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Biomedical subjects

D D Richman

Publications and source records attributed to D D Richman.

At least 163 records · Page 9Linked to original sources
PubMed1994

Combinative interactions of a human immunodeficiency virus (HIV) Tat antagonist with HIV reverse transcriptase inhibitors and an HIV protease inhibitor.

Combinations of the human immunodeficiency virus (HIV) Tat protein antagonist Ro 24-7429 with either the HIV protease inhibitor Ro 31-8959 or the HIV reverse transcriptase inhibitors AZT (3'-azido-3'-deoxythymidine), ddC (2',3'-dideoxycytidine), ddI (2',3'-dideoxyinosine), and nevirapine were synergistic or additive in reducing HIV type 1 p24 antigen production in CEM cells or inhibiting HIV type 1-induced syncytium formation in HT4-6C cells.

Antiviral Agents↗
PubMed1994

Nevirapine resistance mutations of human immunodeficiency virus type 1 selected during therapy.

Drug susceptibility and mutations in the reverse transcriptase (RT) gene were analyzed with 167 virus isolates from 38 patients treated with nevirapine, a potent nonnucleoside inhibitor of human immunodeficiency virus type 1 (HIV-1) RT. Resistant isolates emerged quickly and uniformly in all patients administered nevirapine either as monotherapy or in combination with zidovudine (AZT). Resistance developed as early as 1 week, indicating rapid turnover of the virus population. The development of resistance was associated with the loss of antiviral drug activity as measured by CD4 lymphocyte counts and levels of HIV p24 antigen and RNA in serum. In addition to mutations at amino acid residues 103, 106, and 181 that had been identified by selection in cell culture, mutations at residues 108, 188, and 190 were also found in the patient isolates. Sequences from patient clones documented cocirculating mixtures of populations of different mutants. The most common mutation with monotherapy, tyrosine to cysteine at residue 181, was prevented from emerging by coadministration of AZT, which resulted in the selection of alternative mutations. The observations documented that, under selective drug pressure, the circulating virus population can change rapidly, and many alternative mutants can emerge, often in complex mixtures. The addition of a second RT inhibitor, AZT, significantly altered the pattern of mutations in the circulating population of HIV.

Antiviral Agents↗
PubMed1994

Optimal infectivity in vitro of human immunodeficiency virus type 1 requires an intact nef gene.

The replication competence of human immunodeficiency virus type 1 genomes containing mutations in the nef open reading frame was evaluated in continuous cell lines. Mutants that contained a deletion in the nef open reading frame, premature termination codons, or missense mutations in the N-terminal myristoylation signal were constructed. The replication of these mutants was tested in three ways. First, plasmid genomes were used to transfect T-lymphoblastoid cells. Second, low-passage posttransfection supernatants were used to infect cells with a relatively low virus input. Third, high-titer virus stocks were used to infect cells with a relatively high virus input. These experiments demonstrated a 100- to 10,000-fold decrement in p24 production by the nef mutants compared with that by the wild-type virus. The greatest difference was obtained after infection with the lowest virus input. The myristoylation signal was critical for this positive effect of nef. To investigate the mechanism of the positive influence of nef, nef-positive and nef-minus viruses were compared during a single cycle of replication. These single-cycle experiments were initiated both by infection with high-titer virus stocks and by transfection with viral DNA. Single-cycle infection yielded a three- to fivefold decrement in p24 production by nef-minus virus. Single-cycle transfection yielded equal amounts of p24 production. These results implied that nef does not affect replication after the provirus is established. In support of these results, viral production from cells chronically infected with nef-positive or nef-minus viruses was similar over time. To determine whether the effect of nef was due to infectivity, end point titrations of nef-positive and nef-minus viruses were performed. nef-positive virus had a greater infectivity per picogram of HIV p24 antigen than nef-minus virus. These data indicated that the positive influence of nef on viral growth rate is due to an infectivity advantage of virus produced with an intact nef gene.

Amino Acid Sequence↗
PubMed1994

Antiproliferative effect of retinoid compounds on Kaposi's sarcoma cells.

A panel of retinoid compounds (tretinoin, isotretinoin, acitretin, and RO13-1470) were tested for inhibitory activity against Kaposi's sarcoma cell (KSC) cultures in vitro. Tretinoin was found to be the most effective retinoid tested, inhibiting the growth of KSC in vitro while having no effect on the expression of interleukin-6 and basic fibroblast growth factor, two important cytokines involved in KSC growth. Tretinoin also did not appear to downregulate the expression of receptors for these two cytokines. At low concentrations (10(-9) M), acitretin and tretinoin selectively inhibited growth of early passage KSC. At higher concentrations (10(-6)-10(-5) M), retinoid treatment induced a pattern of DNA degradation and morphological changes in KSC characteristic of apoptosis (programmed cell death). The inhibitory activity of tretinoin on KSC growth was decreased if human serum (but not fetal calf serum) was present in the growth medium, and partially restored by removal of serum lipids. These data suggest that retinoids possess potential as therapeutic agents in Kaposi's sarcoma.

