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Antimicrobial Agents and Chemotherapy, May 2000, p. 1328-1332, Vol. 44, No. 5
Istituto di Malattie Infettive e Tropicali,
Universitá di Milano, Ospedale Luigi Sacco, Milan, Italy
Received 1 June 1999/Returned for modification 14 December
1999/Accepted 18 January 2000
In our study we examined the anti-human immunodeficiency virus type
1 (anti-HIV-1) activity of a novel HIV-1 protease inhibitor, PNU-140690
(tipranavir), against patient-derived isolates resistant to multiple
other protease inhibitors (PIs). The aim of our experiments was to
investigate the genotypes and the in vitro phenotypes of drug
resistance of PNU-140690. We carried out drug susceptibility tests with
peripheral blood mononuclear cells and a fixed amount of infectious
virus (1,000 50% tissue culture infective doses) to determine the 50%
inhibitory concentration (IC50) and IC90, PCR
assays for the detection of drug resistance mutations in RNA in plasma,
and direct sequencing of PCR products. Phenotypic resistance to PIs was
invariably related to genotypic mutations. The substitutions among the
amino acid residues of the protease included L10I, K20R, L24I, M36I,
N37D, G48V, I54V, L63P, I64V, A71V, V77I, V82A, I84V, and L90M.
Isolates from all of the patients had developed a maximal degree of
resistance to indinavir, ritonavir, and nelfinavir (IC50s, >0.1 µM). We also compared these mutations with the amino acid changes previously described in association with in vivo tipranavir administration. The mutations included the following: I15V, E35D, N37D,
R41K, D60E, and A71T. Infections with IIIB, 14aPre, and N70 were
inhibited by an average drug IC90 of 0.18 ± 0.02 µM
in multiple experiments. The average mean ± standard error of
mean IC90 for the entire group of multidrug-resistant
isolates derived from the mean values for two culture wells with p24
antigen supernatant appeared to be 0.619 ± 0.055 µM (range,
0.31 to 0.86 µM). Tipranavir retained a sustained antiviral activity
against PI-MDR clinical isolates and might be useful in combination
regimens with other antiretroviral agents for patients who have already
failed other PI-containing therapies.
0066-4804/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Susceptibility to PNU-140690 (Tipranavir) of Human
Immunodeficiency Virus Type 1 Isolates Derived from Patients with
Multidrug Resistance to Other Protease Inhibitors
*
Corresponding author. Mailing address: Istituto di
Malattie Infettive e Tropicali, Universitá di Milano,
Ospedale Luigi Sacco, Via GB Grassi 74, 20157 Milano, Italy.
Phone: 39.02.35799676. Fax: 39.02.3560805. E-mail:
rusconi{at}mailserver.unimi.it.
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