Transforming growth factor-beta1 increases CXCR4 expression, stromal-derived factor-1alpha-stimulated signalling and human immunodeficiency virus-1 entry in human monocyte-derived macrophages

Stromal-derived factor-1 (SDF-1/CXCL12) and its receptor CXCR4 play crucial roles in leukocyte migration and activation, as well as embryogenesis, angiogenesis, cancer and viral pathogenesis. CXCR4 is one of the major human immunodeficiency virus-1 (HIV-1) coreceptors on macrophages. In many tissues macrophages are one of the predominant cell types infected by HIV-1 and act as a reservoir for persistent infection and viral dissemination. In patients infected by HIV-1, blood and tissue levels of transforming growth factor-beta1 (TGF-beta1) are increased. The purpose of this study was to evaluate the effects of TGF-beta1 on CXCR4 expression and function in primary human monocyte-derived macrophages (MDMs) and rat microglia. TGF-beta1 up-regulated CXCR4 and enhanced SDF-1alpha-stimulated ERK1,2 phosphorylation in these cells. The increased CXCR4 expression in human MDMs resulted in increased susceptibility of the cells to entry by dual-tropic CXCR4-using HIV-1 (D-X4). In contrast, TGF-beta1 failed to increase CCR5 expression or infection by a CCR5-using virus in MDMs. Our data demonstrate that TGF-beta1 enhances macrophage responsiveness to SDF-1alpha stimulation and susceptibility to HIV-1 by selectively increasing expression of CXCR4. The results suggest that increased expression of CXCR4 on macrophages may contribute to the emergence of dual-tropic X4 viral variants at later stages of HIV-1 infection.     

Enhanced replication of R5 HIV-1 over X4 HIV-1 in CD4(+)CCR5(+)CXCR4(+) T cells

To enter human cells, HIV-1 usually uses CD4 and 1 of 2 coreceptors: CCR5 and CXCR4. Interestingly, even though CCR5 is expressed on far fewer T cells than is CXCR4, many patients in early- and late-stage HIV disease maintain high levels of CCR5-tropic (R5) viruses. We hypothesized that such high R5 viral loads may be sustained because, relative to CXCR4-tropic (X4) HIV-1 infection, R5 HIV-1 infection of permissive CD4(+)CCR5(+)CXCR4(+) T cells results in the production of significantly more infectious virus particles per target cell. To investigate this possibility, we compared the levels of virus production per target cell after isogenic R5 and X4 HIV-1 infection of 2 in vitro primary human lymphocyte culture systems: T-cell receptor-stimulated blood-derived CD4(+) T cells and tonsil histoculture (which requires no exogenous stimulation for ex vivo infection). We provide evidence that R5 HIV-1 does indeed compensate for a small target cell population by producing, on average, 5 to 10 times more infectious virus per CCR5(+) target cell than X4 HIV-1. This replicative advantage may contribute to the predominance of R5 HIV-1 in vivo.     

Does AID aid AIDS?

During AIDS, the acquisition of mutations in the HIV-1 gp120 envelope glycoprotein leads to the switch from primary R5 (CCR5-using) to highly cytopathic X4 (CXCR4-using) HIV-1 variants. Based on the already known sequence homology between IgV genes and the gp120-coding region of the env gene, as well as on somatic hypermutation of multiple proto-oncogenes, the somatic hypermutation hypothesis for the mechanism of R5-X4 HIV-1 switching is proposed as follows. This switch takes place in the germinal center (GC) B cells due to the aberrant somatic hypermutation of the gp120-coding part of the HIV-1 env gene. Activation-induced cytidine deaminase (AID) is required for this process. Activation through IL4R and CD40 is required both for infection of GC B cells with HIV-1 and for induction of AID expression in the same cells. B cell infection with R5 HIV-1 variants is the limiting stage in the process of the viral phenotypic switch during the asymptomatic period of AIDS. Overall up-regulation of CXCR4 coreceptor on the GC B cells and the CD4(+) T cells surrounding the GC provides the predominant replication and acquisition of the newly formed X4 HIV-1 variants.     

