Uniform detection of HIV-1 in alveolar macrophages of pediatric but not adult AIDS patients

HIV-1 envelope-receptor interactions required for macrophage infection and implications for current HIV-1 cure strategies

Myeloid cells residing in the CNS and lymphoid tissues are targets for productive HIV-1 replication, and their infection contributes to the pathological manifestations of HIV-1 infection. The Envs can adopt altered configurations to overcome entry restrictions in macrophages via a more efficient and/or altered mechanism of engagement with cellular receptors. This review highlights evidence supporting an important role for macrophages in HIV-1 pathogenesis and persistence, which need to be considered for strategies aimed at achieving a functional or sterilizing cure. We also highlight that the molecular mechanisms underlying HIV-1 tropism for macrophages are complex, involving enhanced and/or altered interactions with CD4, CCR5, and/or CXCR4, and that the nature of these interactions may depend on the anatomical location of the virus.

Proteomic landscape of bronchoalveolar lavage fluid in human immunodeficiency virus infection

The lung is an important reservoir of human immunodeficiency virus (HIV). Individuals infected with HIV are more prone to pulmonary infections and chronic lung disorders. We hypothesized that comprehensively profiling the proteomic landscape of bronchoalveolar lavage fluid (BALF) in patients with HIV would provide insights into how this virus alters the lung milieu and contributes to pathogenesis of HIV-related lung diseases. BALF was obtained from five HIV-negative (HIV(-)) and six asymptomatic HIV-positive (HIV(+)) subjects not on antiretroviral therapy. Each sample underwent shotgun proteomic analysis based on HPLC-tandem mass spectrometry. Differentially expressed proteins between the groups were identified using statistical methods based on spectral counting. Mechanisms of disease were explored using functional annotation to identify overlapping and distinct pathways enriched between the BALF proteome of HIV(+) and HIV(-) subjects. We identified a total of 318 unique proteins in BALF of HIV(-) and HIV(+) subjects. Of these, 87 were differentially up- or downregulated between the two groups. Many of these differentially expressed proteins are known to interact with key HIV proteins. Functional analysis of differentially regulated proteins implicated downregulation of immune responses in lungs of HIV(+) patients. Combining shotgun proteomic analysis with computational methods demonstrated that the BALF proteome is significantly altered during HIV infection. We found that immunity-related pathways are underrepresented in HIV(+) patients. These findings implicate mechanisms whereby HIV invokes local immunosuppression in the lung and increases the susceptibility of HIV(+) patients to develop a wide range of infectious and noninfectious pulmonary diseases.

HIV-1 Tat promotes monocyte chemoattractant protein-1 secretion followed by transmigration of monocytes

The mechanism whereby HIV-infected cells transit from the bloodstream into tissues is not well defined. This phenomenon was addressed by studying the effects of HIV-1 Tat, a protein secreted by infected cells, on human lung microvascular endothelial cells (HMVEC-Ls). It was found that monocyte chemoattractant protein-1 (MCP-1) was released from HMVEC-Ls in a dose- and time-dependent manner after Tat treatment. MCP-1 is a potent beta-chemokine that recruits monocytes and T cells and promotes cell adhesion and transmigration across an endothelial monolayer. It was also observed that MCP-1 and the culture medium from Tat-treated HMVEC-Ls were chemotactic for CD14(+) monocytes from human peripheral blood and for THP-1, a promonocytic cell line used as a model system. To characterize the signaling pathways underlying the observed induction of MCP-1, HMVEC-Ls were treated with 2 different protein kinase inhibitors: PD98059, a MAP kinase inhibitor, and GF109203X, a protein kinase C (PKC) inhibitor. MCP-1 release was significantly reduced when PKC was inhibited, and slightly decreased when PI3 kinase was blocked; no effect on MCP-1 release was observed on MAP kinase inhibition. Similarly, transmigration of THP-1 cells was significantly impaired by the PKC inhibitor, but not by the other tested inhibitors. These data indicate that the HIV-1 Tat protein may act as a protocytokine by causing the release of MCP-1 from the endothelial monolayer, and thereby facilitating monocyte transmigration into tissues via a PKC signaling pathway.