Acitretin↗
PubMed1994

Synthesis and hypnotic and anti-human immunodeficiency virus-1 activities of N3-substituted 2'-deoxy-2'-fluorouridines.

Reaction of 9-[3,5-di-O-(tetrahydropyran-2-yl)-beta-D-arabinofuranosyl]uracil (2) with diethylaminosulfur trifluoride in the presence of pyridine afforded 2'-deoxy-2'-fluororiboside 3a, from which 2'-deoxy-2'-fluorocytidine (4b) has been synthesized in good yield. Compound 3a was deprotected and subsequently treated with various benzyl halides or 2-chloro-4-fluoroacetophenone to give corresponding N3-substituted 2'-deoxy-2'-fluorouridines 5a-c and 6. Compounds 5a-c, as well as 6, showed weak hypnotic activity in mice. Compound 4b showed moderate antiviral activity against human immunodeficiency virus-1 but 3b, 5a-c, and 6 were virtually inactive.

Animals↗
PubMed1994

Resistance to AZT and ddC during long-term combination therapy in patients with advanced infection with human immunodeficiency virus.

To ascertain whether combination therapy with zidovudine (AZT) and zalcitabine (ddC) delayed the emergence of AZT resistance, isolates of human immunodeficiency virus (HIV) were evaluated from 15 previously untreated patients with advanced HIV disease who received combination therapy. Eighteen sequential viral isolates were available from 15 patients who received > or = 6 months of combination therapy. Isolates from eight (73%) of 11 patients obtained between 24 and 48 weeks of therapy were AZT resistant [50% inhibitory concentration (IC50) > or = 0.45 microM; range, 0.45-2.0 microM]. Four of these eight patients yielded virus isolates that were highly AZT resistant (IC50 > 1.0 microM). No changes in ddC susceptibility were discerned. The median IC50 for ddC was 0.2 microM and ranged from 0.07 to 0.5 microM. The CD4 cell counts of patients with AZT-sensitive virus tended to have higher median areas under the curve (AUC) and greater increases compared with patients who had AZT-resistant virus. They also had higher means and ranges of the average CD4 cell counts at week 36 (p = 0.01) and week 48 (p = 0.04). These data would indicate that the previously described more sustained CD4 cell responses conferred by the addition of ddC to AZT therapy cannot be ascribed to delayed emergence of AZT resistance with combination therapy.

CD4-Positive T-Lymphocytes↗
PubMed1994

Stimulation of HIV replication in mononuclear phagocytes by leukemia inhibitory factor.

This study examined the effects of leukemia inhibitory factor (LIF) on human immunodeficiency virus (HIV) replication in mononuclear phagocytes (MNP). LIF induced a dose-dependent increase in p24 antigen production in the chronically infected promonocytic cell line U1. The magnitude and time kinetics of the LIF effects were similar to interleukin 1 (IL-1), IL-6, and tumor necrosis factor (TNF), other cytokines known to induce HIV replication in this cell line. To characterize mechanisms responsible for these LIF effects, levels of HIV mRNA, activation of the DNA binding protein nuclear factor (NF)-kB, signal transduction pathways, and potential interactions with other cytokines were analyzed. LIF increased steady-state levels of HIV mRNA at 2.0, 4.3, and 9.2 kB. This was detectable by 24 h and persisted until 72 h. The DNA binding protein NF-kB is a central mediator in cytokine activation of HIV transcription. NF-kB levels were higher in unstimulated U1 cells as compared to the parent cell line U937. In both cell lines LIF increased NF-kB activity. Induction of NF-kB and HIV replication by cytokines are at least in part dependent on reactive oxygen intermediates. The oxygen radical scavenger N-acetyl-L-cysteine, but not an inhibitor of nitric oxide synthase, inhibited LIF-induced HIV replication. LIF induces the production of other cytokines in monocytes but its effects on HIV replication were not inhibited by antibodies to IL-1, TNF, or IL-6. These results identify LIF as a stimulus of HIV replication.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcysteine↗
PubMed1993

Microtiter format gene quantification by covalent capture of competitive PCR products: application to HIV-1 detection.

