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M Pope

Publications and source records attributed to M Pope.

At least 19 recordsLinked to original sources
PubMed1999

Mucosal dendritic cells and immunodeficiency viruses.

Dendritic cells [DCs] have been implicated in the pathogenesis of human immunodeficiency virus type 1 (HIV-1). When skin was used as a model for mucosae, the cutaneous DC-T cell milieu allowed the growth of HIV-1 and much of the newly produced virus could be detected in multinucleated DC-T cell syncytia. Such virus replication occurs irrespective of the genetic subtype, the syncytium- and non-syncytium-inducing capacities of the viruses, and whether they are classified as T cell- or macrophage-tropic. Similar DC-syncytia have been identified within the mucosal surfaces of the tonsillar tissue of HIV-1-infected persons. More recently, it was demonstrated that DC-T cell mixtures from the skin, mucosae, and blood of healthy macaques similarly support the replication of simian immunodeficiency virus. In both the human and monkey systems, active virus replication requires the presence of both DCs and T cells. Further studies using the macaque model are underway to elucidate the role of DCs in the transmission and spread of HIV infection.

Animals↗
PubMed1998

A physiologic function for p-glycoprotein (MDR-1) during the migration of dendritic cells from skin via afferent lymphatic vessels.

P-glycoprotein (MDR-1) is a well-known transporter that mediates efflux of chemotherapeutic agents from the intracellular milieu and thereby contributes to drug resistance. MDR-1 also is expressed by nonmalignant cells, including leukocytes, but physiologic functions for MDR-1 are poorly defined. Using an initial screening assay that included >100 mAbs, we observed that neutralizing mAbs MRK16, UIC2, and 4E3 against MDR-1 specifically and potently blocked basal-to-apical transendothelial migration of mononuclear phagocytes, a process that may mimic their migration into lymphatic vessels. Antagonists of MDR-1 then were used in a model of authentic lymphatic clearance. In this model, antigen-presenting dendritic cells (DC) migrate out of explants of cultured human skin and into the culture medium via dermal lymphatic vessels. DC and T cells derived from skin expressed MDR-1 on their surfaces. Addition of anti-MDR-1 mAbs MRK16, UIC2, or the MDR-1 antagonist verapamil to skin explants at the onset of culture inhibited the appearance of DC, and accompanying T cells, in the culture medium by approximately 70%. Isotype-matched control mAbs against other DC molecules including CD18, CD31, and major histocompatibility complex I did not block. In the presence of MDR-1 antagonists, epidermal DC were retained in the epidermis, in contrast to control conditions. In summary, this work identifies a physiologic function for MDR-1 during the mobilization of DC and begins to elucidate how these critical antigen-presenting cells migrate from the periphery to lymph nodes to initiate T lymphocyte-mediated immunity.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Resistance of naive mice to murine hepatitis virus strain 3 requires development of a Th1, but not a Th2, response, whereas pre-existing antibody partially protects against primary infection.

Murine hepatitis virus strain 3 (MHV-3) produces a host-strain-dependent spectrum of disease. The development of liver necrosis has been shown to be related to production of a unique macrophage procoagulant activity (PCA), encoded by the gene fgl-2, in susceptible mice. These studies were designed to examine the influence of Th1/Th2 cells on resistance/susceptibility and production of macrophage procoagulant activity (PCA) in resistant (A/J) and susceptible (Balb/cJ) strains of mice following infection with MHV-3. Immunization of A/J mice with MHV-3 induced a Th1 cellular immune response and one Th1 cell line (3F9.1) protected susceptible mice and inhibited production of PCA by macrophages both in vitro and in vivo. In contrast, immunization of Balb/cJ mice with an attenuated variant of MHV-3 derived from passaging MHV-3 in YAC-1 cells resulted in a Th2 response. Transfer of spleen cells and T cell lines from immunized Balb/cJ mice failed to protect naive susceptible syngeneic mice from infection with MHV-3 and augmented production of IL-1 beta, TNF-alpha and PCA by macrophages to MHV-3 in vitro. Serum from immunized Balb/cJ mice contained high titered neutralizing antibody which protected naive Balb/cJ animals from lethal primary MHV-3 infection. These results demonstrate that susceptible Balb/cJ mice generate a Th2 response following MHV-3 infection and that these Th2 cells neither inhibit MHV-3-induced macrophage PCA production nor protect naive mice from MHV-3 infection. The results suggest that antibody protects against primary infection, but could not eradicate ongoing infection. Ribavirin, a synthetic guanosine analogue prolonged survival to MHV-3 infection, inhibited production and transcription of the macrophage pro-inflammatory cytokines IL-1 beta and TNF-alpha and Th2 cytokines while preserving Th1 cytokine production. Thus, this data defines the differential role of Th1/Th2 lymphocytes in primary and secondary MHV-3 infection and further defines the importance of macrophage inflammatory mediators in the pathogenesis of MHV-3 infection.

