UMLS:C0019693 - FACTA Search

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Query: UMLS:C0019693 (HIV)
170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The human immunodeficiency virus type 1 (HIV-1) Vif protein has an important role in the regulation of virus infectivity. This function of Vif is cell type specific, and virions produced in the absence of Vif in restrictive cells have greatly reduced infectivity. We show here that the intracellular localization of Vif is dependent on the presence of the intermediate filament vimentin. Fractionation of acutely infected T cells or transiently transfected HeLa cells demonstrates the existence of a soluble and a cytoskeletal form and to a lesser extent the presence of a detergent-extractable form of Vif. Confocal microscopy suggests that in HeLa cells, Vif is predominantly present in the cytoplasm and closely colocalizes with the intermediate filament vimentin. Treatment of cells with drugs affecting the structure of vimentin filaments affect the localization of Vif accordingly, indicating a close association of Vif with this cytoskeletal component. The association of Vif with vimentin can cause the collapse of the intermediate filament network into a perinuclear aggregate. In contrast, analysis of Vif in vimentin-negative cells reveals significant staining of the nucleus and the nuclear membrane in addition to diffuse cytoplasmic staining. In addition to the association of Vif with intermediate filaments, analyses of virion preparations demonstrate that Vif is incorporated into virus particles. In sucrose density gradients, Vif cosediments with capsid proteins even after detergent treatment of virus preparations, suggesting that Vif is associated with the inner core of HIV particles. We propose a model in which Vif has a crucial function as a virion component either by regulating virus maturation or following virus entry into a host cell possibly involving an interaction with the cellular cytoskeletal network.
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PMID:Cytoskeleton association and virion incorporation of the human immunodeficiency virus type 1 Vif protein. 852 63

Rates of death from tuberculosis in the United States decreased from 194 per 100,000 persons in 1900 to 40 per 100,000 persons in 1945, in part because the epidemic of tuberculosis in the western world was running its course and in part because of public health initiatives and improved socioeconomic conditions. In 1945, 63,000 persons died of tuberculosis and 115,000 new cases of the disease emerged. Streptomycin and para-aminosalicylic acid had just been discovered; the discovery of isoniazid followed, in 1952. Sanitarium care, nonsurgical and surgical collapse therapy, and resectional surgery were in widespread use. By the middle of the 1950s, it was evident that bedrest did not add to the benefit produced by effective chemotherapy, and sanitariums began to close, a process that was completed by the 1970s. As mortality and morbidity due to tuberculosis rapidly decreased, the U.S. government decreased funding for tuberculosis and many states and cities downgraded their tuberculosis control programs. After 1984, the rate of new cases of tuberculosis, which had decreased to 9.4 per 100,000, began to increase and focal outbreaks of multidrug-resistant tuberculosis were reported. Noncompliance with drug therapy, homelessness, immigration to the United States from developing countries, and human immunodeficiency virus (HIV) infection were invoked as explanations. With the reinstitution of federal funding, improved case-finding and surveillance, and the practice of having patients receive therapy while under direct observation, the rate of new cases of tuberculosis decreased to 8.7 per 100,000 in 1995, the lowest rate since national surveillance was begun in 1953. However, at the end of the 20th century, the worldwide burden of tuberculosis, which is engrafted onto the pandemic of HIV infection, is enormous: an estimated 7.6 million new cases in developing countries and 400,000 new cases in industrial nations.
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PMID:Tuberculosis then and now: a personal perspective on the last 50 years. 902 77

