Rectal mucosal pathology varies with human immunodeficiency virus antigen content and disease stage

From dysbiosis to defense: harnessing the gut microbiome in HIV/SIV therapy

BACKGROUND

Although the microbiota has been extensively associated with HIV pathogenesis, the majority of studies, particularly those using omics techniques, are largely correlative and serve primarily as a basis for hypothesis generation. Furthermore, most have focused on characterizing the taxonomic composition of the bacterial component, often overlooking other levels of the microbiome. The intricate mechanisms by which the microbiota influences immune responses to HIV are still poorly understood. Interventional studies on gut microbiota provide a powerful tool to test the hypothesis of whether we can harness the microbiota to improve health outcomes in people with HIV.

RESULTS

Here, we review the multifaceted role of the gut microbiome in HIV/SIV disease progression and its potential as a therapeutic target. We explore the complex interplay between gut microbial dysbiosis and systemic inflammation, highlighting the potential for microbiome-based therapeutics to open new avenues in HIV management. These include exploring the efficacy of probiotics, prebiotics, fecal microbiota transplantation, and targeted dietary modifications. We also address the challenges inherent in this research area, such as the difficulty in inducing long-lasting microbiome alterations and the complexities of study designs, including variations in probiotic strains, donor selection for FMT, antibiotic conditioning regimens, and the hurdles in translating findings into clinical practice. Finally, we speculate on future directions for this rapidly evolving field, emphasizing the need for a more granular understanding of microbiome-immune interactions, the development of personalized microbiome-based therapies, and the application of novel technologies to identify potential therapeutic agents.

CONCLUSIONS

Our review underscores the importance of the gut microbiome in HIV/SIV disease and its potential as a target for innovative therapeutic strategies.

HIV Latency and Nanomedicine Strategies for Anti-HIV Treatment and Eradication

Antiretrovirals (ARVs) reduce Human Immunodeficiency Virus (HIV) loads to undetectable levels in infected patients. However, HIV can persist throughout the body in cellular reservoirs partly due to the inability of some ARVs to cross anatomical barriers and the capacity of HIV-1 to establish latent infection in resting CD4⁺ T cells and monocytes/macrophages. A cure for HIV is not likely unless latency is addressed and delivery of ARVs to cellular reservoir sites is improved. Nanomedicine has been used in ARV formulations to improve delivery and efficacy. More specifically, researchers are exploring the benefit of using nanoparticles to improve ARVs and nanomedicine in HIV eradication strategies such as shock and kill, block and lock, and others. This review will focus on mechanisms of HIV-1 latency and nanomedicine-based approaches to treat HIV.

Inflammatory Bowel Disease in Adult HIV-Infected Patients-Is Sexually Transmitted Infections Misdiagnosis Possible?

Background. The aim of our study was to describe 50 cases of inflammatory bowel disease (IBD) and HIV co-existence that are under medical supervision in Warsaw. Methods. This was a retrospective descriptive study. Fifty HIV-infected patients, diagnosed with IBD during the years 2001–2019, were identified. IBD was diagnosed endoscopically and then confirmed by biopsy. All data was obtained from medical records. Results. All studied patients were male with a median age of 33 years old (range 20–58 years). All, except one, were men who have sex with men (MSM). The median CD4 cell count was 482 cells/µL (range 165–1073 cells/µL). Crohn’s disease (CD) was diagnosed in 7 patients (14%), ulcerative colitis (UC) in 41 patients (82%), and 2 patients (4%) had indeterminate colitis. Forty-nine patients (98%) reported a history of unprotected receptive anal intercourse and different sexual transmitted infections (STIs). Only in 10 patients (20%) were one or more IBD relapses observed. Conclusions. We recommend HIV testing for every MSM with IBD suspicion. Moreover, STIs testing should be performed in every IBD patient with colorectal inflammation, using molecular and serological methods. Persons who reported unprotected receptive anal intercourse seem to have the biggest risk of STI-associated proctitis or proctocolitis mimicking IBD.

Central Nervous System Inflammation and Infection during Early, Nonaccelerated Simian-Human Immunodeficiency Virus Infection in Rhesus Macaques

Studies utilizing highly pathogenic simian immunodeficiency virus (SIV) and simian-human immunodeficiency virus (SHIV) have largely focused on the immunopathology of the central nervous system (CNS) during end-stage neurological AIDS and SIV encephalitis. However, this may not model pathophysiology in earlier stages of infection. In this nonaccelerated SHIV model, plasma SHIV RNA levels and peripheral blood and colonic CD4⁺ T cell counts mirrored early human immunodeficiency virus (HIV) infection in humans. At 12 weeks postinfection, cerebrospinal fluid (CSF) detection of SHIV RNA and elevations in IP-10 and MCP-1 reflected a discrete neurovirologic process. Immunohistochemical staining revealed a diffuse, low-level CD3⁺ CD4⁻ cellular infiltrate in the brain parenchyma without a concomitant increase in CD68/CD163⁺ monocytes, macrophages, and activated microglial cells. Rare SHIV-infected cells in the brain parenchyma and meninges were identified by RNAScope in situ hybridization. In the meninges, there was also a trend toward increased CD4⁺ infiltration in SHIV-infected animals but no differences in CD68/CD163⁺ cells between SHIV-infected and uninfected control animals. These data suggest that in a model that closely recapitulates human disease, CNS inflammation and SHIV in CSF are predominantly mediated by T cell-mediated processes during early infection in both brain parenchyma and meninges. Because SHIV expresses an HIV rather than SIV envelope, this model could inform studies to understand potential HIV cure strategies targeting the HIV envelope.

