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Biomedical subjects

D Havlir

Publications and source records attributed to D Havlir.

At least 19 recordsLinked to original sources
PubMed2001

Evidence for positive selection driving the evolution of HIV-1 env under potent antiviral therapy.

In HIV-infected individuals treated with potent antiretroviral therapy, viable virus can be isolated from latently infected cells several years into therapy, due to the long life of these cells, ongoing replication replenishing this population, or both. We have analysed the V3 region of the HIV-1 env gene isolated from six patients who have undergone 2 years of potent antiretroviral therapy without frank failure of viral suppression. We show that in two (and possibly three) patients, the sequence changes between baseline virus and virus isolated from infected cells persisting 2 years into infection result from positive selection driving adaptive evolution, occurring either prior to or during therapy. Our analyses suggest low-level replication despite absence of drug resistance due to drug sanctuary sites, or to low-level ongoing replication in the presence of alterations in the selective environment during therapy, perhaps due to a decline in HIV-specific immune responsiveness or changes in target cell pools. In one patient, genetic divergence between baseline plasma and infected cells isolated during therapy may reflect the long half-life of some of these persistent cell populations and the divergence of viral subpopulations that occurred prior to therapy.

Amino Acid Sequence↗
PubMed2001

Patterns of plasma human immunodeficiency virus type 1 RNA response to antiretroviral therapy.

Early identification of treatment failure among human immunodeficiency virus (HIV) type 1--infected patients receiving antiretroviral therapy could enable clinicians to modify inadequate regimens and to improve treatment response. Clinical definitions of treatment failure, however, may not be ideally suited for this purpose. This study empirically characterizes the patterns of HIV-1 RNA response to antiretroviral therapy in patients in 4 AIDS clinical trials. The approach assumed 2 patterns of HIV-1 response: "on track," for eventual suppression to HIV-1 RNA levels below the limit of quantification, and "off track," for deviation from this response. The results of this on- or off-track classification generally agreed with the protocol-defined outcomes of virologic success and failure, thus validating these commonly used definitions. Overall, only a minority of patients went off track because of suboptimal HIV-1 RNA response by the first follow-up visit. Most patients who went off track did so at later time points and had sharp unexpected rebounds without prior indication of a suboptimal response.

Antiretroviral Therapy, Highly Active↗
PubMed2001

Productive infection of T cells in lymphoid tissues during primary and early human immunodeficiency virus infection.

Current models suggest that during human immunodeficiency virus type 1 (HIV-1) transmission virions are selected that use the CCR5 chemokine receptor on macrophages and/or dendritic cells. A gradual evolution to CXCR4 chemokine receptor use causes a shift in the proportion of productively infected cells to the CD4 cell population. Productively infected cells during acute and early infection in lymphoid tissue were assessed, as well as the impact of productive infection on the T cell population in 21 persons who had biopsies performed on days 2-280 after symptoms of acute HIV-1 seroconversion. Even in the earliest stages of infection, most productively infected cells were T lymphocytes. There were sufficient infected cells in lymphoid tissue (LT) to account for virus production and virus load in plasma. Despite the relatively high frequency of productively infected cells in LT, the impact on the size of the T cell population in LT at this stage was minor.

CD4-Positive T-Lymphocytes↗
PubMed2000

3-year suppression of HIV viremia with indinavir, zidovudine, and lamivudine.

BACKGROUND: Antiretroviral regimens containing HIV protease inhibitors suppress viremia in HIV-infected patients, but the durability of this effect is not known. OBJECTIVE: To describe the 3-year follow-up of patients randomly assigned to receive indinavir, zidovudine, and lamivudine in an ongoing clinical trial. DESIGN: Open-label extension of a randomized, double-blind study. SETTING: Four clinical research units. PATIENTS: 33 HIV-infected, zidovudine-experienced patients with serum HIV RNA levels of at least 20,000 copies/mL and CD4 counts ranging from 50 to 400 cells/mm3. INTERVENTION: Indinavir, zidovudine, and lamivudine. MEASUREMENTS: Safety assessments, HIV RNA levels, CD4 cell counts, and genotypic analyses. RESULTS: After 3 years of follow-up, 21 of 31 contributing patients (68% [95% CI, 49% to 83%]) had serum viral load levels less than 500 copies/mL. Twenty of 31 (65% [CI, 45% to 80%]) had levels less than 50 copies/mL. The median increase in CD4 count from baseline was 230 cells/mm3 (interquartile range, 150 to 316 cells/mm3). Nephrolithiasis occurred in 12 of 33 patients (36%). CONCLUSION: A three-drug regimen of indinavir, zidovudine, and lamivudine suppressed viremia in two thirds of patients for at least 3 years.