It is now apparent that HIV infection leads to a gradual collapse of a complex system of lymphoid tissue. This collapse tends to be associated with a change in virus tropism from macrophages to T lymphocytes, and a change in phenotype from nonsyncytium inducing (NSI) to syncytium inducing (SI). An experimental system is required to study the role of this change in HIV pathogenesis in lymphoid tissue. Here we describe such a system. Histocultures of human lymphoid tissue preserve their general cytoarchitecture, including a network of follicular dendritic cells (FDCs). Histocultures of tonsils, adenoids, or lymph nodes support productive infection with various laboratory and primary isolates of HIV-1 of different tropism and phenotype and exhibit isolate-dependent CD4+ T lymphocyte depletion. A strong correlation between the extent of CD4+ T cell depletion and the SI/NSI phenotype of the isolates is demonstrated. AZT was used as a model drug to inhibit viral replication and CD4+ T cell depletion in lymphoid histocultures. HIV pathogenesis and the effect of antivirals can now be studied in human lymphoid tissue under controlled conditions in vitro.
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PMID:Experimental HIV infection of human lymphoid tissue: correlation of CD4+ T cell depletion and virus syncytium-inducing/non-syncytium-inducing phenotype in histocultures inoculated with laboratory strains and patient isolates of HIV type 1. 910 Sep 87

Although the high incidence of EBV-associated diffuse large cell lymphomas (DLCL) in HIV-1 infection is believed to be related to loss of immune control due to HIV-induced immune deficiency, it has been claimed that cytotoxic T lymphocyte (CTL) responses to EBV are longer lasting in HIV-1-infected persons than CTL directed against HIV-1 itself. We approached this apparent paradox by performing the first longitudinal study into the kinetics of EBV and HIV-specific CTL responses in HIV-infected patients progressing either to AIDS with non-Hodgkin's lymphoma (NHL) or AIDS with opportunistic infection (OI). Multiple samples were tested from HIV-1 seroconversion to AIDS-diagnosis. Four out of six patients that were either long-term asymptomatic or progressing to OI showed declining HIV-1 CTL precursor (CTLp) frequencies whereas EBV-CTLp remained stable, suggestive for HIV-1-specific immune exhaustion. In two patients rapidly progressing to AIDS-OI, a parallel decline of HIV-1- and EBV-CTL responses was seen, indicative for total collapse of cellular immunity. In all these six patients EBV-load remained low. However, in four out of five patients that progressed to DLCL, EBV-load was high and increasing several months preceding the NHL. In all five patients, EBV-CTLp decreased before the emergence of the NHL. Thus, our data show that in HIV-1 infection loss of HIV-1-specific T cell immunity is not necessarily paralleled by loss of EBV-specific T cell responses. The occurrence of AIDS-related DLCL is preceded by decreasing EBV-CTLp and increasing EBV load. Failing EBV-control might therefore be an important step in the pathogenesis of AIDS-related DLCL.
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PMID:Epstein-Barr virus-specific cytotoxic T cell responses in HIV-1 infection: different kinetics in patients progressing to opportunistic infection or non-Hodgkin's lymphoma. 911 96

The rate of progression to AIDS in human immunodeficiency virus type 1 (HIV-1)-infected individuals is determined by a complex series of interactions between the host and virus. Here we evaluate virologic properties and host responses in two men near-simultaneously infected with HIV-1 from the same sexual partner--one individual progressed to AIDS in less than 2 years, and the other remains asymptomatic 3 years postinfection. Distinct neutralizing antibody and cellular immune responses were evident, with the slower progressor exhibiting generally stronger and broader responses, except for cytotoxic T-lymphocyte responses early in infection. Virtually identical, homogeneous virus populations were found in both patients in the first sample obtained; however, a second unrelated HIV-1 virus population was also found in the fast progressor. Whether the second population emanated from an additional source of infection or the two were transmitted from the original source could not be determined. The virus population in the slower progressor turned over and diversified rapidly, whereas both virus populations in the rapid progressor evolved at a much slower rate. In addition, the character of mutational changes underlying these diversities appeared to be distinct, with a bias for diversifying selection developing in the slower progressor and a reciprocal bias towards purifying selection maintained in both populations in the fast progressor. Thus, the rapid evolution that is a hallmark of HIV replication may be a reflection of strong host resistance against emerging virus variants and a longer period of asymptomatic infection. Furthermore, rapid progression was not linked to a collapse of any appreciable immune response following attainment of some threshold of antigenic diversity but rather to a failure to drive this diversification and a condition of relatively unimpeded expansion of variants with optimized replicative capacity within the host.
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PMID:Divergent patterns of progression to AIDS after infection from the same source: human immunodeficiency virus type 1 evolution and antiviral responses. 915 16

