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Biomedical subjects

K Hertogs

Publications and source records attributed to K Hertogs.

At least 19 recordsLinked to original sources
PubMed2003

Performance of drug resistance assays in testing HIV-1 non-B subtypes.

Antiretroviral susceptibility analyses were performed in plasma samples collected from 32 HIV-1 non-B-infected individuals, most of whom had received antiretroviral drugs. Reverse transcriptase (RT) and protease gene sequences were obtained, and 15 anti-HIV drugs were tested in a recombinant virus phenotypic assay. Phenotypic results were obtained in 25 (78.1%) samples, while genotypic data were recorded in 19 (59.4%). In seven samples (21.9%), neither genotypic nor phenotypic results were obtained. Ten of 13 samples with plasma HIV RNA below 2000 copies/mL did not yield genotypic results. Resistance assays work accurately when testing HIV-1 non-B subtypes. However, as for subtype B variants, a low viral load is the most important factor limiting the application of these tests.

Anti-HIV Agents↗
PubMed2002

Low prevalence of antiretroviral drug resistance among HIV-1 seroconverters in London, 1984-1991.

OBJECTIVES: To examine the prevalence of resistance mutations and natural polymorphisms to reverse transcriptase (RT) and protease inhibitors in a cohort of patients with defined seroconversion dates. METHODS: Eligible patients were those attending an HIV centre in North London who seroconverted from HIV negative to positive status between 01/01/85 and 31/12/91 (n=104). Genotypic resistance analysis was performed on the first positive serum sample after seroconversion and before use of antiretroviral therapy using population-based sequencing of RT-PCR fragments and rule-based sequence interpretation (Vircogen). RESULTS: Protease and RT sequences were successfully amplified from only 37 (35.6%) of the 104 seroconverters. Only one patient who seroconverted in August 1991 showed any evidence of significant mutations in the RT region, and this was associated with resistance to zidovudine (ZDV) (215Y and 210W). An additional patient who seroconverted in July 1991 had a TOR mutation and was classified as having intermediate resistance to ZDV. No spontaneous mutations were detected in the protease region. CONCLUSIONS: Overall only 2 (5%) of these treatment-naïve individuals were infected with HIV variants resistant to ZDV. Although the data at present do not support the need for pretreatment genotyping, there is a need for continued surveillance of the frequency of resistance mutations in antiretroviral naïve patients since the introduction of highly active antiretroviral therapy.

Anti-HIV Agents↗
PubMed2001

Short-cycle structured intermittent treatment of chronic HIV infection with highly active antiretroviral therapy: effects on virologic, immunologic, and toxicity parameters.

Although continuous highly active antiretroviral therapy (HAART) is effective for many HIV-infected patients, it can be toxic and prohibitive in cost. By decreasing the total amount of time patients receive medications, intermittent HAART could reduce toxicity and cost. Therefore, we initiated a pilot study in which 10 HIV-infected individuals receiving effective therapy that resulted in levels of HIV RNA <50 copies per ml of plasma and CD4(+) T cell counts >300 cells per mm(3) of whole blood received repeated cycles of 7 days on HAART followed by 7 days off of HAART. Patients maintained suppression of plasma viremia for 32-68 weeks. There was no significant increase in HIV proviral DNA or replication-competent HIV in peripheral CD4(+) T cells or HIV RNA in peripheral blood or lymph node mononuclear cells. There was no significant change in CD4(+) T cell counts, no significant increase in CD4(+) or CD8(+) T cells expressing activation markers or producing IFN-gamma in response to HIV, no increase in CD4(+) T cell proliferation to p24 antigen, and no evidence for the development of resistance to HAART medications. There was a significant decrease in serum cholesterol and triglyceride levels. Thus, in this proof-of-concept study, short-cycle intermittent HAART maintained suppression of plasma viremia as well as HIV replication in reservoir sites while preserving CD4(+) T cell counts. In addition, there was a decrease in serum cholesterol and triglyceride levels. Intermittent therapy may be an important strategy to reduce cost and toxicity for HIV-infected individuals.

Anti-HIV Agents↗
PubMed2001

Impact of HIV type 1 drug resistance mutations and phenotypic resistance profile on virologic response to salvage therapy.

