CCR5Delta32 protein expression and stability are critical for resistance to human immunodeficiency virus type 1 in vivo

Human immunodeficiency virus type 1 (HIV-1) infection of individuals carrying the two alleles of the CCR5Delta32 mutation (CCR5(-/-)) has rarely been reported, but how the virus overcomes the CCR5Delta32 protective effect in these cases has not been delineated. We have investigated this in 6 infected (HIV(+)) and 25 HIV(-) CCR5(-/-) individuals. CD4(+) T lymphocytes isolated from HIV(-) CCR5(-/-) peripheral blood mononuclear cells (PBMCs) showed lower levels of CXCR4 expression that correlated with lower X4 Env-mediated fusion. Endogenous CCR5Delta32 protein was detected in all HIV(-) CCR5(-/-) PBMC samples (n = 25) but not in four of six unrelated HIV(+) CCR5(-/-) PBMC samples. Low levels were detected in another two HIV(+) CCR5(-/-) PBMC samples. The expression of adenovirus 5 (Ad5)-encoded CCR5Delta32 protein restored the protective effect in PBMCs from three HIV(+) CCR5(-/-) individuals but failed to restore the protective effect in PBMCs isolated from another three HIV(+) CCR5(-/-) individuals. In the latter samples, pulse-chase analyses demonstrated the disappearance of endogenous Ad5-encoded CCR5Delta32 protein and the accumulation of Ad5-encoded CCR5 during the chase periods. PBMCs isolated from CCR5(-/-) individuals showed resistance to primary X4 but were readily infected by a lab-adapted X4 strain. Low levels of Ad5-encoded CCR5Delta32 protein conferred resistance to primary X4 but not to lab-adapted X4 virus. These data provide strong support for the hypothesis that the CCR5Delta32 protein actively confers resistance to HIV-1 in vivo and suggest that the loss or reduction of CCR5Delta32 protein expression may account for HIV-1 infection of CCR5(-/-) individuals. The results also suggest that other cellular or virally induced factors may be involved in the stability of CCR5Delta32 protein.     

Inhibition of human immunodeficiency virus replication by a dual CCR5/CXCR4 antagonist

Here we report that the N-pyridinylmethyl cyclam analog AMD3451 has antiviral activity against a wide variety of R5, R5/X4, and X4 strains of human immunodeficiency virus type 1 (HIV-1) and HIV-2 (50% inhibitory concentration [IC(50)] ranging from 1.2 to 26.5 microM) in various T-cell lines, CCR5- or CXCR4-transfected cells, peripheral blood mononuclear cells (PBMCs), and monocytes/macrophages. AMD3451 also inhibited R5, R5/X4, and X4 HIV-1 primary clinical isolates in PBMCs (IC(50), 1.8 to 7.3 microM). A PCR-based viral entry assay revealed that AMD3451 blocks R5 and X4 HIV-1 infection at the virus entry stage. AMD3451 dose-dependently inhibited the intracellular Ca(2+) signaling induced by the CXCR4 ligand CXCL12 in T-lymphocytic cells and in CXCR4-transfected cells, as well as the Ca(2+) flux induced by the CCR5 ligands CCL5, CCL3, and CCL4 in CCR5-transfected cells. The compound did not interfere with chemokine-induced Ca(2+) signaling through CCR1, CCR2, CCR3, CCR4, CCR6, CCR9, or CXCR3 and did not induce intracellular Ca(2+) signaling by itself at concentrations up to 400 microM. In freshly isolated monocytes, AMD3451 inhibited the Ca(2+) flux induced by CXCL12 and CCL4 but not that induced by CCL2, CCL3, CCL5, and CCL7. The CXCL12- and CCL3-induced chemotaxis was also dose-dependently inhibited by AMD3451. Furthermore, AMD3451 inhibited CXCL12- and CCL3L1-induced endocytosis in CXCR4- and CCR5-transfected cells. AMD3451, in contrast to the specific CXCR4 antagonist AMD3100, did not inhibit but enhanced the binding of several anti-CXCR4 monoclonal antibodies (such as clone 12G5) at the cell surface, pointing to a different interaction with CXCR4. AMD3451 is the first low-molecular-weight anti-HIV agent with selective HIV coreceptor, CCR5 and CXCR4, interaction.     

