Biomedical subjects

E Lavi

Publications and source records attributed to E Lavi.

At least 55 records · Page 3Linked to original sources

PubMed1998

Pharmacokinetics and penetration of danofloxacin from the blood into the milk of cows.

The single-dose disposition kinetics of danofloxacin were determined in clinically normal lactating cows after intravenous (i.v.) and intramuscular (i.m.) administration of the drug at 1.25 mg/kg. The drug concentrations in blood serum and milk were determined by microbiological assay methods and the data were subjected to kinetic analysis. The mean i.v. and i.m. elimination half-lives (t1/2el) in serum were 54.9 and 135.7 min, respectively. The steady-state volume of distribution (Vss) was 2.04 L/kg. The drug was quickly absorbed after i.m. injection but a 'flip flop' effect was clearly evident and bioavailability was > 100%. Penetration of danofloxacin from blood into milk was rapid and extensive with drug concentrations in milk exceeding those in serum beginning 90-120 min after i.v. and i.m. administration and onwards. Milk danofloxacin concentrations equal to or higher than the minimal inhibitory concentrations (MIC) for pathogenic Gram-negative bacteria and Mycoplasma species were maintained over approximately 24 h. Concentrations greater than the MIC for Staphylococcus aureus were maintained in the milk for 12 h.

Animals↗

PubMed1998

Targeted recombination within the spike gene of murine coronavirus mouse hepatitis virus-A59: Q159 is a determinant of hepatotropism.

Previous studies of a group of mutants of the murine coronavirus mouse hepatitis virus (MHV)-A59, isolated from persistently infected glial cells, have shown a strong correlation between a Q159L amino acid substitution in the S1 subunit of the spike gene and a loss in the ability to induce hepatitis and demyelination. To determine if Q159L alone is sufficient to cause these altered pathogenic properties, targeted RNA recombination was used to introduce a Q159L amino acid substitution into the spike gene of MHV-A59. Recombination was carried out between the genome of a temperature-sensitive mutant of MHV-A59 (Alb4) and RNA transcribed from a plasmid (pFV1) containing the spike gene as well as downstream regions, through the 3' end, of the MHV-A59 genome. We have selected and characterized two recombinant viruses containing Q159L. These recombinant viruses (159R36 and 159R40) replicate in the brains of C57BL/6 mice and induce encephalitis to a similar extent as wild-type MHV-A59. However, they exhibit a markedly reduced ability to replicate in the liver or produce hepatitis compared to wild-type MHV-A59. These viruses also exhibit reduced virulence and reduced demyelination. A recombinant virus containing the wild-type MHV-A59 spike gene, wtR10, behaved essentially like wild-type MHV-A59. This is the first report of the isolation of recombinant viruses containing a site-directed mutation, encoding an amino acid substitution, within the spike gene of any coronavirus. This technology will allow us to begin to map the molecular determinants of pathogenesis within the spike glycoprotein.

Amino Acid Substitution↗

PubMed1998

The effect of human herpesvirus-6 (HHV-6) on cultured human neural cells: oligodendrocytes and microglia.

Human herpesvirus-6 (HHV-6) is a betaherpesvirus that has been frequently associated with pediatric encephalitis. In 1995 Challoner et al reported that HHV-6 variant B (HHV-6B) was linked to multiple sclerosis (MS) due to the presence of viral DNA and antigen in the oligodendrocytes surrounding MS plaques. These findings led us to examine HHV-6B's in vitro tropism for primary neural cells. HIV-6B mediated cell-to-cell fusion in cultured adult oligodendroglia. Infection of oligodendrocytes was further confirmed by transmission electron microscopy (EM), which showed the presence of intracellular HHV-6 particles, and by PCR for HHV-6 DNA. However, the release of infectious virus was low or undetectable in multiple experiments. Microglia were also susceptible to infection by HHV-6B, as demonstrated by an antigen capture assay. We did not detect infection of a differentiated neuronal cell line (NT2D). Our findings suggest that HHV-6B infection of oligodendrocytes and/or microglia could potentially play a role in neuropathogenesis.

Adult↗

PubMed1998

Chemokine receptors in the human brain and their relationship to HIV infection.

