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O Narayan

Publications and source records attributed to O Narayan.

At least 19 recordsLinked to original sources
PubMed1995

Lymphocyte-tropic simian immunodeficiency virus causes persistent infection in the brains of rhesus monkeys.

Molecularly cloned SIVmac239 is the prototypical SIVmac lymphocyte-tropic virus that replicates productively in lymphocytes but poorly in macrophages. In macaques, the virus causes activation and productive infection of T lymphocytes which invade the central nervous system (CNS) early after infection in the animal. However, infected animals develop immunosuppression and AIDS but rarely overt neurological disease. In this study, we examined multiple regions of the brain and spinal cord for the presence of SIV env sequences and histological lesions in five macaques that had been infected with SIVmac239 for 1.7 to 2.25 years. Histopathological examination of the brain revealed no lesions consistent with encephalitis; however, viral DNA was found in all five brains. In one animal the virus caused infection in a widely disseminated pattern from the frontal cortex to the distal end of the spinal cord, whereas in the other four animals infection in the CNS occurred in a nonspecific, focal pattern. Sequence analyses were performed on gp120 sequences isolated from selected regions of the CNS and compared to gp120 sequences isolated from corresponding lymph nodes, a tissue known to support productive replication of SIVmac239. Examination of the viral sequences from the CNS tissue from two animals (macaques 10F and 14F) revealed a low mutation rate when compared to the sequences isolated from the lymph node tissues. The percentage change in the amino acid sequence was approximately 1% for CNS clones versus > or = 3% for clones isolated from the lymph node. The majority of the CNS viral sequences of macaques 10F and 14F had none of the genetic markers shown in a previous study to be associated with macrophage-tropic variants and indeed retained a nucleotide sequence of similar to the original lymphocyte-tropic virus used for inoculation despite almost 2 years of persistent infection in the animals. Construction of chimeric viruses with V1-V5 regions of selected macaque 10F and macaque 14F CNS-gp120 clones confirmed the predicted lymphocyte-tropic nature of these env genes. In contrast, the gp120 sequences isolated from the CNS tissue of one of the other three animals (macaque 13F) had a mutation rate comparable to that observed for the lymph node clones. The CNS clones from this animal had amino acid substitutions that were previously shown to be associated with macrophage tropism. Compared to the chimeric viruses constructed with V1-V5 sequences from macaques 10F and 14F, viruses constructed with the V1-V5 sequences of several macaque 13F brain clones did not yield infectious virus.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1995

Interaction of virion protein Vpr of human immunodeficiency virus type 1 with cellular transcription factor Sp1 and trans-activation of viral long terminal repeat.

Acquired immunodeficiency syndrome (AIDS) is a result of replication of the human immunodeficiency virus type 1 (HIV-1) predominantly in CD4+ T lymphocytes and macrophages. However, most of these cells in vivo are immunologically quiescent, a condition restricting HIV-1 replication. Vpr is an HIV-1 virion protein suspected to enhance HIV-1 replication in vivo. We demonstrate in this report that Vpr specifically activates HIV-1 long terminal repeat (LTR)-directed transcription. This effect is most pronounced on a minimal promoter from HIV-1 LTR containing the TATA box and binding motifs for the ubiquitous cellular transcription factor Sp1. Evidence is presented that Vpr interacts with Sp1 when Sp1 is bound to the Sp1 motifs within the HIV-1 LTR Both Vpr-Sp1 interaction and Vpr trans-activation require a central Leu/Ile-rich domain in Vpr. Our findings suggest that Vpr trans-activation through Sp1 is most critical for the immediate early transcription of HIV-1 when other positive regulators, such as NF-kappa B, are limited or inactive, a condition presumably present in vivo. By interacting with Sp1, Vpr also has the potential to influence cellular gene expression and cellular functions. Thus, therapeutic approaches directed toward blocking the Vpr trans-activation function could prove valuable in treating AIDS.

Base Sequence↗
PubMed1995

Early appearance of antibodies to simian immunodeficiency virus in saliva and serum of infected macaques.