Asymmetric HIV-1 co-receptor use and replication in CD4(+) T lymphocytes

Susceptibility to infection by the human immunodeficiency virus type-1 (HIV-1), both in vitro and in vivo, requires the interaction between its envelope (Env) glycoprotein gp120 Env and the primary receptor (R), CD4, and Co-R, either CCR5 or CXCR4, members of the chemokine receptor family. CCR5-dependent (R5) viruses are responsible for both inter-individual transmission and for sustaining the viral pandemics, while CXCR4-using viruses, usually dualtropic R5X4, emerge in ca. 50% of individuals only in the late, immunologically suppressed stage of disease. The hypothesis that such a major biological asymmetry is explained exclusively by the availability of cells expressing CCR5 or CXCR4 is challenged by several evidences. In this regard, binding of the HIV-1 gp120 Env to the entry R complex, i.e. CD4 and a chemokine R, leads to two major events: virion-cell membrane fusion and a cascade of cell signaling. While the fusion/entry process has been well defined, the role of R/Co-R signaling in the HIV-1 life cycle has been less characterized. Indeed, depending on the cellular model studied, the capacity of HIV-1 to trigger a flow of events favoring either its own latency or replication remains a debated issue. In this article, we will review the major findings related to the role of HIV R/Co-R signaling in the steps following viral entry and leading to viral spreading in CD4(+) T lymphocytes.     

Inhibition of R5X4 dualtropic HIV-1 primary isolates by single chemokine co-receptor ligands

The susceptibility of HIV-1 to chemokine-mediated inhibition may be lost as a consequence of the expanded usage of chemokine co-receptors frequently occurring in clade B isolates obtained from individuals with advanced disease. Since chemokine-based immune intervention is under intense investigation, it is crucial to determine its potential effect on primary dualtropic HIV isolates characterized by simultaneous utilization of CCR5 and CXCR4 chemokine co-receptors (R5X4 viruses). In the present study, the CCR5 binding chemokine regulated upon activation normal T cell expressed and secreted (RANTES) strongly inhibited the replication of two of eight primary R5X4 viruses in mitogen-activated primary peripheral blood mononuclear cells (PBMC). The CXCR4 antagonist AMD3100 efficiently suppressed the replication of other two HIV isolates, whereas the remaining four viruses were partially inhibited by treatment with either RANTES or AMD3100. The potency of chemokine-mediated inhibition was influenced by PBMC donor variability, but it was usually independent from the levels of expression of CCR5 or CXCR4. Dual co-receptor usage was maintained by the viruses after two serial passages on U87.CD4 astrocytic cell lines expressing exclusively either CCR5 or CXCR4. The gp120 env variable domains were sequenced before and after passages on U87.CD4 cells. Virus replication into U87.CD4-CXCR4 cells did not result in changes in the V3 region but perturbed the dominant env V4 sequence. Interestingly, double passage onto U87.CD4-CXCR4 cells determined the loss of susceptibility to RANTES inhibition. In conclusion, interference with CCR5 may efficiently inhibit the replication of at least some dualtropic HIV-1 strains, whereas forced CXCR4 usage may result in viral escape from CCR5-dependent inhibitory effects.     

