Development Of Resistance Mutations Research Articles

Emergence of Drug Resistant HIV-1 After Intrapartum Administration of Single-Dose Nevirapine Is Substantially Underestimated

Purpose of the Study. An inexpensive, effective regimen to prevent perinatal HIV transmission in the developing world is highly desirable. Nevirapine, a nonnucleoside reverse transcriptase inhibitor, seems to provide such an intervention. However, drug-resistance mutations have been identified in up to 40% of women shortly after they received a single intrapartum nevirapine dose as part of a transmission-prevention strategy. This study was undertaken to reexamine the incidence of drug-resistant HIV-1 after single-dose nevirapine. Study Population. Fifty South African women infected with HIV subtype C. Methods. Sensitive, real-time polymerase chain reaction assays were sequentially performed for nonnucleoside reverse transcriptase inhibitor–resistance mutation, K103N and Y181C. Results. Resistance mutations emerged in 65% of women after a single dose of nevirapine. Conclusions. Single-dose nevirapine as used in the developing world for prevention of perinatal HIV transmission results in the development of resistance mutations in a very high percentage of women who receive this intervention. Reviewer Comments. Although single-dose nevirapine has been successfully implemented as a strategy to prevent perinatal HIV transmission, it is increasingly apparent that the women who are treated with this regimen more often than not develop resistance mutations to nevirapine. The clinical implications are clear: Will nevirapine work for future perinatal interventions for individual women with drug-resistance mutations? Will women with these drug-resistance mutations fail to respond to nevirapine as part of a highly active retroviral therapy intervention when they need treatment for their own HIV disease? In the same issue of The Journal of Infectious Diseases, Flys et al (J Infect Dis. 2005;192:24–29) demonstrated that drug-resistance variants of HIV may persist for >1 year in this situation. In addition, Lee et al (J Infect Dis. 2005;192:1260–1264) showed that women who developed drug-resistant HIV after exposure to single-dose nevirapine shed drug-resistant HIV in their breast milk. This increases the risk of transmission of resistant virus to uninfected infants. Together, these studies demonstrate that single-dose nevirapine, although an effective strategy for reducing maternal-child transmission of HIV, also predisposes treated women to the development of drug-resistant virus as well as the potential for transmitting drug-resistant virus to their infants via breastfeeding.

HIV-1 viral load blips are of limited clinical significance

Many patients on highly active antiretroviral therapy (HAART) who achieve undetectable HIV-1 RNA levels experience transient episodes of detectable viraemia or blips, suggesting there is incomplete suppression of viral replication. This raises concern that drug resistance mutations could develop and cause eventual treatment failure. However, data from recent studies indicate that most blips are actually random biological and statistical variations around a mean viral load below detectable levels (<50 copies/mL) or due to false elevations of viral load from laboratory processing artefacts. Blips are not typically associated with the development of resistance mutations and most importantly are not associated with virological or clinical failure of previously adequate HAART.

In VitroGeneration of HIV Type 1 Subtype C Isolates Resistant to Enfuvirtide

Enfuvirtide (ENF) is the first in a new class of antiretroviral agents targeting the fusion process of the viral life cycle. ENF is a synthetic 36-amino acid peptide that binds to the HR-1 region of gp41 preventing fusion of viral and cellular membranes. With the introduction of ENF there are now four classes of antiretrovirals each with distinct and different resistance pathways. Resistance to ENF among subtype B HIV-1 isolates is associated with amino acid changes mainly in the HR-1 region, although other regions of envelope have also been implicated. To determine whether subtype C viruses developed resistance mutations similar to subtype B viruses, 11 subtype C and 4 subtype B viruses were passaged in the presence of increasing concentrations of ENF. The subtype C isolates showed varying levels of replication at 1 microg/ml ENF by day 18, but by day 29 all replicated efficiently at 10 microg/ml ENF. All subtype C isolates showed evidence of genotypic changes in gp41 HR-1 following exposure to ENF that included G36S/E/D, I37T, V38M/A/L/E, N/S42D, N43K, L45R/M, and A50T/V. Three subtype C viruses had compensatory changes in the HR-2 region, which corresponds to the ENF sequence, and two isolates had changes in the V3 region. Mutational patterns among the four subtype B viruses were similar to those for subtype C and those previously published in the literature. These data indicate that in vitro resistance to ENF develops rapidly among HIV-1 subtype C isolates. In general, mutational patterns for subtype C were similar to those described for subtype B, suggesting that the mechanism of action for ENF is similar for HIV-1 subtype B and C isolates.

