Glycoprotein H-related complexes of human cytomegalovirus: identification of a third protein in the gCIII complex

Previous studies have described three disulfide-bonded glycoprotein complexes within the envelope of human cytomegalovirus (HCMV). These have been designated gCI, gCII, and gCIII. Although gCI has been identified as homodimeric glycoprotein B (gB, gpUL55), the compositions of gCII and gCIII remain incompletely defined. Earlier studies suggested that gCIII was composed of glycoprotein H (gH, gpUL75) complexed with a second glycoprotein, the gL homolog of HCMV. We characterized the gCIII complex of HCMV using recombinant vaccinia virus-expressed gH and gL. Our results indicated that authentic gCIII was not reconstituted by coexpression of gH and gL. The presence of a third, structurally and antigenically unique glycoprotein with an estimated molecular mass of 125,000 Da in virion-derived gCIII complexes suggested that at least three proteins were necessary for formation of this envelope glycoprotein complex. This third glycoprotein, gp125, contained both simple and complex N-linked carbohydrates and had an estimated deglycosylated mass of 64,000 Da. Furthermore, we demonstrated that mature gH existed as both a covalently complexed and noncovalently associated component of the gCIII complex within the envelope of infectious extracellular virions. These findings provide further evidence for the structural complexity of the envelope of HCMV and emphasize the uncertainties associated with the previous assignment of specific functions to envelope proteins of HCMV.

Neurocognitive impairment is an independent risk factor for death in HIV infection. San Diego HIV Neurobehavioral Research Center Group

OBJECTIVE

To determine if mortality is increased in individuals with human immunodeficiency virus type 1 (HIV-1)-associated neurocognitive disorders less severe than frank dementia.

DESIGN

A prospective cohort study; median duration of follow-up was 2.4 years. Kaplan-Meier analysis and Cox proportional hazards models were used to compare survival times according to neurocognitive classification.

SETTING

University-based research unit.

PARTICIPANTS

A volunteer sample of 414 individuals seropositive for HIV-1. Subjects were classified at their baseline evaluation as neuropsychologically (NP) normal or abnormal (impaired in > or = 2 NP test domains). A subgroup of NP abnormal subjects met operational criteria for HIV-associated minor cognitive motor disorder; the remaining subjects were designated NP impaired. Subjects with frank dementia were excluded.

MAIN OUTCOME MEASURE

Mortality.

RESULTS

At the baseline evaluation, 256 (62%) of 414 subjects were designated normal; 109 (26%). NP impaired; and 49 (12%), minor cognitive motor disorder. One hundred six participants (26%) died during follow-up. Compared with the NP normal group, the unadjusted relative risk (RR) of death for all NP abnormal subjects (minor cognitive motor disorder and NP impaired) was significantly increased (RR, 1.7; 95% confidence interval [CI], 1.2-2.6; P < .005). After adjusting for concurrently measured predictors of survival (CD4 lymphocyte counts, Centers for Disease Control and Prevention HIV disease classification, hemoglobin concentration, and serum beta 2-microglobulin) in proportional hazards models, mortality for all NP abnormal subjects remained elevated (RR, 1.8; 95% CI, 1.2-2.8; P < .01). The elevation in mortality risk for subjects with minor cognitive motor disorder was statistically significant (RR, 2.2; 95% CI, 1.2-3.8; P < .01); for NP impaired subjects it was marginally significant (RR, 1.6; 95% CI, 1.0-2.8; P = .06).

CONCLUSIONS

The HIV-infected individuals with NP impairment had a higher risk of dying than those without impairment. This was particularly true for those meeting syndromic diagnostic criteria.