The purpose of this study was to investigate strategies in the monotherapy treatment of HIV infection in the presence of drug-resistant (mutant) strains. A mathematical system is developed to model resistance in HIV chemotherapy. It includes the key players in the immune response to HIV infection: virus and both uninfected CD4+ and infected CD4+ T-cell populations. We model the latent and progressive stages of the disease, and then introduce monotherapy treatment. The model is a system of differential equations describing the interaction of two distinct classes of HIV--drug-sensitive (wild type) and drug-resistant (mutant)--with lymphocytes in the peripheral blood. We then introduce chemotherapy effects. In the absence of treatment, the model produces the three types of qualitative clinical behavior--an uninfected steady state, an infected steady state (latency), and progression to AIDS. Simulation of treatment is provided for monotherapy, during the progression to AIDS state, in the consideration of resistance effects. Treatment benefit is based on an increase or retention in CD4+ T-cell counts together with a low viral titer. We explore the following treatment approaches: an antiviral drug which reduces viral infectivity that is administered early--when the CD4+ T-cell count is > or = 300/mm3, and the late--when the CD4+ T-cell count is less than 300/mm3. We compare all results with data. When treatment is initiated during the progression to AIDS state, treatment prevents T-cell collapse, but gradually loses effectiveness due to drug resistance. We hypothesize that it is the careful balance of mutant and wild-type HIV strains which provides the greatest prolonged benefit from treatment. This is best achieved when treatment is initiated when the CD4+ T-cell counts are greater than 250/mm3, but less than 400/mm3 in this model (i.e. not too early, not too late). These results are supported by clinical data. The work is novel in that it is the first model to accurately simulate data before, during and after monotherapy treatment. Our model also provides insight into recent clinical results, as well as suggests plausible guidelines for clinical testing in the monotherapy of HIV infection.
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PMID:Understanding drug resistance for monotherapy treatment of HIV infection. 921 52

The GTPase Ran is essential for nuclear import of proteins with a classical nuclear localization signal (NLS). Ran's nucleotide-bound state is determined by the chromatin-bound exchange factor RCC1 generating RanGTP in the nucleus and the cytoplasmic GTPase activating protein RanGAP1 depleting RanGTP from the cytoplasm. This predicts a steep RanGTP concentration gradient across the nuclear envelope. RanGTP binding to importin-beta has previously been shown to release importin-alpha from -beta during NLS import. We show that RanGTP also induces release of the M9 signal from the second identified import receptor, transportin. The role of RanGTP distribution is further studied using three methods to collapse the RanGTP gradient. Nuclear injection of either RanGAP1, the RanGTP binding protein RanBP1 or a Ran mutant that cannot stably bind GTP. These treatments block major export and import pathways across the nuclear envelope. Different export pathways exhibit distinct sensitivities to RanGTP depletion, but all are more readily inhibited than is import of either NLS or M9 proteins, indicating that the block of export is direct rather than a secondary consequence of import inhibition. Surprisingly, nuclear export of several substrates including importin-alpha and -beta, transportin, HIV Rev and tRNA appears to require nuclear RanGTP but may not require GTP hydrolysis by Ran, suggesting that the energy for their nuclear export is supplied by another source.
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PMID:The asymmetric distribution of the constituents of the Ran system is essential for transport into and out of the nucleus. 935 34