IMPORTANCE Animal models of the neurologic effects of HIV are needed because brain pathology is difficult to assess in humans. Many current models focus on the effects of late-stage disease utilizing SIV. In the era of antiretroviral therapy, manifestations of late-stage HIV are less common. Furthermore, new interventions, such as monoclonal antibodies and therapeutic vaccinations, target HIV envelope. We therefore describe a new model of central nervous system involvement in rhesus macaques infected with SHIV expressing HIV envelope in earlier, less aggressive stages of disease. Here, we demonstrate that SHIV mimics the early clinical course in humans and that early neurologic inflammation is characterized by predominantly T cell-mediated inflammation accompanied by SHIV infection in the brain and meninges. This model can be utilized to assess the effect of novel therapies targeted to HIV envelope on reducing brain inflammation before end-stage disease.

Relationship between human immunodeficiency virus (HIV-1) infection and chronic periodontitis

INTRODUCTION

Current studies show that, even in the era of antiretroviral therapies, HIV-1 infection is associated with more severe and frequent refractory chronic periodontitis. Areas covered: This review, based on a systematic analysis of the literature, intends to provide an update on factors that may be involved in the pathogenesis of periodontal disease in HIV-1-infected patients, including local immunosuppression, oral microbial factors, systemic inflammation, salivary markers, and the role of gingival tissue as a possible reservoir of HIV-1. Expert commentary: The therapeutic revolution of ART made HIV-1 infection a chronic controllable disease, reduced HIV-1 mortality rate, restored at least partially the immune response and dramatically increased life expectancy of HIV-1-infected patients. Despite all these positive aspects, chronic periodontitis assumes an important role in the HIV-1 infection status for activating systemic inflammation favoring viral replication and influencing HIV-1 status, and also acting as a possible reservoir of HIV-1. All these issues still need to be clarified and validated, but have important clinical implications that certainly will benefit the diagnosis and management of chronic periodontitis in HIV-1-infected patients, and also contributes to HIV-1 eradication.

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.

Mucosal immunity in human and simian immunodeficiency lentivirus infections

Overwhelming evidence indicates that distinct pathological phenomenon occurs within the gastrointestinal (GI) tract of progressively simian immunodeficiency virus (SIV)-infected Asian macaques and HIV-infected humans compared with other anatomical sites. Massive loss of GI tract lamina propria CD4 T cells, alteration in the profile of lymphocytic cytokine production, changes in the landscape of GI tract antigen-presenting cells, and variations to the structural barrier of the GI tract are hallmarks of progressive HIV/SIV infections. The pathology within the GI tract results in translocation of microbial products from the lumen of the intestine into peripheral circulation. These translocated microbial products directly stimulate the immune system and exacerbate immune activation and, thus, disease progression. Initiation of combination antiretroviral therapy (cART) does not restore completely the immunological abnormalities within the GI tract. This incomplete restoration within the GI tract may contribute to the increased mortality observed within HIV-infected individuals treated for decades with cART. Novel therapeutic interventions aimed at enhancing GI tract anatomy and physiology may improve the prognosis of HIV-infected individuals.

Current and novel approaches to vaccine development against tuberculosis

Antibiotics and vaccines are the two most successful medical countermeasures that humans have created against a number of pathogens. However a select few e.g., Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB) have evaded eradication by vaccines and therapeutic approaches. TB is a global public health problem that kills 1.4 million people per year. The past decade has seen significant progress in developing new vaccine candidates, but the most fundamental questions in understanding disease progression and protective host responses that are responsible for controlling Mtb infection still remain poorly resolved. Current TB treatment requires intense chemotherapy with several antimicrobials, while the only approved vaccine is the classical viable whole-cell based Bacille-Calmette-Guerin (BCG) that protects children from severe forms of TB, but fails to protect adults. Taken together, there is a growing need to conduct basic and applied research to develop novel vaccine strategies against TB. This review is focused on the discussion surrounding current strategies and innovations being explored to discover new protective antigens, adjuvants, and delivery systems in the hopes of creating an efficacious TB vaccine.

Altered distribution of mucosal NK cells during HIV infection

The human gut mucosa is a major site of human immunodeficiency virus (HIV) infection and infection-associated pathogenesis. Increasing evidence shows that natural killer (NK) cells have an important role in control of HIV infection, but the mechanism(s) by which they mediate antiviral activity in the gut is unclear. Here, we show that two distinct subsets of NK cells exist in the gut, one localized to intraepithelial spaces (intraepithelial lymphocytes, IELs) and the other to the lamina propria (LP). The frequency of both subsets of NK cells was reduced in chronic infection, whereas IEL NK cells remained stable in spontaneous controllers with protective killer immunoglobulin-like receptor/human leukocyte antigen genotypes. Both IEL and LP NK cells were significantly expanded in immunological non-responsive patients, who incompletely recovered CD4+ T cells on highly active antiretroviral therapy (HAART). These data suggest that both IEL and LP NK cells may expand in the gut in an effort to compensate for compromised CD4+ T-cell recovery, but that only IEL NK cells may be involved in providing durable control of HIV in the gut.