We have developed a simple gene quantification system using the competitive polymerase chain reaction (CPCR) followed by microtiter format analysis. CPCR is carried out using a mutant competitor with the same size as the target DNA product, and a minimal base exchange to insure the same amplification kinetics. One primer is aminated at the 5' end to produce PCR products that are captured onto carboxylated wells of microtiter plates through peptide bond formation. The non-aminated DNA strands are stripped off from the wells by alkali washing, and the remaining aminated strands are hybridized with either a digoxigenin-labeled wild type-specific oligonucleotide probe or a competitor-specific probe. To standardize the hybridization conditions of the probes, a DNA construct containing wild type and mutant competitor sequences in tandem is captured at different concentrations, hybridized with the probes, and used to generate a standard curve. Bound probes are detected by anti-digoxigenin antibody conjugated with peroxidase and chromogen. Optical densities are recorded with a conventional microtiter plate reader and converted to concentrations according to the standard curves. The ratios of wild type DNA to mutant competitor are used to determine the initial amounts of wild type DNA in the samples. This method was used successfully to quantify human immunodeficiency virus type 1 (HIV-1) env gene in human lymphocytes. It only requires a thermal cycler and a conventional microtiter plate reader, and can be readily done on a large scale. Potential applications include detection of other pathogens, diagnosis of genetic disorders and studies of gene expression.

Base Sequence↗
PubMed1993

Correlation between CD4+ counts and prevalence of cytomegalovirus retinitis and human immunodeficiency virus-related noninfectious retinal vasculopathy in patients with acquired immunodeficiency syndrome.

We prospectively studied 132 patients with acquired immunodeficiency syndrome (AIDS) to determine the cross-sectional prevalence of cytomegalovirus retinitis. All patients had serum CD4+ lymphocyte counts to determine the degree of immune dysfunction. Correlations between CD4+ counts, the presence of cytomegalovirus retinitis or human immunodeficiency virus (HIV)-related noninfectious retinal vasculopathy, and ocular symptoms were made. The study disclosed that 26 of 132 patients with AIDS (20%) had cytomegalovirus retinitis. However, subset analysis according to CD4+ count disclosed that in patients with CD4+ counts of 50 cells/mm3 or less, 26 of 87 (30%) had cytomegalovirus retinitis, whereas in patients with CD4+ counts of 50 cells/mm3 or more, none of 45 was noted to have cytomegalovirus retinitis. Similarly, 46 of 132 patients (35%) were noted to have HIV-related noninfectious retinal vasculopathy, with a trend toward increasing prevalence associated with declining CD4+ count. In patients with CD4+ counts of 50 cells/mm3 or less, 39 of 87 (45%) had HIV-related noninfectious retinal vasculopathy, whereas seven of 45 patients (16%) with CD4+ counts of 50 cells/mm3 or more were noted to have these changes. We confirmed the clinical impression that cytomegalovirus retinitis and HIV-related noninfectious retinal vasculopathy are late manifestations of AIDS, demonstrated an increased risk for patients with low CD4+ counts, and suggested a basis for coherent chemoprophylaxis and screening strategies for cytomegalovirus retinitis.

AIDS-Related Opportunistic Infections↗
PubMed1993

Alternating and intermittent regimens of zidovudine and dideoxycytidine in patients with AIDS or AIDS-related complex.

OBJECTIVE: To determine whether alternating regimens consisting of zidovudine and 2',3'-dideoxycytidine (ddC) reduce the toxicity and maintain or increase the antiretroviral effect associated with each drug alone. DESIGN: An unblinded, randomized (phase II) clinical trial in which seven treatment regimens were compared. SETTING: Outpatient clinics of 12 AIDS Clinical Trials Units. PATIENTS: One hundred thirty-one patients with the acquired immunodeficiency syndrome (AIDS) or AIDS-related complex and serum p24 antigenemia (> or = 70 pg/mL). INTERVENTION: Treatments included weekly or monthly alternating zidovudine (200 mg every 4 hours) and ddC (0.01 or 0.03 mg/kg body weight every 4 hours); weekly intermittent zidovudine, 200 mg every 4 hours, or ddC, 0.03 mg/kg every 4 hours; and continuous zidovudine. MEASUREMENTS: Toxicity, CD4 cell counts, serum p24 antigen levels, and clinical end points. Data were analyzed for the first 48 weeks of therapy (median follow-up, 40 weeks). RESULTS: Hematologic toxicity was significantly less frequent in patients who received zidovudine therapy every other week (11% to 15%) or every other month (11% to 14%) than in those who received continuous zidovudine therapy (33%) (P < 0.02). Weekly alternating therapy with zidovudine and ddC, 0.03 mg/kg, or intermittent therapy with ddC, 0.03 mg/kg, produced high rates of peripheral neuropathy (41% and 50%, respectively). Neuropathy occurred in 10% to 21% of patients in the other three alternating-therapy limbs and in 17% of patients receiving zidovudine alone (intermittently or continuously). Initial increases in CD4 cell counts were sustained in three alternating-therapy limbs, but counts returned to baseline by week 28 in the remaining limbs. The median weight gain at week 48 was significantly greater in patients treated with alternating regimens (0.9 to 3.8 kg) compared with those treated with continuous zidovudine therapy (-0.7 kg) (P = 0.008). Patients treated with alternating regimens and those treated with continuous zidovudine had similarly sustained decreases in p24 antigen levels. CONCLUSIONS: These findings suggest that alternating therapy with zidovudine and ddC reduces the toxicity associated with each drug alone while maintaining strong antiretroviral activity.

