Michael A. Poles

Primary HIV-1 Infection Is Associated with Preferential Depletion of CD4+ T Lymphocytes from Effector Sites in the Gastrointestinal Tract

Given its population of CCR5-expressing, immunologically activated CD4+ T cells, the gastrointestinal (GI) mucosa is uniquely susceptible to human immunodeficiency virus (HIV)-1 infection. We undertook this study to assess whether a preferential depletion of mucosal CD4+ T cells would be observed in HIV-1–infected subjects during the primary infection period, to examine the anatomic subcompartment from which these cells are depleted, and to examine whether suppressive highly active antiretroviral therapy could result in complete immune reconstitution in the mucosal compartment. Our results demonstrate that a significant and preferential depletion of mucosal CD4+ T cells compared with peripheral blood CD4+ T cells is seen during primary HIV-1 infection. CD4+ T cell loss predominated in the effector subcompartment of the GI mucosa, in distinction to the inductive compartment, where HIV-1 RNA was present. Cross-sectional analysis of a cohort of primary HIV-1 infection subjects showed that although chronic suppression of HIV-1 permits near-complete immune recovery of the peripheral blood CD4+ T cell population, a significantly greater CD4+ T cell loss remains in the GI mucosa, despite up to 5 yr of fully suppressive therapy. Given the importance of the mucosal compartment in HIV-1 pathogenesis, further study to elucidate the significance of the changes observed here is critical.

Recognition of bacterial glycosphingolipids by natural killer T cells

Natural killer T (NKT) cells constitute a highly conserved T lymphocyte subpopulation that has the potential to regulate many types of immune responses through the rapid secretion of cytokines. NKT cells recognize glycolipids presented by CD1d, a class I-like antigen-presenting molecule. They have an invariant T-cell antigen receptor (TCR) α-chain, but whether this invariant TCR recognizes microbial antigens is still controversial. Here we show that most mouse and human NKT cells recognize glycosphingolipids from Sphingomonas, Gram-negative bacteria that do not contain lipopolysaccharide. NKT cells are activated in vivo after exposure to these bacterial antigens or bacteria, and mice that lack NKT cells have a marked defect in the clearance of Sphingomonas from the liver. These data suggest that NKT cells are T lymphocytes that provide an innate-type immune response to certain microorganisms through recognition by their antigen receptor, and that they might be useful in providing protection from bacteria that cannot be detected by pattern recognition receptors such as Toll-like receptor 4.

Lack of Mucosal Immune Reconstitution during Prolonged Treatment of Acute and Early HIV-1 Infection

Background During acute and early HIV-1 infection (AEI), up to 60% of CD4+ T cells in the lamina propria of the lower gastrointestinal (GI) tract are lost as early as 2–4 wk after infection. Reconstitution in the peripheral blood during therapy with highly active antiretroviral therapy (HAART) is well established. However, the extent of immune reconstitution in the GI tract is unknown. Methods and Findings Fifty-four AEI patients and 18 uninfected control participants underwent colonic biopsy. Forty of the 54 AEI patients were followed after initiation of antiretroviral therapy (18 were studied longitudinally with sequential biopsies over a 3-y period after beginning HAART, and 22 were studied cross sectionally after 1–7 y of uninterrupted therapy). Lymphocyte subsets, markers of immune activation and memory in the peripheral blood and GI tract were determined by flow cytometry and immunohistochemistry. In situ hybridization was performed in order to identify persistent HIV-1 RNA expression. Of the patients studied, 70% maintained, on average, a 50%–60% depletion of lamina propria lymphocytes despite 1–7 y of HAART. Lymphocytes expressing CCR5 and both CCR5 and CXCR4 were persistently and preferentially depleted. Levels of immune activation in the memory cell population, CD45RO+ HLA-DR+, returned to levels seen in the uninfected control participants in the peripheral blood, but were elevated in the GI tract of patients with persistent CD4+ T cell depletion despite therapy. Rare HIV-1 RNA–expressing cells were detected by in situ hybridization. Conclusions Apparently suppressive treatment with HAART during acute and early infection does not lead to complete immune reconstitution in the GI mucosa in the majority of patients studied, despite immune reconstitution in the peripheral blood. Though the mechanism remains obscure, the data suggest that there is either viral or immune-mediated accelerated T cell destruction or, possibly, alterations in T cell homing to the GI tract. Although clinically silent over the short term, the long-term consequences of the persistence of this lesion may emerge as the HIV-1–infected population survives longer owing to the benefits of HAART.