Mu-opioid modulation of HIV-1 coreceptor expression and HIV-1 replication

A substantial proportion of HIV-1-infected individuals are intravenous drug users (i.v.DUs) who abuse opiates. Opioids induce a number of immunomodulatory effects that may directly influence HIV-1 disease progression. In the present report, we have investigated the effect of opioids on the expression of the major HIV-1 coreceptors CXCR4 and CCR5. For these studies we have focused on opiates which are ligands for the mu-opioid receptor. Our results show that DAMGO, a selective mu-opioid agonist, increases CXCR4 and CCR5 expression in both CD3(+) lymphoblasts and CD14(+) monocytes three- to fivefold. Furthermore, DAMGO-induced elevation of HIV-1 coreceptor expression translates into enhanced replication of both X4 and R5 viral strains of HIV-1. We have confirmed the role of the mu-opioid receptor based on the ability of a mu-opioid receptor-selective antagonist to block the effects of DAMGO. We have also found that morphine enhances CXCR4 and CCR5 expression and subsequently increases both X4 and R5 HIV-1 infection. We suggest that the capacity of mu-opioids to increase HIV-1 coreceptor expression and replication may promote viral binding, trafficking of HIV-1-infected cells, and enhanced disease progression.     

Characterization of a chemokine receptor CCR5-negative T cell line and its use in determining human immunodeficiency virus type 1 phenotype

A human CD4-positive T cell line from a donor homozygous negative for the chemokine receptor CCR5 was established, characterized, and used for determining the coreceptor usage of human immunodeficiency virus type 1 (HIV-1) isolates. Clones of this IL-2 dependent human T-cell lymphotropic virus type 1 (HTLV-I) immortalized cell line, named IsnoR5 clones 1 and 2, are susceptible to infection by HIV-1 isolates that use CXCR4 as a coreceptor but resistant to infection by CCR5 tropic HIV-1 viruses. HIV-1 isolates whose replication is inhibited in IsnoR5 cells in the presence of the bicyclam AMD 3100, a CXCR4 specific inhibitor, utilize a coreceptor distinct from CCR5 and CXCR4. Using a panel of primary HIV-1 isolates we have shown that a single T cell line is sufficient to discriminate between use of CCR5, CXCR4 or an alternative coreceptor. As IsnoR5 clone 1 cells revealed the existence of even minor populations of CXCR4-using virus variants, they could be useful for the early identification of changes in coreceptor usage in HIV infected individuals facilitating the timely introduction of appropriate clinical treatments.     

Restricted replication of primary HIV-1 isolates using both CCR5 and CXCR4 in Th2 but not in Th1 CD4(+) T cells

We have previously reported that CCR5-dependent human immunodeficiency virus type-1 (HIV-1; R5), but not CXCR4-restricted (X4) virus, efficiently replicates in T helper cell type 1 (Th1), Th2, or Th0 polyclonal T cells obtained from human umbilical cord blood (CB lines). The X4 virus restriction was env-dependent but did not occur at the level of viral entry. Here, we describe that in contrast to these monotropic HIVs, primary HIV-1 isolates capable of using CCR5 or CXCR4 indifferently for entry (i.e., R5X4 viruses) efficiently replicated in Th2 but not in Th1 CB lines. Although Th1 cells secreted significantly higher amounts of the three CCR5-binding chemokines in comparison with Th2 cells, this restriction was not explained by a defective infection of Th1 cells. Interferon-gamma (IFN-gamma) down-regulated CCR5 in Th1 cells and inhibited, whereas interleukin-4 (IL-4) up-regulated CXCR4 and enhanced the spreading of R5 and R5X4 viruses in polarized CB lines. However, both cytokines did not rescue the replication of X4 and dualtropic viruses in both types of CB lines or in Th1 cells, respectively, whereas addition of anti-IL-4- or anti-IFN-gamma-neutralizing antibodies did not activate virus expression. These findings together suggest the existence of post-entry restriction pathways influenced by gp120 Env/chemokine coreceptor interaction that may significantly contribute to the superior capacity of R5 and R5X4 HIV-1 strains to spread in vivo in comparison to X4 monotropic viruses.     