Mucosal and peripheral Lin- HLA-DR+ CD11c/123- CD13+ CD14- mononuclear cells are preferentially infected during acute simian immunodeficiency virus infection

Massive infection of memory CD4 T cells is a hallmark of early simian immunodeficiency virus (SIV) infection, with viral infection peaking at day 10 postinfection (p.i.), when a majority of memory CD4 T cells in mucosal and peripheral tissues are infected. It is not clear if mononuclear cells from the monocyte and macrophage lineages are similarly infected during this early phase of explosive HIV and SIV infections. Here we show that, at day 10 p.i., Lin(-) HLA-DR(+) CD11c/123(-) CD13(+) CD14(-) macrophages in the jejunal mucosa were infected, albeit at lower levels than CD4 memory T cells. Interestingly, Lin(-) HLA-DR(+) CD11c/123(-) CD13(+) CD14(-) macrophages in peripheral blood, like their mucosal counterparts, were preferentially infected compared to Lin(-) HLA-DR(+) CD11c/123(-) CD13(+) CD14(+) monocytes, suggesting that differentiated macrophages were selectively infected by SIV. CD13(+) CD14(-) macrophages expressed low levels of CD4 compared to CD4 T cells but expressed similar levels of CCR5 as lymphocytes. Interestingly, CD13(+) CD14(-) macrophages expressed Apobec3G at lower levels than CD13(+) CD14(+) monocytes, suggesting that intracellular restriction may contribute to the differential infection of mononuclear subsets. Taken together, our results suggest that CD13(+) CD14(-) macrophages in mucosal and peripheral tissues are preferentially infected very early during the course of SIV infection.

The HIV-1-specific protein Casp8p41 induces death of infected cells through Bax/Bak

Casp8p41, a novel protein generated when HIV-1 protease cleaves caspase 8, independently causes NF-κB activation, proinflammatory cytokine production, and cell death. Here we investigate the mechanism by which Casp8p41 induces cell death. Immunogold staining and electron microscopy demonstrate that Casp8p41 localizes to mitochondria of activated primary CD4 T cells, suggesting mitochondrial involvement. Therefore, we assessed the dependency of Casp8p41-induced death on Bax/Bak and caspase 9. In wild-type (WT) mouse embryonic fibroblast (MEF) cells, Casp8p41 causes rapid mitochondrial depolarization (P < 0.001), yet Casp8p41 expression in Bax/Bak double-knockout (DKO) MEF cells does not. Similarly, caspase 9-deficient T cells (JMR cells), which express Casp8p41, undergo minimal cell death, whereas reconstituting these cells with caspase 9 (F9 cells) restores Casp8p41 cytotoxicity (P < 0.01). The infection of caspase 9-deficient cells with a green fluorescent protein (GFP) HIV-1 reporter virus results in cell death in 32% of infected GFP-positive cells, while the restoration of caspase 9 expression in these cells restores infected-cell killing to 68% (P < 0.05), with similar levels of viral replication between infections. Our data demonstrate that Casp8p41 requires Bax/Bak to induce mitochondrial depolarization, which leads to caspase 9 activation following either Casp8p41 expression or HIV-1 infection. This understanding allows the design of strategies to interrupt this form of death of HIV-1-infected cells.

Rapid dissemination of SIV follows multisite entry after rectal inoculation

Receptive ano-rectal intercourse is a major cause of HIV infection in men having sex with men and in heterosexuals. Current knowledge of the mechanisms of entry and dissemination during HIV rectal transmission is scarce and does not allow the development of preventive strategies. We investigated the early steps of rectal infection in rhesus macaques inoculated with the pathogenic isolate SIVmac251 and necropsied four hours to nine days later. All macaques were positive for SIV. Control macaques inoculated with heat-inactivated virus were consistently negative for SIV. SIV DNA was detected in the rectum as early as four hours post infection by nested PCR for gag in many laser-microdissected samples of lymphoid aggregates and lamina propria but never in follicle-associated epithelium. Scarce SIV antigen positive cells were observed by immunohistofluorescence in the rectum, among intraepithelial and lamina propria cells as well as in clusters in lymphoid aggregates, four hours post infection and onwards. These cells were T cells and non-T cells that were not epithelial cells, CD68⁺ macrophages, DC-SIGN⁺ cells or fascin⁺ dendritic cells. DC-SIGN⁺ cells carried infectious virus. Detection of Env singly spliced mRNA in the mucosa by nested RT-PCR indicated ongoing viral replication. Strikingly, four hours post infection colic lymph nodes were also infected in all macaques as either SIV DNA or infectious virus was recovered. Rapid SIV entry and dissemination is consistent with trans-epithelial transport. Virions appear to cross the follicle-associated epithelium, and also the digestive epithelium. Viral replication could however be more efficient in lymphoid aggregates. The initial sequence of events differs from both vaginal and oral infections, which implies that prevention strategies for rectal transmission will have to be specific. Microbicides will need to protect both digestive and follicle-associated epithelia. Vaccines will need to induce immunity in lymph nodes as well as in the rectum.

