Exposure to bacterial products renders macrophages highly susceptible to T-tropic HIV-1.

Microbial coinfections variably influence HIV-1 infection through immune activation or direct interaction of microorganisms with HIV-1 or its target cells. In this study, we investigated whether exposure of macrophages to bacterial products impacts the susceptibility of these cells to HIV-1 of different cellular tropisms. We demonstrate that () macrophages exposed to bacterial cell wall components such as lipopolysaccharide (LPS) (Gram-negative rods), lipoteichoic acid (Gram-positive cocci), and lipoarabinomannan (Mycobacteria) become highly susceptible to T cell (T)-tropic HIV-1 (which otherwise poorly replicate in macrophages) and variably susceptible to macrophage (M)-tropic HIV-1; () LPS-stimulated macrophages secrete a number of soluble factors (i.e., chemokines, interferon, and proinflammatory cytokines) that variably affect HIV infection of macrophages, depending on the virus phenotype in question; and () LPS-stimulated macrophages express CCR5 (a major coreceptor for M-tropic HIV-1) at lower levels and CXCR4 (a major coreceptor for T-tropic HIV-1) at higher levels compared with unstimulated macrophages. We hypothesize that a more favorable environment for T-tropic HIV-1 and a less favorable or even unfavorable environment for M-tropic HIV-1 secondary to exposure of macrophages to those bacterial products may accerelate a transition from M- to T-tropic viral phenotype, which is indicative of disease progression.     

Effect of RANTES on the infection of monocyte-derived primary macrophages by human immunodeficiency virus type 1 and type 2

The effect of β chemokines on human immunodeficiency virus type I (HIV-1) infection of primary macrophages is controversial, and their effect on HIV-2 infection of these cells has not yet been documented. We examined the effect of synthetic and recombinant regulated-on-activation, normal T cell-expressed and -secreted (RANTES) on HIV-1 and HIV-2 infection of primary monocyte-derived-macrophages (MDM) that were obtained as the adherent cells of 5-day cultures of blood mononuclear cells (PBMC), followed by 2-day culture without peripheral blood mononuclear cells (PBMCs) nor added cytokines. These MDM expressed CD4, CCR5 and CXCR4, the major coreceptors for HIV macrophage- and T cell-tropic isolates, respectively. Infection of MDM from different donors with HIV-1 or HIV-2 macrophagetropic strains was reproducibly inhibited by RANTES. This inhibition depended on RANTES continuous presence in culture during and after infection. Treatment of MDM with RANTES just before or during, but not after, exposure to virus did not protect MDM from infection. When RANTES was added after MDM had been infected, and was continuously maintained in culture thereafter, no inhibition occurred and limited enhancement of infection could be observed. These data indicate that RANTES inhibits HIV-1 as well as HIV-2 infection of MDM, likely at a post-binding step, and support the role of CCR5 as the major coreceptor for HIV-1 and HIV-2 entry into primary macrophages.     

The B-oligomer of pertussis toxin deactivates CC chemokine receptor 5 and blocks entry of M-tropic HIV-1 strains.

Infection of target cells by HIV-1 requires initial binding interactions between the viral envelope glycoprotein gp120, the cell surface protein CD4, and one of the members of the seven-transmembrane G protein-coupled chemokine receptor family. Most primary isolates (R5 strains) use chemokine receptor CCR5, but some primary syncytium-inducing, as well as T cell line-adapted, strains (X4 strains) use the CXCR4 receptor. Signaling from both CCR5 and CXCR4 is mediated by pertussis toxin (PTX)-sensitive G(i) proteins and is not required for HIV-1 entry. Here, we show that the PTX holotoxin as well as its binding subunit, B-oligomer, which lacks G(i)-inhibitory activity, blocked entry of R5 but not X4 strains into primary T lymphocytes. Interestingly, B-oligomer inhibited virus production by peripheral blood mononuclear cell cultures infected with either R5 or X4 strains, indicating that it can affect HIV-1 replication at both entry and post-entry levels. T cells treated with B-oligomer did not initiate signal transduction in response to macrophage inflammatory protein (MIP)-1beta or RANTES (regulated upon activation, normal T cell expressed and secreted); however, cell surface expression of CCR5 and binding of MIP-1beta or HIV-1 to such cells were not impaired. The inhibitory effect of B-oligomer on signaling from CCR5 and on entry of R5 HIV-1 strains was reversed by protein kinase C (PKC) inhibitors, indicating that B-oligomer activity is mediated by signaling events that involve PKC. B-oligomer also blocked cocapping of CCR5 and CD4 induced by R5 HIV-1 in primary T cells, but did not affect cocapping of CXCR4 and CD4 after inoculation of the cultures with X4 HIV-1. These results suggest that the B-oligomer of PTX cross-deactivates CCR5 to impair its function as a coreceptor for HIV-1.     

