Epithelial uptake and transport of cell-free human immunodeficiency virus type 1 and gp120-coated microparticles

Polysaccharide Submicrocarrier for Improved Pulmonary Delivery of Poorly Soluble Anti-infective Ciprofloxacin: Preparation, Characterization, and Influence of Size on Cellular Uptake

The majority of the currently used and developed anti-infectives are poorly water-soluble molecules. The poor solubility might lead to limited bioavailability and pharmacological action of the drug. Novel pharmaceutical materials have thus been designed to solve those problems and improve drug delivery. In this study, we propose a facile method to produce submicrocarriers (sMCs) by electrostatic gelation of anionic ß-cyclodextrin (aß-CD) and chitosan. The average hydrodynamic size ranged from 400 to 900 nm by carefully adjusting polymer concentrations and N/C ratio. The distinct host-guest reaction of cyclodextrin derivative is considered as a good approach to enhance solubility, and prevent drug recrystallization, and thus was used to develop sMC to improve the controlled release profile of a poorly soluble and clinically relevant anti-infective ciprofloxacin. The optimal molar ratio of ciprofloxacin to aß-CD was found to be 1:1, which helped maximize encapsulation efficiency (∼90%) and loading capacity (∼9%) of ciprofloxacin loaded sMCs. Furthermore, to recommend the future application of the developed sMCs, the dependence of cell uptake on sMCs size (500, 700, and 900 nm) was investigated in vitro on dTHP-1 by both flow cytometry and confocal microscopy. The results demonstrate that, regardless of their size, an only comparatively small fraction of the sMCs were taken up by the macrophage-like cells, while most of the carriers were merely adsorbed to the cell surface after 2 h incubation. After continuing the incubation to reach 24 h, the majority of the sMCs were found intracellularly. However, the sMCs had been designed to release sufficient amount of drug within 24 h, and the subsequent phagocytosis of the carrier may be considered as an efficient pathway for its safe degradation and elimination. In summary, the developed sMC is a suitable system with promising perspectives recommended for pulmonary extracellular infection therapeutics.

(C3) The Oral Epithelial Cell and First Encounters with HIV-1

The oral epithelium is the site of first exposure of HIV-1 to host tissues during oral sex with an infected partner or through breast-feeding by an infected mother. Although the oral epithelium is distinguishable by its apparent resistance, the mucosal surfaces represent a primary target of HIV-1. After oral exposure and swallowing, infection is detected prominently in the gastrointestinal tract, which becomes depleted of CD4+ T-cells. The oral cavity and palatine tonsils appear to resist infection and transfer to susceptible lymphoid cells in the lamina propria by local anti-HIV-1 mechanisms. In some cases, expression of these antiviral mechanisms increases after exposure to HIV-1. During primary exposure and before seroconversion, based on limited in vitro and primate data, a window of opportunity for capture of HIV-1 by the oral epithelium may exist. After seroconversion, the risk of infectious HIV-1 appearing in saliva is negligible. This report considers evidence that oral epithelium has the potential both to enable and to resist infection by HIV-1.

Oral and vaginal epithelial cell lines bind and transfer cell-free infectious HIV-1 to permissive cells but are not productively infected

The majority of HIV-1 infections worldwide are acquired via mucosal surfaces. However, unlike the vaginal mucosa, the issue of whether the oral mucosa can act as a portal of entry for HIV-1 infection remains controversial. To address potential differences with regard to the fate of HIV-1 after exposure to oral and vaginal epithelium, we utilized two epithelial cell lines representative of buccal (TR146) and pharyngeal (FaDu) sites of the oral cavity and compared them with a cell line derived from vaginal epithelium (A431) in order to determine (i) HIV-1 receptor gene and protein expression, (ii) whether HIV-1 genome integration into epithelial cells occurs, (iii) whether productive viral infection ensues, and (iv) whether infectious virus can be transferred to permissive cells. Using flow cytometry to measure captured virus by HIV-1 gp120 protein detection and western blot to detect HIV-1 p24 gag protein, we demonstrate that buccal, pharyngeal and vaginal epithelial cells capture CXCR4- and CCR5-utilising virus, probably via non-canonical receptors. Both oral and vaginal epithelial cells are able to transfer infectious virus to permissive cells either directly through cell-cell attachment or via transcytosis of HIV-1 across epithelial cells. However, HIV-1 integration, as measured by real-time PCR and presence of early gene mRNA transcripts and de novo protein production were not detected in either epithelial cell type. Importantly, both oral and vaginal epithelial cells were able to support integration and productive infection if HIV-1 entered via the endocytic pathway driven by VSV-G. Our data demonstrate that under normal conditions productive HIV-1 infection of epithelial cells leading to progeny virion production is unlikely, but that epithelial cells can act as mediators of systemic viral dissemination through attachment and transfer of HIV-1 to permissive cells.