The mucosal barrier and immune activation in HIV pathogenesis

PURPOSE OF REVIEW

Significant gastrointestinal pathology occurs in progressive HIV and simian immunodeficiency virus (SIV) infections. This review will examine the relationship between the detrimental events to the gastrointestinal tract during the acute phase of infection and disease progression through the chronic phase and, ultimately, AIDS.

RECENT FINDINGS

Gastrointestinal tract CD4 T cells are dramatically depleted in acutely HIV-infected humans and SIV-infected rhesus macaques, sooty mangabeys, and African green monkeys. In addition HIV infection of humans and SIV-infection of rhesus macaques are characterized by enteropathy and increased intestinal permeability. While SIV-infected rhesus macaques and HIV-infected humans manifest chronic and systemic immune activation and microbial translocation, and progress to chronic infection and AIDS, however, SIV-infected sooty mangabeys and African green monkeys do not.

SUMMARY

Recent studies have increased our understanding of the mechanisms relating structural and immunological damage to the gastrointestinal tract during the acute phase of HIV/SIV infection to immune activation and disease progression in the chronic phase.

Advances in sexually transmitted infections of the gastrointestinal tract

The gastrointestinal mucosa is a target of many sexually transmitted infections, and major advances have increased our understanding of the consequences of such infections within the gastrointestinal system. HIV-1 is associated with a marked loss of mucosal CD4(+) T cells that express CC-chemokine receptor 5. This process seems to be more rapid and more severe in mucosa-associated lymphoid tissue than in the peripheral blood. Mechanistic insights into the underlying cause of acute and chronic gastrointestinal damage with HIV infection-microbial translocation, defects in intestinal epithelial barrier function and activation of a systemic immune response-have also been achieved. Increased understanding of the pathogenesis of mucosal HIV-1 infection may identify therapeutic targets to restore immunological function and the integrity of the intestinal mucosal epithelial barrier. The increasing prevalence of lymphogranuloma venereum in Europe, mostly in HIV-positive men who have sex with men, suggests a change in the epidemiology of what was previously considered to be a 'tropical' disease. The increasing incidence of acute HCV infection transmitted via sexual contact has also been fueled by high-risk sexual behaviors among men who have sex with men, many of whom are also HIV-positive. The first part of this Review discusses the pathogenesis and gastrointestinal complications of HIV infection, and the second part summarizes advances in our understanding of other sexually transmitted infections of the gastrointestinal system.

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.

Aspectos funcionais, microbiológicos e morfológicos intestinais em crianças infectadas pelo vírus da imunodeficiência humana

RACIONAL: O trato gastrointestinal é freqüentemente acometido nas crianças infectadas pelo vírus da imunodeficiência humana, com importantes repercussões no seu estado nutricional e sobrevida. A maioria dos estudos relacionados a esse tema foi desenvolvida com adultos, sendo menos investigado o problema nas crianças OBJETIVOS: Estudar aspectos digestivo-absortivos, microbiológicos e morfológicos intestinais em crianças infectadas pelo vírus da imunodeficiência humana MATERIAL E MÉTODOS: Onze crianças infectadas pelo vírus da imunodeficiência humana, menores de 13 anos, pertencentes às categorias clínicas A, B ou C, divididas em dois grupos: cinco pacientes com relato atual ou recente de diarréia e seis pacientes sem diarréia nos 30 dias que antecederam à inclusão no estudo. Investigação proposta: biopsia de intestino delgado e reto para análise morfológica e microbiológica, coprocultura, protoparasitológico de fezes, pesquisa de rotavírus, micobactérias e Cryptosporidium; teste da D-xilose RESULTADOS: Todos os pacientes testados (9/11) apresentavam má absorção da D-xilose (8,4-24,4 mg/dL). Os achados histopatológicos de intestino delgado foram inespecíficos, representados em sua maioria, por enteropatia grau I a II (6/10). Em todos os casos foi constatado aumento do infiltrado celular do córion. As alterações histopatológicas do reto também foram inespecíficas, com presença de aumento do infiltrado celular do córion. A pesquisa de microorganismos enteropatogênicos só foi positiva em dois casos, sendo identificado Mycobacterium avium intracellulare e Cryptosporidium nas fezes CONCLUSÕES: Demonstrou-se alta prevalência (100%) de má absorção intestinal em crianças infectadas pelo vírus da imunodeficiência humana, com ou sem diarréia. Não foi possível estabelecer correlações quanto à presença de agentes enteropatogênicos, má absorção intestinal, alterações morfológicas intestinais e ocorrência ou não de diarréia. Não houve correlação entre os valores de D-xilose e os graus de atrofia vilositária.