Animals↗
PubMed1998

Neutralizing monoclonal antibodies block human immunodeficiency virus type 1 infection of dendritic cells and transmission to T cells.

Prevention of the initial infection of mucosal dendritic cells (DC) and interruption of the subsequent transmission of HIV-1 from DC to T cells are likely to be important attributes of an effective human immunodeficiency virus type 1 (HIV-1) vaccine. While anti-HIV-1 neutralizing antibodies have been difficult to elicit by immunization, there are several human monoclonal antibodies (MAbs) that effectively neutralize virus infection of activated T cells. We investigated the ability of three well-characterized neutralizing MAbs (IgG1b12, 2F5, and 2G12) to block HIV-1 infection of human DC. DC were generated from CD14(+) blood cells or obtained from cadaveric human skin. The MAbs prevented viral entry into purified DC and the ensuing productive infection in DC/T-cell cultures. When DC were first pulsed with HIV-1, MAbs blocked the subsequent transmission to unstimulated CD3(+) T cells. Thus, neutralizing antibodies can block HIV-1 infection of DC and the cell-to-cell transmission of virus from infected DC to T cells. These data suggest that neutralizing antibodies could interrupt the initial events associated with mucosal transmission and regional spread of HIV-1.

Antibodies, Monoclonal↗
PubMed1998

Resistance to murine hepatitis virus strain 3 is dependent on production of nitric oxide.

The strain-specific spectrum of liver disease following murine hepatitis virus type 3 (MHV-3) infection is dependent on inflammatory mediators released by macrophages. Production of nitric oxide (NO) by macrophages has been implicated in resistance to a number of viruses, including ectromelia virus, vaccinia virus, and herpes simplex virus type 1. This study was undertaken to define the role of NO in MHV-3 infection. Gamma interferon-induced production of NO inhibited growth of MHV-3 in a murine macrophage cell line (RAW 264.7). Viral inhibitory activity was reproduced by the NO donor S-nitroso-N-acetyl-DL-penicillamine (SNAP), whereas N-acetyl-DL-pencillamine (NAP), an inactive analog of SNAP, had no effect. Electron microscopy studies confirmed the inhibitory effects of NO on viral replication. Peritoneal macrophages isolated from A/J mice known to be resistant to MHV-3 produced a fivefold-higher level of NO and higher levels of mRNA transcripts of inducible NO synthase in response to gamma interferon than macrophages from susceptible BALB/cJ mice. SNAP inhibited growth of MHV-3 in macrophages from both strains of mice to similar degrees. In vivo inhibition of NO by N-monomethyl-L-arginine resulted in loss of resistance to MHV-3 in A/J mice. These results collectively demonstrate a defect in the production of NO in macrophages from susceptible BALB/cJ mice and define the importance of endogenous NO in resistance to MHV-3 infection in resistant A/J mice.

Animals↗
PubMed1998

Immunophenotypic characterization of simian immunodeficiency virus-infected dendritic cells in cervix, vagina, and draining lymph nodes of rhesus monkeys.

Significant progress has been made in understanding the biology of heterosexual transmission of HIV by utilizing the simian immunodeficiency virus (SIV)/rhesus monkey animal model. Our previous studies have shown that SIV-infected cells within the stratified squamous epithelium of the vagina have a dendritic morphology. However, the type of cell infected was not conclusively determined. The purpose of the present study was to immunophenotype the SIV-infected cells in the lower reproductive tract and genital lymph nodes of the female rhesus monkey. Vagina, cervix, and iliac lymph node from eight chronically SIV-infected adult female monkeys were examined for this study. None of the animals had histologic evidence of opportunistic infections or genital tract pathogens other than SIV. Combined in situ hybridization and immunohistochemistry were used to detect SIV RNA and to determine the immunophenotype of SIV-infected cells in tissue sections and cytospin preparations of cells from the tissues. We now show that SIV-infected cells were most common in iliac lymph node and that the majority of infected cells in the lymph node were T lymphocytes. SIV-infected macrophages, Langerhans' cells, and dendritic cells were also found in the lymph node. SIV-infected cells were found within the epithelium and lamina propria of the vagina. Although most of the infected cells were T cells, a significant proportion (approximately 40%) of the SIV-infected cells in cytospin preparations from explant cultures of vagina and cervix were Langerhans' cells. SIV-infected T cells in the lower genital tract were commonly associated with focal mononuclear cell infiltrates. SIV-infected macrophages were rarely found in the genital tract. The present study provides the first direct demonstration that Langerhans' cells and dendritic cells in the genital tract and lymph nodes are infected with SIV in vivo. Thus, dendritic cells, in general, and Langerhans' cells, in particular, are important reservoirs for HIV/SIV replication in vivo.