Expression and Use of Human Immunodeficiency Virus Type 1 Coreceptors by Human Alveolar Macrophages

Human immunodeficiency virus type 1 (HIV-1) requires, in addition to CD4, coreceptors of the CC or CXC chemokine families for productive infection of T cells and cells of the monocyte-macrophage lineage. Based on the hypothesis that coreceptor expression on alveolar macrophages (AM) may influence HIV-1 infection of AM in the lung, this study analyzes the expression and utilization of HIV-1 coreceptors on AM of healthy individuals. AM were productively infected with five different primary isolates of HIV-1. Levels of surface expression of CCR5, CXCR4, and CD4 were low compared to those of blood monocytes, but CCR3 was not detectable. mRNA for CCR5, CXCR4, CCR2, and CCR3 were all detectable, but to varying degrees and with variability among donors. Expression of CCR5, CXCR4, and CCR2 mRNA was downregulated following stimulation with lipopolysaccharide (LPS). In contrast, secretion of the chemokines RANTES, MIP-1alpha, and MIP-1beta was upregulated with LPS stimulation. Interestingly, HIV-1 replication was diminished following LPS stimulation. Infection of AM with HIV-1 in the presence of the CC chemokines demonstrated blocking of infection. Together, these studies demonstrate that AM can be infected by a variety of primary HIV-1 isolates, AM express a variety of chemokine receptors, the dominant coreceptor used for HIV entry into AM is CCR5, the expression of these receptors is dependent on the state of activation of AM, and the ability of HIV-1 to infect AM may be modulated by expression of the chemokine receptors and by chemokines per se.     

Alterations in mast cell function and survival following in vitro infection with human immunodeficiency viruses-1 through CXCR4

HIV-1 infection leads to a disease that attacks the central regulatory mechanisms of the immune response. As mucosal tissue is one of the primary sites infected with HIV in vivo, we examined the effects of HIV exposure on human mast cells, important components of mucosal defense. Using the human mast cell line, HMC-1, which expresses CXCR4 but not CCR5 on the cell surface, we found that several HIV-1 X4 tropic lab (IIIB, RF) and primary isolates but not R5 (BAL, ADA) isolates productively infected these cells. Furthermore, stem cell factor-dependent mast cells derived from primary fetal liver or cord blood cultures were also productively infected with both X4 and R5 HIV-1 strains. Infection was blocked at the level of viral entry using monoclonal antibodies to CXCR4 and CD4. Treatment of HMC-1 with TNF-alpha and TGF-beta stimulated cell surface expression of CCR5 and up-regulated expression of both CCR5 and CXCR4 on primary mast cells, leading to increased susceptibility to both X4 and R5 viral isolates. HIV-1 infection also resulted in histamine release from these mast cells, most due in part to HIV-mediated cell death. These results demonstrate that X4 viruses can use CD4 and the CXCR4 receptor to infect mast cells, suggesting that mast cell-T cell interactions may contribute to HIV mediated immune dysfunction in the mucosa.     

Inhibition of CXCR4 expression by recombinant adenoviruses containing anti-sense RNA resists HIV-1 infection on MT4 cell lines

CXCR4-tropic (X4) variants are associated with faster disease progression than CCR5-tropic variants in HIV infection. We previously reported inhibition of CCR5 expression on U937 cells could protect the cells from HIV-1 infection. Here, we established recombinant adenoviruses containing anti-sense CXCR4 cDNA, to investigate its role in the protection of HIV entering into target cells. A fragment of 636 bp cDNA from CXCR4 mRNA was recombined into adenoviral vector and the recombinant adenovirus was obtained from AD-293 cells. The rates of CXCR4 expression on the MT4 cells infected with recombinant adenovirus were measured by FACS. The MT4 cells infected by recombinant adenovirus were challenged by T-tropic HIV-1 strains and then P24 antigen was assayed. The rate of expression of CXCR4 on MT4 cell infected with recombinant adenovirus was decreased from 42% to 1.12% at 24 h, and to 1.03%, 1.39%, and 1.23% at 48 h, 72 h and 10 days respectively. Compared with Ad-control cells, recombinant adenovirus infected MT4 cells produced much less P24 antigen after being challenged with HIV-1. Furthermore, the recombinant adenovirus had no effects on chemotactic activity and proliferation of the MT4 cells. In conclusion, recombinant adenoviruses containing anti-sense can inhibit CXCR4 expression and resist HIV-1 infection on MT4 cell lines.     