Progress toward a human CD4/CCR5 transgenic rat model for de novo infection by human immunodeficiency virus type 1

The development of a permissive small animal model for the study of human immunodeficiency virus type (HIV)-1 pathogenesis and the testing of antiviral strategies has been hampered by the inability of HIV-1 to infect primary rodent cells productively. In this study, we explored transgenic rats expressing the HIV-1 receptor complex as a susceptible host. Rats transgenic for human CD4 (hCD4) and the human chemokine receptor CCR5 (hCCR5) were generated that express the transgenes in CD4(+) T lymphocytes, macrophages, and microglia. In ex vivo cultures, CD4(+) T lymphocytes, macrophages, and microglia from hCD4/hCCR5 transgenic rats were highly susceptible to infection by HIV-1 R5 viruses leading to expression of abundant levels of early HIV-1 gene products comparable to those found in human reference cultures. Primary rat macrophages and microglia, but not lymphocytes, from double-transgenic rats could be productively infected by various recombinant and primary R5 strains of HIV-1. Moreover, after systemic challenge with HIV-1, lymphatic organs from hCD4/hCCR5 transgenic rats contained episomal 2-long terminal repeat (LTR) circles, integrated provirus, and early viral gene products, demonstrating susceptibility to HIV-1 in vivo. Transgenic rats also displayed a low-level plasma viremia early in infection. Thus, transgenic rats expressing the appropriate human receptor complex are promising candidates for a small animal model of HIV-1 infection.     

Regulation of nitric oxide synthase activity in human immunodeficiency virus type 1 (HIV-1)-infected monocytes: implications for HIV- associated neurological disease

Mononuclear phagocytes (monocytes, macrophages, and dendritic cells) play major roles in human immunodeficiency virus (HIV) persistence and disease pathogenesis. Macrophage antigen presentation and effector cell functions are impaired by HIV-1 infection. Abnormalities of macrophage effector cell function in bone marrow, lung, and brain likely result as a direct consequence of cellular activation and HIV replication. To further elucidate the extent of macrophage dysfunction in HIV-1 disease, a critical activation-specific regulatory molecule, nitric oxide (NO.), which may contribute to diverse pathology, was studied. Little, if any, NO. is produced by uninfected human monocytes. In contrast, infection with HIV-1 increases NO. production to modest, but significant levels (2-5 microM). Monocyte activation (with lipopolysaccharide, tumor necrosis factor alpha, or through interactions with astroglial cells) further enhances NO. production in HIV-infected cells, whereas its levels are diminished by interleukin 4. These results suggest a possible role for NO. in HIV-associated pathology where virus-infected macrophages are found. In support of this hypothesis, RNA encoding the inducible NO synthase (iNOS) was detected in postmortem brain tissue from one pediatric AIDS patient with advanced HIV encephalitis. Corresponding iNOS mRNA was not detected in brain tissue from five AIDS patients who died with less significant brain disease. These results demonstrate that HIV-1 can influence the expression of NOS in both cultured human monocytes and brain tissue. This newly described feature of HIV-macrophage interactions suggests previously unappreciated mechanisms of tissue pathology that result from productive viral replication.     

Standardized peripheral blood mononuclear cell culture assay for determination of drug susceptibilities of clinical human immunodeficiency virus type 1 isolates. The RV-43 Study Group, the AIDS Clinical Trials Group Virology Committee Resistance Working Group.

