Resistance to antiretroviral therapy among patients in Uganda.

OBJECTIVE: To characterize HIV-1 phenotypic resistance patterns and genotypic mutations among patients taking antiretroviral medications in Uganda. METHODS: We reviewed charts and retrieved archived plasma specimens from patients at an AIDS specialty center in Uganda where antiretroviral therapy has been used since 1996. Phenotypic and genotypic resistance testing was done on specimens associated with a viral load of 1000 copies/ml. RESULTS: Resistance testing of specimens was completed for 16 patients. Among 11 specimens collected before initiation of antiretroviral therapy, no phenotypic resistance or primary genotypic mutations were found. Among 8 patients taking lamivudine, phenotypic resistance was found for 9 (90%) of 10 specimens and was associated with an M184V mutation in all nine cases. Among 12 patients taking zidovudine, no phenotypic resistance and few primary mutations were found. For 6 patients who were receiving protease inhibitors, we observed no phenotypic resistance and only one primary genotypic mutation associated with resistance. CONCLUSIONS: The absence of apparent resistance among samples collected before antiretroviral therapy supports the notion that a similar approach to selection of antiretroviral therapy can generally be used against non-B subtypes. A genotypic marker of antiretroviral resistance to lamivudine in HIV-1 subtypes A, C, and D was similar to those in subtype B infections. These results suggest that the methods used for monitoring for the emergence of drug resistance in antiretroviral programs in Africa may be similar to those used in developed settings.

Prevalence of genotypic and phenotypic resistance to anti-retroviral drugs in a cohort of therapy-naïve HIV-1 infected US military personnel.

OBJECTIVE: While transmission of drug-resistant HIV-1 has been reported, estimates of prevalence of resistance in drug-naïve populations are incomplete. We investigated the prevalence of genotypic mutations and phenotypic antiretroviral resistance in a cohort of HIV-1 infected U.S. military personnel prior to the institution of antiretroviral therapy. DESIGN: Cross-sectional cohort study. METHODS: Plasma was obtained from 114 recently HIV-1 infected subjects enrolled in an epidemiological study. Genotypic resistance was determined by consensus sequencing of a PCR product from the HIV-1 pol gene. Sequences were interpreted by a phenotypic-genotypic correlative database. Resistance phenotypes were determined by a recombinant virus cell culture assay. RESULTS: Genotypic mutations and phenotypic resistance were found at a higher than expected frequency. Resistance to non-nucleoside reverse transcriptase inhibitors was most common, with a prevalence of 15% of 95 subjects by genotype and 26% of 91 subjects by phenotype. Genotypic and phenotypic resistance respectively were found in 4% and 8% of subjects for nucleoside reverse transcriptase inhibitors and in 10% and 1% for protease inhibitors. One subject harbored virus with resistance to all three drug classes. CONCLUSIONS: A substantial frequency of resistance to antiretroviral drugs was identified in a therapy-naïve U.S. cohort. In most cases, the genotypic and phenotypic assays yielded similar results, although the genotypic assay could detect some protease inhibitor resistance-associated mutations in the absence of phenotypic resistance. These data suggest the need for optimization of treatment guidelines based on current estimates of the prevalence of drug resistance in HIV-1 seroconverters.

Human immunodeficiency virus type 1 drug susceptibility during zidovudine (AZT) monotherapy compared with AZT plus 2',3'-dideoxyinosine or AZT plus 2',3'-dideoxycytidine combination therapy. The protocol 34,225-02 Collaborative Group.

Human immunodeficiency virus type 1 (HIV-1) isolates obtained prior to and during a combination therapy trial comparing zidovudine (AZT; 3'-azidothymidine) monotherapy with AZT plus 2',3'-dideoxyinosine (ddI) or AZT plus 2',3'-dideoxycytidine (ddC) were assessed for the development of drug resistance. Drug susceptibility was measured by using two different phenotypic assays, one that requires infection of peripheral blood mononuclear cells with HIV-1 isolated from cocultures and a second based on infection of HeLa CD4+ cells with recombinant virus containing the reverse transcriptase (RT) of the clinical isolate. In addition, genotypic assessment of resistance was obtained by DNA sequencing of the RT coding region. No difference in the development of AZT resistance was noted in isolates from individuals receiving AZT monotherapy or combination therapy. However, a low frequency of ddI or ddC resistance was seen in isolates from the combination arms, which may at least partially explain the enhanced efficacy observed with these drug combinations compared with monotherapy. It was noted from DNA sequencing that a relatively high frequency of the nonnucleoside RT inhibitor resistance mutation, codon 181 changed from encoding Tyr to encoding Cys, was present in some isolates both before and during nucleoside analog combination therapy. Since these patients were unlikely to have access to nonnucleoside RT inhibitors, it is probable that this mutation preexisted at a reasonable level in the wild-type virus population. Comparisons of the AZT susceptibility assays indicated a good correlation between the phenotypic and genotypic determinations. However, direct numerical comparisons between the phenotypic assays were not reliable, suggesting that valid comparisons of different resistance data sets will require the use of the same assay procedure.

Studies on human lactoferrin by electron paramagnetic resonance, fluorescence, and resonance Raman spectroscopy.

Investigations of metal-substituted human lactoferrins by fluorescence, resonance Raman, and electron paramagnetic resonance (EPR) spectroscopy confirm the close similarity between lactoferrin and serum transferrin. As in the case of Fe(III)- and Cu(II)-transferrin, a significant quenching of apolactoferrin's intrinsic fluorescence is caused by the interaction of Fe(III), Cu(II), Cr(III), Mn(III), and Co(III) with specific metal binding sites. Laser excitation of these same metal-lactoferrins produces resonance Raman spectral features at ca. 1605, 1505, 1275, and 1175 cm-1. These bands are characteristic of tyrosinate coordination to the metal ions as has been observed previously for serum transferins and permit the principal absorption band (lambda max between 400 and 465 nm) in each of the metal-lactoferrins to be assigned to charge transfer between the metal ion and tyrosinate ligands. Furthermore, as in serum transferrin the two metal binding sites in lactoferrin can be distinguished by EPR spectroscopy, particularly with the Cr(III)-substituted protein. Only one of the two sites in lactoferrin allows displacement of Cr(III) by Fe(III). Lactoferrin is known to differ from serum transferrin in its enhanced affinity for iron. This is supported by kinetic studies which show that the rate of uptake of Fe(III) from Fe(III)--citrate is 10 times faster for apolactoferrin than for apotransferrin. Furthermore, the more pronounced conformational change which occurs upon metal binding to lactoferrin is corroborated by the production of additional EPR-detectable Cu(II) binding sites in Mn(III)-lactoferrin. The lower pH required for iron removal from lactoferrin causes some permanent change in the protein as judged by altered rates of Fe(III) uptake and altered EPR spectra in the presence of Cu(II). Thus, the common method of producing apolactoferrin by extensive dialysis against citric acid (pH 2) appears to have an adverse effect on the protein.