Chemokine receptor-usage of clinical HIV-1 isolates obtained from patients with HIV-1 infection in late clinical stages using PHA-blast

In the present sudy, chemokine receptor-usage of primary HIV-1 isolates was examined using U87-CD4 cells expressing chemokine receptors CCR3, CCR5 and CXCR4. HIV-1 was isolated from the peripheral blood mononuclear cells (PBMC) and/or plasma of eight HIV-1-infected individuals in late CDC-II and CDC-IV clinical stages using PHA-blast prepared from the PBMC of healthy blood donors. The primary HIV-1 isolates from patients in late CDC-II stage rarely infected monocyte-derived macrophages in the present study, whereas most isolates from patients in the CDC-IV stage infected the macrophages. In the experiments using U87-CD4 cells expressing chemokine receptors, the isolates from patients in the late CDC-II stage infected U87-CD4 cells expressing CXCR4, but not U87-CD4 cells expressing CCR5. In contrast, most isolates from patients in the CDC-IV stage infected both U87-CD4 cells expressing CXCR4 or CCR5. The isolates which infected both U87-CD4 cells were supposed to contain dual tropic HIV-1 or a mixture of CXCR4-tropic and CCR5-tropic HIV-1s. Analysis of the deduced amino acid sequence of the V3 region in proviral env gene showed that the V3 region in U87-CD4 cells infected with CXCR4-tropic HIV-1 isolates was largely different from that in the cells infected with CCR5-tropic isolates, but were highly similar to that in cells infected with dual tropic isolates. These results suggest that PHA-blasts may preferentially support the replication of the CXCR4-tropic and dual tropic HIV-1s, and that CXCR4-tropic and dual tropic HIV-1s are also present in peripheral blood from patients in the late stage of the asymptomatic phase.     

HIV chemokine receptor inhibitors as novel anti-HIV drugs

The chemokine receptors CXCR4 and CCR5 are the main coreceptors used by the T-cell-tropic (CXCR4-using, X4) and macrophage-tropic (CCR5-using, R5) HIV-1 strains, respectively, for entering their CD4⁺ target cells. In this review, we focus on the function of these chemokine receptors in HIV infection and their role as novel targets for viral inhibition. Besides some modified chemokines with antiviral activity, several low-molecular weight CCR5 and CXCR4 antagonistic compounds have been described with potent antiviral activity. The best CXCR4 antagonists described are the bicyclam derivatives, which consistently block X4 but also R5/X4 viral replication in PBMCs. We believe that chemokine receptor antagonists will become important new antiviral drugs to combat AIDS. Both CXCR4 and CCR5 chemokine receptor inhibitors will be needed in combination and even in combinations of antiviral drugs that also target other aspects of the HIV replication cycle to obtain optimum antiviral therapeutic effects.     

CCR5-reactive antibodies in seronegative partners of HIV-seropositive individuals down-modulate surface CCR5 in vivo and neutralize the infectivity of R5 strains of HIV-1 In vitro

Exposure to HIV does not necessarily result in infection. Because primary HIV infection is associated with CCR5-tropic HIV variants (R5), CCR5-specific Abs in the sera of HIV-seronegative, HIV-exposed individuals (ESN) might be associated with protection against infection. We analyzed sera from ESN, their HIV-infected sexual partners (HIV+), and healthy controls (USN) searching for CCR5-specific Abs, studying whether incubation of PBMC with sera could prevent macrophage inflammatory protein 1 beta (Mip1 beta) (natural ligand of CCR5) binding to CCR5. Results showed that Mip1 beta binding to CCR5 was not modified by sera of either 40 HIV+ or 45 USN but was greatly reduced by sera of 6/48 ESN. Binding inhibition was due to Abs reactive with CCR5. The CCR5-specific Abs neutralized the infectivity of primary HIV isolates obtained from the corresponding HIV+ partners and of R5-primary HIV strains, but not that of CXCR4-tropic or amphitropic HIV strains. Immunoadsorption on CCR5-transfected, but not on CXCR4-transfected, cells removed CCR5-specific and virus-neutralizing Abs. Epitope mapping on purified CCR5-specific Abs showed that these Abs recognize a conformational epitope in the first cysteine loop of CCR5 (aa 89-102). Affinity-purified anti-CCR5-peptide neutralized the infectivity of R5 strains of HIV-1. Anti-CCR5 Abs inhibited Mip1beta-induced chemotaxis of PBMC from healthy donors. PBMC from two ESN (with anti-CCR5 Abs) were CCR5-negative and could not be stimulated by Mip1beta in chemotaxis assays. These results contribute to clarifying the phenomenon of immunologic resistance to HIV and may have implications for the development of a protective vaccine.     