Simian immunodeficiency virus (SIV) infection in macaques is an important animal model for human immunodeficiency virus infection in humans. This study evaluated the temporal development of antibodies to SIV in the parotid saliva of macaques inoculated with the virus and compared these findings with the development of antibodies to SIV in the animals' sera. Three animals (ages, 14, 18, and 18 years) were inoculated with the macrophagetropic strain SIVmac239. Prior to inoculation and at consecutive weekly intervals during a four-week period following the initial virus inoculations, parotid saliva and serum were collected from each animal. A fourth animal (age, 9 years) served as a negative control, and the fifth and sixth animals (ages, 2 and 22 years) served as positive controls (6 and 18 months postinoculation, respectively) with SIVmac239. Saliva and serum samples were reacted against SIV antigen in Western blots (immunoblots) prepared in the standard fashion to determine the presence of antibodies. The reactions of these antigen-antibody complexes with biotinylated anti-human immunoglobulin A (IgA), IgM, and IgG and biotinylated anti-human secretory component (SC) determined the class of antibody present or the presence of SC in the original parotid saliva or serum samples. In infected animals, the IgM to SIV was detectable in serum and saliva at 13 days, and antiviral IgA and IgG in serum and saliva were detectable at 20 to 27 days postinoculation. The antibody to SC reacted to saliva from only two animals at 20 and 27 days, and long-term positive controls were positive for SC in saliva, indicating that either secretory IgA or secretory IgM was present in these samples. Antibodies to SIVmac239 antigens have therefore been detected in saliva as early as 13 days postinfection. Saliva may be as useful as serum as a diagnostic specimen and/or disease-monitoring method in this important animal model.

Animals↗
PubMed1993

A gene expression vector useful for protein purification and studies of protein-protein interaction.

This report describes the development of a gene expression vector that adds three features to the C-terminus of the putative synthesized protein: (1) a protein kinase A recognition domain allowing the protein to be radio-labeled in vitro, (2) an epitope marker for immunocharacterization of the protein with a commercial monoclonal antibody, and (3) a (His)6 block facilitating purification of the protein by metal chelating affinity chromatography. These features make it convenient to perform biochemical and functional analysis of the protein of interest.

Amino Acid Sequence↗
PubMed1992

Human immunodeficiency virus infection in microglia: correlation between cells infected in the brain and cells cultured from infectious brain tissue.

In acquired immunodeficiency syndrome, the lesions of the central nervous system in association with the human immunodeficiency virus are thought to be related to an infection of microglia, although no studies are available in which cultured and physiological characteristics of microglia cells infected in vivo have been examined. In this report, we used brain tissue from a child dying of human immunodeficiency virus infection and show that microglia cells were the main cell population being infected. Moreover, isolated macrophage-like cells from fresh brain material revealed a close resemblance to peripheral blood macrophages in their content of surface and intracellular antigens. No virus particles or viral antigens were produced by these cells during the first week of cultivation. Productive infection was readily apparent, however, by day 30. This finding illustrates the slow nature of the virus life cycle in these cells and the minimal cytopathology that accompanied the infection.

Brain↗
PubMed1992

Differences in neutralization of simian lentivirus (SIVMAC) in lymphocyte and macrophage cultures.

Comparison of neutralization of SIVmac251 in primary macrophage cultures with neutralization in lymphocytes (CEM174 cells) showed that neutralizing antibodies induced by SIV251 in infected rhesus macaques protected both macrophages and T lymphocytes against infection when the virus was preincubated with the antibodies. In macrophages, the neutralizing antibodies also protected against infection when added 1 hour after the virus. Addition of antisera to macrophages between 24 and 48 hours after virus inoculation resulted in infection with continuous release of small amounts of p24 into the supernatant fluids but these antibody-treated cultures failed to exhibit cytopathic virus replication. In contrast, the same neutralizing antisera did not protect lymphocytes against infection and subsequent cytopathic replication of the virus when added only 1 hour after virus inoculation. This distinction in the effect that neutralizing antibodies had on the development of cytopathic infection in lymphocytes and macrophages when added after virus inoculation, suggests that they could alter the dynamics of virus replication and therefore the pathogenesis of disease.