Treatment Response and Drug Resistance in Patients Infected with HIV Type 1 Group O Viruses

Information about the efficacy of antiretroviral drugs in HIV-1 group O strains as well on the virus evolution in terms of resistance development in vivo is very limited. We assessed the clinical, immunological, and virological response to antiretroviral therapy as well as the selection of drug resistance in six HIV-1 group O-infected patients. All but one initiated antiretroviral therapy with two nucleoside reverse transcriptase inhibitors (NRTI) plus one protease inhibitor (PI). At baseline, median plasma HIV-1 group O RNA and CD4 counts were 32,256 (15,770-74,132) copies/ml and 88 cells/microl (13-170), respectively. Four patients reached undetectable plasma viremia 12 weeks after beginning treatment. However, viremia rebounded in one of them due to poor compliance. Another two patients had an initial reduction in plasma HIV-RNA greater than 1 log, but rebounded soon thereafter. At baseline, all patients' viruses revealed changes associated with NNRTI resistance (98G and 181C). Two out of three patients failing therapy developed resistance mutations. One selected changes M41L, E44D, D67N, V75M, M184V, and T215Y at the RT, and G48M, F53L, I54V, V82A, and L90M at the protease. Another selected mutations K70N, V75A, and M184V at the RT, and D30D/N and I84V at the protease while failing on indinavir. Interestingly, both patients showed a shift at codon 181 from C to Y, which might restore NNRTI susceptibility. Sustained viral suppression in HIV-1 group O-infected patients can be successfully achieved using antiretroviral regimens based on two NRTI and a boosted PI. Drug resistance mutations in HIV-1 group O seem to be selected at similar positions to those in HIV-1 group M viruses.

Adherence to trizivir and tenofovir as a simplified salvage regimen is associated with suppression of viraemia and a decreased cholesterol

Treatment failure during highly active antiretroviral therapy (HAART) is ultimately common and associated with the development of resistance mutations. Trizivir (zidovudine/lamivudine/abacavir) and tenofovir disoproxil fumarate may improve adherence and enhance virological suppression in individuals who have failed previous regimens. Individuals were identified who had failed previous HAART and who were then prescribed trizivir and tenofovir. Viral load and genotypic information were obtained to assess virological response. One hundred and twenty-two individuals were identified from a database containing 5883 patients. In a last observation carried forward intention to treat analysis, 34% of individuals achieved an undetectable viral load of <50 copies/mL at 1 year. Of those who were able to remain on treatment for 1 year, 65% achieved undetectability. We observed no effect regarding previous regimens on viral outcome. Accumulation of TAMs (thymidine analogue mutations) was associated with a decrease in the number of patients achieving an undetectable viral load (with <2 TAMs present 38% of patients developed undetectable viral loads, > or =1;2 TAMs 17% undetectable; P = 0.03). Using the mean cell volume as a measure of compliance, those with higher values were more likely to achieve a viral load <50 copies/mL (P = 0.04). A beneficial effect on cholesterol was noted regardless of virological outcome. In compliant heavily pre-treated individuals with less than 2 TAMs, salvage therapy with trizivir and tenofovir is associated with suppression of viraemia and an improved lipid profile.