Human immunodeficiency virus type 1 infection and replication in normal human oral keratinocytes

Recent epidemiologic studies show increasing human immunodeficiency virus type 1 (HIV-1) transmission through oral-genital contact. This paper examines the possibility that normal human oral keratinocytes (NHOKs) might be directly infected by HIV or might convey infectious HIV virions to adjacent leukocytes. PCR analysis of proviral DNA constructs showed that NHOKs can be infected by CXCR4-tropic (NL4-3 and ELI) and dualtropic (89.6) strains of HIV-1 to generate a weak but productive infection. CCR5-tropic strain Ba-L sustained minimal viral replication. Antibody inhibition studies showed that infection by CXCR4-tropic viral strains is mediated by the galactosylceramide receptor and the CXCR4 chemokine coreceptor. Coculture studies showed that infectious HIV-1 virions can also be conveyed from NHOKs to activated peripheral blood lymphocytes, suggesting a potential role of oral epithelial cells in the transmission of HIV infection.     

A human immunodeficiency virus type 1 isolate from an infected person homozygous for CCR5Delta32 exhibits dual tropism by infecting macrophages and MT2 cells via CXCR4

The mechanisms of human immunodeficiency virus (HIV) infection of a man (VH) homozygous for the CCR5Delta32 mutation were investigated, and coreceptors other than CCR5 used by HIV type 1 (HIV-1) isolated from this individual were identified. In contrast to previous reports, this individual's rate of disease progression was not accelerated. Homozygosity for CCR5Delta32 mutation was demonstrated by PCR and DNA sequencing (R. Biti et al., Nat. Med. 3:252-253, 1997). CCR5 surface expression was absent on T lymphocytes and macrophages. HIV was isolated by coculture with peripheral blood mononuclear cells (PBMCs) from siblings who were homozygous (VM) or wild type (WT) for the CCR5Delta32 mutation. The virus demonstrated dual tropism for infection of MT2 cell line and primary macrophages. Sequencing of the full HIV genome directly from the patient's PBMCs revealed 21 nucleotide insertions in the V1 region of gp120. The VH envelope sequence segregated apart from both the T-cell-line-adapted tropic strains NL4-3 and SF2 and M-tropic strain JRFL or YU2 by phylogenetic tree analysis. VH was shown to utilize predominantly CXCR4 for entry into T lymphocytes and macrophages by HOS.CD4 cell infection assay, direct envelope protein fusion, and inhibition by anti-CXCR4 monoclonal antibody (12G5), SDF-1, and AMD3100. Microsatellite mapping demonstrated the separate inheritance of CXCR4 by both homozygote brothers (VH and VM). Our study demonstrates the ability of certain strains of HIV to readily use CXCR4 for infection or entry into macrophages, which is highly relevant to the pathogenesis of late-stage disease and presumably also HIV transmission.     

A preponderance of CCR5(+) CXCR4(+) mononuclear cells enhances gastrointestinal mucosal susceptibility to human immunodeficiency virus type 1 infection

The gastrointestinal mucosa harbors the majority of the body's CD4(+) cells and appears to be uniquely susceptible to human immunodeficiency virus type 1 (HIV-1) infection. We undertook this study to examine the role of differences in chemokine receptor expression on infection of mucosal mononuclear cells (MMCs) and peripheral blood mononuclear cells (PBMCs) by R5- and X4-tropic HIV-1. We performed in vitro infections of MMCs and PBMCs with R5- and X4-tropic HIV-1, engineered to express murine CD24 on the infected cell's surface, allowing for quantification of HIV-infected cells and their phenotypic characterization. A greater percentage of MMCs than PBMCs are infected by both R5- and X4-tropic HIV-1. Significant differences exist in terms of chemokine receptor expression in the blood and gastrointestinal mucosa; mucosal cells are predominantly CCR5(+) CXCR4(+), while these cells make up less than 20% of the peripheral blood cells. It is this cell population that is most susceptible to infection with both R5- and X4-tropic HIV-1 in both compartments. Regardless of whether viral isolates were derived from the blood or mucosa of HIV-1-infected patients, HIV-1 p24 production was greater in MMCs than in PBMCs. Further, the chemokine receptor tropism of these patient-derived viral isolates did not differ between compartments. We conclude that, based on these findings, the gastrointestinal mucosa represents a favored target for HIV-1, in part due to its large population of CXCR4(+) CCR5(+) target cells and not to differences in the virus that it contains.     