The oral mucosa immune environment and oral transmission of HIV/SIV

The global spread of human immunodeficiency virus (HIV) is dependent on the ability of this virus to efficiently cross from one host to the next by traversing a mucosal membrane. Unraveling how mucosal exposure of HIV results in systemic infection is critical for the development of effective therapeutic strategies. This review focuses on understanding the immune events associated with the oral route of transmission (via breastfeeding or sexual oral intercourse), which occurs across the oral and/or gastrointestinal mucosa. Studies in both humans and simian immunodeficiency virus (SIV) monkey models have identified viral changes and immune events associated with oral HIV/SIV exposure. This review covers our current knowledge of HIV oral transmission in both infants and adults, the use of SIV models in understanding early immune events, oral immune factors that modulate HIV/SIV susceptibility (including mucosal inflammation), and interventions that may impact oral HIV transmission rates. Understanding the factors that influence oral HIV transmission will provide the foundation for developing immune therapeutic and vaccine strategies that can protect both infants and adults from oral HIV transmission.

The Neonatal Fc receptor (FcRn) enhances human immunodeficiency virus type 1 (HIV-1) transcytosis across epithelial cells

The mechanisms by which human immunodeficiency virus type 1 (HIV-1) crosses mucosal surfaces to establish infection are unknown. Acidic genital secretions of HIV-1-infected women contain HIV-1 likely coated by antibody. We found that the combination of acidic pH and Env-specific IgG, including that from cervicovaginal and seminal fluids of HIV-1-infected individuals, augmented transcytosis across epithelial cells as much as 20-fold compared with Env-specific IgG at neutral pH or non-specific IgG at either pH. Enhanced transcytosis was observed with clinical HIV-1 isolates, including transmitted/founder strains, and was eliminated in Fc neonatal receptor (FcRn)-knockdown epithelial cells. Non-neutralizing antibodies allowed similar or less transcytosis than neutralizing antibodies. However, the ratio of total:infectious virus was higher for neutralizing antibodies, indicating that they allowed transcytosis while blocking infectivity of transcytosed virus. Immunocytochemistry revealed abundant FcRn expression in columnar epithelia lining the human endocervix and penile urethra. Acidity and Env-specific IgG enhance transcytosis of virus across epithelial cells via FcRn and could facilitate translocation of virus to susceptible target cells following sexual exposure.

HIV-1 causes a sexually transmitted disease. However, the mechanisms employed by the virus to cross genital tract tissue and establish infection are uncertain. Since cervicovaginal fluid is acidic and HIV-1 in cervicovaginal fluid is likely coated with antibodies, we explored the effect of low pH and HIV-1-specific antibodies on transcytosis, the movement of HIV-1 across tight-junctioned epithelial cells. We found that the combination of HIV-1-specific antibodies and low pH enhanced transcytosis as much as 20-fold. Virus that underwent transcytosis under these conditions was infectious, and infectivity was highly influenced by whether or not the antibody neutralized the virus. We observed enhanced transcytosis using antibody from cervicovaginal and seminal fluids and using transmitted/founder strains of HIV-1. We also found that the enhanced transcytosis was due to the Fc neonatal receptor (FcRn), which binds immune complexes at acidic pH and releases them at neutral pH. Finally, staining of human tissue revealed abundant FcRn expression on columnar epithelial cells of penile urethra and endocervix. Our findings reveal a novel mechanism wherein HIV-1 may facilitate its own transmission by usurping the antibody response directed against itself. These results have important implications for HIV vaccine development and for understanding the earliest events in HIV transmission.