Immunopathology of the duodenal mucosa of HIV-positive patients during combined antiretroviral therapy

The objective of the present study was to evaluate the duodenal mucosa of HIV-infected patients during antiretroviral therapy. This was an observational study conducted on HIV-positive patients and a control group. Group 1 comprised 22 HIV-negative individuals while 38 HIV-positive individuals were classified according to the CDC 1993 classification into group 2 (A1 or A2) or group 3 (B2, A3, B3, C2, C3). All subjects were submitted to upper gastrointestinal endoscopy with duodenal biopsies. Qualitative, semi-quantitative and quantitative histological analyses were performed. Results were considered significant when P < 0.05. A higher prevalence of inflammatory infiltrate and eosinophilia was observed in the HIV group, together with a reduction in mucosal CD4+ lymphocyte (L) counts [median (lower-upper quartiles), 12.82 (8.30-20.33), 6.36 (1.75-11.66) and 1.75 (0.87-3.14) in groups 1, 2 and 3, respectively] which was not correlated with disease stage. The extent of CD4+L count reduction was similar in blood and duodenal mucosa. Normal CD8+L and CD45RO+L counts, and normal numbers of macrophages and antigen-presenting cells were also found in the HIV patients. The cytokine pattern did not differ among groups. Tissue HIV, assessed by p24 antigen, correlated with a higher CD45RO+L count (77.0 (61-79.8) and 43.6 (31.7-62.8) in p24+ and p24-, respectively, P = 0.003), and IL-4 positivity (100 and 48.2% in p24+ and p24-, respectively, P = 0.005). The duodenal mucosa of HIV+ patients showed a relatively preserved histological architecture. This finding may be characteristic of a population without opportunistic infections and treated with potent antiretroviral therapy, with a better preservation of the immune status.

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.

Intracellular and cell-free (infectious) HIV-1 in rectal mucosa

The intestinal mucosa contains most of the total lymphocyte pool and plays an important role in viral transmission, but only slight attention has been given to the immunological and virological aspects of human immunodeficiency virus-1 (HIV-1) infection at this site. In this study, before initiating or changing antiretroviral therapy, paired blood samples and rectal biopsies (RB) were obtained from 26 consecutive HIV-infected subjects. HIV-1 isolation and biological characterization, DNA, and HIV-1 RNA titration were assessed, as were in vitro tumor necrosis factor-alpha (TNF-alpha) and interleukin-beta (IL-1beta) spontaneous production. The rate of HIV-1 isolation from peripheral blood mononuclear cells (PBMCs) and RBs was 75% and 58%, respectively. All RB-derived isolates were nonsyncytium inducing (NSI), independent of the phenotype of blood-derived isolates. Proviral DNA and detectable HIV-1 RNA levels were measured in 100% and 77% of RBs, respectively. A statistical correlation was observed between HIV-1 DNA and HIV-1 RNA levels in rectal mucosa (P = 0.0075), whereas no correlation was found between these levels in blood samples (P > 0.05). Antiretroviral treatment did not seem to influence HIV-1 detection in RBs. Higher levels of in vitro proinflammmatory cytokine production were found in the RBs of most infected patients when compared with healthy controls. Therefore, the rectal mucosa is an important HIV-1 reservoir that demonstrates a discordant viral evolution with respect to blood. Both the virus type and the mucosa pathway of immunoactive substances might have important implications for therapeutic decision-making and monitoring and could influence the bidirectional transmission of HIV-1 in mucosal surfaces.

Strain-dependent productive infection of a unique eosinophilic cell line by human immunodeficiency virus type 1

Eosinophils are granulocytic leukocytes that function in both protective and pathological immune responses. They can be infected by HIV-1, but characterization of the infection has been hindered by lack of a productive cell culture model. In the present study, the unique eosinophilic cell line AML14.3D10 was used as a model to test the hypothesis that HIV-1 productively infects eosinophilic cells in a strain-dependent fashion. The AML14.3D10 cell line was cultured with one T cell-tropic (T-tropic) strain and two macrophage-tropic (M-tropic) strains of HIV-1 (HTLV-IIIB, HIV-1AdaM, and HIV-1Ba-L strains, respectively). Cytopathic effects were evident in living cultures and in stained slide preparations of AML14.3D10 cells infected with the T-tropic strain of HIV-1. Culture supernatants from infected AML14.3D10 cells contained high levels of HIV-1 p24 protein that peaked at approximately 7-10 days postinfection. A line of AML14.3D10 cells chronically infected with HTLV-IIIB and continuously producing high levels of virus was established. In contrast to the T-tropic strain, the M-tropic strains of HIV-1 did not productively infect the eosinophilic cell line. Thus, the AML14.3D10 eosinophilic cell line was permissive for a T-tropic strain but not for M-tropic strains of HIV-1. Flow cytometry revealed that uninfected AML14.3D10 cells were positive for the HIV-1 receptor CD4 and coreceptors CXCR4 and CCR5; the cell line was negative for CCR3. The lack of productive infection by M-tropic strains despite CCR5 expression indicates that strain-dependent infection may not be determined at the coreceptor level in AML14.3D10 cells.

Intestinal epithelial cell apoptosis following Cryptosporidium parvum infection

Cryptosporidium parvum induces moderate levels of apoptosis of cultured human intestinal epithelial cells, which are maximal at 24 h after infection. Apoptosis is further increased in C. parvum-infected cells by inhibition of NF-kappaB. C. parvum infection also attenuates epithelial apoptosis induced by strongly proapoptotic agents. The data suggest C. parvum has developed strategies to limit apoptosis in order to facilitate its growth and maturation in the early period after epithelial cell infection.