A standardized antiviral drug susceptibility assay for clinical human immunodeficiency virus type 1 (HIV-1) isolates has been developed for use in clinical trials. The protocol is a two-step procedure that first involves cocultivation of patient infected peripheral blood mononuclear cells (PBMC) with seronegative phytohemagglutinin-stimulated donor PBMC to obtain an HIV-1 stock. The virus stock is titrated for viral infectivity (50% tissue culture infective dose) by use of serial fourfold virus dilutions in donor PBMC. A standardized inoculum of 1,000 50% tissue culture infective doses per 10(6) cells is used in the second step of the procedure to acutely infect seronegative donor PBMC in a 7-day microtiter plate assay with triplicate wells containing zidovudine (ZDV) concentrations ranging from 0 to 5.0 microM. The ZDV 50% inhibitory concentrations (IC50) for reference ZDV-susceptible and ZDV-resistant HIV-1 isolates ranged from 0.002 to 0.113 microM and from 0.15 to > 5.0 microM, respectively. Use of this consensus protocol reduced interlaboratory variability for ZDV IC50 determinations with reference HIV-1 isolates. Among eight laboratories, the coefficient of variation ranged from 0.85 to 1.25 with different PBMC protocols and was reduced to 0.39 to 0.98 with the standardized assay. Among the clinical HIV-1 isolates assayed by the standardized drug susceptibility assay, the median ZDV IC50 increased gradually with more ZDV therapy. This protocol provides an efficient and reproducible means to assess the in vitro susceptibility to antiretroviral agents of virtually all clinical HIV-1 isolates.     

Cytokines and HIV-1: interactions and clinical implications

Cytokines play an important role in controlling the homoeostasis of the immune system. Infection with HIV results in dysregulation of the cytokine profile in vivo and in vitro. During the course of HIV-1 infection secretion of T-helper type 1 (Th1) cytokines, such as interleukin (IL)-2, and antiviral interferon (IFN)-gamma, is generally decreased, whereas production of T helper type 2 (Th2) cytokines, IL-4, IL-10, proinflammatory cytokines (IL-1, IL-6, IL-8) and tumour necrosis factor (TNF)-alpha, is increased. Such abnormal cytokine production contributes to the pathogenesis of the disease by impairing cell-mediated immunity. A number of cytokines have been shown to modulate in vitro HIV-1 infection and replication in both CD4 T lymphocytes and cells of macrophage lineage. HIV-inductive cytokines include: TNF-alpha, TNF-beta, IL-1 and IL-6, which stimulate HIV-1 replication in T cells and monocyte-derived macrophages (MDM), IL-2, IL-7 and IL-15, which upregulate HIV-1 in T cells, and macrophage-colony stimulating factor, which stimulates HIV-1 in MDM. HIV-suppressive cytokines include: IFN-alpha, IFN-beta and IL-16, which inhibit HIV-1 replication in T cells and MDM, and IL-10 and IL-13, which inhibit HIV-1 in MDM. Bifunctional cytokines such as IFN-gamma, IL-4 and granulocyte-macrophage colony-stimulating factor have been shown to have both inhibitory and stimulatory effects on HIV-1. The beta-chemokines, macrophage-inflammatory protein (MIP)-1alpha, MIP-1beta and RANTES are important inhibitors of macrophage-tropic strains of HIV-1, whereas the alpha-chemokine stromal-derived factor-1 suppresses infection of T-tropic strains of HIV-1. This review outlines the interactions between cytokines and HIV-1, and presents clinical applications of cytokine therapy combined with highly active antiretroviral therapy or vaccines.     

Interleukin-4 inhibits tumor necrosis factor-alpha-induced and spontaneous apoptosis of biomaterial-adherent macrophages

Biocompatibility of implanted materials is determined by the host foreign-body response, which is comprised of cellular (adherent monocytes and macrophages) and soluble (secreted cytokines) components. Modulating the presence, activity or both of adherent macrophages may increase or decrease the biocompatibility of implants because these cells remain adherent to the implant surface and fuse to form foreign-body giant cells (FBGCs), leading to failure of the implant. An attractive mechanism of eliminating these cells is through the induction of apoptosis; therefore ways of inducing or inhibiting apoptosis of biomaterial-adherent inflammatory cells are being investigated. We hypothesized that interleukin-4 (IL-4) promotes macrophage survival by inhibiting tumor necrosis factor-alpha (TNF-alpha)-induced apoptosis. We found that TNF-alpha induces apoptosis in a time- and dose-dependent manner, whereas IL-4 inhibits TNF-alpha-induced and spontaneous apoptosis of biomaterial-adherent macrophages. Blocking experiments and evaluation of shedding of soluble TNF receptor type I (TNF-RI) demonstrated that endogenous TNF-alpha production is responsible for spontaneous apoptosis of biomaterial-adherent cells and that IL-4 inhibits this apoptosis by increasing levels of shedding of soluble TNF-RI. These findings suggest that TNF-alpha and IL-4 play key roles in determining the fate of biomaterial-adherent cells and that fusion of macrophages into FBGCs is a mechanism for promoting inflammatory-cell survival on implanted materials.     