Steroid hormones act directly to trigger segment-specific programmed cell death of identified motoneurons in vitro

In larvae of the hawkmoth, Manduca sexta, accessory planta retractor (APR) motoneurons undergo a segment-specific pattern of programmed cell death at pupation. APR death is triggered hormonally by the prepupal peak of the ecdysteroid, 20-hydroxyecdysone (20-HE). Previous studies found no evidence that cellular interactions regulate the segmental pattern of APR death in vivo. To test the hypothesis that 20-HE acts directly on APRs to trigger a cell-autonomous, segment-specific pattern of death, APRs were labeled with the fluorescent dyes DiI or DiA, removed from the nervous system before the prepupal peak, and placed in low-density cell culture. Physiological levels of 20-HE triggered the same segment-specific pattern of APR death in vitro as seen in vivo, both in cultures containing a single APR and in cultures containing two APRs removed from the same donor animal. The presence or absence of contact with other cells did not influence the APRs' responses to 20-HE. The death of APRs in culture was characterized by fragmentation or rounding up of the cell body and fragmentation of the neurites. These findings suggest that intrinsic segmental identity regulates whether these motoneurons live or die when exposed to a steroid hormone during development.

Gay, lesbian, and bisexual adolescents: providing esteem-enhancing care to a battered population

Suicide, HIV infection, violent victimization, homelessness, and substance use are known to affect gay (gay males, lesbians, and bisexual persons of both genders) youths at disproportionately high rates. This article explores the difficulties gay youths experience in this society specific to their sexual orientation. These difficulties become internalized by many gay youths, leading to high rates of preventable morbidities and mortalities. Stages of the "coming out" process for gay persons are reviewed within the framework of child and adolescent development. Barriers within the health care system, as well as within other social systems, specific to gay youths are examined. Such barriers include language use by the provider, sexual and social history questions asked by the provider, environmental images in the health care setting, and the responses of the provider to the adolescent. Strategies such as the use of gender-neutral wording, homosexual inclusive questioning in history taking, and the use of inclusive environmental clues to allow gay adolescents to feel safe and accepted are discussed. Health care providers are encouraged to employ such strategies to help reduce these barriers within various health care settings.

Antiviral pressure exerted by HIV-1-specific cytotoxic T lymphocytes (CTLs) during primary infection demonstrated by rapid selection of CTL escape virus

The HIV-1-specific cytotoxic T lymphocyte (CTL) response is temporally associated with the decline in viremia during primary HIV-1 infection, but definitive evidence that it is of importance in virus containment has been lacking. Here we show that in a patient whose early CTL response was focused on a highly immunodominant epitope in gp 160, there was rapid elimination of the transmitted virus strain and selection for a virus population bearing amino acid changes at a single residue within this epitope, which conferred escape from recognition by epitope-specific CTL. The magnitude (> 100-fold), kinetics (30-72 days from onset of symptoms) and genetic pathways of virus escape from CTL pressure were comparable to virus escape from antiretroviral therapy, indicating the biological significance of the CTL response in vivo. One aim of HIV-1 vaccines should thus be to elicit strong CTL responses against multiple codominant viral epitopes.

Retinal findings and characteristics in AIDS patients with systemic Mycobacterium avium-intracellulare complex and toxoplasmic encephalitis

BACKGROUND AND OBJECTIVE

The purpose of this study was to evaluate the incidence and characteristics of retinal and choroidal manifestations of toxoplasmosis and/or Mycobacterium avium-intracellulare complex (MAC) in patients with acquired immunodeficiency syndrome (AIDS).

PATIENTS AND METHODS

The authors analyzed their prospectively collected data and found 120 patients with new retinal lesions (group A) that were diagnosed 3 months or longer following the diagnosis of MAC and/or toxoplasmic encephalitis. The authors also performed a point prevalence study of retinal/choroidal findings in 25 consecutive AIDS patients (group B) without known eye disease who had been recently treated for toxoplasmic encephalitis and/or disseminated MAC infections. In addition, the characteristics of retinochoroidal toxoplasmosis scars in 5 AIDS patients were studied and compared with the characteristics of scars in 18 immunocompetent patients.

RESULTS

In this study the incidence of ocular manifestations of MAC was zero (95% confidence interval [CI] 0.0% to 3.8%). Two of 25 patients (8%) (95% CI 1% to 26%) in group A and 2 of 11 patients (18.1%) (95% CI 3.3% to 51.8%) in group B had toxoplasmic retinochoroiditis.

CONCLUSION

In AIDS patients, ocular manifestations of toxoplasmosis are more common than ocular MAC. In addition, when compared with immunocompetent patients, AIDS patients tend to have retinochoroidal scars with less retinal pigment epithelium hyperplasia (1.8+ vs 3+) (P = .03).