Mechanisms of Gastrointestinal CD4+ T-Cell Depletion during Acute and Early Human Immunodeficiency Virus Type 1 Infection

ABSTRACT During acute and early human immunodeficiency virus type 1 (HIV-1) infection (AEI) more than 50% of CD4+ T cells are preferentially depleted from the gastrointestinal (GI) lamina propria. To better understand the underlying mechanisms, we studied virological and immunological events within the peripheral blood (PB) and GI tract during AEI. A total of 32 AEI subjects and 18 uninfected controls underwent colonic biopsy. HIV-1 viral DNA and RNA levels were quantified in CD4+ T cells derived from the GI tract and PB by using real-time PCR. The phenotype of infected cells was characterized by using combinations of immunohistochemistry and in situ hybridization. Markers of immunological memory, activation, and proliferation were examined by flow cytometry and immunohistochemistry, and the host-derived cytotoxic cellular response was examined by using immunohistochemistry. GI CD4+ T cells harbored, on average, 13-fold higher HIV-1 viral DNA levels and 10-fold higher HIV-1 RNA levels than PB CD4+ T cells during AEI. HIV-1 RNA was detected in both “activated” and“ nonactivated” mucosal CD4+ T cells. A significantly higher number of activated and proliferating T cells were detected in the GI tract compared to the PB, and a robust cytotoxic response (HIV-1 specificity not determined) was detected in the GI tract as early as 18 days postinfection. Mucosal CD4+ T-cell depletion is multifactorial. Direct viral infection likely accounts for the earliest loss of CD4+ T cells. Subsequently, ongoing infection of susceptible CD4+ T cells, along with activation-induced cellular death and host cytotoxic cellular response, are responsible for the persistence of the lesion.

Diversity of 16S rRNA Genes within Individual Prokaryotic Genomes

ABSTRACT Analysis of intragenomic variation of 16S rRNA genes is a unique approach to examining the concept of ribosomal constraints on rRNA genes; the degree of variation is an important parameter to consider for estimation of the diversity of a complex microbiome in the recently initiated Human Microbiome Project (http://nihroadmap.nih.gov/hmp ). The current GenBank database has a collection of 883 prokaryotic genomes representing 568 unique species, of which 425 species contained 2 to 15 copies of 16S rRNA genes per genome (2.22 ± 0.81). Sequence diversity among the 16S rRNA genes in a genome was found in 235 species (from 0.06% to 20.38%; 0.55% ± 1.46%). Compared with the 16S rRNA-based threshold for operational definition of species (1 to 1.3% diversity), the diversity was borderline (between 1% and 1.3%) in 10 species and >1.3% in 14 species. The diversified 16S rRNA genes in Haloarcula marismortui (diversity, 5.63%) and Thermoanaerobacter tengcongensis (6.70%) were highly conserved at the 2° structure level, while the diversified gene in B. afzelii (20.38%) appears to be a pseudogene. The diversified genes in the remaining 21 species were also conserved, except for a truncated 16S rRNA gene in “Candidatus Protochlamydia amoebophila.” Thus, this survey of intragenomic diversity of 16S rRNA genes provides strong evidence supporting the theory of ribosomal constraint. Taxonomic classification using the 16S rRNA-based operational threshold could misclassify a number of species into more than one species, leading to an overestimation of the diversity of a complex microbiome. This phenomenon is especially seen in 7 bacterial species associated with the human microbiome or diseases.