Susceptibility of diverse primary HIV isolates with varying co-receptor specificity's to CXCR4 antagonistic compounds

The chemokine receptors CCR5 and CXCR4 are an obvious target for HIV therapies. Two compounds, T-22 and AMD-3100, have been shown to inhibit infection of CXCR4-using HIV-1 isolates. The specificity of T-22 and AMD-3100 was further confirmed by their ability to block entry of HIV-1 in GHOST-CXCR4 transfected cells with no effect on viral entry in the GHOST-CCR5 cells. The ability of T-22 to block replication of diverse HIV-1 isolates (group M, subtypes A, B, D, E, and F as well as group O) and HIV-2 primary isolates with varying coreceptor specificities ranging from exclusive CCR5 usage to multiple coreceptor usage was examined in detail. T-22 was found to be highly effective (>90%) at blocking infection of diverse HIV-1 (subtypes A-F, and group O) and HIV-2 isolates that use multiple coreceptors in human PBMCs homozygous for a 32-bp deletion in CCR5 (CCR5-/-), but less effective in CCR5 +/+ PBMCs. Additionally, sequential primary HIV-1 isolates obtained from a longitudinal cohort who had switched from single coreceptor usage to a broad range of multiple receptors could be blocked effectively by both T-22 and AMD-3100 in CCR5-/- PBMCs. Our data suggest that CXCR4 antagonistic compounds are highly effective in blocking the entry of X4-tropic HIV-1, and that these compounds could be a useful additive to current anti-retroviral therapy for clinical management of HIV disease.     

HIV-1 gp120 chemokine receptor-mediated signaling in human macrophages

The chemokine receptors CCR5 and CXCR4 serve as the cellular receptors in conjunction with CD4 for HIV-1 entry and infection of target cells. Although the virus has subverted these molecules for its own use, their natural function is to respond to activation and migration signals delivered by extracellular chemokines. A principal research objective of our laboratory is to understand the consequences of virus-chemokine receptor interactions for cellular function, as well as for entry and infection. We hypothesized that CXCR4-using (X4) and CCR5-using (R5) HIV-1 strains might elicit signals through the chemokine receptors that result in aberrant function and/or regulate virus entry or postentry steps of infection. We have focused on primary human macrophages, which express both CXCR4 and CCR5, because macrophages are a principal target for HIV-1 in vivo, in appropriate macrophage activation appears to play a major role in the pathogenesis of certain sequelae of AIDS, such as HIV encephalopathy, and macrophage infection is regulated at several steps subsequent to entry in ways that are linked to envelope-receptor interactions. This review summarizes our recent findings regarding the mechanisms of chemokine-receptor signaling in macrophages, the role of viral envelope glycoproteins in eliciting macrophage signals, and how these activation pathways may participate in macrophage infection and affect cell functions apart from infection.     

R5X4 HIV-1 coreceptor use in primary target cells: implications for coreceptor entry blocking strategies

Entry coreceptor use by HIV-1 plays a pivotal role in viral transmission, pathogenesis and disease progression. In many HIV-1 infected individuals, there is an expansion in coreceptor use from CCR5 to include CXCR4, which is associated with accelerated disease progression. While targeting HIV-1 envelope interactions with coreceptor during viral entry is an appealing approach to combat the virus, the methods of determining coreceptor use and the changes in coreceptor use that can occur during disease progression are important factors that may complicate the use of therapies targeting this stage of HIV-1 replication. Indicator cells are typically used to determine coreceptor use by HIV-1 in vitro, but the coreceptors used on these cells can differ from those used on primary cell targets. V3 based genetic sequence algorithms are another method used to predict coreceptor use by HIV-1 strains. However, these algorithms were developed to predict coreceptor use in cell lines and not primary cells and, furthermore, are not highly accurate for some classes of viruses. This article focuses on R5X4 HIV-1, the earliest CXCR4-using variants, reviewing the pattern of coreceptor use on primary CD4+ lymphocytes and macrophages, the relationship between primary cell coreceptor use and the two principal approaches to coreceptor analysis (genetic prediction and indicator cell phenotyping), and the implications of primary cell coreceptor use by these strains for treatment with a new class of small molecule antagonists that inhibit CCR5-mediated entry. These are important questions to consider given the development of new CCR5 blocking therapies and the prognosis associated with CXCR4 use.     