N-linked glycosylation facilitates sialic acid-independent attachment and entry of influenza A viruses into cells expressing DC-SIGN or L-SIGN

It is widely recognized that sialic acid (SA) can mediate attachment of influenza virus to the cell surface, and yet the specific receptors that mediate virus entry are not known. For many viruses, a definitive demonstration of receptor function has been achieved when nonpermissive cells are rendered susceptible to infection following transfection of the gene encoding a putative receptor. For influenza virus, such approaches have been confounded by the abundance of SA on mammalian cells so that it has been difficult to identify cell lines that are not susceptible to infection. We examined influenza virus infection of Lec2 Chinese hamster ovary (CHO) cells, a mutant cell line deficient in SA. Lec2 CHO cells were resistant to influenza virus infection, and stable cell lines expressing either DC-SIGN or L-SIGN were generated to assess the potential of each molecule to function as SA-independent receptors for influenza A viruses. Virus strain BJx109 (H3N2) bound to Lec2 CHO cells expressing DC-SIGN or L-SIGN in a Ca(2+)-dependent manner, and transfected cells were susceptible to virus infection. Treatment of Lec2-DC-SIGN and Lec2-L-SIGN cells with mannan, but not bacterial neuraminidase, blocked infection, a finding consistent with SA-independent virus attachment and entry. Moreover, virus strain PR8 (H1N1) bears low levels of mannose-rich glycans and was inefficient at infecting Lec2 CHO cells expressing either DC-SIGN or L-SIGN, whereas other glycosylated H1N1 subtype viruses could infect cells efficiently. Together, these data indicate that human C-type lectins (DC-SIGN and L-SIGN) can mediate attachment and entry of influenza viruses independently of cell surface SA.

Oral keratinocytes support non-replicative infection and transfer of harbored HIV-1 to permissive cells

Background

Oral keratinocytes on the mucosal surface are frequently exposed to HIV-1 through contact with infected sexual partners or nursing mothers. To determine the plausibility that oral keratinocytes are primary targets of HIV-1, we tested the hypothesis that HIV-1 infects oral keratinocytes in a restricted manner.

Results

To study the fate of HIV-1, immortalized oral keratinocytes (OKF6/TERT-2; TERT-2 cells) were characterized for the fate of HIV-specific RNA and DNA. At 6 h post inoculation with X4 or R5-tropic HIV-1, HIV-1gag RNA was detected maximally within TERT-2 cells. Reverse transcriptase activity in TERT-2 cells was confirmed by VSV-G-mediated infection with HIV-NL4-3Δenv-EGFP. AZT inhibited EGFP expression in a dose-dependent manner, suggesting that viral replication can be supported if receptors are bypassed. Within 3 h post inoculation, integrated HIV-1 DNA was detected in TERT-2 cell nuclei and persisted after subculture. Multiply spliced and unspliced HIV-1 mRNAs were not detectable up to 72 h post inoculation, suggesting that HIV replication may abort and that infection is non-productive. Within 48 h post inoculation, however, virus harbored by CD4 negative TERT-2 cells trans infected co-cultured peripheral blood mononuclear cells (PBMCs) or MOLT4 cells (CD4+ CCR5+) by direct cell-to-cell transfer or by releasing low levels of infectious virions. Primary tonsil epithelial cells also trans infected HIV-1 to permissive cells in a donor-specific manner.

Conclusion

Oral keratinocytes appear, therefore, to support stable non-replicative integration, while harboring and transmitting infectious X4- or R5-tropic HIV-1 to permissive cells for up to 48 h.

Porphyromonas gingivalis induces CCR5-dependent transfer of infectious HIV-1 from oral keratinocytes to permissive cells

Background

Systemic infection with HIV occurs infrequently through the oral route. The frequency of occurrence may be increased by concomitant bacterial infection of the oral tissues, since co-infection and inflammation of some cell types increases HIV-1 replication. A putative periodontal pathogen, Porphyromonas gingivalis selectively up-regulates expression of the HIV-1 coreceptor CCR5 on oral keratinocytes. We, therefore, hypothesized that P. gingivalis modulates the outcome of HIV infection in oral epithelial cells.

Results

Oral and tonsil epithelial cells were pre-incubated with P. gingivalis, and inoculated with either an X4- or R5-type HIV-1. Between 6 and 48 hours post-inoculation, P. gingivalis selectively increased the infectivity of R5-tropic HIV-1 from oral and tonsil keratinocytes; infectivity of X4-tropic HIV-1 remained unchanged. Oral keratinocytes appeared to harbor infectious HIV-1, with no evidence of productive infection. HIV-1 was harbored at highest levels during the first 6 hours after HIV exposure and decreased to barely detectable levels at 48 hours. HIV did not appear to co-localize with P. gingivalis, which increased selective R5-tropic HIV-1 trans infection from keratinocytes to permissive cells. When CCR5 was selectively blocked, HIV-1 trans infection was reduced.

