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Biomedical subjects

W A O'Brien

Publications and source records attributed to W A O'Brien.

At least 37 records · Page 2Linked to original sources
PubMed1997

Changes in plasma HIV RNA levels and CD4+ lymphocyte counts predict both response to antiretroviral therapy and therapeutic failure. VA Cooperative Study Group on AIDS.

BACKGROUND: Markers are needed for assessing response to antiretroviral therapy over time. The CD4+ lymphocyte count is one such surrogate, but it is relatively weak. OBJECTIVE: To assess the association of changes in plasma human immunodeficiency virus (HIV) RNA level and CD4+ lymphocyte count with progression to the acquired immunodeficiency syndrome (AIDS). DESIGN: Analysis of data from a subset of patients in a multicenter, randomized, clinical trial. SETTING: Six Veterans Affairs medical centers and one U.S. Army medical center. PATIENTS: 270 symptomatic HIV-infected patients from the Veterans Affairs Cooperative Study on AIDS. INTERVENTION: Patients were randomly assigned to receive zidovudine or placebo initially; a cross-over protocol was established for patients receiving placebo who had disease progression. MEASUREMENTS: Reverse transcriptase polymerase chain reaction on cryopreserved plasma samples, previously obtained CD4+ lymphocyte counts, and clinical events. RESULTS: For each decrease of 0.5 log10 copies/mL in plasma HIV RNA level, averaged over the 6 months after randomization, the relative risk (RR) for progression to AIDS was 0.67 (P < 0.001). In a subset of 70 treated patients with long-term follow-up, a return to baseline plasma HIV RNA levels within 6 months of randomization was associated with progression to AIDS (RR, 4.28; P = 0.004). Plasma HIV RNA levels or CD4+ lymphocyte counts over time were more strongly associated with progression to AIDS than were baseline levels or counts. CONCLUSIONS: An adequate virologic response after initiation of antiretroviral therapy seems to require a decrease in plasma HIV RNA level of at least 0.5 log10 copies/mL that is sustained for at least 6 months. The independent relation between plasma HIV RNA level and CD4+ lymphocyte count over time and clinical outcome suggests that the measurement of plasma HIV RNA level, in addition to the CD4+ lymphocyte count, has a role in guiding the management of antiretroviral therapy.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Changes in plasma HIV-1 RNA and CD4+ lymphocyte counts and the risk of progression to AIDS. Veterans Affairs Cooperative Study Group on AIDS.

BACKGROUND: Clinical trials of antiretroviral drugs can take years to complete because the outcomes measured are progression to the acquired immunodeficiency syndrome (AIDS) or death. Trials could be accelerated by the use of end points such as changes in CD4+ lymphocyte counts and plasma levels of human immunodeficiency virus type 1 (HIV-1) RNA and beta 2-microglobulin, but there is uncertainty about whether these surrogate measures are valid predictors of disease progression. METHODS: We analyzed data from the Veterans Affairs Cooperative Study on AIDS, which compared immediate with deferred zidovudine therapy. Patients' plasma levels of HIV-1 RNA and beta 2-microglobulin were measured in stored plasma. RESULTS: Among the 129 patients in the immediate-treatment group, 34 had disease that progressed to AIDS, as compared with 57 of the 141 patients in the deferred-treatment group (P = 0.03). Progression to AIDS correlated strongly with base-line CD4+ lymphocyte counts (P = 0.001) and plasma levels of HIV-1 RNA (P < 0.001), but not with base-line levels of beta 2-microglobulin (P = 0.14). A decrease of at least 75 percent in the plasma level of HIV-1 RNA over the first six months of zidovudine therapy accounted for 59 percent of the benefit of treatment, defined as the absence of progression to AIDS (95 percent confidence interval, 13 to 112 percent). Plasma beta 2-microglobulin levels and CD4+ lymphocyte counts explained less of the effect of treatment. A 75 percent decrease in the plasma HIV-1 RNA level plus a 10 percent increase in the CD4+ lymphocyte count could explain 79 percent of the treatment effect (95 percent confidence interval, 27 to 145 percent). CONCLUSIONS: Treatment-induced changes in the plasma HIV-1 RNA level and the CD4+ lymphocyte count, taken together, are valid predictors of the clinical progression of HIV-related disease and can be used to assess the efficacy of zidovudine and possibly other antiretroviral drugs as well.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Long-term follow-up of symptomatic HIV-infected patients originally randomized to early versus later zidovudine treatment; report of a Veterans Affairs Cooperative Study. VA Cooperative Study Group on AIDS Treatment.