NF-kappa B modulates TNF-alpha production by alveolar macrophages in asymptomatic HIV-seropositive individuals

Local TNF-alpha production in different organs may affect HIV replication and pathogenesis. Alveolar macrophages (AMs) obtained by bronchoalveolar lavage from asymptomatic HIV-seropositive and HIV-seronegative individuals did not spontaneously release TNF-alpha, but LPS stimulation of these cells significantly increased TNF-alpha production. We tested whether NF-kappa B affects TNF-alpha production by AMs using N-tosyl-<cmd SC>l<cmd /SC> -phenylalanine chloromethylketone (TPCK) or N-benzoyl-<cmd SC>l<cmd /SC> -tyrosine ethyl ester (BTEE), which inhibit the degradation of I kappa B, or tricyclodecan-9-yl-xanthogenate-potassium (D609), which inhibits phospholipase C. Alveolar macrophages were exposed to LPS alone and with the chemical protease inhibitors TPCK, BTEE, and D609. NF-kappa B DNA binding induced by LPS treatment of AMs was inhibited by TPCK, BTEE, and D609. These agents also inhibited TNF-alpha mRNA and TNF-alpha protein production. After 24 h, the levels of TNF-alpha mRNA reached equilibrium, as assessed by RT-PCR. The levels of NF-kappa B mRNA remained constant under all conditions. The levels of I kappa B-alpha mRNA were similar after 30, 60, and 180 min, but the I kappa B-beta mRNA concentration was initially low and increased over time under all conditions. I kappa B-alpha and I kappa B-beta protein production was not affected by the chemical protease inhibitors. Our data show that TNF-alpha production by LPS-stimulated AMs from asymptomatic HIV-seropositive and -seronegative individuals is regulated via the phospholipase C pathway and by NF-kappa B DNA binding activity without obvious changes in I kappa B-alpha or I kappa B-beta protein concentrations.

The growth and the control of human immunodeficiency virus in the lung: implications for highly active antiretroviral therapy

In recent years, it has become apparent that the lung is an important niche for the proliferation of human immunodeficiency virus (HIV), which may have implications for highly active antiretroviral therapy (HAART). The lung itself is a major site for the opportunistic infections associated with the progression to acquired immune deficiency syndrome (AIDS), specifically Pneumocystis carinii, Myobacterium tuberculosis and pyogenic bacteria. These cases of active pulmonary complications are direct indicators of enhanced progression to AIDS-defining illness and increased morbidity and mortality. It is therefore essential that the interaction between the lung and HIV is fully understood. Recent research indicates the lung may be a major sanctuary for the virus, with distinct evolution and replication in contrast to other target organs for HIV. In this review, we will discuss the recent findings of HIV infection, evolution, host factors involved in the control of HIV within the lung and the impact this may have on current therapy.

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.

Pediatric AIDS-associated lymphocytic interstitial pneumonia and pulmonary arterio-occlusive disease: role of VCAM-1/VLA-4 adhesion pathway and human herpesviruses

Because the mechanisms of lymphocyte accumulation in the lungs of children with AIDS-associated lymphocytic interstitial pneumonia (LIP) are unknown, we studied the relative contributions of known adhesion pathways in mediating lymphocyte adherence to endothelium and the potential role of human herpesviruses in the expansion of these lesions. LIP was characterized by lymphoid hyperplasia of the bronchus-associated lymphoid tissue (BALT) and infiltration of the pulmonary interstitium with CD8(+) T lymphocytes. In some individuals there was expansion of the alveolar septae with dense aggregates of B lymphocytes, many containing the Epstein-Barr viral (EBV) genome. Patients with concurrent EBV infection also demonstrated large-vessel arteriopathy characterized by thickening of the intimae with collagen and smooth muscle. Venular endothelium from the lung of children with LIP, but not uninflamed lung from other children with AIDS or lung from children with nonspecific pneumonitis, expressed high levels of vascular cell adhesion molecule-1 (VCAM-1) protein. In turn, inflammatory cells expressing very late activation antigen-4 (VLA-4), the leukocyte ligand for VCAM-1, were the predominant perivascular infiltrate associated with vessels expressing VCAM-1. Expression of other endothelial adhesion molecules, including intracellular adhesion molecule-1 and E-selectin, was not uniformly associated with LIP. Using a tissue adhesion assay combined with immunohistochemistry for VCAM-1, we show that CD8(+) T cell clones that express VLA-4 bind preferentially to pulmonary vessels in sites of LIP: vessels that expressed high levels of VCAM-1. When tissues and cells were pretreated with antibodies to VCAM-1 or VLA-4, respectively, adhesion was inhibited by >/=80%. Thus, infiltration of alveolar septae with CD8(+) T cells was highly correlative with VCAM-1/VLA-4 adhesive interactions, and focal expansion of B cells was coincidental to co-infection with EBV.