Animals↗
PubMed1998

SIV replication and the dendritic cell.

To evaluate the potential involvement of dendritic cells (DCs) in the mucosal transmission of HIV-1 we have used a model system of skin-derived DCs to study the cell-virus interactions in vitro. More recently we have extended these studies to the macaque system to further investigate DCs from a variety of more accessible tissues, particularly the mucosae. The DCs isolated from macaque body surfaces exhibit an almost identical phenotype and morphology to mature human DCs. Both CD4+ and CD8+ T cells are also present in the suspensions isolated from these tissues, with some T cells being tightly bound to the DCs. As in the human system, the skin-derived DCs support active replication of SIV in collaboration with syngeneic skin-derived T cells. Much of the virus is produced by multinucleated syncytia. On separation of the cell subsets by cell sorting, it was revealed that most active viral replication occurs in the DC-T cell conjugate fraction. Virus growth is also detected within the DC-T cell mixtures isolated from the nasopharyngeal and vaginal mucosae, but not in those isolated from the cervical mucosa. This animal model is being used to further dissect the role of DCs in the transmission and pathogenesis of infection with immunodeficiency viruses.

Animals↗
PubMed1997

Generation of monocyte-derived dendritic cells from precursors in rhesus macaque blood.

While the dendritic cells (DCs) of mouse and man have been extensively studied, until recently those of non-human primates remained poorly characterized. We present a method for generating large numbers of DCs from precursors in rhesus macaque blood, based on techniques developed for human blood. For 7 days, a T cell-depleted population of mononuclear cells was cultured in 1% human plasma with GM-CSF and IL-4, both to initiate DC differentiation and to inhibit macrophage development. On day 7, 50% of the culture medium was replaced with a monocyte-conditioned medium (MCM), which is required for the final maturation of the DCs into potent stimulators of the allogeneic MLR. Between 0.5 and 1.0 x 10(6) DCs can be generated from 20 ml of rhesus macaque blood. We compared these cytokine-generated DCs to the adherent macrophages present in the same cultures. Cytokine-generated DCs were considerably more potent at stimulating allogeneic T cells than adherent macrophages. Furthermore, the DCs had a distinct morphology and phenotype, with long processes, high levels of p55, and a characteristic perinuclear collection of intracellular CD68. In contrast, adherent macrophages expressed very low levels of p55, and high diffuse levels of CD68. Macaque DCs generated by this method may be useful in vaccine development and for studies of SIV pathogenesis.

Animals↗
PubMed1997

Morphine- and anandamide-stimulated nitric oxide production inhibits presynaptic dopamine release.

Morphine and anandamide stimulate the release of nitric oxide (NO) in diverse tissues. The present study examines the consequences of this action on neurotransmitter release in ganglia from two invertebrates: ventral chain ganglia from the leech Hirudo medicinalis and the pedal ganglion from the mussel Mytilus edulis. In these ganglia, preloaded serotonin (5-HT) and dopamine (DA) can be released by 50 mM KCl. Anandamide, an endogenous cannabinoid substance, suppresses the potassium-stimulated release of [3H]DA (80%), but not 5-HT, in a concentration-dependent manner, from the neural tissues of both. The effect of anandamide can be antagonized by pre-exposing the neural tissues of both animals to SR 141716A, a potent cannabinoid receptor antagonist. Prior treatment of the ganglia with N-omega-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, significantly diminishes the inhibitory effect of anandamide. Morphine also inhibits [3H]DA release in a naloxone- and L-NAME-sensitive manner. Anandamide and morphine act through separate mechanisms since the respective antagonists show no cross-reactivity. The NO donor, SNAP, depressed the potassium-stimulated release of preloaded [3H]DA, but not 5-HT, in the neural tissues of both animals. D-Ala2-Met5 enkephalinamide (DAMA) also inhibited the potassium-stimulated release of [3H]DA in a naloxone-sensitive process. However, the effect of DAMA was seen in the presence of L-NAME (10(-4) M), indicating that the opioid peptide inhibition of the presynaptic release of DA is not coupled to NO. We postulate that cannabinoids and their endogenous effectors play a prominent role in the regulation of catecholamine release in invertebrates via NO release as is the case for opiate alkaloids.