Following a 4-year controlled trial comparing early and later zidovudine treatment, we conducted an additional 3-year follow-up. Of the original 338 patients, 275 participated. Clinical outcome measures were AIDS and death. In the early therapy group (n = 170), 67 patients progressed to AIDS compared with 85 in the later therapy group (n = 168); the relative risk (RR) comparing early with later therapy was 0.72% (95% confidence interval [CI] 0.52-0.99; p = 0.044). The early therapy group had 74 deaths compared with 73 in the later therapy (RR = 0.98; 95% CI, 0.71-1.36; p = 0.91). The early group had a peak CD4+ count increase at 1-2 months and a delay of 1 year before CD4+ counts fell below baseline. For patients who received zidovudine for more than the median duration (20.3 months) before their first AIDS diagnosis, the RR for death was 2.08 (95% CI, 1.36-3.19, p = 0.001). Additional factors independently associated with poor prognosis following AIDS were a CD4+ count of < 100 cells/mm3 and increased severity of the first AIDS diagnosis, whereas use of another antiretroviral agent was associated with improved survival. We conclude that early zidovudine therapy delays progression to AIDS but does not affect survival. Patients who progress to AIDS while on prolonged zidovudine monotherapy many benefit from a change to other antiretroviral therapy(ies).

Acquired Immunodeficiency Syndrome↗
PubMed1996

HIV viral load markers in clinical practice.

Plasma HIV RNA determinations are an important prognostic marker of disease progression and, when used appropriately, provide a valuable tool for the management of individual patients. But what constitutes appropriate use?

Antiviral Agents↗
PubMed1996

Human immunodeficiency virus type 1 activation after blood transfusion.

BACKGROUND: Anemia and transfusion are predictors of disease progression in AIDS patients. This study was designed to examine the effects of blood transfusion on human immunodeficiency virus type 1 (HIV-1) expression. STUDY DESIGN AND METHODS: Assays of plasma viral load were performed before and after transfusion in nine HIV-1-infected patients who required blood transfusion for refractory anemia. RESULTS: There was a modest rise in plasma HIV-1 p24 antigen and plasma HIV-1 RNA beginning 1 to 2 weeks after the blood transfusion. The mean change in plasma p24 antigen for all patients was 9.3 +/- 5.1 (mean +/- SE) pg per mL at Week 2 after transfusion and 18 +/- 11.1 pg per mL at Week 4. Plasma HIV-1 RNA levels were unchanged immediately after transfusion and exceeded pretransfusion levels with a mean rise of 84 +/- 40 percent (SE) at Week 1, 70 +/- 27 percent at Week 2, and 67 +/- 38 percent at Week 4 (p = 0.006, exact permutation test). There was no increase in spontaneous or interleukin 2-induced lymphocyte proliferation or p24 antigen production by patients' lymphocytes that were examined immediately after blood transfusion. CONCLUSION: The transfusion of blood to persons with advanced HIV-1 infection modestly increases plasma levels of HIV-1. The activation of HIV-1 expression by transfusion may help to explain the accelerated course of HIV-1 disease in recipients of blood transfusion.

Anemia↗
PubMed1996

Anti-human immunodeficiency virus type 1 activity of an oligocationic compound mediated via gp120 V3 interactions.

An oligocationic peptide compound (ALX40-4C) was developed for consideration in the treatment of human immunodeficiency virus type 1 (HIV-1) infection. This compound was designed to mimic the basic domain of the HIV-1 transactivation protein, Tat, and will competitively inhibit Tat binding to its specific RNA hairpin target (TAR [transactivation region]), found at the 5' end of all HIV-1 transcripts. Blocking Tat-TAR interactions can abrogate HIV-1 replication. ALX40-4C was shown to inhibit replication of HIV-1NL4-3 in a range of cell types, including primary cells and transformed cell lines, by as much as 10(4)-fold. In some experiments, virus rescue was not possible even after removal of ALX40-4C from the cultures. Strain-dependent resistance has been demonstrated for all antiretroviral agents tested; therefore, we tested for variable sensitivity to ALX40-4C. The cloned primary strains, HIV-JR-CSF and HIV-JR-FL, were less sensitive to ALX40-4C inhibition. Unexpectedly, determinants for efficient ALX40-4C inhibition were mapped by using recombinant virus strains to the V3 region of gpl20 and were shown to act at early events in viral replication, which include viral entry. If entry and reverse transcription are bypassed by transfection, a more modest, virus strain-independent inhibition is shown; this inhibition is likely due to blocking of Tat-TAR interaction. Thus, the highly basic oligocationic Tat inhibitor ALX40-4C appears to interfere with initial virus-target cell interactions which involve HIV-1 gp120 V3 determinants, most efficiently for T-cell line-adapted strains.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Human immunodeficiency virus-type 1 replication can be increased in peripheral blood of seropositive patients after influenza vaccination.

