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E A Emini

Publications and source records attributed to E A Emini.

At least 37 records · Page 2Linked to original sources
PubMed1996

Genetic correlates of in vivo viral resistance to indinavir, a human immunodeficiency virus type 1 protease inhibitor.

Indinavir (IDV) (also called CRIXIVAN, MK-639, or L-735,524) is a potent and selective inhibitor of the human immunodeficiency virus type 1 (HIV-1) protease. During early clinical trials, in which patients initiated therapy with suboptimal dosages of IDV, we monitored the emergence of viral resistance to the inhibitor by genotypic and phenotypic characterization of primary HIV-1 isolates. Development of resistance coincided with variable patterns of multiple substitutions among at least 11 protease amino acid residues. No single substitution was present in all resistant isolates, indicating that resistance evolves through multiple genetic pathways. Despite this complexity, all of 29 resistant isolates tested exhibited alteration of residues M-46 (to I or L) and/or V-82 (to A, F, or T), suggesting that screening of these residues may be useful in predicting the emergence of resistance. We also extended our previous finding that IDV-resistant viral variants exhibit various patterns of cross-resistance to a diverse panel of HIV-1 protease inhibitors. Finally, we noted an association between the number of protease amino acid substitutions and the observed level of IDV resistance. No single substitution or pair of substitutions tested gave rise to measurable viral resistance to IDV. The evolution of this resistance was found to be cumulative, indicating the need for ongoing viral replication in this process. These observations strongly suggest that therapy should be initiated with the most efficacious regimen available, both to suppress viral spread and to inhibit the replication that is required for the evolution of resistance.

Base Sequence↗
PubMed1995

Assessment of antiretroviral therapy by plasma viral load testing: standard and ICD HIV-1 p24 antigen and viral RNA (QC-PCR) assays compared.

To assess the utility of quantitative competitive-polymerase chain reaction (QC-PCR) measurements of plasma human immunodeficiency virus type 1 (HIV-1) RNA and other viral load markers for assessment of antiretroviral therapy, we used archived cryopreserved specimens from a randomized controlled clinical trial of 135 patients (CD4+ T cell count < or = 500/mm3), comparing zidovudine (500 mg/day) versus the nonnucleoside reverse transcriptase inhibitor L-697, 661 (50, 300, or 1,000 mg daily). We evaluated treatment-associated changes in plasma viral load by standard and immune complex-dissociated (ICD) HIV-1 p24 antigen assays, and, in a representative subset of patients (n = 46), by QC-PCR determination of virion-associated HIV-1 RNA. At baseline, HIV-1 RNA was quantifiable by QC-PCR in all patients tested (100%), whereas standard and ICD HIV-1 p24 antigen tests were positive (> or = 30 pg/ml) in 42% and 56%, respectively. All viral load parameters showed significant decreases from baseline within 1 week of initiation of zidovudine, as measured by standard p24 antigen assay, ICD p24 assay, and QC-PCR. At 1 week, patients treated with either 300 or 1,000 mg/day of L-697,661 showed significant decreases from baseline in plasma standard and ICD p24 antigen and QC-PCR-determined HIV-1 RNA levels. Whereas viral load decreases seen with zidovudine were sustained for the duration of treatment, plasma viral markers often returned to pretreatment levels despite ongoing L-697,661 treatment, with evidence of the emergence of drug-resistant virus. Whereas standard p24, ICD p24, and viral RNA levels changed similarly in response to treatment, the superior sensitivity and available dynamic range of plasma viral RNA assays like QC-PCR analysis provide an advantage for clinical monitoring of plasma viral load, allowing tracking of treatment-related changes even in patients with earlier stage disease and lower levels of viral load.

Antiviral Agents↗
PubMed1995

Viral dynamics in human immunodeficiency virus type 1 infection.

The dynamics of HIV-1 replication in vivo are largely unknown yet they are critical to our understanding of disease pathogenesis. Experimental drugs that are potent inhibitors of viral replication can be used to show that the composite lifespan of plasma virus and virus-producing cells is remarkably short (half-life approximately 2 days). Almost complete replacement of wild-type virus in plasma by drug-resistant variants occurs after fourteen days, indicating that HIV-1 viraemia is sustained primarily by a dynamic process involving continuous rounds of de novo virus infection and replication and rapid cell turnover.