Animals↗
PubMed1997

Dendrite cell-T cell mixtures, isolated from the skin and mucosae of macaques, support the replication of SIV.

Previous studies have shown that HIV-1 exploits dendritic cells (DCs) to replicate and spread among CD4+ T cells. The DCs within mucosal surfaces may be especially important, but these are more difficult to access. To study more extensively the properties of DCs and other leukocytes from skin and different mucosae, DCs were isolated from uninfected macaques and their sensitivity assessed to infection with SIV in vitro. Dendritic cells and T cells readily emigrated from organ cultures of macaque skin, as described previously for humans. In addition, characteristic cells emigrated from explants of mucosae, both nasopharyngeal (adenoid and tonsil) and genital (vagina and cervix). The macaque DCs reacted with the monoclonals that are used to study human DCs, such as MAbs to CD40, CD86, CD83, and the p55 protein. When SIV was added to the DC-T cell mixtures from these different organs, extensive replication was observed in all but the cervical leukocytes. SIV replication occurred without the use mitogens, and with virus that had been grown in a cell line in the absence of mitogens and IL-2. Most of the newly synthesized viral protein is observed in syncytia. Therefore, mixtures of DCs and T cells isolated from mucosal surfaces served as a naturally permissive environment for SIV replication.

Animals↗
PubMed1997

Cutaneous dendritic cells promote replication of immunodeficiency viruses.

The cutaneous or mucosal DC-T cell environments seem extremely supportive of immunodeficiency virus replication. Apart from very early after SIV infection, similar virus producing cells have been difficult to detect in the lymphoid tissues where DCs and T cells are also known to interact. Large amounts of virus can be visualized in the germinal centers of the lymph nodes, much of which represents immune complexed virus that is trapped on the follicular dendritic cell surface. However, whether these virus-carrying cells actually make virus or even virus proteins requires further investigation. We believe that once an individual is systemically infected, free virus and/or virus-infected cells will seed peripheral tissues and when encountering similar DC-T cell environments as described in the oral mucosae, can set up sites of chronic virus replication. For instance, a virus-carrying T cell that migrates to the periphery would, on entering this milieu, interact with the mature DCs and activate virus production. This likely occurs at similar sites around the body, such as the mucosal associated lymphoid tissue of the gut, and is probably independent of the route of infection.

Animals↗
PubMed1997

Type III Ehlers-Danlos syndrome and pregnancy.

We report a case of type III Ehlers-Danlos syndrome with a favourable outcome. We review the literature and do not consider that pregnancy in patients with type III Ehlers-Danlos Syndrome represents a high risk situation.

Adult↗
PubMed1997

Aortic transgraft hemorrhage after systemic thrombolytic therapy.

Aortic transgraft hemorrhage is an unusual complication following thrombolytic therapy that can occur months to years after aortic surgery. It is critical to differentiate this from other potential causes of hemorrhage, such as an acute bleed from an anastomotic false aneurysm which is a surgical emergency. One such case that was managed conservatively with success is reported.

Aged↗
PubMed1997

Human immunodeficiency virus type 1 strains of subtypes B and E replicate in cutaneous dendritic cell-T-cell mixtures without displaying subtype-specific tropism.

A report that genetic subtype E human immunodeficiency virus type 1 (HIV-1) strains display a preferential tropism for Langerhans cells (epidermal dendritic cells [DCs]) compared to genetic subtype B strains suggested a possible explanation for the rapid heterosexual spread of subtype E strains in Thailand (L. E. Soto-Ramirez et al., Science 271:1291-1293, 1996). In an independent system, we applied subtype E and B isolates to skin leukocytes, since skin is a relevant model for the histologically comparable surfaces of the vagina and ectocervix. Isolates of both HIV-1 subtypes infected DC-T-cell mixtures, and no subtype-specific pattern of infection was observed. Purified DCs did not support the replication of strains of either subtype B or E. Our findings do not support the conclusion that subtype E strains have a preferential tropism for DCs, suggesting that other explanations for the rapid heterosexual spread of subtype E strains in Asia should be considered.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Active replication of HIV-1 at the lymphoepithelial surface of the tonsil.