The drug verapamil inhibits bystander killing but not cell suicide in thymidine kinase-ganciclovir prodrug-activated gene therapy

The bystander effect, in which unmodified cells are killed as the result of enzyme-prodrug activation in genetically modified neighboring cells, amplifies the suicide response in a tumor in which only a fraction of the cells are targeted. The drug verapamil (VRP), a calcium channel antagonist that is also used to counteract the multidrug resistance of tumor cells, is shown to inhibit the bystander effect by herpes simplex virus thymidine kinase (HSVtk) enzyme-prodrug therapy with ganciclovir by protecting beta geo marked bystander cells in both in vitro coculture assays and in an in vivo animal tumor model. VRP had no stimulatory or inhibitory effect on the proliferation of CT 26 cells, their tumorigenicity, or prodrug-activated cell death produced by the action of the HSVtk gene. The kinetics of the protection afforded by VRP was time dependent with respect to the time of addition of the prodrug, and protection was ineffective when added two or more days after prodrug administration.

Human cytomegalovirus US3 impairs transport and maturation of major histocompatibility complex class I heavy chains

The human cytomegalovirus (HCMV) early glycoprotein products of the US11 and US2 open reading frames cause increased turnover of major histocompatibility complex (MHC) class I heavy chains. Since US2 is homologous to another HCMV gene (US3), we hypothesized that the US3 gene product also may affect MHC class I expression. In cells constitutively expressing the HCMV US3 gene, MHC class I heavy chains formed a stable complex with beta 2-microglobulin. However, maturation of the N-linked glycan of MHC class I heavy chains was impaired in US3+ cells. The glycoprotein product of US3 (gpUS3) occurs mostly in a high-mannose form and coimmunoprecipitates with beta 2-microglobulin associated class I heavy chains. Mature class I molecules were detected at steady state on the surface of US3+ cells, as in control cells. Substantial perinuclear accumulation of heavy chains was observed in US3+ cells. The data suggest that gpUS3 impairs egress of MHC class I heavy chains from the endoplasmic reticulum.

European Lyme borreliosis: 231 culture-confirmed cases involving patients with erythema migrans

In 1994, we isolated Borrelia burgdorferi sensu lato from 231 patients with erythema migrans who presented to the University Medical Center in Ljubljana, Slovenia. Samples of erythema migrans-affected skin were placed in media to support the growth of Borrelia species and evaluated in Ljubljana and Chicago. Patients whose cultures were positive included 132 women and 99 men; 136 of these 231 patients recalled a tick bite. Patients noted a rash an average of 24 days after a bite and presented a mean of 34 days after the bite with erythema migrans (mean diameter. 16 cm). Itching (44%) burning (18%), and pain (11%) were the most common local symptoms. Systemic complaints (40%) included headache, fatigue, malaise, and arthralgia. Other than erythema migrans, findings on physical examination were minimal (< 5% had fever, and in < 10% local lymph nodes were affected). Serial serological studies using indirect immunofluorescence assay, ELISA, and Western blot methods were performed, and antibodies to B, burgdorferi sensu lato were detected in < 50% of samples from patients. This is the largest series reported to date of patients with culture-confirmed Lyme borreliosis. It highlights the deficiencies of serological tests in early disease, demonstrates the sensitivity of direct detection methods for evaluation of patients with erythema migrans, and suggests that patients with early Lyme borreliosis in Slovenia may suffer a milder illness than those in the United States.

Sequences regulating tropism of human immunodeficiency virus type 1 for brain capillary endothelial cells map to a unique region on the viral genome

Two infectious molecular clones of human immunodeficiency virus type 1, NL4-3 and JR-CSF, differ in their abilities to productively infect human brain capillary endothelial (HBCE) cells. The phenotypes of recombinants between these two molecular strains were examined to identify viral sequences responsible for the difference in HBCE cell tropism between the two parental strains. Our results indicate that HBCE cell tropism maps to a region that encompasses the C1 region of env and includes overlapping reading frames for the accessory genes vpr, vpu, tat, and rev. This region was unique for HBCE cell tropism and did not cosegregate with either macrophage or T-cell line tropism. However, several recombinant clones displayed dual tropism for both HBCE cells and macrophages. These endothelial cell- and macrophage-tropic strains may have a unique pathogenic advantage by entering the brain via HBCE cells and subsequently infecting microglial cells with high efficiency, leading to the induction of human immunodeficiency virus dementia.