Excretory-secretory product of newly excysted metacercariae of Paragonimus westermani directly induces eosinophil apoptosis

Eosinophils are important effector cells in host defense against parasites. Excretory-secretory product (ESP) produced by helminthic worms plays important roles in the uptake of nutrients, migration in the host tissue, and in immune modulation. However, little is known about the ability of the ESP to directly trigger eosinophil apoptosis. This study investigated whether the ESP of newly excysted metacercariae of Paragonimus westermani could induce apoptosis in human eosinophils. Apoptosis was assayed by staining the cells with FITC-annexin V, and the cells were analyzed by flow cytometry. It was found that the ESP of newly excysted metacercariae of P. westermani induced a direct time- and concentration-dependent increase in the rate of constitutive apoptosis in mature human eosinophils. Eosinophil apoptosis was first apparent 3 hr after treatment with the ESP and continued to increase after 6 hr of incubation with respect to the cells cultured in the absence of the ESP. While only 2.8% of the eosinophils incubated in the medium for 3 hr were apoptotic, 7.6%, 10.9% and 22.6% of the eosinophils treated with 10, 30 and 100 micrograms/ml ESP were apoptotic, respectively. This result suggests that the ESP of newly excysted metacercariae of P. westermani directly induce eosinophil apoptosis, which may be important for the survival of the parasites and the reduction of eosinophilic inflammation in vivo.

Cells of the monocyte-macrophage lineage and pathogenesis of HIV-1 infection

It is thought that monocyte-macrophages and probably dendritic cells play a central role in HIV-1 primary infection, as well as in its evolution, given that they are among the first cells infected and later function as important reservoirs for the virus. These cells may participate in the selection of certain viral strains instead of others. Levels of CCR5 coreceptor expression on the surface of monocytes and macrophages determine their susceptibility to infection by HIV-1 strains using this coreceptor and may explain, in part, the differences in the infectivity of these cells through the maturation process. However, selection for certain strains is not only determined by the level of coreceptor expression, but by the biochemical properties of the different coreceptors and their relationship with other surface molecules and the chemokine and cytokine networks, which also influence the selective viral infection and replication in these cells. Any current or newly designed therapies need to be evaluated, including careful analysis of the levels of HIV-1 infection of the cells of the monocyte-macrophage lineage, because these cells are both significant viral reservoirs and a center of virus production at all stages of the disease.

Human intestinal lamina propria lymphocytes are naturally permissive to HIV-1 infection

The presence of HIV-1 in the intestinal mucosa of AIDS patients has been reported and human intestinal lamina propria lymphocytes (LPL) have been proposed as important targets for HIV-1 infection. However, little information is available concerning the permissiveness of human intestinal CD4+ T lymphocytes to HIV-1 infection. Here, we show that human LPL, in contrast to autologous peripheral blood lymphocytes (PBL), are permissive to both X4 T-tropic and R5 M-tropic strains of HIV-1, as well as to clinical isolates, in the absence of exogenous stimuli. Flow cytometry showed that the vast majority of T LPL were CD45RO+ and CD69+, and that CD4+ T LPL highly expressed CC chemokine receptor 5 (CCR5) as compared to PBL, while CX chemokine receptor 4 was equally expressed on LPL and PBL. Exogenous RANTES and macrophage inflammatory protein-1alpha (natural CCR5 ligands) virtually abolished the entry of the R5 M-tropic strain HIV-1 into human LPL. Thus, we infer that human intestinal CD4+ T lymphocytes are naturally susceptible to HIV-1 infection, due to their physiological state of activation and to marked expression of HIV-1 coreceptors, independently of the route of primary (either mucosal or parental) infection and the shifts of the virus phenotype occurring during the course of AIDS.

Apoptosis of human intestinal epithelial cells after bacterial invasion

Epithelial cells that line the human intestinal mucosa are the initial site of host invasion by bacterial pathogens. The studies herein define apoptosis as a new category of intestinal epithelial cell response to bacterial infection. Human colon epithelial cells are shown to undergo apoptosis following infection with invasive enteric pathogens, such as Salmonella or enteroinvasive Escherichia coli. In contrast to the rapid onset of apoptosis seen after bacterial infection of mouse monocyte-macrophage cell lines, the commitment of human intestinal epithelial cell lines to undergo apoptosis is delayed for at least 6 h after bacterial infection, requires bacterial entry and replication, and the ensuing phenotypic expression of apoptosis is delayed for 12-18 h after bacterial entry. TNF-alpha and nitric oxide, which are produced as components of the intestinal epithelial cell proinflammatory program in the early period after bacterial invasion, play an important role in the later induction and regulation of the epithelial cell apoptotic program. Apoptosis in response to bacterial infection may function to delete infected and damaged epithelial cells and restore epithelial cell growth regulation and epithelial integrity that are altered during the course of enteric infection. The delay in onset of epithelial cell apoptosis after bacterial infection may be important both to the host and the invading pathogen since it provides sufficient time for epithelial cells to generate signals important for the activation of mucosal inflammation and concurrently allows invading bacteria time to adapt to the intracellular environment before invading deeper mucosal layers.

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.

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.

Molecular diagnosis of gastrointestinal infections associated with HIV infection

Developments in medical microbiology in the past 20 years have had a profound impact on our understanding of infectious diseases and have led the way in the development of new diagnostic techniques. Molecular diagnostic techniques are generally more sensitive, specific, and rapid than conventional methods by which infectious agents are detected. For many of the opportunistic infectious agents of the gastrointestinal tract found in HIV-infected individuals, the application of molecular diagnostic techniques to the clinical laboratory is in its infancy. In this article, methods by which these techniques can be evaluated are demonstrated, and the current status and potential future application of these techniques for each gastrointestinal opportunistic pathogen are described.