This study examines the association between presence of drug resistance mutations and phenotypic resistance at baseline to virologic response to salvage therapy in a community setting. The study population consisted of 58 antiretroviral drug-experienced patients with HIV-1 infection who had recently switched therapy because of virologic failure. Drug resistance mutations in the reverse transcriptase- and protease-coding regions and phenotypic susceptibility to 13 antiretroviral drugs were assessed at baseline. Plasma HIV-1 RNA levels were assessed at baseline and at subsequent clinic visits. Results showed that three variables were significant in predicting virologic response: HIV-1 levels at baseline, number of protease mutations, and phenotypic sensitivity score for the regimen at baseline. For four drugs there was a significant association between the presence of specific drug resistance mutations and >10-fold phenotypic resistance to that drug. With phenotypic resistance defined as >4-fold resistance, the association between specific drug resistance mutations and phenotypic resistance was significant for seven drugs. Overall, these data show that phenotypic susceptibility and absence of drug resistance mutations, particularly protease mutations, are significant predictors of virologic response. For several drugs, specific combinations of drug resistance mutations are associated with decreased phenotypic susceptibility and might provide useful clinical guidelines in selecting therapeutic options.

Adult↗
PubMed2001

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.

Anti-HIV Agents↗
PubMed2001

High prevalence of genotypic and phenotypic HIV-1 drug-resistant strains among patients receiving antiretroviral therapy in Abidjan, Côte d'Ivoire.

To describe prevalence of antiretroviral (ARV) drug-resistant HIV-1 strains among patients with a history of earlier treatment with ARV drugs in Abidjan, Côte d'Ivoire, we determined mutations that confer HIV-1 ARV drug resistance by sequencing the viral reverse-transcriptase and protease genes derived from plasma viral RNA of 68 individuals consecutively enrolled in the Joint United Nations Program on AIDS Drug Access Initiative (UNAIDS-DAI) with a history of earlier ARV drug treatment in Abidjan between August 1998 and April 1999. Phenotypic ARV drug resistance was assessed using a recombinant virus assay. Primary mutations associated with ARV drug resistance to at least one of the reverse-transcriptase inhibitors or protease inhibitors were detected in 39 (57.4%) of the 68 patients. The prevalence of mutations associated with resistance to ARV drugs was: 29 (42.6%) to zidovudine, 10 (14.7%) to lamivudine, one (1.5%) to didanosine, one K103N mutation (associated with resistance to delavirdine, nevirapine, and efavirenz), one Y181C mutation (associated with resistance to delavirdine and nevirapine), two to both indinavir (M46I/L and V82A) and saquinavir (G48V and L90M), and one each to ritonavir (V82A) and nelfinavir (D30N). Phenotypic resistance to at least one nucleoside reverse transcriptase inhibitor (RTI) was seen in 25 (39.7%) patients, to nonnucleoside RTIs in 5 (8%) patients, and to protease inhibitors in 4 (6%) patients. The high prevalence we observed in this study may limit in future the effectiveness of ARV programs in the Côte d'Ivoire.

Anti-HIV Agents↗
PubMed2001

Phenotypic cross-resistance to nelfinavir: the role of prior antiretroviral therapy and the number of mutations in the protease gene.

Cross-resistance to nelfinavir (NFV) is observed in patients failing protease inhibitor (PI)-containing therapies. We performed a study with 111 patients who started an NFV-based salvage regimen after failing PI-based therapy to evaluate genotypic changes and to identify factors associated with resistance to NFV. Genotypic and phenotypic resistance data at entry (111 and 51 samples) and after NFV failure (74 and 31 samples) were available. Median CD4(+) cell count was 208 x 10(6)/liter, HIV RNA level was 4.6 log(10) copies/ml, and median number of mutations in the protease was 9. At baseline, 51 and 14% of viral isolates showed high or intermediate phenotypic resistance to NFV. Phenotypic data correlated with virological outcome, reaching undetectability at the third month in 40, 14, and 0% of those patients with susceptible, intermediate, or resistant viral isolates, respectively. Phenotypic resistance to NFV was associated with the presence of the L90M mutation: 46% for resistant vs. 6% in susceptible strains. The number of mutations in the protease correlated with the fold-increase in the IC(50)-NFV. The D30N mutation was detected in only 1 of 74 patients who failed. In a logistic regression analysis, the number of mutations in the protease was associated with NFV cross-resistance (RR, 2.09 per each additional mutation; 95% CI 1.23-3.55; p < 0.01). In conclusion, phenotypic cross-resistance to NFV for PI-experienced patients can be predicted by the number of mutations in the protease. The L90M mutation is significantly associated with the subsequent failure of NFV-containing regimens. The presence of the D30N mutation was rare and not useful in identifying NFV-resistant isolates.