Studies of Plasmodium falciparum cytoadherence using immortalized human brain capillary endothelial cells

The cytoadherence of Plasmodium falciparum-infected erythrocytes was studied using immortalized human brain capillary endothelial cells. The immortalized cells, denoted as BB19, derived from the human brain endothelium, were transformed with the E6E7 genes of human papilloma virus and retained their endothelial nature, i.e. tubule formation occurred with Matrigel as a substratum and the cells stained positive for Factor VIII-related antigen, or vonWillebrand's factor. Surface expression of ICAM-1, VCAM, E-selectin, and CD36 was demonstrated by immunofluorescence staining with monoclonal antibodies to these ligands. Exposure to cytokines (TNF, IFN gamma, IL-1 alpha, and IL-6) and lipopolysaccharide resulted in an increase in expression of ICAM-1, VCAM, E-selectin, and CD36. The BB19 cells bound P. falciparum-infected red blood cells with both the FCR-3 and the ITO4 strains. Antibodies to CD36 and ICAM-1 partially inhibited the binding of the FCR-3 and the ITO4 lines, respectively. These findings suggest that BB19 cells may be useful in the analysis of receptor-based cytoadherence and sequestration, as well as in the cell biology of microvessel formation.

The enhancer domain of the human cytomegalovirus major immediate-early promoter determines cell type-specific expression in transgenic mice

The human cytomegalovirus (HCMV) major immediate-early promoter (MIEP) is one of the first promoters to activate upon infection. To examine HCMV MIEP tissue-specific expression, transgenic mice were established containing the lacZ gene regulated by the MIEP (nucleotides -670 to +54). In the transgenic mice, lacZ expression was demonstrated in 19 of 29 tissues tested by histochemical and immunochemical analyses. These tissues included brain, eye, spinal cord, esophagus, stomach, pancreas, kidney, bladder, testis, ovary, spleen, salivary gland, thymus, bone marrow, skin, cartilage, and cardiac, striated and smooth muscles. Although expression was observed in multiple organs, promoter activity was restricted to specific cell types. The cell types which demonstrated HCMV MIEP expression included retinal cells of the eye, ductile cells of the salivary gland, exocrine cells of the pancreas, mucosal cells of the stomach and intestine, neuronal cells of the brain, muscle fibers, thecal cells of the corpus luteum, and Leydig and sperm cells of the testis. These observations indicate that the HCMV MIEP is not a pan-specific promoter and that the majority of expressing tissues correlate with tissues naturally infected by the virus in the human host.

Developmental analysis of the cytomegalovirus enhancer in transgenic animals

The major immediate-early promoter (MIEP) of human, cytomegalovirus (HCMV) constitutes a primary genetic switch for viral activation. In this study, regulation of the enhancer-containing segment (nucleotides -670 to +54) of the HCMV MIEP attached to the 1acZ reporter gene was examined in the developing embryos of transgenic mice to identify temporal and tissue-specific expression. We find that the transgene reporter is first detected as a dorsal stripe of expression in the neural folds of embryos at day 8.5 postcoitum (p.c.). A broad expression pattern is exhibited in embryos at day 9.5 p.c. This pattern becomes more restricted by day 10.5 p.c. as organogenesis progresses. By day 14.5 p.c., prominent expression is observed in a subpopulation of central nervous system cells and spinal ganglia, endothelial cells, muscle, skin, thyroid, parathyroid, kidney, lung, liver, and gut cells, and the pancreas and submandibular and pituitary glands. This distribution pattern is discussed in relation to human congenital HCMV infection. These results suggest that the transcriptional activity of the HCMV MIEP may determine in part, the ability of the virus to specifically target developing fetal tissues in utero.