Preventing Infection-Associated Cancer: From Bench to Hillside

Preventing Infection-Associated Cancer: From Bench to Hillside

Early Virological Failure with a Combination of Tenofovir, Didanosine and Efavirenz

To describe the occurrence of a high early virological failure (VF) rate and development of resistance mutations in antiretroviral-naive patients receiving tenofovir, didanosine and efavirenz. HIV-infected antiretroviral-naive patients with viral load > or =30 000 copies/ml were enrolled in a pilot randomized trial of tenofovir/didanosine (250 mg)/ efavirenz with (arm A) or without (arm B) lopinavir/r for the first 12 weeks. As six cases of early VF (a drop of <2 log at month 3, or a rebound of >1 log from the nadir) were detected (five in arm B and one in arm A who had previously stopped lopinavir/r) an unplanned interim analysis was performed. A total of 29 out of 36 enrolled patients completed at least 3 months of follow-up and were included in the interim analysis. An intent-to-treat analysis showed treatment failure in 7/15 (46.7%) patients in arm B (five VF, one lost, one switched) versus 2/14 (14.3%) in arm A (one lost, one switched) (P=0.109). The patient in arm A who interrupted lopinavir/r at day 3 and continued with tenofovir/didanosine/efavirenz later developed VF. At baseline, 6/6 VF patients had VL >100000 copies/ml and an advanced stage of disease (CD4 <200 plus CDC stage C or B3) versus 0/8 non-VF patients taking the triple drug regimen (P<0.001). At failure, G190S/E alone or associated with K103N and K101R mutations was detected in five patients, and K103N/L1001/V108l in the sixth patient. Additionally, L74V/I and K65R were detected in four and two patients, respectively. A high early virological failure rate and the occurrence of resistance mutations were detected in a group of antiretroviral-naive patients treated with tenofovir/didanosine/efavirenz.

Drug Monitoring and Viral Response to Lopinavir/Ritonavir or Saquinavir/Ritonavir Containing Regimens in Individuals Infected with the Human Immunodeficiency Virus Type1

The aim of this study was to correlate results of therapeutic drug monitoring, genotypic resistance and viral response to lopinavir/ritonavir (LPV/r) or saquinavir/ritonavir (SQV/r) containing antiretroviral regimens. The retrospective short-term study included 20 patients with LPV/r and 20 patients with SQV/r containing highly active antiretroviral therapy (HAART). At baseline 7 LPV/r patients and 10 SQV/r patients had CD4+T cell counts above 410 cells/microl. After 6 months CD4+T cells had doubled in 5 LPV/r and 2 SQV/r patients. In LPV/r patients the mean serum concentration of lopinavir (LPV) was 2.6 ppm and 67% of all LPV/r samples had 50 or fewer viral copies/ml. In SQV/r patients the mean serum concentration of saquinavir (SQV) was 2.1 ppm. 79% of all SQV/r samples had 50 or fewer viruses/ml. Pharmacoenhanced regimens efficiently suppress human immunodeficiency virus type 1 (HIV-1) and the risk of developing resistance mutations is therefore reduced. The implementation of drug monitoring is an additional tool to determine optimal treatment conditions.

Approche clinique des antiprotéases boostées chez les adultes

When boosted by ritonavir, protease inhibitors trough concentration and inhibitory quotient are increased, thus enhancing their therapeutic margin. Although the inhibitory quotient is less high when patients are pre-treated and have developed resistance mutations, it nonetheless offers a precious alternative for patients experiencing therapeutic failure. Despite great inter-individual variability in virologic responses, boosted protease inhibitors can be compared to boosted lopinavir. The latter seems superior to saquinavir boosted and indinavir boosted in terms of virologic efficacy and resistance mutations selection. A conclusion regarding boosted atazanavir and boosted fos-amprenavir versus lopinavir cannot be absolutely drawn on the basis of present results.

Is Efavirenz Effective After Short-Course Nevirapine?

Short-course nevirapine is an effective and affordable option for preventing perinatal transmission in resource-limited nations, but such monotherapy has been associated with the development of resistance mutations. Even following single doses, mutations such as K103N and Y181C -- which confer broad cross-resistance to other NNRTIs -- were detected in 15% to 19% of women 6 weeks' postpartum. Follow-up in most cases revealed viral reversion to wild-type virus 12 months later. However, the significance of the transient …

Secondary mutations M36I and A71V in the human immunodeficiency virus type 1 protease can provide an advantage for the emergence of the primary mutation D30N.