Infection with multidrug resistant, dual-tropic HIV-1 and rapid progression to AIDS: a case report

BACKGROUNDnRapid progression to AIDS after acute HIV-1 infection, though uncommon, has been noted, as has the transmission of multidrug resistant viruses. Here, we describe a patient in whom these two factors arose concomitantly and assess the effects.nnnMETHODSnWe did a case study of a patient with HIV-1 seroconversion. We genotyped the virus and host genetic markers by PCR and nucleotide sequencing. To ascertain the drug susceptibility of our patients HIV-1 we did phenotypic studies with the PhenoSense assay. We assessed viral coreceptor use via syncytium formation in vitro and with a modified PhenoSense assay.nnnFINDINGSnOur patient seems to have been recently infected by a viral variant of HIV-1 resistant to multiple classes of antiretroviral drugs. Furthermore, his virus population is dual tropic for cells that express CCR5 or CXCR4 coreceptor. The infection has resulted in progression to symptomatic AIDS in 4-20 months.nnnINTERPRETATIONnThe intersection of multidrug resistance and rapid development of AIDS in this patient is of concern, especially in view of his case history, which includes high-risk sexual contacts and use of metamfetamine. The public health ramifications of such a case are great.

Absence of HIV-1 Evolution in the Gut-Associated Lymphoid Tissue from Patients on Combination Antiviral Therapy Initiated during Primary Infection

Mucosal mononuclear (MMC) CCR5+CD4+ T cells of the gastrointestinal (GI) tract are selectively infected and depleted during acute HIV-1 infection. Despite early initiation of combination antiretroviral therapy (cART), gut-associated lymphoid tissue (GALT) CD4+ T cell depletion and activation persist in the majority of HIV-1 positive individuals studied. This may result from ongoing HIV-1 replication and T-cell activation despite effective cART. We hypothesized that ongoing viral replication in the GI tract during cART would result in measurable viral evolution, with divergent populations emerging over time. Subjects treated during early HIV-1 infection underwent phlebotomy and flexible sigmoidoscopy with biopsies prior to and 15–24 months post initiation of cART. At the 2nd biopsy, three GALT phenotypes were noted, characterized by high, intermediate and low levels of immune activation. A representative case from each phenotype was analyzed. Each subject had plasma HIV-1 RNA levels <50 copies/ml at 2nd GI biopsy and CD4+ T cell reconstitution in the peripheral blood. Single genome amplification of full-length HIV-1 envelope was performed for each subject pre- and post-initiation of cART in GALT and PBMC. A total of 280 confirmed single genome sequences (SGS) were analyzed for experimental cases. For each subject, maximum likelihood phylogenetic trees derived from molecular sequence data showed no evidence of evolved forms in the GALT over the study period. During treatment, HIV-1 envelope diversity in GALT-derived SGS did not increase and post-treatment GALT-derived SGS showed no substantial genetic divergence from pre-treatment sequences within transmitted groups. Similar results were obtained from PBMC-derived SGS. Our results reveal that initiation of cART during acute/early HIV-1 infection can result in the interruption of measurable viral evolution in the GALT, suggesting the absence of de-novo rounds of HIV-1 replication in this compartment during suppressive cART.

IL-22-producing CD4+ cells are depleted in actively inflamed colitis tissue.

T helper type (Th17) cytokines such as interleukin (IL)-17A and IL-22 are important in maintaining mucosal barrier function and may be important in the pathogenesis of inflammatory bowel diseases (IBDs). Here, we analyzed cells from the colon of IBD patients and show that Crohn’s disease (CD) patients had significantly elevated numbers of IL-17+, CD4+ cells compared with healthy controls and ulcerative colitis (UC) patients, but these numbers did not vary based on the inflammatory status of the mucosa. By contrast, UC patients had significantly reduced numbers of IL-22+ cells in actively inflamed tissues compared with both normal tissue and healthy controls. There was a selective increase in mono-IL-17-producing cells from the mucosa of UC patients with active inflammation together with increased expression of transforming growth factor (TGF)-β and c-Maf. Increasing concentrations of TGF-β in lamina propria mononuclear cell cultures significantly depleted Th22 cells, whereas anti-TGF-β antibodies increased IL-22 production. When mucosal microbiota was examined, depletion of Th22 cells in actively inflamed tissue was associated with reduced populations of Clostridiales and increased populations of Proteobacteria. These results suggest that increased TGF-β during active inflammation in UC may lead to the loss of Th22 cells in the human intestinal mucosa.