AIDS-Related Complex↗
PubMed1993

Zidovudine treatment of the AIDS dementia complex: results of a placebo-controlled trial. AIDS Clinical Trials Group.

The efficacy of two doses of zidovudine was examined for the treatment of the acquired immunodeficiency syndrome (AIDS) dementia complex in a randomized, double-blinded, placebo-controlled trial conducted at nine study centers. For the initial 16 weeks, 40 subjects with mild to moderate AIDS dementia complex were randomized to one of three treatment arms: 400 mg of zidovudine five times daily, 200 mg of zidovudine five times daily, or placebo five times daily. After week 16, patients initially randomized to the placebo group were rerandomized to one of the two zidovudine treatment arms. The primary efficacy end point was improvement in performance on a battery of seven neuropsychological tests; the secondary end point was improvement on a protocol neurological evaluation directed at the cardinal features of the AIDS dementia complex. For the initial 16-week period, average z scores based on the neuropsychological test battery revealed a significant improvement in the combined treatment groups compared to the placebo group; however, when the two treatment groups were compared separately to the placebo group, only the group receiving the higher zidovudine dose exhibited significant improvement. After rerandomization of the placebo patients to one of the two treatment arms at week 16, this group also showed significant improvement in the average neuropsychological z score by week 32. These results extend previous observations that indicate a therapeutic benefit of zidovudine for the treatment of AIDS dementia complex.

AIDS Dementia Complex↗
PubMed1993

Vitamin D3 compounds regulate human immunodeficiency virus type 1 replication in U937 monoblastoid cells and in monocyte-derived macrophages.

We studied the effects of vitamin D3 compounds on the replication of human immunodeficiency virus type 1 (HIV-1) in the monoblastoid cell line U937 and in primary monocyte-derived macrophage cultures to understand how modulators of monocyte/macrophage effector function might affect the pathogenesis of HIV-1 infection. U937 cell cultures exposed to 1, alpha 25-dihydroxyvitamin D3 prior to HIV-1 infection showed enhanced virus replication that was apparently due to increased cellular resistance to viral cytopathic effects; a marked inhibition of virus replication was noted in cells exposed to 1 alpha,25-dihydroxyvitamin D3 subsequent to infection. Exposure of blood-derived monocyte/macrophages to vitamin D3 compounds prior to infection also affected virus growth; in most cases, substantial inhibition of HIV-1 replication was noted in vitamin D3-treated macrophage cultures. Our results demonstrate that vitamin D3 compounds with recognized abilities to induce cellular differentiation can modulate HIV-1 infection of human macrophages.

Calcifediol↗
PubMed1993

Mechanisms for the inhibition of HIV replication by interferons-alpha, -beta, and -gamma in primary human macrophages.

Interferons (IFNs) inhibit the replication of a wide range of animal viruses by acting at various steps of the life cycle. Interferons display a particularly potent antiviral effect on HIV-1 replication in primary human macrophages. A high virus-to-cell multiplicity of infection was used to investigate which steps in a single replicative cycle in these primary human cells were affected by IFNs. Monocyte-derived macrophages from healthy seronegative donors were infected with HIV-1BaL. Virus production was assessed by immunoassay for p24 antigen. Viral DNA was detected by PCR while mRNA was detected specifically by RT-PCR with primers bracketing the 5' introns of HIV-1 to detect only spliced transcripts such as tat, rev, nef, and env mRNAs. Macrophages pretreated with IFN-alpha, -beta or -gamma had a reduced viral DNA signal while the spliced mRNA signal was essentially abolished. No virus was produced. To test whether IFNs could reduce HIV transcripts in cells with established productive infection, macrophages were infected and reinfection was then prevented by azidothymidine before starting interferon treatment. Under such conditions, the addition of interferons did not affect significantly the levels of HIV spliced transcripts. No intracellular accumulation of p24 antigen was observed. Therefore, the major effect of IFNs was at an early step of the virus life cycle and resulted in a reduced viral DNA synthesis.