Development of resistance mutations in enzymatic targets of human immunodeficiency virus 1 (HIV-1) hampers the ability to provide adequate therapy. Of special interest is the effect mutations outside the active site of HIV-1 protease have on inhibitor binding and virus viability. We engineered protease mutants containing the active site mutation D30N alone and with the nonactive site polymorphisms M36I and/or A71V. We determined the K(i) values for the inhibitors nelfinavir, ritonavir, indinavir, KNI272, and AG1776 as well as the catalytic efficiency of the mutants. Single and double mutation combinations exhibited a decrease in catalytic efficiency, while the triple mutant displayed catalytic efficiency greater than that of the wild type. Variants containing M36I or A71V alone did not display a significant change in binding affinities to the inhibitors tested. The variant containing mutation D30N displayed a 2-6-fold increase in K(i) for all inhibitors tested, with nelfinavir showing the greatest increase. The double mutants containing a combination of mutations D30N, M36I, and A71V displayed -0.5-fold to +6-fold changes in the K(i) of all inhibitors tested, with ritonavir and nelfinavir most affected. Only the triple mutant showed a significant increase (>10-fold) in K(i) for inhibitor nelfinavir, ritonavir, or AG-1776 displaying 22-, 19-, or 15-fold increases, respectively. Our study shows that the M36I and A71V mutations provide a greater level of inhibitor cross-resistance combined with active site mutation D30N. M36I and A71V, when present as natural polymorphisms, could aid the virus in developing active site mutations to escape inhibitor binding while maintaining catalytic efficiency.

The management of chronic hepatitis B infection.

Chronic hepatitis B infection is frequently diagnosed within the genitourinary clinic setting with sexual transmission the commonest route of acquisition in the United Kingdom. Only 3--5% of adults who contract acute hepatitis B will progress to chronic infection, and these individuals can be identified by the presence of hepatitis B surface antigen (HBsAg) in the bloodstream 6 months after infection. Individuals at highest risk of long-term complications such as cirrhosis and hepatocellular carcinoma, carry HBeAg and have high levels of circulating hepatitis B virus (HBV) deoxyribonucleic acid (DNA). Therapy should be targeted towards this group of patients. Two forms of therapy are now licensed for use in chronic hepatitis B infection: interferon-alpha and lamivudine. Seroconversion occurs in 30--40% of patients treated with interferon and treatment is often limited by toxicity. Lamivudine is well tolerated with seroconversion rates of 15--20% at one year, rising with increasing duration of therapy. Long-term monotherapy is limited however by the development of resistance mutations and combination nucleoside therapy is likely to become the treatment of choice in the future. Patients with chronic hepatitis B should be counselled regarding transmission, partner vaccination and alcohol intake and co-infection with other hepatitis viruses should be excluded.

Emergence of zidovudine and multidrug-resistance mutations in the HIV-1 reverse transcriptase gene in therapy-naive patients receiving stavudine plus didanosine combination therapy

Assessment of genotypic changes in the reverse transcriptase gene of HIV-1 occurring in antiretroviral naive patients treated by stavudine plus didanosine combination therapy. Sequence analysis (codons 1-230) was performed after amplification of the reverse transcriptase gene from plasma samples collected at baseline and at the end of treatment from 39 previously treatment-naive patients treated for 24-48 weeks. At baseline, mutations associated with zidovudine resistance were detected in plasma from two patients: Asp67Asn/Lys219Gln and Leu210Trp. Among the 39 subjects, 18 (46%) developed mutations: one developed the Val75Thr/Ala mutation, four (10%) developed a Gln151Met multidrug-resistance mutation (MDR), associated in one of them with the Phe77Leu and the Phe116Tyr MDR mutations and 14 (36%) developed one or more zidovudine-specific mutations (Met41Leu, Asp67Asn, Lys70Arg, Leu210Trp, Thr215Tyr/Phe). The development of a Met41Leu zidovudine-specific mutation was associated with the development of a Gln151Met mutation in one patient. Other reverse transcriptase mutations known to confer resistance to nucleoside analogues were not detected. At inclusion, there was no statistical difference in HIV-1 load between patients who developed resistance mutations and those who did not. RNA HIV-1 load decrease was higher (P = 0.05) in patients who maintained a wild-type reverse transcriptase genotype (-2.22 log10 copies/ml) than in patients who developed resistance mutations (-1.14 log10 copies/ml). Stavudine/didanosine combination therapy is associated with emergence of zidovudine-related resistance or MDR mutations in naive patients. These findings should be considered when optimizing salvage therapy for patients who have received a treatment including stavudine/didanosine combination.