Animals↗
PubMed1992

Infection with Borna disease virus: molecular and immunobiological characterization of the agent.

Borna disease virus (BDV), which seems to be distinct from all other known viruses, exhibits a unique mechanism of pathogenesis. This review highlights several aspects of the biology of infection with this virus and summarizes the preliminary characterization of the agent. Studies on BDV may help to illuminate several important areas of neurobiology, including the mechanisms regulating the replication of a new type of RNA virus in the nuclei of neural cells, the neuroinvasiveness and neurotropism of such viruses, their T cell-mediated immunopathology, tolerance in newborn animals to persistent viral infection of the central nervous system, and behavioral diseases and eating disorders induced by such agents.

Animals↗
PubMed1992

Pathogenesis of acute infection in rhesus macaques with a lymphocyte-tropic strain of simian immunodeficiency virus.

The simian immunodeficiency virus, SIVmac, causes disease affecting multiple organ systems in macaques similar to human immunodeficiency virus infection in humans. Molecularly cloned SIVmac with a strong lymphocyte tropism was used in pathogenesis experiments to correlate viral cell tropism with disease. In 5 animals, exhaustive analyses on viruses from tissues and identification of infected precursor cells were done at multiple times during infection to ensure the virus had not mutated into a macrophage-tropic variant. Viral replication was measured by infectivity, infectious center assays, and in situ hybridization. Lymphocytes produced most virus in tissues, indicating the virus maintained its cell tropism in vivo. Lymphocytes in bone marrow were latently infected and those in the spleen and lymph nodes were productively infected. The virus failed to replicate in the brain after intracerebral inoculation. SIVmac that maintained a strong tropism for lymphocytes and a corresponding poor tropism for macrophages can cause persistent infection and AIDS but not other diseases such as primary pneumonia and encephalitis in rhesus macaques.

Acute Disease↗
PubMed1992

Tumour necrosis factor and interleukin 6 production during interaction between activated CD4+ lymphocytes and simian immunodeficiency virus-infected macrophages.

The mechanism for the gradual loss of CD4+ T lymphocytes and the development of the slowly progressive inflammatory/degenerative lesions that accompany human immunodeficiency virus infection are poorly understood. Using the Simian immunodeficiency virus (SIVmac) macaque model of AIDS, we found that persistently infected primary macrophages fuse with primary activated CD4+ lymphocytes and that this interaction results in production of tumour necrosis factor-alpha (TNF alpha) and interleukin 6 (IL-6). An earlier report had shown that SIV-infected macaque macrophages fuse with CEM174 cells (a human CD4+ cell line) and cause their lysis. In the present report, we have shown that TNF-alpha and IL-6 are also produced during the early stages of this interaction. Data from cocultivation of infected macrophages with several CD4+ T cell lines, including CEM174, suggested that the cytokines are produced by the T cells, and that cytokine production is restricted to those cells which not only express CD4, but are also capable of fusing with the infected macrophages. These data suggest that infected macrophages in vivo could fuse with and eliminate activated CD4+ lymphocytes and, during this interaction, release cytokines, which would contribute to the degenerative and inflammatory lesions characteristic of this disease.

Animals↗
PubMed1992

Neutralizing antibodies modulate replication of simian immunodeficiency virus SIVmac in primary macaque macrophages.

Cultured macaque macrophages are permissive for the replication of SIVmac251, and inoculation with virus is followed by the production of viral p27. Neutralizing macaque polyclonal and murine monoclonal antibodies preincubated with the virus prevented infection but did not prevent cytopathic virus replication when added more than 3 days after inoculation with virus. However, application of the neutralizing antibodies to macrophages 24 h after inoculation with virus resulted in sustained, low-level production of viral antigen. Cell lysates and individual macrophages from treated cultures contained less viral protein by Western blot (immunoblot) and immunocytochemistry than untreated controls. In situ hybridization and polymerase chain reaction procedures for detecting and estimating relative amounts of viral RNA and DNA showed that both viral nucleic acids failed to increase beyond the levels obtained before the addition of neutralizing antibodies. The data suggest that macrophages may need to be infected with a minimum threshold of virus particles in order to reach their full potential for virus replication and that their exposure to neutralizing antibodies prior to reaching this threshold resulted in limited virus replication.