Conclusion

P. gingivalis up-regulation of CCR5 increases trans infection of harbored R5-tropic HIV-1 from oral keratinocytes to permissive cells. Oral infections such as periodontitis may, therefore, increase risk for oral infection and dissemination of R5-tropic HIV-1.

Lactobacilli-expressed single-chain variable fragment (scFv) specific for intercellular adhesion molecule 1 (ICAM-1) blocks cell-associated HIV-1 transmission across a cervical epithelial monolayer

The vaginal and cervical epithelia provide an initial barrier to sexually acquired HIV-1 infection in women. To study the interactions between HIV-1-infected cells or cell-free HIV-1 and the reproductive epithelium, the transmission of HIV-1 by infected cells or cell-free virus across human cervical epithelial cells was examined using a Transwell culture system. Cell-associated HIV-1 was transmitted more efficiently than cell-free virus, and monocyte-associated virus was transmitted most efficiently. Abs to ICAM-1 added to the apical side of the epithelium blocked cell-mediated transepithelial HIV-1 transmission in vitro. When used in a previously described model of vaginal HIV-1 transmission in human PBL-SCID mice, anti-murine ICAM-1 Abs (0.4 microg/10 microl) also blocked vaginal transmission of cell-associated HIV-1 in vivo. To evaluate a candidate delivery system for the use of this Ab as an anti-HIV-1 microbicide, anti-ICAM single-chain variable fragment Abs secreted by transformed lactobacilli were evaluated for their protective efficacy in the Transwell model. Like the intact Ab and Fab derived from it, the single-chain variable fragment at a concentration of 6.7 microg/100 microl was able to reduce HIV-1 transmission by 70 +/- 5%. These data support the potential efficacy of an anti-ICAM Ab delivered by lactobacilli for use as an anti-HIV-1 microbicide.

Alcohol enhances HIV type 1 infection in normal human oral keratinocytes by up-regulating cell-surface CXCR4 coreceptor

Recent studies suggest that normal human oral keratinocytes (NHOKs) can be infected by HIV-1, and alcohol can enhance HIV infection and replication in lymphocytes. In this study, we examined the possibility that alcohol might facilitate HIV-1 infection of NHOKs by up-regulating cell surface expression of the coreceptor, CXCR4. Alcohol enhanced in vitro infection of NHOKs by CXCR4-tropic strains of HIV-1 as indicated by synthesis of viral reverse transcripts and production of p24gag protein. Alcohol had no effect on CXCR4 gene expression or on total cellular complements of CXCR4 protein. However, alcohol did enhance the fraction of total CXCR4 expressed on the cell surface relative to intracellular stores. Alcohol-induced up-regulation of cell surface CXCR4 expression and HIV-1 infectivity could be blocked by SDF-1alpha-mediated internalization. These data suggest that alcohol may influence oral HIV transmission by altering the cellular compartmentalization of CXCR4 in cells of the oral cavity.

Breast-feeding and Transmission of HIV-1

Breast-feeding substantially increases the risk of HIV-1 transmission from mother to child, and although peripartum antiretroviral therapy prophylaxis significantly decreases the risk of mother-to-child transmission around the time of delivery, this approach does not affect breast-feeding transmission. Increased maternal RNA viral load in plasma and breast milk is strongly associated with increased risk of transmission through breast-feeding, as is breast health, and it has been suggested that exclusive breast-feeding could be associated with lower rates of breast-feeding transmission than mixed feeding of both breast- and other milk or feeds. Transmission through breast-feeding can take place at any point during lactation, and the cumulative probability of acquisition of infection increases with duration of breast-feeding. HIV-1 has been detected in breast milk in cell-free and cellular compartments; infant gut mucosal surfaces are the most likely site at which transmission occurs. Innate and acquired immune factors may act most effectively in combination to prevent primary HIV-1 infection by breast milk.