Tumor necrosis factor-alpha responses are depressed and interleukin-6 responses unaltered in feline immunodeficiency virus infected cats

Feline immunodeficiency virus (FIV), a lentivirus similar to HIV, causes an acquired immunodeficiency syndrome in cats. Similar to human immunodeficiency virus (HIV), the pathogenesis of FIV is associated with dysregulation of the cytokine network. While alterations in tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) expression have been reported in HIV-infected patients, changes attributable to HIV and those caused by cofactors such as secondary infections cannot always be readily distinguished. This study evaluated the effect of FIV infection on TNF-alpha and IL-6 production in cats not exposed to other potential cofactors such as secondary infections. TNF-alpha and IL-6 activities were evaluated in bronchoalveolar lavage (BAL) cells from FIV-infected and uninfected specific pathogen free (SPF) cats. Supernatants from lipopolysaccharide (LPS)-stimulated BAL cells from uninfected SPF cats had high levels of TNF-alpha and IL-6 activity, while stimulated BAL cell supernatants from FIV-infected SPF cats had significantly lower levels of TNF-alpha but unaltered IL-6 activity. Similarly, Con A/phorbol myristate acetate (PMA) stimulated non-adherent (NA-) peripheral blood mononuclear cells (PBMC) from FIV infected cats synthesized less TNF-alpha than similarly treated NA-PBMC from uninfected cats. Feline immunodeficiency virus could be recovered from the culture supernatants of BAL cells from infected cats by co-cultivation with susceptible lymphocytes. In situ hybridization identified FIV mRNA in a small fraction of alveolar macrophages in the BAL cell cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Dysregulation of interleukin 8, interleukin 10, and interleukin 12 release by alveolar macrophages from HIV type 1-infected subjects

We examined the in vitro release of interleukin 8 (IL-8), interleukin 10 (IL-10), and interleukin 12 (IL-12) by alveolar macrophages from normal volunteers and HIV-1-infected subjects. Normal volunteers had very low levels of IL-8 and IL-10 and undetectable IL-12 in the cell-free bronchoalveolar lavage fluid (BALF). Asymptomatic HIV-1-infected subjects had elevated levels of IL-8 and IL-10 in their BALF, and HIV-1-infected subjects with nonspecific interstitial pneumonitis (NIP) or infected with Pneumocystis carinii had the highest BALF levels of IL-10 and IL-8. It was found that alveolar macrophages from asymptomatic HIV-1 subjects and from NIP subjects spontaneously released elevated IL-8, IL-10, and IL-12. However, AIDS subjects infected with P. carinii had cells that released elevated levels of IL-10 and IL-8, but low levels of IL-12. When alveolar macrophages were stimulated with Staphylococcus aureus Cowan (SAC), cells from normal volunteers responded with a considerably increased release of IL-8, IL-10, and IL-12; cells from HIV-1-infected subjects without P. carinii infection responded with a moderate increase in release of all three monokines. SAC stimulation did not enhance the release of monokines by cells from AIDS subjects with P. carinii infection, and IL-12 levels remained low. There was no strict relationship between spontaneous cytokine release and p24 HIV-1 antigen expression by alveolar macrophages. Finally, we showed that neutralizing IL-10 production by alveolar macrophages from AIDS subjects substantially increased IL-12 releasability.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of surface markers on alveolar macrophages from symptomatic patients with HIV infection as detected by flow cytometry