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.

Gastrointestinal pathology in HIV-infected patients

Specific pathologic processes, particularly oral, esophageal, and intestinal infections, are common in the alimentary tract of AIDS patients. Many of these diseases are adequately assessed only by biopsy with histologic examination. Most are rare or unreported in immunocompetent hosts and are easily missed by those not familiar with them. This article describes the gross or endoscopic and histologic appearances and the diagnostic criteria for enteric pathologic processes seen in HIV-infected individuals.

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.

Guidelines for the initial biopsy diagnosis of suspected chronic idiopathic inflammatory bowel disease. The British Society of Gastroenterology Initiative

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Vaginal and rectal infection of cats with feline immunodeficiency virus

The objective of this study was to examine the potential of vaginal and rectal mucosal routes for feline immunodeficiency virus (FIV) uptake and infection, as a model of mucosal HIV infection, and to determine the fate of virus at these mucosal sites following transmission of infection. SPF cats were exposed to FIV isolates (PET, GL-8, T637), administered as either cell-associated or cell-free inocula, via the rectum or vagina. Establishment of infection was confirmed by isolation of infectious FIV from peripheral blood mononuclear cells (PBMC), and by presence of FIV proviral DNA in PBMC using a nested polymerase chain reaction. Fate of virus in tissue taken at necropsy from cats infected for 6-48 weeks was assessed by localizing FIV core and envelope proteins, p24 and gp41, using a biotin-streptavidin linked immunoperoxidase (IP) technique. Cells susceptible to infection were identified by an in situ hybridization technique for FIV viral DNA and RNA. Cell-free, as well as cell-associated, virus was infectious across intact vaginal and rectal mucosal surfaces. Transmission was most successful using cell-associated inocula, and via the rectal route. Cells infected with FIV were detected by IP staining in the colon of 6/9 rectally challenged cats and 1/5 vaginally challenged cats. Virus was predominantly localized within the epithelium at the base of the colonic crypts associated with lymphoid aggregates (follicle associated epithelium; FAE), and within the lymphoid follicle itself. Occasional infected cells were also noted within the lamina propria. The distribution of FIV DNA positive cells in the colon was similar to that for FIV antigen whilst FIV RNA positive cells were found more extensively, including within the lamina propria and lymphoid follicle. FIV infected cells were not detected within the vagina, or colonic and ileac lymph nodes. Similar patterns of infected cells were seen in all of the positive cats, indicating that colonic tissues remain persistently actively infected with FIV. We conclude that the FIV/cat model of rectal and vaginal mucosal infection should prove useful for characterizing the mechanism by which HIV infects mucosal surfaces and as a challenge system for the design of vaccines effective at preventing HIV infection via rectal and vaginal routes.

Isolation of human immunodeficiency virus type 1 (HIV-1) RNA from feces by a simple method and difference between HIV-1 subpopulations in feces and serum

A simple method for the isolation and subsequent detection of human immunodeficiency virus type 1 (HIV-1) RNA from feces is described. Viral RNA was isolated by the method developed by Boom et al. (R. Boom, C.J.A. Sol, M.M.M. Salimans, C.L. Jansen, P.M.E. Wertheim-van Dillen, and J. van der Noordaa, J. Clin. Microbiol. 28:495-503, 1990), which was adapted for feces. HIV-1 RNA was detected by reverse transcription (RT) followed by a nested PCR encompassing the V3 region. Reconstruction experiments revealed that the efficiencies of the extraction technique and the subsequent RT-PCR were not considerably affected by the varied composition of feces. The method was applied on fecal specimens from 18 HIV-1-infected individuals, among which were samples that had been stored for 9 years. It appeared that HIV-1 RNA was detectable in the feces of 12 persons (67%). Viral RNA was present in the feces of persons who fulfilled the criteria for CDC class II and CDC class III HIV infection as well as in patients who were diagnosed with AIDS (CDC class IV). Direct sequencing of amplimers obtained from paired fecal and serum specimens showed that differences in sequence heterogeneity existed. In one patient a remarkable difference in the HIV-1 sequences between isolates from feces and serum was observed. In conclusion, HIV-1 RNA is frequently present in the feces of HIV-1-infected individuals, and in some cases the HIV-1 subpopulation in feces differs from the HIV-1 subpopulation in serum.

Inefficacy of intestinal secretory immune response to Cryptosporidium in acquired immunodeficiency syndrome

BACKGROUND/AIMS

An alteration of the secretory immune response has been forwarded to explain frequent and chronic mucosal infections in patients with acquired immunodeficiency syndrome (AIDS). The aim of this study was to explore the intestinal immunoglobulin (Ig) secretions in patients with AIDS and their relationships to cryptosporidiosis.

METHODS

Patients with AIDS and enteric cryptosporidiosis (n = 12), other enteric infections (n = 10), and no identifiable enteric pathogen (n = 10) and human immunodeficiency virus-seronegative controls (n = 18) were studied. The number of intestinal IgA and IgM plasma cells of the duodenal lamina propria mucosa and total and anti-Cryptosporidium IgA, IgM, and IgG were measured in serum and feces.