Molecular characterization of Borrelia burgdorferi sensu lato from Slovenia revealing significant differences between tick and human isolates

One hundred twenty-nine Slovenian isolates of Borrelia burgdorferi sensu lato derived from patients (69 strains) or Ixodes ricinus ticks (60 strains) were characterized. All of the strains were first- or second-passage isolates obtained in 1992 and 1993 from the same endemic region. The techniques used for the molecular analysis of strains included species-specific polymerase chain reaction (PCR) typing, and pulsed-field gel electrophoretic separation of undigested and MluI-digested genomic DNA. Isolates were identified to the species level by large restriction fragment pattern (LRFP) analysis and the results compared with the species-specific PCR result. Fifty-two patient isolates (75%) were typed as Borrelia afzelii (LRFP MLa1), 6 (9%) as Borrelia garinii (LRFPs MLg1-4), and 11 (16%) as Borrelia burgdorferi sensu stricto. The latter included 9 isolates (13%) with a new LRFP that is not typical of Borrelia burgdorferi sensu stricto and for which the designation MLx is suggested. In contrast, only 32 of 60 (53%) tick isolates were typed as Borrelia afzelii, while 20 strains (33%) were typed as Borrelia garinii and 8 strains (13%) as Borrelia burgdorferi sensu stricto. Three new LRFPs were found among the Borrelia garinii (MLg5 and 6) and Borrelia burgdorferi sensu stricto (MLb15) tick isolates. Large restriction fragment pattern analysis identified new groups of Borrelia burgdorferi sensu lato and revealed an apparent difference in the isolation frequency of different species from patients and ticks in the same endemic region.

A novel mechanism for persistence of human cytomegalovirus in macrophages

Human cytomegalovirus (HCMV) infection of monocyte-derived macrophages (MDM) results in delayed and nonlytic productive viral growth. During late stages of replication, infectious virus remains cell associated in cytoplasmic vacuoles. In order to understand HCMV survival and persistence in MDM, we examined mechanisms involved in the formation and trafficking of HCMV-containing vacuoles in these cells. Utilizing double-label immunofluorescence with antibodies to viral and cellular proteins, HCMV-containing vacuoles were associated with the Golgi apparatus marker mannosidase II but not with markers to early endosomes (transferrin receptor and rab5) or late endosomes and early lysosomes (LAMP-1 and -2). In addition, as late-stage viral infection progressed in MDM, the cells displayed increasing abnormalities in the Golgi apparatus. Analysis of structural features of infected cells revealed the disruption of the microtubule network. These observations suggest a novel mechanism by which HCMV is vacuolized in MDM, avoiding degradation and release from the cell.

Natural killer cell activity in chronic lymphocytic leukemia patients treated with fludarabine

Fludarabine, the 5'-monophosphate of 9-beta-D-arabinofuranosyl-2- fluoroadenine (FaraAMP), is effective in the treatment of chronic lymphocytic leukemia (CLL) and has been demonstrated to increase natural killer (NK) cell lytic activity (NKa) in humans and mice. To determine the effect of FaraAMP on NK cells in CLL, we analyzed NKa toward K562 targets after in vitro incubation with FaraAMP and after in vivo exposure to fludarabine. Pretreatment analysis of peripheral blood from 12 CLL patients (9 untreated) revealed: median number of NK cells 500/microliter (range 290-1160); median NKa lytic unit30/10(6) cells (range 5-80). These results were similar to those from healthy adult donors. After exposure to 3, 30 or 300 microM FaraAMP, the median maximum stimulation index (NKa FaraAMP/NKa) was 1.2 (range 0.9-1.5), within the range observed in normal adults. FaraA also stimulated NKa in vitro toward autologous CLL cells in two of five patients as measured by a dye-exclusion assay. In three patients following three or more treatment courses of fludarabine (30 mg/m2 per day for 5 days) the NK cell number and NKa were maintained near pretreatment values. Phenotypic analysis of the peripheral mononuclear cells in 34 consecutive CLL patients revealed a marked reduction in CD5/CD20 and CD4 cell numbers after three courses of fludarabine with less effect on CD8 and CD56 cells. These results indicate that fludarabine spares NK cells and may stimulate NKa in some CLL patients.