Antiviral Agents↗
PubMed1995

Inhibition of human immunodeficiency virus integrase by bis-catechols.

The human immunodeficiency virus type 1 (HIV-1) integrase protein is required for the productive infection of T-lymphoid cells in culture (R. L. LaFemina, C. L. Schneider, H. L. Robbins, P. L. Callahan, K. LeGrow, E. Roth, W. A. Schleif, and E. A. Emini, J. Virol. 66:7414-7419, 1992). This observation suggests that chemical inhibitors of integrase may prevent the spread of HIV in infected individuals. In our search for such potential chemotherapeutic agents, we observed that beta-conidendrol inhibits both the sequence-dependent and sequence-independent endonucleolytic activities of integrase with comparable potencies in vitro (50% inhibitory concentration, 500 nM). Structurally related compounds tested for their abilities to inhibit integrase generated a limited structure-activity analysis which demonstrated that potency is associated with the bis-catechol structure: two pairs of adjacent hydroxyls on separate benzene rings. beta-Conidendrol did not inhibit several other endonucleases and/or phosphoryltransferases. Although beta-conidendrol was not effective in preventing HIV-1 infection in cell culture, the in vitro data demonstrate that it is possible to identify selective agents targeted against this essential HIV-1 function.

Base Sequence↗
PubMed1995

Turnover of circulating virion RNA and of cell-associated viral DNA reflects active viral replication in human immunodeficiency virus type 1-infected individuals.

A quantitative assessment of human immunodeficiency virus type 1 turnover in patient cell-free virion and infected-cell compartments under the dynamic conditions imposed by an effective antiviral therapy was performed. The turnover was rapid, and following a temporal lag, the extent of viral population replacement was eventually similar in both compartments. Each compartment therefore reflects considerable active virus replication.

Antiviral Agents↗
PubMed1994

L-735,524: the design of a potent and orally bioavailable HIV protease inhibitor.

A series of HIV protease inhibitors possessing a hydroxylaminepentanamide transition state isostere have been developed. Incorporation of a basic amine into the backbone of the L-685,434 (2) series provided antiviral potency combined with a highly improved pharmacokinetic profile in animal models. Guided by molecular modeling and an X-ray crystal structure of the inhibited enzyme complex, we were able to design L-735,524. This compound is potent and competitively inhibits HIV-1 PR and HIV-2 PR with Ki values of 0.52 and 3.3 nM, respectively. It also stops the spread of the HIV-1IIIb-infected MT4 lymphoid cells at concentrations of 25-50 nM. To date, numerous HIV-PR inhibitors have been reported, but few have been studied in humans because they lack acceptable oral bioavailability. L-735,524 is orally bioavailable in three animals models, using clinically acceptable formulations, and is currently in phase II human clinical trials.

Animals↗
PubMed1994

Human immunodeficiency virus 1 (HIV-1)-specific reverse transcriptase (RT) inhibitors may suppress the replication of specific drug-resistant (E138K)RT HIV-1 mutants or select for highly resistant (Y181C-->C181I)RT HIV-1 mutants.

Mutant HIV-1 that expresses a Glu138-->Lys substitution in its RT [(E138K)RT] is resistant to the HIV-1-specific RT inhibitor 2',5'-bis-O-(tert-butyldimethylsilyl)-3'-spiro-5"-(4"-amino-1",2"- oxathiole-2",2"-dioxide)pyrimidine (TSAO). However, cell cultures infected with this mutant were completely protected against virus-mediated destruction by micromolar concentrations of the HIV-1-specific RT inhibitors tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepin-2(1H)-one and -thione (TIBO), nevirapine, and bis(heteroaryl)piperazine (BHAP). In contrast, cells infected with a virus mutant that expresses a Tyr181-->Cys substitution in its RT [(Y181C)RT] were not protected by nevirapine and TIBO and were only temporarily protected by BHAP. HIV-1 mutant that emerged under the latter conditions contained a Cys181-->Ile substitution in their RT [(LC181I)RT]. This mutant proved highly resistant to all HIV-1-specific RT inhibitors tested, except for several 1-(2-hydroxyethoxymethyl)-6-(phenylthio)thymine (HEPT) derivatives. When recombinant (C181I)RT was evaluated for susceptibility to the HIV-1-specific RT inhibitors, it was resistant to all inhibitors except the HEPT compounds. Since a (Y181F)RT HIV mutant strain was isolated from cells infected with (Y181C)RT HIV-1 and treated with BHAP, we postulate that the Ile codon was derived from a Cys-->Phe transversion mutation (TGT-->TTT), followed by a Phe-->Ile transversion mutation (TTT-->ATT).