Animals↗
PubMed1992

Ovine lentivirus is macrophagetropic and does not replicate productively in T lymphocytes.

The lentiviruses of sheep, goats, and horses cause chronic multiorgan disease in which macrophages are highly permissive for viral replication. Monocytes, which mature into macrophages, are thought to be latently infected with lentivirus, but the extent to which other leukocytes are infected is unknown. Dendritic cells have not been studied separately from monocytes and T-cell subsets have not been examined in previous attempts to identify infected cells in peripheral blood mononuclear cells (PBMC). We found no evidence of T-cell tropism using an animal-passaged, pathogenic ovine lentivirus. Phytohemagglutinin-stimulated infectious PBMC produced 20-fold less virus than differentiated macrophages, and cocultivation of infectious PBMC with fresh, uninfected phytohemagglutinin blasts did not facilitate virus replication. Furthermore, central lymph cells, the best in vivo source of purified lymphocytes, lacked virus and did not yield virus upon in vitro cultivation. In contrast, cultivated blood-derived macrophages were highly permissive for viral replication. To identify the latently infected PBMC, PBMC from infected sheep were selectively depleted of monocytes and B cells by passage over nylon wool and then of nonadherent cells bearing CD4, CD8, T19, gamma delta T-cell receptor, CD45RA, or major histocompatibility complex class II antigens by panning. Removal of adherent monocytes and B cells or of adherent cells and the three major T-cell subsets (CD4+, CD8+, T19+) did not decrease the infectivity of PBMC. The richest sources of infected cells in fresh PBMC were CD45RA+ and major histocompatibility complex class II+ nonadherent cells, which are three characteristics of dendritic cells. Thus, the dendritic cell, and not the monocyte or the CD4+ cell, is probably the predominant infected cell type in blood.

Animals↗
PubMed1992

Derivation of neurotropic simian immunodeficiency virus from exclusively lymphocytetropic parental virus: pathogenesis of infection in macaques.

Neurological disease resulting from lentivirus (including human immunodeficiency virus) infections is usually caused by a strain of virus that replicates productively in microglia in vivo and in macrophage cultures in vitro. We undertook this study using the model of simian immunodeficiency virus in macaques (SIVmac) to test the hypothesis that macrophage tropism is a prerequisite for neurotropism of the virus. Using molecularly cloned SIVmac239, a virus which is lymphocyte- but not macrophagetropic, we showed that this virus failed to infect brain after intracerebral (i.c.) inoculation into two macaques. Rather, these inoculations resulted in disseminated infection in lymphoid organs and the bone marrow. Two sequential passages of infected bone marrow cells inoculated i.c. into new macaques resulted in severe neurological disease and classical neuropathological lesions. Virus obtained from affected brain answered the hypothetical question: it was neurotropic and macrophagetropic. New findings in the study were that both lymphocyte- and macrophage-tropic viruses were present in the animals, but the viruses localized in different tissues: the lymphotropic virus in the spleen, lymph nodes, and plasma and the macrophagetropic virus in the brain and lungs. To determine whether the brain virus was preferentially neurotropic and whether it had neuroinvasive properties, infectious brain homogenate was inoculated into one animal i.c. and into two others peripherally. The i.c. inoculated animal developed fatal encephalitis 5 months later, and examination of tissues showed cell-free virus only in brain homogenates. Only microglia were infected despite persistent viremia and infection in bone marrow cells. The two macaques inoculated peripherally remained healthy and were euthanized at 6 months. Virus replication was detected only in the bone marrow cells and peripheral blood mononuclear cells. No infection in any macrophage population in visceral organs was detected, and the virus did not invade the brain. The strictly microglial specificity of this virus suggested that different macrophage populations in the body may select specific phenotypes of lentivirus from the quasispecies of virus in the bone marrow. This could provide the basis for specific disease affecting different organ systems.