Oral epithelial cells are susceptible to cell-free and cell-associated HIV-1 infection in vitro

Epithelial cells lining the oral cavity are exposed to HIV-1 through breast-feeding and oral-genital contact. Genital secretions and breast milk of HIV-1-infected subjects contain both cell-free and cell-associated virus. To determine if oral epithelial cells can be infected with HIV-1 we exposed gingival keratinocytes and adenoid epithelial cells to cell-free virus and HIV-1-infected peripheral blood mononuclear cells and monocytes. Using primary isolates we determined that gingival keratinocytes are susceptible to HIV-1 infection via cell-free CD4-independent infection only. R5 but not X4 viral strains were capable of infecting the keratinocytes. Further, infected cells were able to release infectious virus. In addition, primary epithelial cells isolated from adenoids were also susceptible to infection; both cell-free and cell-associated virus infected these cells. These data have potential implications in the transmission of HIV-1 in the oral cavity.

Enhanced transcytosis of R5-tropic human immunodeficiency virus across tight monolayer of polarized human endometrial cells under pro-inflammatory conditions

Most cases of human immunodeficiency virus (HIV) infection worldwide occur following sexual contact, implying that the virus may breach the protective epithelial barrier lining the genital tract. HIV infection is known to preferentially occur when the genital epithelial integrity is altered, particularly when epithelial micro-ulcerations occur during heterosexual intercourse or ulcerations appear, due to sexually transmitted infections or else in the context of ectopy of the endocervical mucosa, which may leave the genital tissue. We report that R5-tropic infectious HIV-1 isolates are capable of in vitro transcytosis through a tight and polarized monolayer of human endometrial HEC-1 cells. Transcytosis of HIV particles was increased 2-fold within a pro-inflammatory micro-environment. Our findings suggest that transcytosis may be a relevant mechanism for the passage of virus through the genital mucosa in vivo, particularly when inflammatory cells and mediators are present in the vicinity of the mucosal surface.

Transepithelial transport of HIV-1 by M cells is receptor-mediated

Human colon carcinoma Caco-2 cell monolayers undergo conversion into cells that share morphological and functional features of M cells when allowed to interact with B lymphocytes. A lymphotropic (X4) HIV-1 strain crosses M cell monolayers and infects underlying CD4(+) target cells. Transport requires both lactosyl cerebroside and CXCR4 receptors, which are expressed on the apical surface of Caco-2 and M cells. Antibodies specific for each receptor block transport. In contrast, a monotropic (R5) HIV-1 strain is unable to cross M cell monolayers and infect underlying monocytes, despite efficient transport of latex beads. Caco-2 and M cells do not express CCR5, but transfection of these cells with CCR5 cDNA restores transport of R5 virus, which demonstrates that HIV-1 transport across M cells is receptor-mediated. The follicle-associated epithelium covering human gut lymphoid follicles expresses CCR5, but not CXCR4, and lactosyl cerebroside, suggesting that HIV-1 infection may occur through M cells and enterocytes at these sites.

Role of N-glycans and SDF-1alpha on the coassociation of CD4 with CXCR4 at the plasma membrane of monocytic cells and blood lymphocytes

CXCR4 is a coreceptor, along with CD4, for human immunodeficiency virus type 1 (HIV-1). Trimolecular complexes between HIV-1 glycoprotein (gp)120, CD4 and CXCR4 constitute a prerequisite for HIV entry. We studied whether CD4 is associated with CXCR4 on CD4+ CXCR4+ cells. Using the conformation-dependent anti-CXCR4 mAb 12G5, CD4 was coimmunoprecipitated with CXCR4 from the membrane of U937 cells which support HIV-1(LAI) efficient infection, and from that of peripheral blood lymphocytes (PBL). CD4 association with CXCR4 increased upon PBL coculture for 5 days with autologous monocytes, decreased upon treatment of the cells or the CD4-CXCR4 complex with either N-glycanase or stromal cell derived factor-1alpha (SDF-1alpha) and was abolished by incubation of the cells with both, N-glycanase and SDF-1alpha. This indicates that glycans are partly involved in CD4 association with CXCR4 and may partly explain the inhibitory effect of SDF-1alpha on HIV infection.

Active and selective transcytosis of cell-free human immunodeficiency virus through a tight polarized monolayer of human endometrial cells

We report that both primary and laboratory-adapted infectious human immunodeficiency virus type 1 (HIV-1) isolates in a cell-free form are capable of transcytosis through a tight and polarized monolayer of human endometrial cells. Trancytosis of cell-free HIV occurs in a strain-selective fashion and appears to be dependent on interactions between HIV envelope glycoproteins and lectins on the apical membrane of the epithelial cells. These findings provide new insights into the initial events occurring during heterosexual transmission of the virus.