RESULTS

Although not significantly increased, the number of IgA and IgM plasma cells was greater in patients with AIDS (n = 20) than in controls (n = 5). In feces, total IgA outputs and specific anti-Cryptosporidium IgA levels were significantly higher in patients with AIDS and cryptosporidiosis than in the two other groups of patients with AIDS (P < 0.05 and P < 0.01, respectively) and controls (P < 0.001 and P < 0.01, respectively). Total fecal IgM output and specific anti-Cryptosporidium IgM coproantibodies were increased only in the Cryptosporidium-infected patients relative to the controls (P < 0.05).

CONCLUSIONS

Despite the development of pathogen-specific mucosal antibody responses, patients with AIDS and cryptosporidiosis fail to clear the parasite.

Etiology and management of toxic megacolon in patients with human immunodeficiency virus infection

We report six cases of toxic megacolon in patients with human immunodeficiency virus (HIV). One case, at an early stage of HIV infection, mimicked a severe attack of Crohn's disease, with a negative search for infectious agents. Subtotal colectomy was successfully performed with an uneventful postoperative course. The five other cases concerned patients with acquired immunodeficiency syndrome at a late stage of immunodeficiency. They were related to Clostridium difficile or cytomegalovirus (CMV) intestinal infection in two and three patients, respectively. One case of CMV colitis presented macroscopically and histologically as pseudomembranous colitis. Emergency subtotal colectomy, performed in the first four patients with acquired immunodeficiency syndrome was followed by a fatal postoperative outcome. The last patient treated conservatively by colonoscopic decompression, in association with anti-CMV therapy, had a favorable short-term outcome. From the experience of our series and data from the literature, we discuss the best diagnostic and therapeutic approach to toxic megacolon in patients with HIV.

Abnormalities in subset distribution, activation, and differentiation of T cells isolated from large intestine biopsies in HIV infection. The Berlin Diarrhoea/Wasting Syndrome Study Group

Intestinal T cells have a unique state of activation and differentiation which might specifically affect or be affected by HIV infection. Lymphocyte subsets in the peripheral blood are well characterized, but our knowledge about intestinal lymphocytes in HIV infection is incomplete. We therefore analysed lymphocytes isolated from large intestine biopsies of AIDS patients and controls by three-colour cytofluorometry. In the large intestine of HIV-infected patients CD4 T cells were reduced and CD8 T cells were increased compared with controls. Most of the CD8 T cells in the colorectal mucosa of AIDS patients were of the cytotoxic phenotype. Activated and resting CD4 T cells were similarly reduced, the expression of CD25 and HLA-DR of CD8 T cells was unaltered and increased, respectively. In intestinal CD4 T cells the expression of CD29 was decreased, but the expression of CD45RO and HML-1 was normal. CD8 T cells had a decreased expression of all these differentiation markers. Our findings demonstrate substantial alterations in subset distribution, activation, and differentiation of large intestine T cells, which may contribute to the secondary infections and malignancies commonly observed in the gut of AIDS patients.

Detection and localization of HIV RNA and TNF mRNA in rectal biopsies from patients with AIDS

The objective of this study was to compare the localization of cells containing human immunodeficiency virus (HIV) RNA and tumor necrosis factor (TNF)-alpha mRNA in rectal mucosa by RNA in-situ hybridization in a retrospective analysis of archived rectal biopsy specimens. RNA in-situ hybridization studies were performed in 27 HIV-seropositive individuals and seven controls, using antisense and sense 35S-labeled riboprobes. The detection and localization of positive cells were compared. HIV was RNA detected in 44% of biopsies, while TNF-alpha mRNA detected in 22%. TNF mRNA was found in biopsies from patients with and without opportunistic infections. All cells expressing TNF-alpha mRNA and most of the cells expressing HIV RNA were found in close proximity to the epithelial surface. The content of an HIV-associated protein, p24, in mucosal homogenates, determined by a quantitative ELISA technique was significantly higher in the subgroup of patients with positive in situ hybridization studies for TNF-alpha mRNA than in the subgroup with negative studies. The colocalization of TNF-alpha mRNA and HIV RNA immediately beneath the epithelium suggests a specific relationship between them, as well as a possible relationship to a luminal factor.

Intestinal mucosal inflammation associated with human immunodeficiency virus infection

The role of the human immunodeficiency virus type-1 (HIV) in producing intestinal disease was studied prospectively in 74 HIV-infected individuals with (43) or without (31) the acquired immunodeficiency syndrome (AIDS). Thirty-one subjects had enteric infections; all but one had AIDS. Alteration in bowel habits was the most common symptom and occurred independently of enteric infections. Abnormal histopathology was present in 69% of cases, and the finding was associated with altered bowel habits. An HIV-associated protein, p24, was detected in 71% of biopsies by ELISA assay. Tissue p24 contents varied with disease stage and were highest in HIV-infected individuals without AIDS (Walter Reed classes 3 and 4). Tissue p24 detection was associated with both altered bowel habits and histologic mucosal abnormalities. Tissue contents of the cytokines, tumor necrosis factor-alpha and interleukin-1 beta, were higher in HIV-infected individuals than in controls and their elevations were independent of enteric infection. We conclude that HIV reactivation in the intestinal mucosa may be associated with an inflammatory bowel syndrome in the absence of other enteric pathogens.