Adaptation, Biological↗
PubMed1992

Lentivirus induced arthritis in animals.

Retroviral arthritis in sheep and goats depends on persistent infection in the animals. Virus is latent in macrophage precursor cells and viral replication is initiated when these cells are induced to differentiate. Antiviral antibodies and cytokines modulate the efficiency of viral gene product expression. Specific cytokines induced during replication of the lentivirus in mononuclear cells are also responsible for directing infected cells from peripheral blood through the vascular endothelium to particular tissues. Cytokines induced by other infectious agents such as bacteria, mycoplasma or protozoa, may also contribute to this chemotactic process. Once in the tissue, macrophages interact with lymphocytes to induce an inflammatory cascade with further production of cytokines which enhances expression of class II major histocompatibility complex antigens and proliferation of B and CD8 lymphocytes. In addition, immune complexes between viral glycoproteins and immunoglobulins are produced locally and probably lead to further enhancement of pathological changes in the tissues.

Animal Diseases↗
PubMed1991

Rhesus monkey macrophages infected with simian immunodeficiency virus cause rapid lysis of CD4-bearing lymphocytes.

Inoculation of simian immunodeficiency virus into cultures of primary rhesus monkey macrophages or CD4-bearing transformed T lymphocytes resulted in persistent infection, with minimal virus replication in the macrophages and extensive replication in the lymphocytes. However, uninfected T cells added to infected macrophages underwent rapid fusion and lysis and were almost completely eliminated without the production of virus particles. Lysis required direct contact between the T cells and the infected macrophages, which enabled binding between CD4 on the former and viral gp120 on the latter to occur. This process was blocked by soluble CD4 and dextran sulphate. Neutralizing antibodies in the serum of an infected macaque prevented cell fusion by preventing infection of the macrophages. However, these antibodies did not prevent fusion when added to previously infected macrophages. Infected macrophages were incorporated into the syncytia of lymphocytes and continued incorporation of new lymphocytes into the syncytia required infected macrophages to be metabolically active. One inference from these studies is that infected macrophages in vivo could help mediate the well known depletion of T4 cells in patients with AIDS.

Animals↗
PubMed1991

Analysis of Borna disease virus-specific RNAs in infected cells and tissues.

Borna disease virus (BDV) is an infectious agent that causes profound disturbances in motor function and behaviour in a wide range of animal species and possibly humans. The infectious nature of BDV has long been established, but the aetiological agent has not been isolated or classified. Recently, we have reported the isolation of BDV-specific cDNA clones using subtractive libraries constructed from mRNA from infected material. Here we describe studies on one of these cDNA clones, B8, and confirm its specificity by in situ hybridization on sections of BDV-infected brain. The complete nucleotide sequence of BDV-specific clone B8 was determined. Oligonucleotides of positive and negative polarity synthesized from sequences from the 5' and 3' ends, as well as the central part, of clone B8 identified both positive- and negative-strand BDV-specific RNAs in infected rat brain. All B8 sequences used as oligonucleotide probes were found to be contained in the larger positive- and negative-strand RNAs. Thus, the structure of the BDV-specific RNAs appears to be a nested set of multiple, overlapping subgenomic positive- and negative-strand RNA transcripts.

Amino Acid Sequence↗
PubMed1991

Molecular and immunopathological studies of borna disease virus infection in rats.

Borna disease virus is an agent distinct from all known viruses. Pathogenesis of its infection is also unique. This review highlights several aspects of the biology of this viral infection and the preliminary characterization of the agent. BDV can be used to answer important questions in neurobiology. These include neuroinvasiveness and neurotropism of viral agents, CD4+ T cell-mediated immunopathology and tolerance in newborn animals to a persistent viral infection in the CNS and behavioral diseases and eating disorders induced by neurotropic viruses. This review is dedicated to Prof. Dr. Rott on occasion of his 65th birthday in recognition of his immense contributions to studies on Borna disease and also for his success focusing the attention of the scientific community to this still evolving unique viral disease.

Animals↗