细胞内表达CCR5Delta32蛋白对HIV-1感染抑制作用的研究

人CCR5Delta32突变个体能有效抵制HIV-1感染,主要是由于该个体淋巴细胞内表达的CCR5Delta32突变蛋白能通过反式显性失活效应(TDN)抑制细胞表面HIV-1辅受体CCR5和CXCR4的产生．通过构建CCR5Delta32慢病毒载体,体外转染人外周血单个核细胞(PBMCs),研究细胞内表达CCR5Delta32蛋白对HIV-1感染的抑制作用．结果表明,表达CCR5Delta32蛋白的人PBMCs对HIV-1 R5、X4及R5X4毒株感染均具有显著的抑制作用．这些工作为后续的AIDS基因治疗研究奠定了基础．     

Influence of the CCR2-V64I Polymorphism on Human Immunodeficiency Virus Type 1 Coreceptor Activity and on Chemokine Receptor Function of CCR2b, CCR3, CCR5, and CXCR4

The chemokine receptors CCR5 and CXCR4 are used by human immunodeficiency virus type 1 (HIV-1) in conjunction with CD4 to infect cells. In addition, some virus strains can use alternative chemokine receptors, including CCR2b and CCR3, for infection. A polymorphism in CCR2 (CCR2-V64I) is associated with a 2- to 4-year delay in the progression to AIDS. To investigate the mechanism of this protective effect, we studied the expression of CCR2b and CCR2b-V64I, their chemokine and HIV-1 coreceptor activities, and their effects on the expression and receptor activities of the major HIV-1 coreceptors. CCR2b and CCR2b-V64I were expressed at similar levels, and neither molecule affected the expression or coreceptor activity of CCR3, CCR5, or CXCR4 in cotransfected cell lines. Peripheral blood mononuclear cells (PBMCs) from CCR2-V64I heterozygotes had normal levels of CCR2b and CCR5 but slightly reduced levels of CXCR4. CCR2b and CCR2b-V64I functioned equally well as HIV-1 coreceptors, and CCR2-V64I PBMCs were permissive for HIV-1 infection regardless of viral tropism. The MCP-1-induced calcium mobilization mediated by CCR2b signaling was unaffected by the polymorphism, but MCP-1 signaling mediated by either CCR2b- or CCR2-V64I-encoded receptors resulted in heterologous desensitization (i.e., limiting the signal response of other receptors) of both CCR5 and CXCR4. The heterologous desensitization of CCR5 and CXCR4 signaling by both CCR2 allele receptor types provides a mechanistic link that might help explain the in vivo effects of CCR2 gene variants on progression to AIDS as well as the reported antiviral activity of natural CCR2 ligands.     

CD4-independent infection of two CD4(-)/CCR5(-)/CXCR4(+) pre-T-cell lines by human and simian immunodeficiency viruses

The infection of CD4-negative cells by variants of tissue culture-adapted human immunodeficiency virus type 1 (HIV-1) or HIV-2 strains has been shown to be mediated by the CXCR4 coreceptor. Here we show that two in vitro-established CD4(-)/CCR5(-)/CXCR4(+) human pre-T-cell lines (A3 and A5) can be productively infected by wild-type laboratory-adapted T-cell-tropic HIV-1 and HIV-2 strains in a CD4-independent, CXCR4-dependent fashion. Despite the absence of CCR5 expression, A3 and A5 cells were susceptible to infection by the simian immunodeficiency viruses SIVmac239 and SIVmac316. Thus, at least in A3 and A5 cells, one or more of the chemokine receptors can efficiently support the entry of HIV and SIV isolates in the absence of CD4. These findings suggest that to infect cells of different compartments, HIV and SIV could have evolved in vivo to bypass CD4 and to interact directly with an alternative receptor.     

Antiviral action of membranotropic compounds modified by adamantane and norbornene pharmacophores exerted on different HIV-1 strains

The anti-HIV activity of new membranotropic compounds, i.e. of the polycarboxylate matrix and of its derivatives modified by adamantane and norbonene, was studied in respect of HIV-1 strains, whose tropicity to coreceptors CCR5 and CXCR4 was different, as well as in respect of HIV-1 variants resistant to azidothymidine (AZT) in a continuous culture of human lymphoid cells (MT-4) and in mononuclear cells of peripheral blood from healthy donors. Testing of complex compounds in a culture of infected MT-4 human lymphoid cells showed an effective inhibition of viral reproduction of LAV.04 (CXCR4-tropic variant) and of HIV11(EVK) as well as AZT-resistant variants. The studied pharmacophores-modified compounds displayed, in infection of the primary culture of human mononuclear cells of the HIV-1 R5 and X4 strains, a notable antiviral activity with their HIV efficiency significantly exceeding the one of the original matrix.     