Adult↗
PubMed2000

Rapid accumulation of human immunodeficiency virus (HIV) in lymphatic tissue reservoirs during acute and early HIV infection: implications for timing of antiretroviral therapy.

The follicular dendritic cell network (FDC) in lymphoid tissues (LTs) is the major site of human immunodeficiency virus (HIV) storage in presymptomatic and late stages of disease. However, little is known about the rate of virus accumulation during the acute and early stages. In situ hybridization and quantitative image analysis were used to determine the amount of virus bound to the FDC network during the first year of infection. The FDC pool was already >7.0 log10 copies of HIV RNA/g LT in the first year, and 2 patients biopsied within 2-4 days of symptom onset had 7.3 and 8.2 log10 copies of HIV RNA/g LT, respectively. There was no correlation between duration of infection and accumulation of HIV into the FDC network. These data suggest that a large pool of infectious virus is established soon after infection and that initiation of antiretroviral therapy when symptoms of primary HIV infection are recognized is unlikely to prevent substantial accumulation of virus in the FDC network.

Acute Disease↗
PubMed2000

Effect of influenza vaccination on viral replication and immune response in persons infected with human immunodeficiency virus receiving potent antiretroviral therapy.

Nineteen patients infected with human immunodeficiency virus (HIV) with varying levels of viral suppression achieved with antiretroviral therapy were evaluated to determine whether trivalent influenza vaccine activated HIV replication. Humoral immune responses and CD4+ lymphocyte subsets were compared in 5 HIV-uninfected vaccinated subjects. Transient elevations of plasma HIV RNA levels (76-89 copies/mL) appeared within 2 weeks in 3 of 11 patients with <50 copies/mL at baseline. Sustained elevation in HIV plasma RNA was observed in 7 of 8 patients with baseline HIV RNA of >50 copies/mL. HIV DNA decreased in patients with <400 RNA copies/mL at baseline and showed an HIV RNA increase after vaccination (n=8) when compared with 8 patients with <50 copies/mL at baseline who lacked viral response to vaccination. Concurrent decreases in proviral DNA and memory phenotype CD4+ cells in association with increased plasma HIV RNA after vaccination in patients with <400 RNA copies/mL at baseline suggest that in vivo mobilization of the latently infected cell reservoir may occur during potent antiretroviral therapy.

Adult↗
PubMed1999

Sexual transmission and propagation of SIV and HIV in resting and activated CD4+ T cells.

In sexual transmission of simian immunodeficiency virus, and early and later stages of human immunodeficiency virus-type 1 (HIV-1) infection, both viruses were found to replicate predominantly in CD4(+) T cells at the portal of entry and in lymphoid tissues. Infection was propagated not only in activated and proliferating T cells but also, surprisingly, in resting T cells. The infected proliferating cells correspond to the short-lived population that produces the bulk of HIV-1. Most of the HIV-1-infected resting T cells persisted after antiretroviral therapy. Latently and chronically infected cells that may be derived from this population pose challenges to eradicating infection and developing an effective vaccine.

Animals↗
PubMed1999

Efficacy of azithromycin in prevention of Pneumocystis carinii pneumonia: a randomised trial. California Collaborative Treatment Group.

BACKGROUND: Azithromycin in combination with sulphonamides is active against Pneumocystis carinii pneumonia (PCP) in animals. We assessed the clinical efficacy of azithromycin for PCP prophylaxis in human beings. METHODS: We identified HIV-1-infected patients with PCP during a prospective randomised trial comparing azithromycin, rifabutin, and the two drugs in combination for prevention of disseminated Mycobacterim avium infection. Patients had CD4-cell counts less than 100/microL at entry and received PCP prophylaxis according to the standard practice of their clinician. Analysis was by intention to treat. FINDINGS: Patients receiving azithromycin, either alone (n=233) or in combination with rifabutin (n=224), had a 45% lower risk of developing PCP than those receiving rifabutin alone (n=236; p=0.008). Compared with rifabutin alone, hazard ratio for azithromycin was 0.54 (95% CI 0.32-0.94), for azithromycin plus rifabutin was 0.55 (0.32-0.94), and for regimens containing azithromycin was 0.55 (0.35-0.86). The most common side-effects involved the gastrointestinal tract with dose-limiting toxicities, and were mainly seen in patients receiving combination therapy. INTERPRETATION: Azithromycin as prophylaxis for M. avium complex disease provides additional protection against P. carinii over and above that of standard PCP prophylaxis. Use of azithromycin is beneficial only as primary prophylaxis.