Adult↗
PubMed2001

Primary genotypic and phenotypic HIV-1 drug resistance in recent seroconverters in Madrid.

OBJECTIVE: Transmission of drug-resistant HIV-1 strains is increasing with widespread use of antiretroviral drugs in developed countries. This study examined the prevalence of resistant viruses in recent seroconverters in Madrid, Spain. DESIGN: HIV isolates from 30 consecutive participants with positive or indeterminate HIV antibody test results and a negative test result at a mean of 6.6 months earlier were examined for HIV drug resistance. All study subjects admitted to having very recently engaged in high-risk practices. All were therapeutically naive and were recruited between 1997 and 1999 in a referring health care facility for sexually transmitted diseases. METHODS: Population-based sequencing of the viral reverse transcriptase (RT) and protease (PR) regions derived from plasma viral RNA was performed. Phenotypic resistance was assessed by a recombinant virus assay. RESULTS: Overall prevalence of genotypes associated with reduced susceptibility was 26.7% (8 of 30 participants). Resistance mutations were seen against nucleoside analogues in 7 (23.3%), nonnucleoside reverse transcriptase inhibitors in 1 (3.3%), and protease inhibitors in 2 (6.7%). Zidovudine-resistance mutations M41L and/or T215Y were the commonest, found in 20% (6 of 30 participants). Resistance mutations to at least two antiretroviral families (multidrug-resistance) were detected in 2 (6.7%) study subjects. A median infectious dose (IC50) increase of fourfold for any drug was found in 7 patients, and in 2 was > tenfold for zidovudine (genotype M41L + T215Y) and lamivudine (genotype M184V), respectively. CONCLUSIONS: Drug-resistant HIV variants were present in over one quarter of individuals recently diagnosed as infected in Madrid, Spain. Therefore, resistance testing at baseline should be considered for the optimal design of first-line antiretroviral combinations.

Drug Resistance, Microbial↗
PubMed2001

Efficacy, tolerance, and pharmacokinetics of the combination of stavudine, nevirapine, nelfinavir, and saquinavir as salvage regimen after ritonavir or indinavir failure.

The high rate of protease inhibitor treatment failure in clinical cohorts makes it necessary to define novel salvage therapies. In a prospective study of 31 HIV-infected patients included in a salvage regimen with stavudine, nevirapine, nelfinavir, and saquinavir, viral load decreased a median of 1.65 log(10) and 1.95 log(10) after 6 and 12 months of treatment, respectively, and 35 and 56% of patients had an HIV RNA level below 50 copies/ml at the same time points. At baseline, the mean number of mutations in the protease gene was 10 (2-19), and the V82A and L90M mutations were present in 54 and 21% of patients. The presence of the V82A mutation did not affect significantly the rate of response (36 vs. 38%), whereas the L90M mutation was associated with treatment failure (0 vs. 43%). Plasma trough levels of nelfinavir (NFV) and saquinavir (SQV), in a twice daily dosing regimen, were above the protein-corrected IC(95) in most patients despite the addition of an enzymatic inducer such as nevirapine, and peak levels were 2- and 5-fold increased with respect to standard doses. However, pharmacokinetics of saquinavir-hard gel capsule (SQV-hgc) did not improve significantly in the three times daily dosing regimen. In conclusion, the combination of stavudine, nevirapine, nelfinavir, and saquinavir increased plasma drug levels and produced an adequate virological response in patients who had failed indinavir or ritonavir therapy. This degree of response is not significantly decreased in the presence of genotypic mutations associated with indinavir/ritonavir (IDV/RTV) resistance.

Adult↗
PubMed2001

Genotypic and phenotypic evidence of different drug-resistance mutation patterns between B and non-B subtype isolates of human immunodeficiency virus type 1 found in Brazilian patients failing HAART.