Chemokine receptors have been recently identified as the important co-factors which in conjunction with CD4, mediate entry of HIV into its target cells. The brain is one of the most prominent targets of HIV infection, where it leads to HIV encephalitis (HIVE) and HIV-associated dementia. Knowledge of the distribution, physiology, and pathology of chemokines and chemokine receptors in the human brain is fundamental for understanding the pathogenesis of the interaction between HIV and the central nervous system (CNS). There is also increasing evidence that chemokine receptors expression in the CNS increases during pathological, especially inflammatory, conditions. The major co-factors for HIV infection, CCR5, CCR3, and CXCR4 have been detected in the human brain in a variety of cell types including microglia, astrocytes, neurons, and vascular endothelial cells. Furthermore, antibodies to chemokine receptors can also block HIV infectivity in cultured CNS cells. This indicates that chemokine receptors are likely to have a functional role in the pathogenesis of HIVE.

Acquired Immunodeficiency Syndrome↗

PubMed1998

Case of the month: April 1997--a 32 year old man with mental status changes and a severe occipital headache.

A 32 year old man with symptoms of an upper respiratory infection one week prior presented with mental status changes, diffuse hyperreflexia, and bilateral extensor plantar responses. An MRI scan showed multifocal areas of high signal intensity predominantly in the parietal and occipital white matter, unassociated with mass affect. Despite aggressive treatment, the patient's symptoms rapidly progressed and he was declared brain dead. Post-mortem examination revealed acute hemorrhagic leukoencephalopathy. The clinical and pathologic features of this disorder are reviewed.

Adult↗

PubMed1998

Case of the month: March 1998--48 year old man with back pain and weakness.

A 48 year old man with long history of end stage renal disease (ESRD) and secondary hyperparathyroidism presented with back pain and incontinence. MRI and CT showed T2 expansion with bony destruction and spinal cord compression. Other vertebral bodies showed destructive lesions as well. Microscopic examination showed a brown tumor composed of multinucleated giant cells and bone uninvolved by tumor showed "tunneling" resorption. Brown tumors are an exaggerated form of "local" osteitis fibrosa cystica in patients with ESRD and secondary hyperparathyroidism, but spinal cord compression is rare.

Back Pain↗

PubMed1998

Case of the month: May 1998--a patient with HIV infection and multiple cranial neuritis.

A 36-year old male with a three year history of HIV infection and more recently, CMV retinitis, had several episodes of polyradiculitis with severe bilateral leg pain and urinary retention which resolved slowly over several months. He then presented with high fevers and severe dysphagia with dehydration. Examination showed oral thrush, dyarthric speech and mild memory impairment. Fundoscopic exam showed CMV retinitis and HIV retinopathy. Further examination revealed other cranial nerve signs and leg weakness. MRI scans showed several contrast enhancing abnormalities of cranial nerve roots. The patient died from massive barium aspiration. At autopsy the brain showed multiple CMV cranial neuritis, CMV polyradiculitis and CMV ventriculo-ependymitis. While spinal nerve root involvement by CMV may occur in up to 1% of AIDS patients, involvement of cranial nerves is unusual and CMV infection of multiple cranial nerves is distinctly rare.

Adult↗

PubMed1997

Altered pathogenesis of a mutant of the murine coronavirus MHV-A59 is associated with a Q159L amino acid substitution in the spike protein.

C12, an attenuated, fusion delayed, very weakly hepatotropic mutant of mouse hepatitis virus strain A59 (MHV-A59( has been further characterized. We have previously shown that C12 has two amino acid substitutions relative to wild type virus in the spike protein, Q159L (within a region of S1 shown to bind to viral receptor in an in vitro assay) and H716D (in the proteolytic cleavage recognition site). We have sequenced the rest of the 31-kb genome of C-12 and compared it to wild type virus. Only three additional amino acids substitutions were found, all encoded within the replicase gene. Analysis of C12 in vivo in C57Bl/6 mice has shown that despite the fact that this virus replicates in the brain to titers at least as high as wild type and causes acute encephalitis similar to wild-type, this virus causes a minimal level of demyelination and only at very high levels of virus inoculation. Thus acute encephalitis is not sufficient for the induction of demyelination by MHV-A59. Analysis of mutants isolated at earlier times from the same persistently infected glial cell culture as C12, as well as mutants isolated from a second independent culture of persistently infected glial cells, suggests that both the weakly demyelinating and the weakly hepatotropic phenotypes of C12 are associated with the Q159L amino acid substitution.