Human immunodeficiency virus infection of bone marrow endothelium reduces induction of stromal hematopoietic growth factors

The majority of human immunodeficiency virus (HIV)-seropositive patients develop bone marrow abnormalities associated with hematopoietic malfunction during the progression of disease. One important manifestation of HIV-associated hematopoietic dysfunction is that after myelosuppression, bone marrow recovery, a process known to be mediated in part by the production of stromal cell-derived hematopoietic growth factors, is impaired. We sought to test the hypothesis that bone marrow stromal cells are infected by HIV-1 in vivo and that production of certain stromal cell-derived hematopoietic growth factors is deficient as a consequence. In this report, we demonstrate that bone marrow microvascular endothelial cells (MVEC), a key element of the stroma, are the predominant cells infected by HIV (5% to 20%) in bone marrow stromal cultures obtained from 11 consecutive HIV-seropositive patients. Although HIV-infected stromal cultures enriched for MVEC constitutively express normal levels of interleukin (IL)-4, IL-6, granulocyte (G)-colony-stimulating factor (CSF), granulocyte-macrophage (GM)-CSF, tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta, and Steel factor, IL-1 alpha-induced release of IL-6 and G-CSF is significantly reduced in these cultures. These observations suggest that HIV infection of bone marrow MVEC reduces the capacity of hematopoietic stroma to respond to regulatory signals that normally augment blood cell production during periods of increased demand.

Azole phenoxy hydroxyureas as selective and orally active inhibitors of 5-lipoxygenase

Azole phenoxy hydroxyureas are a new class of 5-lipoxygenase (5-LO) inhibitors. Structure-activity relationship studies have demonstrated that electronegative substituents on the 2-phenyl portion of the oxazole tail increased the ex vivo potency of these inhibitors. Similar substitutions on the thiazole analogs had only minor contribution to the ex vivo activity. The trifluoromethyl-substituted oxazole 24 was the best compound of the oxazole series in both the ex vivo (6 h pretreated rats) and in vivo (3 h pretreated rats) RPAR assay with ED50 values of approximately 1 and 3.6 mg/kg, respectively, but was weakly active in the allergic guinea pig assay. Oxazole 50 was equally active in both the RPAR and guinea pig in vivo models and was similar to zileuton. The unsubstituted thiazole 52 was the best compound of the thiazole series, by inhibiting the leukotriene B4 biosynthesis in the RPAR assay (3 h pretreated rats) by 99%, at an oral dose of 10 mg/kg, and the bronchoconstriction in the allergic guinea pig by 50%, at an intravenous dose of 10 mg/kg. Oxazole 24 demonstrated high and selective 5-LO inhibitory activity in the in vitro assays, with IC50 values ranging from 0.08 microM in mouse macrophages to 0.8 microM in human peripheral monocytes to 1.2 microM in human whole blood. This activity was selective for 5-LO, as concentrations up to 15 microM in mouse macrophages did not affect prostaglandin formation. Oxazole 59 was the most active inhibitor in the human monocyte assay with an IC50 value of 7 nM.

Magnetic resonance imaging to study lesions of atherosclerosis in the hyperlipidemic rabbit aorta

We have developed a high resolution magnetic resonance (MR) imaging technique to serially assess lesions of atherosclerosis in a rabbit model. A volume phased array coil was designed and used to image the abdominal aortas of six atherosclerotic rabbits and two age-, sex-, and weight-matched controls. Lesions of atherosclerosis were induced by a combination of repeat balloon injury and a hyperlipidemic diet. All animals were imaged on at least two occasions 9-16 months after initiation of atherosclerosis. In addition, animals were imaged immediately after sacrifice. Anatomic dissection and histology were performed to verify the MR findings. The volume phased array coil improves the image signal-to-noise ratio over existing extremity coils and resulted in higher resolution images of the abdominal aorta. Proton density-weighted images acquired with 2D/3D fast spin-echo are the most useful sequence to outline the vessel wall and to differentiate wall from lumen and background. Progressive wall thickening and lumen stenosis were observed in the serial images of the diseased rabbits. Wall thickness and lumen area derived noninvasively from the in vivo MR images correlate with postmortem MR images and sections of aorta examined by dissection microscopy and histology. Spin-echo and fast spin-echo imaging with a phased array body coil can be used to accurately assess plaque dimensions, and potentially can be used to image intraplaque features and to monitor lesion progression or regression. It should also be possible to adapt these techniques to assess human disease, especially for peripheral vascular problems.