Despite considerable evidence that cell activation enhances human immunodeficiency virus-type 1 (HIV-1) replication in vitro, there is very little data on the role of immune activation on in vivo HIV-1 replication. In this study, we examined the effect of influenza vaccination on HIV-1 replication in the peripheral blood of 20 study subjects, and in 14 control subjects who did not receive influenza vaccination. Blood was obtained from each subject on three occasions during the month before vaccination and again on three occasions during the following month. Over the study period, there was little change in levels of proviral DNA in peripheral blood mononuclear cells (PBMCs). However, peak PBMC viral RNA levels after influenza vaccination were significantly increased over the mean of prevaccination values. This change was not observed to the same extent in unvaccinated controls. Therefore, this is the first report showing that HIV-1 replication can increase in temporal association with influenza vaccination. Our results suggest that continued immunologic (antigenic) stimulation may result in increased virus load in vivo. To address the appropriateness of influenza vaccination in HIV-infected patients, expanded studies will be required to examine specific and generalized immune responses to vaccination, and differences in patient response based on disease stage.

Adult↗
PubMed1994

HIV-1 entry and reverse transcription in macrophages.

Although CD4 is required for efficient virus entry, it is not sufficient for entry of all primary HIV-1 strains. There may be additional virus-cell interactions, possibly involving the V3 region of the extracellular envelope protein, gp120, that occur following conformational changes induced by CD4 binding. This second interaction would precede fusion events and entry of the virus core. Primary HIV-1 strains appear to have a higher virion envelope density and retain gp120 better than HIV-1 strains adapted to growth in T cell lines in culture. These properties may confer a growth advantage in vivo to primary strains on the basis of less well exposed CD4 binding and neutralization domains. HIV-1 entry into both activated and quiescent T cells, as well as macrophages, is efficient for most primary strains, but there are different patterns of reverse transcription. Productive infection of activated T cells is associated with cell proliferation and accumulation of full-length reverse transcripts within 4 to 6 h. In resting, nondividing T cells, reverse transcription is aborted prior to full-length viral DNA formation. A third pattern of reverse transcription is seen in nondividing cultured macrophages with slow kinetics and accumulation of full-length viral DNA between 36 and 48 h. This rate can be increased by adding exogenous nucleotides, but still not to the rate seen in activated T cells. Future antiretroviral therapies may involve interference with cell-specific functions involved in reverse transcription.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Kinetics of human immunodeficiency virus type 1 reverse transcription in blood mononuclear phagocytes are slowed by limitations of nucleotide precursors.

Human immunodeficiency virus type 1 infection of mononuclear phagocytes has been implicated in disease manifestations, but postentry viral replication events in these cells have not been well characterized. Productive infection of activated T cells is associated with cell proliferation and accumulation of full-length viral DNA within 6 h. In infected, nondividing quiescent peripheral blood lymphocytes, reverse transcription is aborted prior to full-length viral DNA formation. For nondividing, cultured mononuclear phagocytes, we now report a third pattern of reverse transcription with relatively slow kinetics, in which full-length viral DNA did not accumulate until 36 to 48 h. The reverse transcription rate in mononuclear phagocytes could be accelerated by addition of exogenous nucleotide precursors, but still not to the rate seen in activated T cells. These results indicate that substrate limitations in mononuclear phagocytes slow but do not arrest human immunodeficiency virus type 1 reverse transcription.

AIDS Dementia Complex↗
PubMed1994

Macrophage-tropic and T-cell line-adapted chimeric strains of human immunodeficiency virus type 1 differ in their susceptibilities to neutralization by soluble CD4 at different temperatures.