Amino Acid Substitution↗

PubMed1997

OlP-1, a novel protein that distinguishes early oligodendrocyte precursors.

Oligodendrocyte development may be divided into three distinct stages: I) commitment of neuroectoderm cells to the oligodendrocyte lineage, II) migration of precursors into the surrounding parenchyma concomitant with increased proliferation, and III) cessation of migration and proliferation and initiation of myelination. Stage II of development has remained enigmatic because of the paucity of known molecules that distinguish these immature migratory cells. We describe a novel surface protein, termed OlP-1, which is restricted in expression to this developmental stage in the mouse. Cytofluorographic comparisons with known developmental markers showed OlP-1 to be expressed primarily by stage II precursors in vitro. Histologic analyses supported this conclusion by showing co-localization of OlP-1 with stage II molecules in vivo. Two conclusions were drawn from these results. First, OlP-1 was a novel protein expressed by murine oligodendrocyte precursors at a point in development that suggested a role in migration or proliferation. Second, dispersal of OlP-1-positive cells throughout the developing brain did not correlate with the location of myelination which, observed days later, progressed in a caudal to rostral manner. These data supported the concept that the final steps of maturation and myelin gene expression may be dependent upon extrinsic factors located predominantly within white matter tracts.

Animals↗

PubMed1997

Tumor necrosis factor alpha and lymphotoxin alpha are not required for induction of acute experimental autoimmune encephalomyelitis.

Immunization of mice with myelin components results in experimental autoimmune encephalomyelitis (EAE), which is mediated by myelin-specific CD4(+) T cells and anti-myelin antibodies. Tumor necrosis factor alpha (TNF-alpha) and lymphotoxin alpha (LT-alpha) are thought to be involved in the events leading to inflammatory demyelination in the central nervous system. To ascertain this hypothesis 129 x C57BL/6 mice with an inactivation of the tnf and lta genes (129 x C57BL/6(-/-)) and SJL/J mice derived from backcrosses of the above mentioned mutant mice (SJL-/-) were immunized with mouse spinal cord homogenate (MSCH) or proteolipid protein. Both 129 x C57BL/6(-/-) mice and SJL-/- mice developed EAE. In SJL-/- mice immunized with MSCH, a very severe form of EAE with weight loss, paralysis of all four limbs, and lethal outcome was observed. The histologic hallmark was an intense perivascular and parenchymal infiltration with predominantly CD4(+) T cells and some CD8(+) T cells associated with demyelination in both brain and spinal cord. These results indicate that TNF-alpha and LT-alpha are not essential for the development of EAE.

Acute Disease↗

PubMed1997

Defensin stimulates the binding of lipoprotein (a) to human vascular endothelial and smooth muscle cells.

There is evidence to suggest that elevated plasma levels of lipoprotein (a) [Lp(a)] represent a risk factor for the development of atherosclerotic vascular disease, but the mechanism by which this lipoprotein localizes to involved vessels is only partially understood. In view of studies suggesting a link between inflammation and atherosclerosis and our previous finding that leukocyte defensin modulates the interaction of plasminogen and tissue-type plasminogen activator with cultured human endothelial cells, we examined the effect of this peptide on the binding of Lp(a) to cultured vascular endothelium and vascular smooth muscle cells. Defensin increased the binding of Lp(a) to endothelial cells approximately fourfold and to smooth muscle cells approximately sixfold. Defensin caused a comparable increase in the amount of Lp(a) internalized by each cell type, but Lp(a) internalized as a consequence of defensin being present was not degraded, resulting in a marked increase in the total amount of cell-associated lipoprotein. Abundant defensin was found in endothelium and in intimal smooth muscle cells of atherosclerotic human cerebral arteries, regions also invested with Lp(a). These studies suggest that defensin released from activated or senescent neutrophils may contribute to the localization and persistence of Lp(a) in human vessels and thereby predispose to the development of atherosclerosis.