In vitro comparison of topical microbicides for prevention of human immunodeficiency virus type 1 transmission

A standardized protocol was used to compare cellular toxicities and anti-human immunodeficiency virus type 1 (HIV-1) activities of candidate microbicides formulated for human use. The microbicides evaluated were cellulose acetate phthalate (CAP), Carraguard, K-Y plus nonoxynol-9 (KY-N9), PRO 2000 (0.5 and 4%), SPL7013 (5%), UC781 (0.1 and 1%), and Vena Gel, along with their accompanying placebos. Products were evaluated for toxicity on cervical and colorectal epithelial cell lines, peripheral blood mononuclear cells (PBMCs), and macrophages (MPhi) by using an ATP release assay, and they were tested for their effect on transepithelial resistance (TER) of polarized epithelial monolayers. Anti-HIV-1 activity was evaluated in assays for transfer of infectious HIV-1 from epithelial cells to activated PBMCs and for PBMC and MPhi infection. CAP, Carraguard, PRO 2000, SPL7013, and UC781 along with their placebos were 20- to 50-fold less toxic than KY-N9 and Vena Gel. None of the nontoxic product concentrations disrupted the TER. Transfer of HIV-1(Ba-L) from epithelial cells to PBMCs and PBMC and MPhi infection with laboratory-adapted HIV-1(Ba-L) and HIV-1(LAI) isolates were inhibited by all products except Carraguard, KY-N9, and Vena Gel. KY-N9, Vena Gel, and Carraguard were not effective in blocking PBMC infection with primary HIV-1(A), HIV-1(C), and HIV-1(CRF01-AE) isolates. The concordance of these toxicity results with those previously reported indicates that our protocol may be useful for predicting toxicity in vivo. Moreover, our systematic anti-HIV-1 testing provides a rational basis for making better informed decisions about which products to consider for clinical trials.     

人外周血NKT细胞体外扩增及其分泌细胞因子的研究

目的　建立人外周血自然杀伤T细胞 (NKT)体外扩增及检测NKT细胞所分泌的细胞因子的方法。方法　分别采用单加α 半乳糖神经酰胺 (α Galcer组 ) ,单加树突状细胞 (DC组 )以及同时加α Galcer、DC(α Galcer、DC组 )的方法从人外周血单个核细胞 (PBMC)和纯化T淋巴细胞中扩增TCRVα2 4+ /TCRVβ1 1 + NKT细胞。采用细胞内细胞因子流式细胞术检测手段测定NKT细胞中IL 4 ,IFN γ、TNF α阳性细胞比例。结果　PBMC中的α Galcer组 ,DC、α Galcer组和纯化T淋巴细胞中的DC、α Galcer组 ,NKT细胞扩增 1 9d后分别占淋巴细胞的 (2 5 .5± 7.2 ) %、(1 8.2± 8.2 ) %和 (2 4 .8± 5 .5 ) % ,NKT细胞分别扩增了 (1 5 .1± 9.1 )× 1 0 3 倍、(2 1 .8± 1 7.3)× 1 0 3 倍和 (2 3.0± 1 6 .7)× 1 0 3 倍 ,与其它各组差异有显著性意义 (P <0 .0 1 )。扩增过程TCRVβ1 1+ NKT细胞中分泌IL 4 ,IFN γ和TNF α的细胞比例均高于TCRVβ1 1 T淋巴细胞 (P <0 .0 5 )。结论　α Galcer具有体外大量扩增NKT细胞的能力 ,同时α Galcer的激活能力受CD1d分子的限制。由于PBMC中的单核系细胞也表达CD1d分子 ,因此直接从PBMC扩增NKT也能获得良好的效果     

Transduction of Human PBMC-Derived Dendritic Cells and Macrophages by an HIV-1-Based Lentiviral Vector System