We have investigated the phenotypic and genotypic susceptibility of 14 HIV-1 strains isolated from individuals failing HAART therapy to protease inhibitors (PI). Proviral and plasma viral pol gene fragment were amplified, sequenced and subtyped. Nine samples clustered with protease subtype B reference strains and the remaining samples were classified as non-B subtype corresponding to subtype F (n = 4) and subtype A (n = 1). Although all patients were treated with similar P1 drug regimen, the non-B subtype isolates did not present the L90M and 184V mutations and used mainly G48V and V82A/F to achieve drug resistance. A strong cross-resistance phenotype among all four PI was associated with the mutation L90M in the subtype-B isolates, and with G48V and V82A/F in the non-B counterparts. This observation revealed that the non-B viruses tested had specific genotypic characteristics contrasting with the subtype-B isolates.

Amino Acid Sequence↗
PubMed2001

Distribution of K103N and/or Y181C HIV-1 mutations by exposure to zidovudine and non-nucleoside reverse transcriptase inhibitors.

Our aim was to identify whether zidovudine has a role in the emergence of the K103N resistance mutation in the HIV-1 reverse transcriptase gene on non-nucleoside reverse transcriptase inhibitors (NNRTIs). No difference was found in the exposure to zidovudine or major zidovudine mutations between the resistance patterns K103N-/Y181C+, K103N+/Y181C- and K103N+/ Y181C+, either in group A (patients on nevirapine and previously NNRTI naive) or in group B (on any NNRTI and experience of two or more NNRTIs including nevirapine). Group B patients had the highest prevalence of K103N+/Y181C+. In conclusion, zidovudine seems not to determine the emergence of K103N; however, there appears to be an accumulation of NNRTI resistance mutations with sequential use of NNRTIs.

Anti-HIV Agents↗
PubMed2001

High degree of interlaboratory reproducibility of human immunodeficiency virus type 1 protease and reverse transcriptase sequencing of plasma samples from heavily treated patients.

We assessed the reproducibility of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) and protease sequencing using cryopreserved plasma aliquots obtained from 46 heavily treated HIV-1-infected individuals in two laboratories using dideoxynucleotide sequencing. The rates of complete sequence concordance between the two laboratories were 99.1% for the protease sequence and 99.0% for the RT sequence. Approximately 90% of the discordances were partial, defined as one laboratory detecting a mixture and the second laboratory detecting only one of the mixture's components. Only 0.1% of the nucleotides were completely discordant between the two laboratories, and these were significantly more likely to occur in plasma samples with lower plasma HIV-1 RNA levels. Nucleotide mixtures were detected at approximately 1% of the nucleotide positions, and in every case in which one laboratory detected a mixture, the second laboratory either detected the same mixture or detected one of the mixture's components. The high rate of concordance in detecting mixtures and the fact that most discordances between the two laboratories were partial suggest that most discordances were caused by variation in sampling of the HIV-1 quasispecies by PCR rather than by technical errors in the sequencing process itself.

Amino Acid Sequence↗
PubMed2001

Genotypic correlates of phenotypic resistance to efavirenz in virus isolates from patients failing nonnucleoside reverse transcriptase inhibitor therapy.

Efavirenz (also known as DMP 266 or SUSTIVA) is a potent nonnucleoside inhibitor of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) activity and of HIV-1 replication in vitro and in vivo. Most patients on efavirenz-containing regimens have sustained antiviral responses; however, rebounds in plasma viral load have been observed in some patients in association with the emergence of mutant strains of HIV-1. Virus isolates from the peripheral blood mononuclear cells (PBMCs) of patients with such treatment failures, as well as recombinant viruses incorporating viral sequences derived from patient plasma, show reduced in vitro susceptibility to efavirenz in association with mutations in the RT gene encoding K103N, Y188L, or G190S/E substitutions. Patterns of RT gene mutations and in vitro susceptibility were similar in plasma virus and in viruses isolated from PBMCs. Variant strains of HIV-1 constructed by site-directed mutagenesis confirmed the role of K103N, G190S, and Y188L substitutions in reduced susceptibility to efavirenz. Further, certain secondary mutations (V106I, V108I, Y181C, Y188H, P225H, and F227L) conferred little resistance to efavirenz as single mutations but enhanced the level of resistance of viruses carrying these mutations in combination with K103N or Y188L. Viruses with K103N or Y188L mutations, regardless of the initial selecting nonnucleoside RT inhibitor (NNRTI), exhibited cross-resistance to all of the presently available NNRTIs (efavirenz, nevirapine, and delavirdine). Some virus isolates from nevirapine or delavirdine treatment failures that lacked K103N or Y188L mutations remained susceptible to efavirenz in vitro, although the clinical significance of this finding is presently unclear.