Effect of a CCR5 inhibitor on viral loads in macaques dual-infected with R5 and X4 primate immunodeficiency viruses

Human immunodeficiency virus type 1 (HIV-1) fusion with its target cells is initiated by sequential interactions between its envelope glycoprotein, CD4, and a co-receptor, usually CCR5 or CXCR4. Small molecules that bind to CCR5 and prevent its use by R5 HIV-1 strains are now being developed clinically as antiviral drugs. To test whether a block to CCR5 promotes the replication of viruses that enter cells via CXCR4 and are associated with accelerated disease progression, we administered a small molecule CCR5 inhibitor, CMPD 167, to three macaques dual-infected with both R5 (SIVmac251) and X4 (SHIV-89.6P) viruses. CMPD 167 caused a rapid and substantial (on average, 50-fold) suppression of R5 virus replication in each animal. In two of the animals, but not in the third, a rapid, transient, 8- to 15-fold increase in the amount of plasma X4 virus occurred. In neither animal was the increase in X4 viral load sustained throughout therapy, however. These observations may have relevance for the development of CCR5 inhibitors for treatment of HIV-1 infection of humans.     

Enhanced replicative capacity and pathogenicity of HIV-1 isolated from individuals infected with drug-resistant virus and declining CD4+ T-cell counts

Virologic failure on continuous antiretroviral therapy (ART) is associated with variable changes in CD4 T-cell counts: peripheral CD4 T-cell counts decrease in conjunction with a resurgence of plasma virus (nonresponders) or remain stable or continue to increase despite ongoing virus replication (discordant responders). This study found that HIV-1 isolated from nonresponders had significantly greater replicative capacity in activated peripheral blood mononuclear cells (PBMCs) as well as an enhanced ability to induce apoptosis in both HIV-1-infected and HIV-1-uninfected CD4 T cells compared with virus isolated from discordant responders. Enhanced replicative capacity in PBMCs of virus isolated from nonresponders was inhibited by AMD3100, a CXCR4 antagonist. Virus quasispecies isolated from PBMCs from nonresponders used both CC chemokine receptor 5 (CCR5) and CX chemokine receptor 4 (CXCR4) for entry, in contrast to virus isolated from PBMCs from discordant responders, which predominantly used CCR5. In contrast, virus isolated from plasma from both groups predominantly used CCR5. In summary, although drug resistance may lead to impaired viral fitness, the capacity of virus quasispecies from PBMCs to use CXCR4 may have significant consequences on viral replicative capacity and potentially on clinical outcome.     

R5 to X4 switch of the predominant HIV-1 population in cellular reservoirs during effective highly active antiretroviral therapy

HIV-1 coreceptor usage plays a critical role for virus tropism and pathogenesis. A switch from CCR5 to CXCR4-using viruses can occur in the natural course of infection and correlates with subsequent disease progression. To investigate whether HIV-1 genetic evolution might lead to changes in virus coreceptor usage during highly active antiretroviral therapy (HAART), a longitudinal genotypic analysis of the virus found in cellular reservoirs was conducted in 32 patients with undetectable viral loads on HAART for 5 years. The genotype of the 3rd variable region of the env gene predicting coreceptor usage was retrospectively determined in the plasma or in peripheral blood mononuclear cells (PBMC) at baseline and then in PBMCs at months 30 and 60 of HAART. There was a switch from R5 to X4 variants in 11 of the 23 patients who harbored a majority virus population of R5 variants at baseline. X4 variants remained predominant in the 9 patients who harbored mainly X4 variants at baseline. The patients harboring predominantly X4 variants during HAART, either from baseline or after an R5 to X4 switch, tended to have lower CD4+ T-cell counts on HAART than did patients harboring continuously a majority population of R5 variants. These results suggest that potent antiretroviral therapy produces the conditions necessary for the gradual emergence of X4 variants in cellular reservoirs.     