Transport of human immunodeficiency virus type 1 pseudoviruses across the blood-brain barrier: role of envelope proteins and adsorptive endocytosis

Blood-borne human immunodeficiency virus type 1 (HIV-1) crosses the blood-brain barrier (BBB) to induce brain dysfunction. How HIV-1 crosses the BBB is unclear. Most work has focused on the ability of infected immune cells to cross the BBB, with less attention devoted to the study of free virus. Since the HIV-1 coat glycoprotein gp120 can cross the BBB, we postulated that gp120 might be key in determining whether free virus can cross the BBB. We used radioactive virions which do (Env+) or do not (Env-) bear the envelope proteins to characterize the ability of HIV-1 to be taken up by the murine BBB. In vivo and in vitro studies showed that the envelope proteins are key to the uptake of free virus and that uptake was enhanced by wheat germ agglutinin, strongly suggesting that the envelope proteins induce viral adsorptive endocytosis and transcytosis in brain endothelia. Capillary depletion showed that Env+ virus completely crossed the vascular BBB to enter the parenchyma of the brain. Virus also entered the cerebrospinal fluid, suggesting passage across the choroid plexus as well. About 0.22% of the intravenously injected dose was taken up per g of brain. In vitro studies showed that postinternalization membrane cohesion (membrane binding not reversed with acid wash or cell lysis) was a regulated event. Intact virus was recovered from the brain endothelial cytosol and was effluxed from the endothelial cells. These results show that free HIV-1 can cross the BBB by an event related to adsorptive endocytosis and mediated by the envelope proteins.

Secretory leukocyte protease inhibitor inhibits infection of monocytes and lymphocytes with human immunodeficiency virus type 1 but does not interfere with transcytosis of cell-associated virus across tight epithelial barriers

In the present study, we demonstrate that recombinant human secretory leukocyte protease inhibitor (rhSLPI) inhibits infection of lymphocyte- and monocyte-derived tumor cell lines and peripheral blood lymphocytes with laboratory-adapted isolates and with the primary isolate, NDK, of free human immunodeficiency virus type 1 (HIV-1). In contrast, rhSLPI did not exhibit inhibitory activity toward transcytosis of cell-associated HIV-1 through a tight monolayer of endometrial epithelial cells. These observations indicate that the inhibitory effect of SLPI is restricted to free HIV-1 in corporal fluids.

Glycans and proteoglycans are involved in the interactions of human immunodeficiency virus type 1 envelope glycoprotein and of SDF-1alpha with membrane ligands of CD4(+) CXCR4(+) cells

We demonstrate that human immunodeficiency virus HIV-1(LAI) envelope glycoprotein 120 (gp120(LAi)) specifically interacts with several membrane ligands on lymphoid CEM or monocytic U937 cells in addition to its previously identified receptor, CD4, and CXCR4, its coreceptor. In its native state, gp120(LAI) is able to elicit specific multimolecular complexes with these membrane ligands at the surface of the cells; most of the interactions are abolished by mannan or heparin but not by dextran. Similarly, stromal cell-derived factor (SDF)-1alpha interacts not only with CXCR4 expressed by CXCR4(+) CD4(+) U937, CEM, and HOS-CD4(+) CXCR4(+) cells but also with CD4 expressed by intact U937, CEM, and HOS-CD4(+) CXCR4(+/-) cells or electroblotted onto Immobilon. SDF-1alpha binding to CD4(+) CXCR4(+/-) cells, or soluble CD4 electroblotted onto Immobilon, is significantly inhibited by sCD4, whereas truncated sCD4 lacking D3 and D4 domains had no significant effect, which indicates that SDF-1 binds to CD4 but at regions different from the HIV-gp120-binding site. Heparin and mannan also inhibit SDF-1alpha binding to intact CD4(+) CXCR4(+/-) cells, and electroblotted soluble CD4. Heparitinase treatment of such cells reduced SDF-1alpha binding. These data demonstrate that glycans and glycosaminoglycans are directly or indirectly involved in the interactions of HIV-1 gp120(LAI) and of SDF-1alpha with membrane ligands of CD4(+) CXCR4(+) cells and thus could play a role both in HIV-1 infection and in the physiology of SDF-1alpha.