Professional antigen-presenting cells, such as dendritic cells (DCs) and macrophages, are target cells for gene therapy of infectious disease and cancer. However, transduction of DCs and macrophages has proved difficult by most currently available gene transfer methods. Several recent studies have shown that lentiviral vector systems can efficiently transduce many nondividing and differentiated cell types. In this study, we examined the gene transfer to DCs and macrophages using a lentiviral vector system. Human DCs were propagated from the adherent fraction of peripheral blood mononuclear cells (PBMCs) by culture in medium containing GM-CSF, IL-4, and TNF-α. Human macrophages were propagated from adherent PBMCs in medium containing GM-CSF. High titers of a replication-defective vesicular stomatitis virus glycoprotein G pseudotyped HIV-1-based vector encoding the enhanced yellow fluorescent protein were produced. In immature DCs (culture days 3 and 5), transduction efficiencies of 25 to 35% were achieved at a multiplicity of infection of 100. However, the transduction efficiency was decreased in more mature DCs (culture day 8 or later). Furthermore, monocyte-derived macrophages were also transduced by the lentiviral vector system. In addition, Alu-LTR PCR demonstrated the integration of the HIV-1 provirus into the cellular genome of the transduced DCs and macrophages. Allogeneic mixed lymphocyte reactions revealed similar antigen-presenting functions of untransduced and lentivirally transduced DCs. Thus, the results of this study demonstrate that both PBMC-derived DCs and macrophages can be transduced by lentiviral vectors.     

CCR5 Levels and Expression Pattern Correlate with Infectability by Macrophage-tropic HIV-1, In Vitro

Chemokine receptors serve as coreceptors for HIV entry into CD4⁺ cells. Their expression is thought to determine the tropism of viral strains for different cell types, and also to influence susceptibility to infection and rates of disease progression. Of the chemokine receptors, CCR5 is the most important for viral transmission, since CCR5 is the principal receptor for primary, macrophage-tropic viruses, and individuals homozygous for a defective CCR5 allele (Δ32/ Δ32) are highly resistant to infection with HIV-1. In this study, CCR5-specific mAbs were generated using transfectants expressing high levels of CCR5. The specificity of these mAbs was confirmed using a broad panel of chemokine receptor transfectants, and by their non-reactivity with T cells from Δ32/Δ32 individuals. CCR5 showed a distinct pattern of expression, being abundant on long-term activated, IL-2–stimulated T cells, on a subset of effector/memory T cells in blood, and on tissue macrophages. A comparison of normal and CCR5 Δ32 heterozygotes revealed markedly reduced expression of CCR5 on T cells from the heterozygotes. There was considerable individual to individual variability in the expression of CCR5 on blood T cells, that related to factors other than CCR5 genotype. Low expression of CCR5 correlated with the reduced infectability of T cells with macrophage-tropic HIV-1, in vitro. Anti-CCR5 mAbs inhibited the infection of PBMC by macrophage-tropic HIV-1 in vitro, but did not inhibit infection by T cell–tropic virus. Anti-CCR5 mAbs were poor inhibitors of chemokine binding, indicating that HIV-1 and ligands bind to separate, but overlapping regions of CCR5. These results illustrate many of the important biological features of CCR5, and demonstrate the feasibility of blocking macrophage-tropic HIV-1 entry into cells with an anti-CCR5 reagent.     

Cellular Pharmacology and Potency of HIV-1 Nucleoside Analogs in Primary Human Macrophages

Understanding the cellular pharmacology of antiretroviral agents in macrophages and subsequent correlation with antiviral potency provides a sentinel foundation for definition of the dynamics between antiretroviral agents and viral reservoirs across multiple cell types, with the goal of eradication of HIV-1 from these cells. Various clinically relevant nucleoside antiviral agents, and the integrase inhibitor raltegravir, were selected for this study. The intracellular concentrations of the active metabolites of the nucleoside analogs were found to be 5- to 140-fold lower in macrophages than in lymphocytes, and their antiviral potency was significantly lower in macrophages constitutively activated with macrophage colony-stimulating factor (M-CSF) during acute infection than in resting macrophages (EC₅₀, 0.4 to 9.42 μM versus 0.03 to 0.4 μM, respectively). Although tenofovir-treated cells displayed significantly lower intracellular drug levels than cells treated with its prodrug, tenofovir disoproxil fumarate, the levels of tenofovir-diphosphate for tenofovir-treated cells were similar in lymphocytes and macrophages. Raltegravir also displayed significantly lower intracellular concentrations in macrophages than in lymphocytes, independent of the activation state, but had similar potencies in resting and activated macrophages. These data underscore the importance of delivering adequate levels of drug to macrophages to reduce and eradicate HIV-1 infection.     