HIV-1 replication in CD4+ T cell lines: the effects of adaptation on co-receptor use, tropism, and accessory gene function

We studied the replication of HIV-1 macrophage-tropic CCR5-using strains (R5) in CD4+ T cell lines to better understand the switch in co-receptor use of such strains during disease progression and to assess resulting changes in cell tropism. We found that the majority of R5 strains cannot replicate in CD4+ T cell lines without adaptation by serial passage. A small minority of primary R5 isolates, however, were able to infect two T cell lines, Molt4 and SupT1. This expanded tropism was due to the use of undetectable levels of CCR5 rather than CXCR4 or alternative receptors. In contrast, HIV-1sF162 adaptation for replication in the C8166 T cell line was due to the emergence of variant strains that could use CXCR4. Of two variants, one was dual-tropic and one T-tropic, although both could use CCR5 as well as CXCR4. A single mutation in the start codon of the accessory gene vpu accounted for the T-tropic phenotype of the second variant, indicating that a non-functional vpu impairs macrophage tropism. Thus, in vitro and in the absence of an immune response, R5 strains naturally adapt to infect CXCR4+ T cell lines. Such adaptation resembles the rare R5 to X4 switch that occurs in vivo. Mutations in accessory genes (e.g., vpu) not required for replication in rapidly dividing cell lines may also occur in vitro, abrogating replication in primary cell types such as macrophages. Such mutations, however, are normally selected against in vivo.     

Entry of R5X4 and X4 human immunodeficiency virus type 1 strains is mediated by negatively charged and tyrosine residues in the amino-terminal domain and the second extracellular loop of CXCR4

CXCR4 mediates the fusion and entry of X4 and R5X4 strains of human immunodeficiency virus type 1 (HIV-1). The residues involved in CXCR4 coreceptor function have not all yet been identified, but tyrosine and negatively charged residues in the amino-terminal domain of CCR5 were shown to be indispensable for gp120 binding and entry of R5 and R5X4 strains. We therefore evaluated the role of such residues in CXCR4 coreceptor function by replacing tyrosines (Y), aspartic acids (D), and glutamic acids (E) with alanines (A) and testing the ability of these mutants to mediate the entry of X4 and R5X4 HIV-1 isolates. Our results show that viral entry depends on YDE-rich clusters in both the amino-terminus and the second extracellular loop of CXCR4. Different viral isolates vary in their dependence on residues in one or the other domain. The determinants of CXCR4 coreceptor function are, therefore, more diffuse and isolate-dependent than those of CCR5.     

Effect of HIV-1 subtype and tropism on treatment with chemokine coreceptor entry inhibitors; overview of viral entry inhibition

Abstract

HIV-1 entry begins with viral envelope glycoprotein gp120 interacting with host-cell CD4 and an entry coreceptor (mainly chemokine receptors CCR5 or CXCR4). Inhibitors of particular coreceptors are being developed in order to exploit this step of cellular infection. However, effectiveness of these drugs requires matching of the administered therapeutic to coreceptor use by the viral variants infecting each patient. Patient viruses may use only CCR5 (R5), only CXCR4 (X4) or both (D/M). Most patients in early disease have R5 variants, with the presence of X4 variants increasing as disease progresses; the infecting subtype also affects the prevalence of X4 variants. Phenotypic, genotypic and clinical trial tests are in use to determine coreceptor utilization by HIV-1 variants, termed tropism, and to predict the response to entry inhibitors. Maraviroc is the only approved entry-coreceptor inhibitor and inhibits CCR5-gp120 interaction. Clinical trials of maraviroc in specific patient subgroups are elucidating the drug’s role in contemporary clinical practice. Treatment failure to this and other CCR5 inhibitors has been shown to result from either outgrowth of X4 variants or through resistance mutations leading to R5 variants that are able to enter cells using drug-bound CCR5; thus, new entry inhibitors seek to circumvent this mechanism of resistance.     