Amino Acid Sequence↗
PubMed1994

Peptide substrate cleavage specificity of the human cytomegalovirus protease.

The human cytomegalovirus UL80 gene encodes an 80-kDa precursor polyprotein whose N-terminal 256-amino acid domain is a protease. This enzyme cleaves a specific peptide bond that results in its own release from the precursor, as well as a peptide bond near the C terminus of the viral assembly protein. The latter cleavage is apparently required for encapsidation of the viral genomic DNA and maturation of the viral capsid. A series of peptide substrates, representing the assembly protein cleavage site, was used to study the enzyme's substrate requirements and specificity. It was found that efficient cleavage minimally required the amino acid residues spanning the P4 to P4' positions. Substitution at any of these residues adversely affected the reaction. Conservation of the hydrophobic residues at P3 and P4 was essential. In addition, cleavage of a peptide representing the protease domain release site was reduced almost 100-fold relative to cleavage of the assembly protein maturation site peptide substrate.

Amino Acid Sequence↗
PubMed1994

Neutralization of divergent human immunodeficiency virus type 1 variants and primary isolates by IAM-41-2F5, an anti-gp41 human monoclonal antibody.

The antiviral characteristics of monoclonal antibody IAM-41-2F5 (2F5) were determined in cell culture. The antibody had been previously shown to bind a specific sequence, ELDKWA, within the external domain of the gp41 envelope glycoprotein human immunodeficiency virus type 1 (HIV-1). Selection by 2F5 of recombinant phage from an epitope library confirmed the identification of the antibody's binding determinant. The antibody was found to be capable of neutralizing a broad range of lymphoid cell culture-adapted HIV-1 variants as well as HIV-1 primary isolates. Sequence analysis of the latter showed that neutralization was related to the presence of the antibody binding site. From kinetic measurements using an epitope-containing peptide or gp41, the half-time of dissociation for 2F5 was determined to be 122 min for the peptide and 156 min for gp41. The region of gp41 expressing this sequence exhibits greater conservation among HIV-1 isolates than do the variable domains of gp120.

Amino Acid Sequence↗
PubMed1994

Viral long terminal repeat substrate binding characteristics of the human immunodeficiency virus type 1 integrase.

A DNA binding assay was developed for the human immunodeficiency virus type 1 (HIV-1) integrase. The assay was capable of defining discrete complexes between the enzyme and the viral long terminal repeat (LTR) substrate. DNA binding reflected the sequence requirements previously demonstrated for the enzyme's 3'-end processing activity. Binding exhibited a nonlinear dependence on integrase concentration, suggesting that the enzyme functions as a multimer. The oligomeric state was investigated by UV-photo-cross-linking of integrase-LTR oligonucleotide complexes using DNA substrates substituted with 5-bromo-2'-deoxycytidine within the integrase recognition sequence. In the absence of divalent cation, integrase cross-linked to the LTR oligonucleotide as a single species whose mobility by SDS-polyacrylamide gel electrophoresis was consistent with the formation of tetramers. Using these techniques, analysis of the binding properties of integrase mutants demonstrated that the catalytic and sequence-specific DNA binding activities of the enzyme are distinct, involving residues within the conserved "DD(35)E" and zinc finger motifs, respectively.

Base Sequence↗
PubMed1994

The genetic and functional basis of HIV-1 resistance to nonnucleoside reverse transcriptase inhibitors.

The nonnucleoside reverse transcriptase (RT) inhibitors are structurally diverse compounds that are specific inhibitors of the human immunodeficiency virus type 1 RT enzyme. The compounds are largely functionally identical and bind to a common site in the enzyme. HIV-1 variants that exhibit reduced susceptibility to these inhibitors have been derived in cell culture and, more recently, from HIV-1-infected patients undergoing experimental therapy. The variants express amino acid substitutions at RT positions that apparently interact directly with the inhibitors. Effects of specific substitutions at these positions vary among the compounds, suggesting subtle differences in how the compounds physically interact with the enzyme.