Interaction of the 72-kilodalton human cytomegalovirus IE1 gene product with E2F1 coincides with E2F-dependent activation of dihydrofolate reductase transcription

Three polypeptides are produced from the major immediate-early (IE) region of human cytomegalovirus by alternative splicing. The IE gene products regulate subsequent viral and cellular gene expression. We previously reported that cotransfection of a genomic clone of the major IE region stimulated transient expression of chloramphenicol acetyltransferase driven by the dihydrofolate reductase (DHFR) promoter and that an intact E2F site was required for the trans activation (M. Wade, T. F. Kowalik, M. Mudryj, E.-S. Huang, and J. C. Azizkhan, Mol. Cell. Biol. 12:4364-4374, 1992). With the availability of cDNA clones for the individual major IE proteins, we sought to determine which of these proteins exerted this effect and whether the IE protein(s) interacted with E2F. In this study, we use cotransfection to demonstrate that the 55- and 86-kDa major IE proteins from the IE2 region can each moderately trans activate the DHFR promoter and that the 72-kDa IE1 protein stimulates DHFR transcription to a much higher level. Furthermore, trans activation through the 72-kDa IE1 protein is in part E2F dependent, while activation by the 55- and 86-kDa IE proteins is E2F independent. We also demonstrate by in vitro pull-down assays that the 72-kDa IE1 protein can specifically interact with the DNA binding domain of E2F1 (amino acids 88 to 191) in the presence of nuclear extract. Moreover, antibodies to either E2F1 or IE72 will immunoprecipitate both E2F and IE72 from cells that stably express IE72, and antibody to E2F1 will immunoprecipitate IE72 from normal human fibroblast cells infected with human cytomegalovirus.

Liver contrast enhancement in primates using iopromide liposomes

RATIONALE AND OBJECTIVES

We studied the feasibility of using iodinated liposomes as computed tomography (CT) liver contrast agents in nonhuman primates.

METHODS

Iopromide-containing liposomes were investigated as reticuloendothelial (RES) contrast agents for CT scanning of the liver in normal adult baboons. For intravenous (i.v.) injection, liposomes were resuspended in mannitol solution, filtered under sterile conditions, and injected i.v. at doses of 200 and 400 mg l/kg to each of five anesthetized adult baboons.

RESULTS

Animals tolerated the injections without measurable electrocardiographic changes and recovered uneventfully from anesthesia. Sequential CT scans of the baboons' upper abdomen acquired up to 60 min postinjection showed persistent enhancement of the liver 10-60 min after injection. Maximum enhancement levels were 36 and 61 delta Hounsfield units (delta H) after the 200- and 400-mg/kg doses, respectively. The mean time to plateau enhancement was 20 min with the 200-mg/kg dose and 10 min with the 400-mg/kg dose. The greatest splenic enhancements were 181 and 301 delta H after the 200- and 400-mg/kg doses, respectively.

CONCLUSION

Iopromide liposomes are effective as RES contrast agents in primates.

Magnetic resonance imaging of the hepatobiliary system: intestinal absorption studies of manganese mesoporphyrin

RATIONALE AND OBJECTIVES

We studied the intestinal absorption of manganese mesoporphyrin (Mn-mesoporphyrin), a potential oral hepatobiliary contrast agent.

METHODS

Mn-mesoporphyrin was complexed with monoolein and taurocholate (mixed micelles). Portal venous delivery and biliary excretion were measured after intestinal administration in rats and rabbits, and the mechanism of intestinal transport was studied in a combined lymph-bile fistula model in rats. T1-weighted magnetic resonance (MR) images of the liver were obtained in rats and domestic pigs before and after gastric administration of Mn-mesoporphyrin in mixed micelles.

RESULTS

A 2.2-fold increase of portal venous Mn concentration was found 90 min after intestinal administration of the complex. None was found in the lymph collected from the thoracic duct, indicating a transcellular transport mechanism through the intestinal mucosa with portal venous delivery. Mn-mesoporphyrin levels in bile peaked between 240 and 270 min after administration (200-fold increase). The greatest liver enhancement (20-90%) was measured 360 min after administration.

CONCLUSION

The feasibility of intestinal delivery of Mn-mesoporphyrin, a lipophilic hepatobiliary contrast agent was demonstrated.