Adult↗

PubMed1997

Role of CCR5 in infection of primary macrophages and lymphocytes by macrophage-tropic strains of human immunodeficiency virus: resistance to patient-derived and prototype isolates resulting from the delta ccr5 mutation.

The alpha-chemokine receptor fusin (CXCR-4) and beta-chemokine receptor CCR5 serve as entry cofactors for T-cell (T)-tropic and macrophage (M)-tropic human immunodeficiency virus type 1 (HIV-1) strains, respectively, when expressed with CD4 in otherwise nonpermissive cells. Some M-tropic and dual-tropic strains can also utilize other beta-chemokine receptors, such as CCR2b and CCR3. A mutation of CCR5 (delta ccr5) was recently found to be common in certain populations and appears to confer protection against HIV-1 in vivo. Here, we show that this mutation results in a protein that is expressed intracellularly but not on the cell surface. Primary CD4 T cells from delta ccr5 homozygous individuals were highly resistant to infection with prototype M-tropic HIV-1 strains, including an isolate (YU-2) that uses CCR5 and CCR3, but were permissive for both a T-tropic strain (3B) and a dual-tropic variant (89.6) that uses CXCR-4, CCR5, CCR3, or CCR2b. These cells were also resistant to M-tropic patient isolates but were readily infected by T-tropic patient isolates. Primary macrophages from delta ccr5 homozygous individuals were also resistant to infection with M-tropic strains, including YU-2, but the dual-tropic strain 89.6 was able to replicate in them even though macrophages are highly resistant to CXCR-4-dependent T-tropic isolates. These data show that CCR5 is the essential cofactor for infection of both primary macrophages and T lymphocytes by most M-tropic strains of HIV-1. They also suggest that CCR3 does not function for HIV-1 entry in primary lymphocytes or macrophages, but that a molecule(s) other than CCR5 can support entry into macrophages by certain virus isolates. These studies further define the cellular basis for the resistance to HIV-1 infection of individuals lacking functional CCR5.

CD4 Antigens↗

PubMed1997

CD4+ and CD8+ T cells are not major effectors of mouse hepatitis virus A59-induced demyelinating disease.

We examined murine hepatitis virus strain A59 (MHV-A59)-induced demyelinating disease in C57BL/6 mice which had previously been thymectomized at 25 days of age. Demyelination was observed in 51-96% of spinal cord quadrants examined 30 or 60 days post infection (dpi), indicating that neither an intact thymus nor thymic infection is a prerequisite to demyelination. Depletion of CD4+ or CD8+ T cells at 5, 7 or 10 dpi did not influence the extent of demyelination indicating that neither T cell subset is a major effector of demyelination. However, these findings do not exclude the possibility that T cells are involved in initiating demyelinating disease very early in infection.

Animals↗

PubMed1997

CXCR-4 (Fusin), a co-receptor for the type 1 human immunodeficiency virus (HIV-1), is expressed in the human brain in a variety of cell types, including microglia and neurons.

Entry of the type 1 human immunodeficiency virus into most cells requires the presence of the CD4 protein in combination with one of several recently described co-receptors. CXCR-4 (fusin) was the first identified, and it serves as co-receptor for T-cell-line tropic (T-tropic) HIV-1 isolates. To determine the expression of CXCR-4 in the brain, a major target of HIV pathology, we used immunohistochemistry and reverse transcriptase polymerase chain reaction with CXCR-4-specific antibodies and probes. We found that CXCR-4 was expressed in several cell types in brain, but notably in neurons and microglia, a finding that was replicated in tissue culture. The study of the expression of CXCR-4 in the brain, which may be one of many chemokine receptors in the central nervous system, may provide further insight into the interactions between brain cells, pathogens, and the immune system, and help understand the pathogenesis of HIV dementia.

AIDS Dementia Complex↗

PubMed1996

Syncytia formation induced by coronavirus infection is associated with fragmentation and rearrangement of the Golgi apparatus.