Entry inhibitor-based microbicides are active in vitro against HIV-1 isolates from multiple genetic subtypes

Inhibitors of viral entry are under consideration as topical microbicides to prevent HIV-1 sexual transmission. Small molecules targeting HIV-1 gp120 (BMS-378806) or CCR5 (CMPD167), and a peptide fusion inhibitor (C52L), each blocks vaginal infection of macaques by a SHIV. A microbicide, however, must be active against multiple HIV-1 variants. We therefore tested BMS-C (a BMS-378806 derivative), CMPD167, C52L and the CXCR4 ligand AMD3465, alone and in combination, against 25 primary R5, 12 X4 and 7 R5X4 isolates from subtypes A-G. At high concentrations (0.1-1 microM), the replication of most R5 isolates in human donor lymphocytes was inhibited by >90%. At lower concentrations, double and triple combinations were more effective than individual inhibitors. Similar results were obtained with X4 viruses when AMD3465 was substituted for CMPD167. The R5X4 viruses were inhibited by combining AMD3465 with CMPD167, or by the coreceptor-independent compounds. Thus, combining entry inhibitors may improve microbicide effectiveness.     

Biological parameters of HIV-1 infection in primary intestinal lymphocytes and macrophages

Mucosal surfaces are the portal of entry for most HIV-1 infections and play an important role in disease pathogenesis. To characterize the biological parameters of HIV-1 infection in mucosal cells, we used purified lamina propria lymphocytes and macrophages from normal human small intestine to determine the distribution of the HIV-1 receptor and coreceptors on intestinal mononuclear cells and the permissiveness of these cells to HIV-1 infection. Lamina propria lymphocytes expressed CD4, CCR5, and CXCR4. In contrast, lamina propria macrophages expressed CD4 but not CCR5 or CXCR4. Intestinal lymphocytes supported replication by R5 and X4 isolates of HIV-1, but lamina propria macrophages were permissive to neither. RANTES, macrophage inflammatory protein-1alpha (MIP-1alpha), and MIP-1beta inhibited infection of intestinal lymphocytes by BaL, indicating that R5 infection of the intestinal lymphocytes was mediated by CCR5. Thus, resident lamina propria lymphocytes, not macrophages, are the target mononuclear cell for HIV-1 infection in the intestinal mucosa during early HIV-1 infection.     

CCR5 and CXCR4 expression on memory and naive T cells in HIV-1 infection and response to highly active antiretroviral therapy

OBJECTIVE: To measure CCR5 and CXCR4 chemokine receptor expression on CD4 and CD8 T cells in HIV-1 infection and to relate levels to the distribution of CD45RO memory and CD45RA-naive subsets, measures of disease activity, and response to highly active antiretroviral therapy (HAART). DESIGN: Fourteen untreated HIV-1-infected patients, 18 patients at 3-to 4-weeks after beginning HAART, and 35 uninfected control subjects were studied. METHODS: Four-color cytofluorometry with appropriate conjugated monoclonal antibodies (mAbs) was performed to define CD45RA and CD45RO subsets of CD4 and CD8 T cells and measure their expression of CCR5, CXCR4, and CD38. RESULTS: HIV-1-infected patients had higher CCR5 levels and lower CXCR4 levels on CD4 and CD8 T cells and their CD45RO/CD45RA subsets than control subjects did. However, CCR5 elevation was statistically significant only for CD4 T cells and their subsets, and CXCR4 depression was significant for CD8 T cells and their subsets (and for CD4:CD45RO cells). The elevation of CCR5 and depression of CXCR4 were not due to shifts in CD45RO/CD45RA subset proportions but to upregulation or downregulation within the subsets. CCR5 elevation on CD4 T cells was significantly restored toward normal by HAART, but the CXCR4 depression was not. CCR5 expression but not CXCR4 expression correlated with other measures of immunodeficiency (CD4 T-cell levels), active infection (viral load), and cellular activation (CD38). CONCLUSIONS: CCR5 elevation is a concomitant of immune activation and viral replication that occurs in HIV-1 infection, but the relation of CXCR4 depression to severity of infection, disease progression, and response to therapy remains undefined.