources to document fat malabsorption, subjects were randomly assigned to one of two groups. Each group received a liquid formula containing 35% of energy as fat for 12 days. One group received a formula containing 85% medium-chain triglycerides (MCTs) and the control group received a formula containing 100% long-chain triglycerides.

MAIN OUTCOME MEASURES

Determinations included stool number, consistency, weight, and fat and nitrogen content; urine nitrogen and creatinine levels; and body weight.

STATISTICAL ANALYSIS PERFORMED

Subject demographic and other baseline characteristics were compared using two-sample t tests; stool and urine assessments were compared between groups at the initial experimental period using two-sample t tests; changes from initial to final experimental periods were assessed by means of analysis of covariance; changes in pooled intake, body weight, and the number and consistency of bowel movements were also assessed using analysis of covariance. All statistical tests were two-tailed and considered significant at P < .05.

RESULTS

Within-group comparisons indicated that subjects fed the MCT formula showed significantly decreased stool fat and stool nitrogen content (P = .01 and P = .03, respectively) and increased fat absorption (P = .03), whereas those fed the control formula did not. Differences in stool fat between the groups were not statistically significant. However, the difference in fat absorption from the initial to final formula period was significant (P = .04). Subjects consuming the MCT formula also tended to have a decreased number of bowel movements and abdominal symptoms, whereas subjects fed the control formula showed no improvement. All subjects maintained their body weights.

APPLICATIONS

There may be advantages to using an MCT-based formula in the treatment of AIDS-associated malabsorption.

Pathophysiology of HIV-associated diarrhea

Considerable advances have been made in the evaluation and treatment of diarrhea in HIV-infected individuals, although gaps in knowledge still exist. The availability of newer and more powerful antiretroviral agents should allow a better definition of the effect of local HIV infection on intestinal function. Further attention to the pathophysiology of diarrhea should lead to improvements in diagnosis and treatment.

Advances in mucosal immunology

HIV infection is likely to remain a significant medical and scientific problem well into the twenty-first century. During the first 15 years of the epidemic, much has been learned about the biology of HIV infection, but the majority of biomedical research has focused on the peripheral circulation. It is likely that the behavior of the virus within the unique immunologic environment of the intestinal mucosa differs from that which is observed in the periphery. Many clinical and epidemiologic features of HIV infection offer compelling reasons to encourage further examination of the mucosal immune system's role in AIDS pathogenesis. This article has touched on most of the significant observations concerning the mucosal immune system and HIV infection, and it is clear that much remains to be done. As mentioned earlier, the mucosal abnormalities observed in HIV infection are likely to have many causes. Careful evaluation of patients with early disease and fewer confounding variables may provide fresh insight into AIDS pathogenesis. Similarly, prospective evaluation of selected patient populations may be more informative in characterizing the progressive alterations in mucosal immune function than random cross-sectional studies of poorly defined groups. It is equally important for immunologic assessment to be correlated with nutritional and symptomatic evaluation. Finally, the success or failure of future antiretroviral therapies will be critically related to the impact of such agents on lymphoid reservoirs of HIV infection such as the gastrointestinal tract, which are at present refractory to treatment.

Perturbations of glucose metabolism associated with HIV infection in human intestinal epithelial cells: a multinuclear magnetic resonance spectroscopy study

OBJECTIVE

To analyse the effect of HIV-1 infection on the glucose metabolism of human intestinal epithelial cells.

METHODS

HT-29 cells were infected with HIV-1NDK and studied 3 weeks (acutely infected cells) or 9 months (chronically infected cells) post-infection. Perchloric acid extracts were analysed by high-resolution 1H, 31P and 13C nuclear magnetic resonance spectroscopy. Metabolite concentrations and specific 13C enrichments were quantified for chronically infected, acutely infected and control cells grown in Dulbecco's modified Eagle's medium containing natural-abundance or 1-13C-enriched glucose to determine significant differences between infected and non-infected cells.

RESULTS

Chronically HIV-infected cells showed alterations in glycerol-3-phosphate (+40%), fructose-1,6-diphosphate (-66%), uridine diphosphate glucuronic acid (-33%), lactate (+75%) and [1-13C]glucose (+181%) levels, and in specific lactate 3-13C enrichment (+19%) when compared with controls. Acutely infected cells exhibited decreased fructose-1,6-diphosphate (-58%) and increased nicotinamide adenine dinucleotide (+33%) levels relative to controls.

CONCLUSION

HIV-1 infection results in a disturbance of glycolytic and oxidative activities in human intestinal epithelial cells. This finding supports the concept that HIV-1 may directly impair some metabolic functions of the intestinal epithelium, and that it can be considered a potential aetiological agent for HIV-associated enteropathy.

Steatorrhea: a common manifestation in patients with HIV/AIDS

Multiple infectious causes of diarrhea are known in patients with HIV/AIDS. Maldigestion and malabsorption have been reported in patients with HIV/AIDS and may be independent of infectious etiologies. Among ambulatory patients with HIV/AIDS, we examined the prevalence of fat malabsorption (steatorrhea). Sixty-one patients with unexplained diarrhea (defined as > 2 stools/d) and/or weight loss despite adequate caloric intake (and without clinical evidence of chronic pancreatitis) were evaluated in our outpatient Gastroenterology-Nutrition Clinic between March 1, 1993, and July 1994. Patients were instructed by a dietitian to follow a > or = 100 g/d fat diet for 24 h before submitting a stool sample for qualitative (or quantitative) fecal fat determination. Forty-five patients, 32 with ongoing diarrhea and 13 without diarrhea, submitted stool samples. Twenty-two of 45 patients (49%) had qualitative or quantitative steatorrhea, 16/32 with diarrhea (50%) and 6/13 patients without diarrhea (46%). Thirty of 32 patients with diarrhea had had extensive microbiologic and/or endoscopic evaluations. Only 9 patients had a detectable intestinal pathogen, 5 patients had cytomegalovirus (4 treated), 4 patients had cryptosporidia (3 treated), and 1 patient had microsporidia. Steatorrhea, as determined by abnormal qualitative fecal fat, is detectable in nearly 50% of patients with HIV/AIDS. Fat malabsorption appears to be a primary defect in these patients independent of detectable pathogens. Assessment of fat malabsorption should be considered in patients with unexplained weight loss or diarrhea before extensive evaluation for opportunistic infections.