Molecular clones of three macrophage-tropic and three T-cell line-adapted strains of human immunodeficiency virus type 1 (HIV-1) were used to explore the mechanism of HIV-1 resistance to neutralization by soluble CD4 (sCD4). The three macrophage-tropic viruses, each possessing the V3 and flanking regions of JR-FL, were all resistant to sCD4 neutralization under the standard conditions of a short preincubation of the virus and sCD4 at 37 degrees C prior to inoculation of peripheral blood mononuclear cells. In contrast, the three T-cell line-adapted viruses, NL4-3 and two chimeras possessing the V3 and flanking regions of NL4-3 in the envelope background of JR-FL, were all sCD4 sensitive under these conditions. Sensitivity to sCD4 neutralization at 37 degrees C corresponded with rapid, sCD4-induced gp120 shedding from the viruses. However, when the incubation temperature of the sCD4 and virus was reduced to 4 degrees C, the three macrophage-tropic viruses shed gp120 and became more sensitive to sCD4 neutralization. In contrast, the rates of sCD4-induced gp120 shedding and virus neutralization were reduced for the three T-cell line-adapted viruses at 4 degrees C. Thus, HIV resistance to sCD4 is a conditional phenomenon; macrophage-tropic and T-cell line-adapted strains can be distinguished by the temperature dependencies of their neutralization by sCD4. The average density of gp120 molecules on the macrophage-tropic viruses exceeded by about fourfold that on the T-cell line-adapted viruses, suggesting that HIV growth in T-cell lines may select for a destabilized envelope glycoprotein complex. Further studies of early events in HIV-1 infection should focus on primary virus strains.

Adaptation, Physiological↗
PubMed1993

Rapid enzymatic analysis for human immunodeficiency virus type 1 DNA in clinical specimens.

A clinical procedure for rapid detection of human immunodeficiency virus type 1 (HIV-1) by DNA amplification is demonstrated. The rapid procedure reduces handling requirements and amplification time and eliminates use of radioactivity for the detection of the amplification product. Total leukocyte lysates are the amplification substrates. Two conserved regions in the HIV-1 genome are amplified by 45 cycles of a two-temperature thermal cycle and the amplification products are detected by ultraviolet light after electrophoresis on agarose gels. Twenty-four specimens clinically diagnosed by detection of antibody (IgG) to HIV-1 were confirmed by the rapid DNA amplification procedure. In a blind study, 56 samples positive for HIV-1 DNA were detected in 503 individuals by the current classical polymerase chain reaction method; the same 56 positive samples were also detected by the rapid amplification protocol. No false-positive or false-negative results were obtained. The turnaround time for analysis has been reduced to < 24 h without compromising test results.

Base Sequence↗
PubMed1992

Human immunodeficiency virus type 1 tropism for brain microglial cells is determined by a region of the env glycoprotein that also controls macrophage tropism.

Human immunodeficiency virus type 1 (HIV-1), the agent of AIDS, frequently infects the central nervous system. We inoculated adult human brain cultures with chimeric viruses containing parts of the env gene of a cloned primary isolate from brain tissue, HIV-1 JRFl, inserted into the cloned DNA of a T-cell-tropic strain. A chimeric virus containing the carboxy-terminal portion of HIV-1 JRFl env did not replicate in these brain tissue cultures, while a chimera expressing an env-encoded protein containing 158 amino acids of HIV-1 JRFl gp120, including the V3 loop, replicated well in brain microglial cells, as it does in blood macrophages. Infection of brain microglial cells with such a chimera was blocked by an antibody to the V3 loop of gp 120. Thus, env determinants in the region of gp120, outside the CD4-binding site and comprising the V3 loop, are critical for efficient viral binding to and/or entry into human brain microglia.

Base Sequence↗
PubMed1992

Mapping genetic determinants for human immunodeficiency virus type 1 resistance to soluble CD4.

Neutralization of human immunodeficiency virus type 1 (HIV-1) infection with soluble CD4 (sCD4) can be achieved over a broad range of concentrations for different virus strains. Laboratory virus strains passaged in transformed T-cell lines are typically sensitive to sCD4 neutralization, whereas primary virus isolates require over 100-fold-higher sCD4 concentrations. Using recombinant viruses generated from a laboratory strain, HIV-1NL4-3, and a primary macrophagetropic strain, HIV-1JR-FL, we mapped a region of gp120 important for determining sensitivity to sCD4 neutralization. This same region has previously been defined as important for macrophage and transformed T-cell line tropism and includes the V3 neutralization domain but does not include regions of gp120 that have been shown to be most important for CD4 binding.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Viral determinants of cellular tropism.