Cells that are infected with HIV-1 were visualized at the mucosal surface of the nasopharyngeal and palatine tonsils in 14 specimens from patients with CD4+ T-cell counts of 200 to 900/microliter and 2- to 10-year histories of HIV-1 infection. Most of the cells with intracellular HIV-1 protein were small but multinucleated. The majority of these syncytia could be double labeled for HIV-1 RNA and a dendritic cell marker S100. In the palatine tonsil, the infected cells were not found in the stratified squamous epithelium that is adjacent to the pharynx. Instead, the S100+ infected syncytia were localized to the surface of tonsil invaginations or crypts. This mucosa, termed lymphoepithelium, contains antigen-transporting M cells that lie above regions where S100+ dendritic cells are juxtaposed with CD4+ lymphocytes. Likewise, infected cells were found in lymphoepithelium and not respiratory epithelium of nasopharyngeal tonsils or adenoids. We propose that lymphoepithelia, the histological term that describes the specialized regions where antigens access mucosa-associated lymphoid tissue, are sites where HIV-1 replication can be enhanced in syncytia derived from dendritic cells.

Adenoids↗
PubMed1996

Efficient interaction of HIV-1 with purified dendritic cells via multiple chemokine coreceptors.

HIV-1 actively replicates in dendritic cell (DC)-T cell cocultures, but it has been difficult to demonstrate substantial infection of purified mature DCs. We now find that HIV-1 begins reverse transcription much more efficiently in DCs than T cells, even though T cells have higher levels of CD4 and gp120 binding. DCs isolated from skin or from blood precursors behave similarly. Several M-tropic strains and the T-tropic strain IIIB enter DCs efficiently, as assessed by the progressive formation of the early products of reverse transcription after a 90-min virus pulse at 37 degrees C. However, few late gag-containing sequences are detected, so that active viral replication does not occur. The formation of these early transcripts seems to follow entry of HIV-1, rather than binding of virions that contain viral DNA. Early transcripts are scarce if DCs are exposed to virus on ice for 4 h, or for 90 min at 37 degrees C, conditions which allow virus binding. Also the early transcripts once formed are insensitive to trypsin. The entry of a M-tropic isolates is blocked by the chemokine RANTES, and the entry of IIIB by SDF-1. RANTES interacts with CCR5 and SDF-1 with CXCR4 receptors. Entry of M-tropic but not T-tropic virus is ablated in DCs from individuals who lack a functional CCR5 receptor. DCs express more CCR5 and CXCR4 mRNA than T cells. Therefore, while HIV-1 does not replicate efficiently in mature DCs, viral entry can be active and can be blocked by chemokines that act on known receptors for M- and T-tropic virus.

Cells, Cultured↗
PubMed1996

Resistance of naive mice to murine hepatitis virus strain 3 requires development of a Th1, but not a Th2, response, whereas pre-existing antibody partially protects against primary infection.

Murine hepatitis virus strain 3 (MHV-3) produces a strain-dependent spectrum of disease. The development of liver necrosis has been shown to be related to production of a unique macrophage procoagulant activity (PCA), encoded by the gene fgl-2, in susceptible mice. These studies were designed to examine the influence of Th1/Th2 cells on resistance/susceptibility and production of macrophage PCA in resistant (A/J) and susceptible (BALB/cJ) strains of mice following infection with MHV-3. Immunization of A/J mice with MHV-3 induced a Th1 cellular immune response, and one Th1 cell line (3E9.1) protected susceptible mice and inhibited PCA production by macrophages both in vitro and in vivo. In contrast, immunization of BALB/cJ mice with an attenuated variant of MHV-3 derived from passaging MHV-3 in YAC-1 cells resulted in a Th2 response. Transfer of spleen cells and T cell lines from immunized BALB/cJ mice failed to protect naive susceptible syngeneic mice from infection with MHV-3 and augmented macrophage PCA production to MHV-3 in vitro. However, serum from immunized BALB/cJ mice contained high titrated neutralizing Ab that protected naive BALB/cJ animals from lethal primary MHV-3 infection. These results demonstrate that susceptible BALB/cJ mice generate a Th2 response following MHV-3 infection and that these Th2 cells neither inhibit MHV-3-induced macrophage PCA production nor protect naive mice from MHV-3 infection. The results suggest that Ab protects against primary infection but cannot eradicate ongoing infection. Thus, these data define the differential role of Th1/Th2 lymphocytes in primary and secondary MHV-3 infection and emphasize the importance of PCA in the pathogenesis of MHV-3 infection.

Animals↗