In vivo evolution of X4 human immunodeficiency virus type 1 variants in the natural course of infection coincides with decreasing sensitivity to CXCR4 antagonists

CXCR4-using (X4) human immunodeficiency virus type 1 (HIV-1) variants evolve from CCR5-restricted (R5) HIV-1 variants. Early after their first appearance in vivo, X4 HIV-1 variants additionally use CCR5. The ability to use CCR5 in addition to CXCR4 is generally lost late in infection. Here we studied whether this evolution of the coreceptor repertoire is also reflected in a changing sensitivity of X4 variants to CXCR4 antagonists such as peptide T22 and the synthetic compound AMD3100. We observed differences in the concentrations of CXCR4 antagonists needed to suppress replication of X4 HIV variants from different patients. In general, late X4 HIV variants were less sensitive to AMD3100 than were early R5X4 HIV variants. The differences between early R5X4 HIV variants and late X4 variants were less pronounced for T22-mediated inhibition. These results suggest an ongoing evolution of X4 virus variants toward more efficient usage of the cellular entry complex.     

Identification of a subset of human immunodeficiency virus type 1 (HIV-1), HIV-2, and simian immunodeficiency virus strains able to exploit an alternative coreceptor on untransformed human brain and lymphoid cells

The chemokine receptors CCR5 and CXCR4 are the major coreceptors for human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV). At least 12 other chemokine receptors or close relatives support infection by particular HIV and SIV strains on CD4(+) transformed indicator cell lines in vitro. However, the role of these alternative coreceptors in vivo is presently thought to be insignificant. Infection of cell lines expressing high levels of recombinant CD4 and coreceptors thus does not provide a true indication of coreceptor use in vivo. We therefore tested primary untransformed cell cultures that lack CCR5 and CXCR4, including astrocytes and brain microvascular endothelial cells (BMVECs), for naturally expressed alternative coreceptors functional for HIV and SIV infection. An adenovirus vector (Ad-CD4) was used to express CD4 in CD4(-) astrocytes and thus confer efficient infection if a functional coreceptor is present. Using a large panel of viruses with well-defined coreceptor usage, we identified a subset of HIV and SIV strains able to infect two astrocyte cultures derived from adult brain tissue. Astrocyte infection was partially inhibited by several chemokines, indicating a role for the chemokine receptor family in the observed infection. BMVECs were weakly positive for CD4 but negative for CCR5 and CXCR4 and were susceptible to infection by the same subset of isolates that infected astrocytes. BMVEC infection was efficiently inhibited by the chemokine vMIP-I, implicating one of its receptors as an alternative coreceptor for HIV and SIV infection. Furthermore, we tested whether the HIV type 1 and type 2 strains identified were able to infect peripheral blood mononuclear cells (PBMCs) via an alternative coreceptor. Several strains replicated in Delta32/Delta32 CCR5 PBMCs with CXCR4 blocked by AMD3100. This AMD3100-resistant replication was also sensitive to vMIP-I inhibition. The nature and potential role of this alternative coreceptor(s) in HIV infection in vivo is discussed.     

Human immunodeficiency virus type 1 (HIV-1)-induced GRO-alpha production stimulates HIV-1 replication in macrophages and T lymphocytes

We examined the early effects of infection by CCR5-using (R5 human immunodeficiency virus [HIV]) and CXCR4-using (X4 HIV) strains of HIV type 1 (HIV-1) on chemokine production by primary human monocyte-derived macrophages (MDM). While R5 HIV, but not X4 HIV, replicated in MDM, we found that the production of the C-X-C chemokine growth-regulated oncogene alpha (GRO-alpha) was markedly stimulated by X4 HIV and, to a much lesser extent, by R5 HIV. HIV-1 gp120 engagement of CXCR4 initiated the stimulation of GRO-alpha production, an effect blocked by antibodies to CXCR4. GRO-alpha then fed back and stimulated HIV-1 replication in both MDM and lymphocytes, and antibodies that neutralize GRO-alpha or CXCR2 (the receptor for GRO-alpha) markedly reduced viral replication in MDM and peripheral blood mononuclear cells. Therefore, activation of MDM by HIV-1 gp120 engagement of CXCR4 initiates an autocrine-paracrine loop that may be important in disease progression after the emergence of X4 HIV.