Antiviral Agents↗
PubMed1994

Susceptibilities of human immunodeficiency virus type 1 enzyme and viral variants expressing multiple resistance-engendering amino acid substitutions to reserve transcriptase inhibitors.

To evaluate the potential that multiply resistant human immunodeficiency virus type 1 variants may arise during combination nucleoside and nonnucleoside reverse transcriptase inhibitor therapy, we constructed a series of mutant reverse transcriptase enzymes and viruses that coexpressed various combinations of resistance-associated amino acid substitutions. Substitutions at residues 100 (Leu-->Ile) and 181 (Tyr-->Cys), which mediate resistance to the nonnucleosides, suppressed resistance to 3'-azido-3'-deoxythymidine (AZT) when coexpressed with AZT-specific substitutions. However, a number of viral variants that exhibited significantly reduced susceptibilities to both classes of inhibitors were constructed.

Drug Resistance, Microbial↗
PubMed1994

Neutralization of primary human immunodeficiency virus type 1 isolates by the broadly reactive anti-V3 monoclonal antibody, 447-52D.

Human monoclonal antibody 447-52D binds to the V3 determinant of the human immunodeficiency virus type 1 (HIV-1) gp120 external glycoprotein. Its binding requires the expression of the GPxR sequence at the center of the V3 domain. HIV-1 variants that are adapted to replication in T-lymphoid cell lines and express this sequence motif are efficiently neutralized by the antibody (M. K. Gorny, A. J. Conley, S. Karwowska, A. Buchbinder, J.-Y. Xu, E. A. Emini, S. Koenig, and S. Zolla-Pazner, J. Virol. 66:7538-7542, 1992). In the present study, the antiviral activity of 447-52D was further defined with regard to its ability to mediate neutralization of primary HIV-1 clinical isolates. Again, the antibody was found to potently neutralize those isolates that expressed the binding sequence. We confirmed that this determinant is commonly expressed by virus isolates belonging to the subtype (clade) B sequence classification. As such, 447-52D may be useful for prophylactic and immunotherapeutic intervention. In addition, the study demonstrated that neutralization of primary HIV-1 isolates is possible if mediated by an appropriate antibody.

AIDS Vaccines↗
PubMed1993

A short-term clinical evaluation of L-697,661, a non-nucleoside inhibitor of HIV-1 reverse transcriptase. L-697,661 Working Group.

BACKGROUND: The non-nucleoside reverse transcriptase inhibitors are novel antiretroviral agents with selective activity in vitro against human immunodeficiency virus type 1 (HIV-1). They act through direct inhibition of reverse transcriptase and are not incorporated into DNA. METHODS: We evaluated a pyridinone non-nucleoside reverse transcriptase inhibitor, L-697,661, in separate six-week double-blind trials in patients with HIV-1 infection whose CD4 counts ranged from 200 to 500 cells per cubic millimeter (68 patients) or less than 200 cells per cubic millimeter (67 patients). Eligible patients were randomly assigned to receive L-697,661 orally in one of three doses (25 mg twice a day, 100 mg three times a day, or 500 mg twice a day) or zidovudine (100 mg five times a day). Clinical and laboratory assessments were performed weekly. Viral isolates were obtained from a subgroup of patients before and after treatment and were evaluated for in vitro sensitivity to L-697,661. RESULTS: Both L-697,661 and zidovudine were well tolerated. Transient increases in CD4 counts were noted in the patients with fewer than 200 CD4 cells per cubic millimeter who received the two higher doses of L-697,661, but not in those who received the lowest dose or zidovudine. Patients who received L-697,661 had rapid, dose-related decreases in plasma p24 antigen levels. However, this response virtually disappeared after six weeks in some patients receiving L-697,661, coincidently with the emergence of resistant viruses. This change in susceptibility was more frequent among patients receiving the higher doses of L-697,661 and was associated with amino acid substitutions at positions 103 and 181 in the HIV-1 reverse transcriptase gene. CONCLUSIONS: L-697,661 is safe and well tolerated and has significant dose-related activity against HIV-1. However, resistant strains of the virus emerge rapidly and may limit the effectiveness of non-nucleoside reverse transcriptase inhibitors as monotherapy for HIV-1 infection.

Adult↗