Cells, Cultured↗
PubMed1993

In vitro differentiation of monocytoid THP-1 cells affects their permissiveness for HIV strains: a model system for studying the cellular basis of HIV differential tropism.

The prototypic macrophage-tropic HIV-1 isolate, HIV-1BaL, cannot replicate in the monocytoid cell line THP-1. After induction of differentiation by a phorbol diester, a fraction of THP-1 cells became permissive to HIV-1BaL. In contrast, this treatment decreased permissiveness for the lymphotropic isolate HIV-1LAI. Viral DNA was not synthesized in unstimulated THP-1 cells, as determined with PCR, suggesting that the block to HIV-1BaL replication in these cells occurred at an early step of the virus replicative cycle prior to or at the level of reverse transcription. Virus binding studies showed that differences in cell permissiveness for HIV-1BaL were not due to altered virus binding. Substantial amounts of HIV-1BaL bound to both undifferentiated and differentiated THP-1 cells, and this binding could not be prevented by blocking with the anti-CD4 antibody Leu3a, which did prevent the binding of HIV-1LAI to CEM T lymphoid cells. While Leu3a was very effective at preventing the infection by HIV-1LAI in CEM cells, it was less effective in preventing HIV-1BaL infection of differentiated THP-1 cells or primary macrophages. Although it is likely that molecules other than CD4 on monocytic cells can mediate binding of macrophage-tropic HIV, the binding of HIV-1BaL to THP-1 cells was not sufficient for infection, because binding was the same in nonpermissive undifferentiated cells as in permissive differentiated cells. Thus, the restriction of viral replication in this model cell system occurs at some step after virion binding. Comparison of differentiated THP-1 cells with their undifferentiated counterparts may provide an approach to defining cellular determinants of HIV host range other than CD4 expression and to characterizing the incompletely defined steps of viral entry.

Antibodies, Monoclonal↗
PubMed1993

A cross-sectional comparison of persons with syncytium- and non-syncytium-inducing human immunodeficiency virus.

The association between isolation of the syncytium-inducing (SI) phenotype of human immunodeficiency virus (HIV) and unfavorable clinical and immune status was evaluated in a cross-sectional study. Data on HIV phenotype were available for 341 of 878 persons entering clinical trials of antiretroviral therapies. Patients with SI virus were demographically similar to those with non-SI (NSI) virus but were more likely to have a diagnosis of AIDS and detectable circulating HIV p24 antigen. Patients with SI virus also had a lower CD4+ cell count and a higher serum level of beta 2-microglobulin. The association between phenotype and present status was explained statistically by CD4+ cell count. Phenotype, serum level of beta 2-microglobulin, and the presence of detectable p24 antigen were all independent predictors of present CD4+ cell count. The likelihood of finding SI virus increased with unfavorable virologic and immunologic parameters and varied with the amount of prior antiretroviral therapy.

Adult↗
PubMed1993

Designing phase II studies of chemotherapy for HIV infection using CD4 as an end-point.

OBJECTIVE: To provide information that will be helpful in designing AIDS clinical trials that use CD4 as an end-point. DESIGN: Meta-analysis of randomized AIDS clinical trials comparing zidovudine and placebo. SETTING: Tertiary care. PATIENTS: Eight hundred and twenty-seven patients with HIV infection. INTERVENTIONS: Treatment with zidovudine at various dosages compared with placebo. MAIN OUTCOME MEASURE: Differences in the log-ratio CD4 count. RESULTS: The mean difference in the log-ratio CD4 count divided by its standard deviation varied from 0.31 to 0.76 depending on the study. Of the variation in CD4 count 63% is short-term variation. CONCLUSION: Trials of 12 weeks duration can be used to test for the effect of a new drug on CD4 counts. Testing combination therapies may require somewhat longer trial periods. The sample size for clinical trials can be reduced by replicating baseline and follow-up measurements. Trials of new agents should test for an increase in CD4 over baseline. Such trials will require between 25 and 190 patients per arm depending on the patient population. Trials that compare combinations to standard therapies will require between 32 and 235 patients per arm depending on disease stage and prior therapy of study participants.

AIDS-Related Complex↗