The first case of HIV infection in Russia was detected in 1987, there have since been 142 million HIV tests in the country, and 196 and 1535 new HIV cases were reported in 1995 and 1996, respectively. By 2000, the Ministry of Health forecasts that there will be 800,000 HIV-positive people in the country. It is culturally accepted in Russia to use drugs intravenously. There has been a rapid rise in the number of IV drug users in Russia, with an estimated 100,000 users in Moscow forming an important core group for HIV transmission, and similar numbers of users in Leningrad, Kalinigrad, and Rostov. Russian IV drug users are mainly aged 15-25 years who lead regular lives, attend school, and socialize freely with non-users, including having sexual relationships. Such behavior among IV drug users facilitates the rapid spread of HIV to the rest of society. Ketamine is popular among schoolchildren, who inject it intramuscularly, while homemade IV drugs also abound. High levels of IV drug use, a health system in a state of collapse, a growing incidence and prevalence of sexually transmitted diseases (STDs), and government inexperience with the HIV epidemic mean that an HIV epidemic in Russia is inevitable. Medecins Sans Frontieres has launched an HIV prevention campaign together with the government.
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PMID:Russia: sex, drugs, and AIDS and MSF. 946 23

Two different structures of ligand-free HIV protease have been determined by X-ray crystallography. These structures differ in the position of two 12 residue, beta-hairpin regions (or "flaps") which cap the active site. The movements of the flaps must be involved in the binding of substrates since, in either conformation, the flaps block the binding site. One of these structures is similar to structures of the ligand-bound enzyme; however, the importance of both structures to enzyme function is unclear. This transformation takes place on a time scale too long for conventional molecular dynamics simulations, so the process was studied by first identifying a reaction path between the two structures and then calculating the free energy along this path using umbrella sampling. For the ligand-free enzyme, it is found that the two structures are nearly equally stable, with the ligand-bound-type structure being less stable, consistent with X-ray crystallography data. The more stable open structure does not have a lower potential energy, but is stabilized by entropy. The transition occurs through a collapse and reformation of the beta-sheet structure of the conformationally flexible, glycine-rich flap ends. Additionally, some problems in studying conformational changes in proteins through the use of a single reaction path are addressed.
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PMID:Reaction path and free energy calculations of the transition between alternate conformations of HIV-1 protease. 967 38

In 1986, Weiss et al reported a group of patients with nephrotic syndrome, progressive chronic renal failure, and the histopathologic features of glomerular capillary collapse. Similar lesions are often described in human immunodeficiency virus (HIV) nephropathy. We evaluated 893 consecutive nontransplant renal biopsies performed in our department and the follow-up of the patients at our outpatient service. Sixteen specimens were identified with the pathological features of collapsing glomerulopathy (focal segmental or global glomerular capillary collapse and visceral epithelial cell hyperplasia), with no evidence of HIV infection and/or intravenous drug abuse. Their clinical characteristics were analyzed and compared with a group of 29 patients with noncollapsing focal segmental glomerulosclerosis (FSGS). The follow-up period of both patient groups was 5 +/- 1.46 years. The Kaplan-Meier life table method was used to present survival of the patients. The age of both groups was similar, 34 +/- 4 years (mean +/- standard error of the mean) for patients with collapsing glomerulopathy and 35 +/- 3 years for those with FSGS. The serum creatinine level was greater in patients with collapsing glomerulopathy (183 +/- 31 micromol/L) compared with those with FSGS (115 +/- 18 micromol/L), but the difference was not significant (P = 0.0504). The difference in proteinuria was not significant (P = 0.7668); it was 5.83 +/- 0.74 g/d in patients with collapsing glomerulopathy and 5.42 +/- 0.84 g/d in those with focal sclerosing glomerulonephritis. The difference in systolic (P = 0.4) and diastolic blood pressure (P = 0.556) was also not significant. Survival of the patients with collapsing glomerulopathy was worse than that of patients with FSGS (P = 0.025). Renal function survived 5 years in 40% of the patients with FSGS, but patients with collapsing glomerulopathy had no renal function survival. Our data suggest that idiopathic collapsing glomerulopathy is a distinct clinicopathologic entity with similar clinical features to focal sclerosing glomerulonephritis, but a worse prognosis and a rapidly progressive course toward end-stage renal disease.
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PMID:Collapsing glomerulopathy: clinical characteristics and follow-up. 1019 29

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