Ganciclovir and lamivudine combination therapy after orthotopic liver transplantation

Backeround: Orthotopic liver transplantation (OLT) in patients infected with hepatitis B virus (HBV) is known to be associated with a high recurrence rate and poor long term prognosis. While interferon treatment alone is not effective in patients after OLT; prolonged treatment with lamivudine may not be effective due to the development of resistant mutations of the virus. Combined treatment with different virostatic agents may overcome this problem and increase the efficacy. However, data are lacking. We report our experience in a patient with hepatitis B after OLT. Case report: In August 1996, OLT was performed in a 23 years old male patient l~ecause of liver cirrhosis due to hepatitis B. After OLT the patient was treated with imrnunoglobulins and HBsAg disappeared for 8 months. April 1997, recurrence of hepatitis B was noted with presence of HBV-DNA and elevated transaminases. Thus treatment with lamividine (100 mg o.d.) and immunoglobulins was initiated. However, this resulted only in a moderate reduction of the viral load and no change of transaminases. Consequently, treatment with immunoglobulins was terminated and Ganciclovir 250 nag (b.d.) added. After two months, the PCR became negative for virus DNA and the HBsAg disappeared. Treatment was continued for another 4 months. At follow-up visits, the patient's serum remained negative for virus DNA and HBsAg and transaminases were within the normal range. The virostatic therapy with lamivudine and ganciclovir was continued. The therapy was well tolerated Conclusion: In a patient with recurrent hepatitis B after OLT, initially unresponsive to treatment with lamivudine, adding ganciclovir to the regimen, yielded in a response with a disappearance of viral DNA and complete normalization of transaminases. Even though long term outcome is not yet available, this combination antiviral therapy deserves further evaluation.

Lymph Node Human Immunodeficiency Virus RNA Levels and Resistance Mutations in Patients Receiving High‐Dose Saquinavir

The development of resistance mutations and human immunodeficiency virus (HIV) RNA levels were compared in lymph nodes and plasma of patients receiving antiretroviral therapy. Ten HIV-positive patients receiving high-dose saquinavir monotherapy (3600 or 7200 mg/day) underwent 14 lymph node biopsies before and during therapy. HIV RNA levels and appearance of resistance mutations to saquinavir were determined in simultaneous lymph node and plasma samples. HIV RNA levels were found to be consistently higher (mean, 3.16 log RNA copies; SD, 1.04; range, 2.23-5.59) in lymph nodes than in simultaneous plasma samples. Saquinavir therapy resulted in a reduction in HIV RNA levels in both plasma and lymph nodes. The presence or absence of a resistance mutation to saquinavir at codons 48 or 90 of the HIV-1 protease gene was identical in 13 of 14 biopsies, suggesting that resistance mutations to saquinavir appear within close temporal proximity in lymph nodes and plasma.

Patient Compliance and Drug Failure in Protease Inhibitor Monotherapy

To the Editor. —We conducted a 2-dose study of saquinavir in which 40 human immunodeficiency virus type 1 (HIV-1)positive patients received either three or six 200-mg capsules of saquinavir (Roche Products, Welwyn, United Kingdom) 6 times daily (total dose, 3600 mg/d or 7200 mg/d). 1 Analysis of an early cohort of patients enrolled in the study demonstrated that the duration of the response as measured by HIV-1 plasma RNA copy number varied widely within the 2 groups. This variation was not accounted for by the development of resistant mutations alone. To investigate whether decreased patient compliance with this intensive regimen could explain the observed variation in viral responses, we monitored drug-taking behavior in the remaining patients on their enrollment into the high-dose group for the initial 24 weeks of therapy using medication container closures or caps that record the precise date and time of the opening and closing of the