Coronavirus mouse hepatitis virus (MHV) possesses a membrane glycoprotein (M) which is targeted to the Golgi apparatus (GA). We used immunocytochemistry with an organelle-specific antiserum to investigate the morphologic changes of the GA during infection of L2 murine fibroblasts with MHV-A59. Twenty-four hours after infection the GA was fragmented and translocated in the center of syncytia, while the microtubular network was also rearranged displaying radiating elements toward the center of syncytia. Two fusion-defective mutants, which contain an identical amino acid substitution in the cleavage signal sequence of the spike glycoprotein (S), induced fragmentation of the GA. However, the GA migrated only partially to the centers of syncytia during infection with these mutants. Revertant viruses, in which the above mutation was corrected, had fusion properties and GA staining similar to wtMHV-A59. Experiments with brefeldin A (BFA), which induces redistribution of the GA into the rough endoplasmic reticulum (RER), revealed that an intact GA for a period of 4-16 hr postinfection, is required for coronavirus replication and syncytia formation. Thus, during MHV infection, syncytia formation is associated with fragmentation of the GA, followed by a previously undescribed phenomenon of migration of the organelle into the centers of syncytia. The fragmentation of the GA, however, may occur without the formation of syncytia. Therefore, two distinct mechanisms may be responsible for the fragmentation of the GA and its subsequent migration to the center of syncytia.

Animals↗

PubMed1996

HIV-1 infection of cultured human adult oligodendrocytes.

The mechanism through which HIV-1 causes HIV dementia (HIVD) is not well understood. Myelin pallor is a common pathological finding in HIVD and could be explained by a direct infection of oligodendrocytes or interaction with HIV-1 gp 120. To determine if oligodendrocytes could be infected by HIV-1, we purified oligodendrocytes from adult human brain tissues obtained from temporal lobe resections. These cells were exposed to HIV-1 and infectivity was assayed by detection of p24gag antigen, PCR amplification, and cocultivation with CD4+ cells. These results indicate that HIV-1(IIIB and BaL) and one of four primary isolates tested can infect oligodendrocytes, resulting in the production of infectious virus. Furthermore, in an experiment that mimics a potential in vivo scenario, infected microglia were able to transmit virus to oligodendrocytes in a trans-well culture system. These experiments indicate that oligodendrocyte infection should be considered in studying the pathophysiology of HIVD.

Adult↗

PubMed1996

Varicella-zoster ventriculo-encephalitis and spinal cord infarction in a patient with AIDS.

Varicella-zoster virus (VZV) infection is usually benign and self-limited. However, particularly in the immunosuppressed host, serious central nervous system complications may occur, including encephalitis, myelitis, and cerebral vascular occlusion. We report the case of a 57-year-old male with AIDS, who rapidly developed a sixth cranial nerve palsy and progressive myelopathy. There was no antecedent zoster rash. Autopsy revealed VZV ventriculo-encephalitis and vasculitis, as well as a transverse infarction of the spinal cord without evidence of direct infection of the cord parenchyma. Spinal cord infarction secondary to VZV vasculitis is an unusual cause of myelopathy in immunosuppressed patients.

AIDS-Related Opportunistic Infections↗

PubMed1996

Suppression of experimental autoimmune neuritis by phosphodiesterase inhibitor pentoxifylline.

Phosphodiesterase inhibitor pentoxifylline (POX) has been shown to have multiple immunomodulatory effects in vitro and in vivo. It inhibits T cell proliferation, T helper 1-type cytokines, and tumor necrosis factor. We postulated that POX might have an in vivo immunomodulatory effect on a T-cell-mediated autoimmune peripheral nervous system disease, experimental autoimmune neuritis (EAN). We investigated the effect of POX on EAN in rats immunized with peripheral nerve myelin containing neuritogenic peptide SP26. At 200 mg/kg/day, there was significant suppression of clinical EAN, weight loss, and T cell proliferation to SP26 compared to controls. Proliferation of T cells from immunized rats to SP26 was suppressed by POX in vitro. These studies demonstrate a beneficial role for POX in EAN, with potential applicability to human autoimmune demyelination.

Animals↗