Alveolar macrophages (AMs) harvested from 32 HIV-infected patients with respiratory problems (opportunistic pulmonary infections, n = 12; other lung disease, n = 20) and 13 healthy controls were stained with a panel of 15 monoclonal antibodies directed against surface antigens implicated in cell function. Antigen expression was quantified by flow cytometry and expressed as relative linear median fluorescence intensity (RLMFI). On AMs of patients, as compared with controls, there was a significant enhancement of HLA DP (12.1 +/- 1.5 vs 6.5 +/- 0.9, p = 0.01, M +/- SEM, RLMFI units), CD11b (3.4 +/- 0.5 vs 1.7 +/- 0.4, p = 0.014), CD11c (8.9 +/- 1.0 vs 4.8 +/- 0.8, p = 0.0046), CD14 (2.1 +/- 0.3 vs 1.0 +/- 0.2, p = 0.0009), and CD33 (1.7 +/- 0.1 vs 1.0 +/- 0.2, p = 0.0093). No significant differences could be established for HLA-DR (36.9 +/- 5.8 vs 30.9 +/- 7.5, NS), HLA-DQ (3.4 +/- 0.3 vs 3.1 +/- 0.6, NS), CD54 (1.9 +/- 0.3 vs 1.2 +/- 0.1, NS), CD13 (2.5 +/- 0.6 vs 1.5 +/- 0.3, NS), CD36 (1.4 +/- 0.2 vs 0.9 +/- 0.3, NS), CD71 (10.3 +/- 1.9 vs 8.9 +/- 1.8, NS), CD25 (0.8 +/- 0.0 vs 0.9 +/- 0.1, NS), 27E10 (1.1 +/- 0.1 vs 0.8 +/- 0.3, NS), RM3/1 (1.9 +/- 0.4 vs 1.5 +/- 0.4, NS), and CD4 (1.5 +/- 0.3 vs 1.0 +/- 0.0, NS). The expression of CD14 and CD11b, but not of HLA class II antigens and CD71, was increased in the smaller cell population compared with the larger, thus suggesting monocyte recruitment. The increased expression of HLA-DP, CD11c, CD14, and CD33 on the patients' AMs was independent of smoking habits. The degree of immunodeficiency as indicated by the absolute peripheral CD4 count, the character of HIV-related pulmonary disease, and the prophylactic use of pentamidine or zidovudine did not significantly modify the antigen expression pattern. It is concluded that HIV infection may lead, most probably indirectly, to enhanced expression of surface antigens by local upregulation and/or recruitment of monocytes from the peripheral circulation. The functional significance of enhanced marker expression requires further clarification.

Alveolar macrophages from subjects infected with HIV-1 express macrophage inflammatory protein-1 alpha (MIP-1 alpha): contribution to the CD8+ alveolitis

We examined the synthesis and release of MIP-1 alpha in alveolar macrophages obtained from normal subjects or subjects infected with HIV-1, at different stages of the disease. HIV-1-infected subjects in groups II, III and IV all had significant interstitial pneumonitis, featuring a significant infiltration of CD8+ lymphocytes in the bronchoalveolar lavage. Alveolar macrophages from HIV-1-infected subjects were shown to express significant levels of MIP-1 alpha via immunohistochemistry, both spontaneously and in response to lipopolysaccharide (LPS), whereas cells from normal subjects expressed very low levels of the cytokine. Supernatants of alveolar macrophages from HIV-1-infected subjects exerted strong chemotactic activity for purified activated blood CD8+ T lymphocytes, which was strongly inhibited by neutralizing MIP-1 alpha. Studies of patients with HIV-1 infection at different stages of the disease showed that MIP-1 alpha secretion increased as viral infection developed. There was a significant positive correlation between MIP-1 alpha secretion and the CD8+ alveolitis in HIV-1-infected subjects. Infection of alveolar macrophages in vitro with three distinct strains of HIV-1 which replicated profusely in macrophages did not induce the expression of MIP-1 alpha. Collectively, these data suggest that HIV-1 infection in vivo induces MIP-1 alpha expression and release in alveolar macrophages, and this appears to contribute significantly to the alveolar lymphocytosis seen in HIV-1-infected subjects.