Alkynes↗
PubMed2001

Correlation between viral resistance to zidovudine and resistance at the reverse transcriptase level for a panel of human immunodeficiency virus type 1 mutants.

Using a large panel of human immunodeficiency virus type 1 site-directed mutants, we have observed a higher correlation than has previously been demonstrated between zidovudine (AZT)-triphosphate resistance data at the reverse transcriptase (RT) level and corresponding viral AZT resistance. This enhanced-resistance effect at the RT level was seen with ATP and to a lesser extent with PP(i) when ATP was added at physiological concentrations. The ATP-dependent mechanism (analogous to pyrophosphorolysis) appears to be dominant in the mutants bearing the D67N and K70R or 69 insertion mutations, whereas the Q151M mutation seems independent of ATP for decreased binding to AZT-triphosphate.

Adenosine Triphosphate↗
PubMed2001

Resistance analyses in HIV infected patients with a history of multiple antiretroviral treatment regimens.

OBJECTIVE: To assess HIV-1 isolate based resistance profiles from extensively pretreated patients and effects of a resistance guided switch of antiretroviral therapy. METHODS: In a prospective study phenotypic and genotypic resistance analyses were performed on HIV infected individuals with failure of the current therapy and history of at least three antiretroviral regimens. Antiretroviral therapy was changed according to the results. Viral load and CD4 lymphocyte counts were measured at baseline, after 10 (SD 2), and 24 (2) weeks. RESULTS: All patients (n=52) failed their actual regimen. Currently versus ever previously taking the specific drug, resistance associated mutations and phenotypic resistance to AZT and 3TC were found in over 80% of individuals; resistance to DDI and D4T was detected in less than 10% of cases. A resistance guided switch of therapy was followed by a median decrease of viral load of 0.5 log10 units after 24 weeks. Individuals resistant to two or more drugs compared with patients with resistance to less than two drugs of ongoing treatment, were switched to a regimen containing DDI, D4T, and a PI or NNRTI. After 10 (SD 2) weeks viral load decrease was pronounced in patients with resistance to at least two drugs in the previous regimen. CONCLUSIONS: Among different RTI, the profile of clinically relevant resistance indicates pronounced differences when looking at separate drugs. Regarding virological response, in the context of available drugs, resistance tested with currently used methods is of limited value in extensively pretreated patients and seems to have its value primarily in first or second switch of therapy.

Adult↗
PubMed2001

Laboratory guidelines for the practical use of HIV drug resistance tests in patient follow-up.

HIV drug resistance is one of the major limitations in the successful treatment of HIV-infected patients using currently available antiretroviral combination therapies. When appropriate, drug susceptibility profiles should be taken into consideration in the choice of a specific combination therapy. Guidelines recommending resistance testing in certain circumstances have been issued. Many clinicians have access to resistance testing and will increasingly use these results in their treatment decisions. In this document, we comment on the different methods available, and the relevant issues relating to the clinical application of these tests. Specifically, the following recommendations can be made: (i) genotypic and phenotypic HIV-1 drug resistance analyses can yield complementary information for the clinician. However, insufficient information currently exists as to which approach is preferable in any particular clinical setting; (ii) when HIV-1 drug resistance testing is required, it is recommended that testing be performed on plasma samples obtained before starting, stopping or changing therapy, on samples that have a viral load above the detection limit of the resistance test; (iii) the panel recommends that genotypic and phenotypic HIV-1 drug resistance testing for clinical purposes be performed in a certified laboratory under strict quality control and quality assurance standards; and (iv) the panel recommends that resistance testing laboratories provide clinicians with resistance reports that include a list of drug-related resistance mutations (genotype) and/or a list of drug-related fold resistance values (phenotype), with interpretations of each by an experienced virologist. The interpretation of genotypic and phenotypic analysis is a complex and developing science, and in order to understand HIV-1 drug resistance reports, communication between the requesting clinician and the expert that interpreted the resistance report is recommended.

Acquired Immunodeficiency Syndrome↗