Colorectal Cancer Screening in HIV-Infected Patients 50 Years of Age and Older: Missed Opportunities for Prevention

OBJECTIVES:Although human immunodeficiency virus (HIV)-infected patients are now living longer, there are no published data on colorectal cancer (CRC) screening in this population. We hypothesized that HIV-infected patients were less likely to be screened for CRC compared to patients without HIV.METHODS:Consecutive HIV-infected patients ≥50 yr old seen in our outpatient clinic from 1/1/01 to 6/30/02 were identified. For each HIV-infected patient, we selected one age- and gender-matched control subject without HIV infection who was seen during the same time period. The electronic medical records were reviewed to determine the proportion of patients that had a fecal occult blood test (FOBT), flexible sigmoidoscopy, air-contrast barium enema (ACBE), or colonoscopy.RESULTS:During the 18-month study period, 538 HIV-infected outpatients were seen and 302 (56.1%) were ≥50 yr old. Despite significantly more visits with their primary care provider, HIV-infected patients were less likely to have ever had at least one CRC screening test (55.6% vs 77.8%, p < 0.001). The proportion of HIV-infected patients who ever had a FOBT (43.0% vs 66.6%, p < 0.001), flexible sigmoidoscopy (5.3% vs 17.5%, p < 0.001), ACBE (2.6% vs 7.9%, P = 0.004), or colonoscopy (17.2% vs 27.5%, P = 0.002) was significantly lower than in control subjects. In addition, HIV-infected patients were significantly less likely to be up-to-date with at least one CRC screening test according to current guidelines (49.3% vs 65.6%, p < 0.001).CONCLUSIONS:A substantial number of HIV-infected patients are ≥50 yr of age and CRC screening is underutilized in this population. Public health strategies to improve CRC screening in HIV-infected patients are needed.

Preferential HIV Infection of CCR6+ Th17 Cells Is Associated with Higher Levels of Virus Receptor Expression and Lack of CCR5 Ligands

ABSTRACT Th17 cells are enriched in the gut mucosa and play a critical role in maintenance of the mucosal barrier and host defense against extracellular bacteria and fungal infections. During chronic human immunodeficiency virus (HIV) infection, Th17 cells were more depleted compared to Th1 cells, even when the patients had low or undetectable viremia. To investigate the differential effects of HIV infection on Th17 and Th1 cells, a culture system was used in which CCR6+ CD4+ T cells were sorted from healthy human peripheral blood and activated in the presence of interleukin 1β (IL-1β) and IL-23 to drive expansion of Th17 cells while maintaining Th1 cells. HIV infection of these cultures had minimal effects on Th1 cells but caused depletion of Th17 cells. Th17 loss correlated with greater levels of virus-infected cells and cell death. In identifying cellular factors contributing to higher susceptibility of Th17 cells to HIV, we compared Th17-enriched CCR6+ and Th17-depleted CCR6− CD4 T cell cultures and noted that Th17-enriched CCR6+ cells expressed higher levels of α4β7 and bound HIV envelope in an α4β7-dependent manner. The cells also had greater expression of CD4 and CXCR4, but not CCR5, than CCR6− cells. Moreover, unlike Th1 cells, Th17 cells produced little CCR5 ligand, and transfection with one of the CCR5 ligands, MIP-1β (CCL4), increased their resistance against HIV. These results indicate that features unique to Th17 cells, including higher expression of HIV receptors and lack of autocrine CCR5 ligands, are associated with enhanced permissiveness of these cells to HIV.