AIDS-Related Opportunistic Infections↗
PubMed1999

Rapid screening of phenotypic resistance to nevirapine by direct analysis of HIV type 1 reverse transcriptase activity in plasma.

Drug susceptibility testing for the clinical management of human immunodeficiency virus type 1 (HIV-1)-infected persons is often curtailed because such testing is expensive and time consuming. We describe a non-culture-based phenotypic assay for the rapid analysis of HIV-1 resistance to nevirapine. The assay measures the susceptibility of plasma reverse transcriptase (RT) activity to inhibition by nevirapine by using the PCR-based Amp-RT assay. Assay validation was made using two reference wild-type (WT) and six other nevirapine-resistant (>100-fold) HIV-1 isolates. Amp-RT IC50 values were found to correlate with those obtained by a conventional replication-based assay. The results also indicated that 50 microM nevirapine can be used in a single screening test to detect nevirapine resistance. Analysis of virus mixtures showed a detection threshold of 10% of nevirapine-resistant HIV-1 in a background of WT virus. To evaluate the assay on clinical samples, 30 plasma specimens collected longitudinally from 4 patients before and after treatment with nevirapine were analyzed, and results were compared with codon 181 genotypes. Preteatment samples and those obtained during the first 6 days of therapy (n = 21) were sensitive to nevirapine, and none had detectable Y181C mutation. Phenotypic resistance was seen in eight samples obtained after 1 week of treatment and was correlated with detection of the Y181C mutation. An increase in the level of phenotypic resistance was seen over time. These data validate this rapid and simple assay for monitoring phenotypic resistance to nevirapine.

Anti-HIV Agents↗
PubMed1998

Aberrant and unstable expression of immunoglobulin genes in persons infected with human immunodeficiency virus.

We examined the IgM VH gene subgroup use-distribution in serial blood samples of 37 human immunodeficiency virus (HIV)-infected patients and a group of HIV-seronegative healthy adults. The IgM VH gene repertoires of healthy adults were relatively similar to one another and were stable over time. In contrast, individuals infected with HIV had IgM VH gene repertoires that were significantly more heterogeneous and unstable. Persons at early stages of HIV infection generally had abnormal expression levels of Ig VH3 genes and frequently displayed marked fluctuations in the relative expression levels of this VH gene subgroup over time. In contrast, persons with established acquired immunodeficiency syndrome (AIDS) had a significantly lower incidence of abnormalities in Ig VH3 expression levels, although continued to display abnormalities and instability in the expression levels of the smaller Ig VH gene subgroups. Moreover, the skewing and/or fluctuations in the expressed-IgM VH gene repertoire appeared greatest for persons at earlier stages of HIV infection. These studies show that persons infected with HIV have aberrant and unstable expression of immunoglobulin genes suggestive of a high degree humoral immune dysregulation and ongoing humoral immune responses to HIV-associated antigens and superantigens.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Simultaneous vs sequential initiation of therapy with indinavir, zidovudine, and lamivudine for HIV-1 infection: 100-week follow-up.

CONTEXT: Combination antiretroviral therapy can markedly suppress human immunodeficiency virus (HIV) replication but the duration of HIV suppression varies among patients. OBJECTIVE: To compare the antiretroviral effect of a 3-drug regimen started simultaneously or sequentially in patients with HIV infection. DESIGN: A multicenter, randomized, double-blind study, modified after at least 24 weeks of blinded therapy to provide open-label 3-drug therapy with follow-up through 100 weeks. SETTING: Four clinical research units PATIENTS: Ninety-seven patients with HIV infection who had taken zidovudine for at least 6 months with serum HIV RNA level of at least 20000 copies/mL and CD4 cell count of 0.05 to 0.40 x 10(9)/L. INTERVENTIONS: Patients were initially randomized to receive 1 of 3 antiretroviral regimens: indinavir, 800 mg every 8 hours; zidovudine, 200 mg every 8 hours and lamivudine, 150 mg every 12 hours; or all 3 drugs. After at least 24 weeks of blinded therapy, all patients received open-label 3-drug therapy. MAIN OUTCOME MEASURES: Antiretroviral activity was assessed by changes in HIV RNA level and CD4 cell count from baseline. Data through 100 weeks were summarized. RESULTS: Simultaneous initiation of indinavir, zidovudine, and lamivudine suppressed HIV RNA in 78% (25/32) of contributing patients to less than 500 copies/mL and increased CD4 cell count to a median of 0.209 x 10(9)/L above baseline at 100 weeks. When these 3 drugs were initiated sequentially, only 30% to 45% of contributing patients (10 of 33 in the zidovudine-lamivudine group and 13 of 29 in the indinavir group, respectively) had a sustained reduction in HIV RNA to less than 500 copies/mL, and median CD4 cell count increased to 0.101 to 0.163 x 10(9)/L above baseline at 100 weeks. CONCLUSIONS: A 3-drug combination of indinavir, zidovudine, and lamivudine started simultaneously has durable antiretroviral activity for at least 2 years. Sequential initiation of the same 3 drugs is much less effective.