C-reactive protein contributes to the hypercoagulable state in coronary artery disease

OBJECTIVES: Elevated plasma C-reactive protein (CRP) levels predict coronary events, but it is unclear whether CRP plays a role in thrombosis associated with these events. We investigated tissue factor (TF) induction by CRP on peripheral blood mononuclear cells (PBMC) from patients with coronary disease. PATIENTS AND METHODS: PBMC from 35 patients with stable angina (SA) in study 1, 10 male patients with SA, 10 with unstable angina (UA) and 10 matched controls in study 2, and 25 patients with inflammatory disorders (ID) and 24 normal controls in study 3 were stimulated with CRP, interferon-gamma (IFN) or lipopolysaccharide (LPS), or their combination. PBMC from additional normal donors were also stimulated with CRP in adherent and non-adherent conditions, and TF activity, antigen and mRNA expression detected. RESULTS: CRP (5-25 microg mL(-1)) dose dependently induced more TF on PBMC from SA patients than 42 contemporary controls (P = 0.001, study 1). Compared with controls, patients with SA or UA had higher basal, and much higher CRP- or CRP/LPS-induced monocyte TF activity although serum CRP levels were similar (study 2). IFN induced monocyte TF activity in patients with angina, but not in controls. Basal or CRP-induced TF levels did not differ between controls and ID, even though ID patients had much higher serum CRP levels (study 3). CRP-induced monocyte TF activity correlated with serum CRP levels in controls (P = 0.005) and ID (P = 0.007) in study 3, but not in patients with angina (P =0.84) in study 2. CRP induced more TF activity, protein and mRNA under adherent than non-adherent conditions implying that it may mainly target macrophages in lymphocyte-rich lesions. CONCLUSIONS: Our results indicate that monocytes from patients with angina are preactivated and express TF but CRP is unlikely to be a major priming factor in vivo. IFN and CRP further increase TF levels that may contribute to the hypercoagulable state in coronary disease.     

Prognostic value of blood and bone marrow T-colony-forming cells (T-CFC) in patients with lymphadenopathy syndrome (LAS)

The in vitro proliferation capacity of peripheral blood committed T-cell precursors (T-CFC) from LAS patients was studied in order to define whether this parameter could be associated with transition to AIDS. In all patients a significantly (P less than 0.0001) decreased plating efficiency was detected. However, the lowest T-cell colony growth (less than 50 colonies/5 x 10(4) cells) was observed in the 23 patients who subsequently developed the full-blown disease within 150-570 days. Conversely, only one patient (n = 107) whose T-CFC generated greater than 50 colonies/5 x 10(4) cells developed AIDS after a mean follow-up of 867 days (range 120-1260 days). T-CFC from these patients displayed an impaired in vitro differentiation and self-renewal capacity which was independent of the clinical evolution of the disease. In 5 out of 12 AIDS patients, adherent cell-depletion of peripheral blood mononuclear cells (PBMC) enhanced the plating efficiency. Moreover, patients' but not normal adherent cells could inhibit normal T-cell colony growth in a dose-dependent manner. Media conditioned by patients' unstimulated adherent cells (LCM-A+p) also inhibited normal T-cell colony formation. In addition, LCM-A+p were capable of inhibiting interleukin 2-receptor (IL 2-R) expression and interleukin 2 (IL 2) production by normal mitogen-stimulated T-cells. These findings suggest that adherent cell-derived inhibitory activity(ies) could be responsible for the low T-cell colony formation observed in some AIDS patients.     

Blockade of CC chemokine receptor 5 (CCR5)-tropic human immunodeficiency virus-1 replication in human lymphoid tissue by CC chemokines.

The CC chemokines MIP-1alpha, MIP-1beta, and RANTES suppress replication of certain HIV-1 strains in cultured PBMC and T cell lines by blocking interaction of gp120 with CC chemokine receptor 5 (CCR5). However, the same chemokines can enhance HIV-1 replication in cultured macrophages. The net effect of chemokines on HIV-1 infection in intact lymphoid tissue, the major reservoir of HIV-1 in vivo, is unknown and unpredictable since the tissue contains both T lymphocytes and macrophages. Here we show that exogenous MIP-1alpha, MIP-1beta, and RANTES markedly suppressed replication of CCR5-tropic HIV-1 strains in blocks of human lymphoid tissue infected ex vivo. Moreover, endogenous MIP-1alpha, MIP-1beta, and RANTES were upregulated in tissues infected ex vivo with CXC chemokine receptor 4-tropic but not CCR5-tropic HIV-1. Such an upregulation may contribute to the virus phenotype shift in the course of HIV disease in vivo.