Cells of mononuclear phagocyte lineage are the predominant cell type producing human immunodeficiency virus type 1 (HIV-1) in extravascular tissues; HIV-1 infection of mononuclear phagocytes may be directly related to primary disease manifestations and also appears to contribute to the immune deficiency of AIDS. Whereas peripheral blood lymphocytes are permissive for nearly all strains of HIV-1, only some HIV-1 strains replicate efficiently in mononuclear phagocytes. Recombinant virus strains have been used to identify a 157-amino acid region of gp120 that can confer macrophage tropism. This region is distinct from the principal CD4 binding domain of gp120 and includes the major type-specific neutralizing epitope located in the third hypervariable domain, V3. Quantitative assay of HIV-1-specific DNA by polymerase chain reaction early after infection suggests that HIV-1 strain differences in macrophage tropism are determined at the level of entry. These studies suggest that target cell interactions with gp120 in addition to or in conjunction with the CD4 binding domain are necessary for efficient entry into mononuclear phagocytes.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Increased susceptibility of differentiated mononuclear phagocytes to productive infection with human immunodeficiency virus-1 (HIV-1).

Differences in susceptibility to infection of most mononuclear phagocytes with HIV-1 are not known. We investigated the relative susceptibility of autologous freshly isolated blood monocytes (MN), MN cultured in vitro to allow differentiation (CM), and alveolar macrophages (AM) from healthy subjects to productive infection with HIV-1. Cells were infected with the macrophage tropic strain HIV-1JR-FL and p24 gag antigen levels measured in supernatants by ELISA. Freshly isolated MN had negligible levels of p24 in supernatants. In contrast AM had peak p24 levels of 4145 +/- 1456 pg/ml, mean +/- SE, and CM 9216 +/- 3118. As a measure of entry and extent of reverse transcription, levels of viral DNA in infected mononuclear phagocytes were analyzed by quantitative polymerase chain reaction (PCR). The data using primers that amplify all transcripts including incompletely formed reverse transcripts indicated that differences in entry of the virus may contribute to differences in virus production observed with MN, AM, and CM. Other primer pairs that detect intermediate and full-length double-stranded DNA showed that the ability to complete reverse transcription was similar among these mononuclear phagocytes. Since the lung is a major site of opportunistic infection and noninfectious complications in HIV-1-infected individuals, this increase in productive infection with HIV-1 in AM compared with MN could contribute to the immunopathogenesis of the lung disorders seen in the acquired immunodeficiency syndrome.

Adult↗
PubMed1991

HIV-1 env sequence variation in brain tissue of patients with AIDS-related neurologic disease.

We investigated sequence variation in the human immunodeficiency virus type 1 (HIV-1) env gene region that encodes the fourth disulfide-bonded domain of the external membrane glycoprotein, gp120, among three HIV-1 isolates from patients with AIDS-related neurologic disease. The sequences of HIV-1 isolated directly from brain tissue, blood cells, and in vitro cell cultures were compared. The results suggest that there may be many closely related HIV-1 genomes of several distinct subtypes in an HIV-1-infected individual. Differences were observed in the frequency distribution of sequence variants obtained from brain versus blood of the same individuals. Overall, the proportion of silent mutations is much lower than expected by random occurrence. Taken together, these results favor the possibility that selective forces may play a role in the tissue distribution of certain HIV-1 strains.

AIDS Dementia Complex↗
PubMed1990

HIV-1 tropism for mononuclear phagocytes can be determined by regions of gp120 outside the CD4-binding domain.

Cells of the mononuclear phagocyte system are the predominant cell producing HIV-1 in most tissues including the central nervous system (CNS), spinal cord, lung and skin; infection is associated with dementia, neuropathy, pneumonitis, and dermatitis respectively. Different HIV-1 isolates vary markedly in their ability to infect mononuclear phagocytes productively. Here we describe molecular clones of a CNS-derived isolate, HIV-1(JR-FL), which can replicate efficiently in mononuclear phagocytes. Analysis by polymerase chain reaction of early events after infection indicates that the early phase of viral replication before reverse transcription determines tropism. Genetic mapping of the macrophage-tropic phenotype by construction of recombinant viruses indicates that mononuclear phagocyte infectivity can be determined by a 157-amino-acid region of the gp 120 glycoprotein of HIV-1(JR-FL). Significantly, this region is upstream from the previously defined CD4-binding domain. We propose that at least one determinant for mononuclear phagocyte tropism involves target cell interactions with regions of gp120 distinct from the CD4-binding domain.

AIDS Dementia Complex↗