Anti-HIV Agents↗
PubMed1997

Treatment with indinavir, zidovudine, and lamivudine in adults with human immunodeficiency virus infection and prior antiretroviral therapy.

BACKGROUND: The new protease inhibitors are potent inhibitors of the human immunodeficiency virus (HIV), and in combination with other antiretroviral drugs they may be able to cause profound and sustained suppression of HIV replication. METHODS: In this double-blind study, 97 HIV-infected patients who had received zidovudine treatment for at least 6 months and had 50 to 400 CD4 cells per cubic millimeter and at least 20,000 copies of HIV RNA per milliliter were randomly assigned to one of three treatments for up to 52 weeks: 800 mg of indinavir every eight hours; 200 mg of zidovudine every eight hours combined with 150 mg of lamivudine twice daily; or all three drugs. The patients were followed to monitor the occurrence of adverse events and changes in viral load and CD4 cell counts. RESULTS: The decrease in HIV RNA over the first 24 weeks was greater in the three-drug group than in the other groups (P<0.001 for each comparison). RNA levels decreased to less than 500 copies per milliliter at week 24 in 28 of 31 patients in the three-drug group (90 percent), 12 of 28 patients in the indinavir group (43 percent), and none of 30 patients in the zidovudine-lamivudine group. The increase in CD4 cell counts over the first 24 weeks was greater in the two groups receiving indinavir than in the zidovudine-lamivudine group (P< or =0.01 for each comparison). The changes in the viral load and the CD4 cell count persisted for up to 52 weeks. All the regimens were generally well tolerated. CONCLUSIONS: In most HIV-infected patients with prior antiretroviral therapy, the combination of indinavir, zidovudine, and lamivudine reduces levels of HIV RNA to less than 500 copies per milliliter for as long as one year.

Adult↗
PubMed1997

In vivo compartmentalization of human immunodeficiency virus: evidence from the examination of pol sequences from autopsy tissues.

High rates of mutation and replication of human immunodeficiency virus (HIV) allow for the continuous generation of diverse genetic variants in vivo. Selective pressures within the microenvironments of different anatomic compartments result in the emergence of dominant quasispecies which can be distinguished by their envelope sequences. It is not known whether comparable tissue-specific selective pressures lead to the independent evolution of pol sequences within different tissue compartments, nor is it known how differing rates of virus turnover in tissues might affect the pace of such evolution. These issues are of importance for the formulation of a model for the emergence of drug resistance in vivo and for a general understanding of virus trafficking and virus turnover. Regions of the HIV type 1 reverse transcriptase (RT) which carry the majority of the known resistance codons to RT inhibitors (700 nucleotides from each clone) were cloned and sequenced directly from autopsied brain, spleen, and lymph node specimens from four subjects who had received zidovudine therapy. Clones from proviral DNA (143) and from viral cDNA (14) were analyzed. In three of four subjects, a discordance in distribution of resistance codons was noted. Moreover, brain-derived sequences appeared to be phylogenetically distinct from spleen- and lymph node-derived sequences even after exclusion of resistance codons from analysis. In each case, evidence for differential immune selective pressure, based on comparison of inferred amino acid sequences corresponding to known major histocompatibility complex class I cytotoxic T-lymphocyte epitopes, was found. These observations support the concept of anatomically distinct, independently evolving quasispecies (virodemes).

Acquired Immunodeficiency Syndrome↗
PubMed1996

Kinetic analysis of intravirion reverse transcription in the blood plasma of human immunodeficiency virus type 1-infected individuals: direct assessment of resistance to reverse transcriptase inhibitors in vivo.

Intravirion reverse transcripts have been identified in the blood plasma of human immunodeficiency virus type 1 (HIV-1)-infected individuals. In the present studies, the kinetic processes of intravirion HIV-1 reverse transcription, in the blood plasma of HIV-1-infected persons treated with nevirapine, were investigated. Nevirapine is a nonnucleoside inhibitor of reverse transcriptase (RT) which decreases the level of HIV-1 viral particles in the blood plasma of infected individuals. By analyzing HIV-1 virions at different time points prior to and after initiation of nevirapine therapy in vivo, the levels of intravirion reverse transcripts have been demonstrated to be dramatically susceptible to this anti-RT agent, out of proportion to effects on plasma virion load. The intravirion reverse transcripts were also documented to rebound to the pretreatment levels, concomitant with the development of resistant viral mutants. In addition, the infectivity of HIV-1 virions dramatically decreased after nevirapine treatment, further indicating that the effects of this anti-RT agent begin within the cell-free virions. Since the levels of intravirion reverse transcripts were altered according to the susceptibility or resistance of the HIV-1 RT enzyme to this inhibitor, these data demonstrate that the formation of intravirion reverse transcripts is a dynamic process in vivo. Moreover, because the alteration in ratios between intravirion HIV-1 reverse transcripts and viral genomic RNA directly reflects the efficiency of reverse transcription, we propose that the determination of these ratios in the blood plasma of HIV-1-positive patients may be a useful and, most importantly, a direct assay to monitor the efficacy of anti-RT agents in vivo.

Base Sequence↗
PubMed1995

Phase I/II evaluation of nevirapine alone and in combination with zidovudine for infection with human immunodeficiency virus.

In these Phase I/II open-label clinical trials, 62 persons with human immunodeficiency virus type 1 (HIV-1) infection and CD4+ cell counts < 400/mm3 received nevirapine at doses of 12.5, 50, and 200 mg/day, alone or in combination with zidovudine, 200 mg q8h. Nevirapine was well tolerated in the doses tested. Mean steady-state trough levels were 0.23, 1.1, and 1.9 micrograms/ml for the 12.5, 50, and 200 mg/day doses, respectively. Early suppression of p24 antigen levels and increase in CD4+ cell count were reversed following rapid emergence of virus less susceptible to nevirapine. Resistant strains were isolated from all participants by 8 weeks. Nevertheless, reduction of p24 antigen levels to < 50% of baseline values persisted for 12 weeks or more in four of seven persons who received 200 mg nevirapine/day in combination with zidovudine: these individuals had been antigenemic on long-term zidovudine therapy. This study demonstrates a direct relationship between drug resistance and effects on surrogate markers in HIV-1 infection.

Adult↗
PubMed1995

High-dose nevirapine: safety, pharmacokinetics, and antiviral effect in patients with human immunodeficiency virus infection.

Nevirapine, a potent nonnucleoside reverse transcriptase inhibitor, produces a transient antiviral effect at < or = 200 mg/day due to the selection of resistant virus. To examine if higher levels of nevirapine could produce sustained antiviral activity, its safety, pharmacokinetics, and antiviral activity at 400 mg/day were studied in 21 patients. There was a rapid reduction in immune complex-dissociated p24 antigen and serum human immunodeficiency virus RNA concentration in all patients, and 8 of 10 patients had > 50% reduction at 8 weeks. Nevirapine-resistant virus was isolated from all subjects tested at 12 weeks: The mean plasma trough level (4.0 micrograms/mL [15.8 microM]) exceeded the mean IC50 of resistant virus. Rash developed in 48% of patients and was a dose-limiting toxicity factor in 6. These data suggest that clinical testing of potent antiviral compounds that select for drug-resistant virus is justified to determine if serum levels of drug sufficient to overcome resistant virus can be attained.

Adult↗
PubMed1995

A pilot study to evaluate the development of resistance to nevirapine in asymptomatic human immunodeficiency virus-infected patients with CD4 cell counts of > 500/mm3: AIDS Clinical Trials Group Protocol 208.

Treatment of human immunodeficiency virus (HIV) infection with nevirapine in patients with < 400 CD4 cells/mm3 rapidly selects for virus with reduced susceptibility to nevirapine. To test whether resistance would develop less quickly in patients with a lower virus burden, nevirapine was studied in asymptomatic patients with > 500 CD4 cells/mm3. With 400 mg of nevirapine daily, the median reduction in HIV RNA was 0.51 log10 copies/mL, and all isolates recovered by 12 weeks were resistant to nevirapine. As in patients with lower CD4 cell counts, some patients experienced sustained reduction in plasma HIV RNA despite the presence of resistant virus. These results suggest that lower levels of HIV RNA and immunosuppression did not retard the rate of emergence of nevirapine-resistant virus; also, a polymerase chain reaction-based HIV RNA assay is sufficiently sensitive to evaluate the antiviral effect of a drug in patients with > 500 CD4 cells/mm3.

Antiviral Agents↗