Prevalence of HIV-1 drug resistance in antiretroviral-naive patients: a prospective study

Does highly active antiretroviral therapy improve neurocognitive function? A systematic review

Highly active antiretroviral therapy (HAART) reduces the incidence of human immunodeficiency virus (HIV) dementia (HAD), whereas the overall prevalence appears to have increased. Recent changes to diagnostic nosology have emphasized the presence of neurocognitive deficits. Uniform methods of ascertaining neuropsychological impairment and excluding confounding causes are critical to between-study comparison. We conducted a systematic review on all studies that use single-cohort prospective treatment effect design that reported on the neurocognitive or neuropsychological profile of individuals commencing HAART. Fifteen 15 relevant studies were included. A large number of studies using observational or cross-sectional designs were excluded, as these do not allow for a within-subject description of pre- and post-HAART predictive factors. Eleven studies reported a significant improvement in neurocognitive status or neuropsychological profile over an average study period of 6 months. Variable or nonreporting of HAART regimens in these studies did not allow for an analysis of individual agent or regimen effectiveness. The results show that although HAART does improve cognition, it does not appear to fully eradicate impairments. The methods used in this research differ widely and therefore comparison across studies is difficult. Studies examining the long-term effects of HAART on HIV-associated neurocognitive disorders (HANDs) using uniform methods of data collection are needed, together with clear reporting of HAART regimens.

Monitoring HIV drug resistance in treatment-naive individuals: molecular indicators, epidemiology and clinical implications

Transmitted drug resistance (TDR) has been documented to occur soon after the introduction of HAART. The purpose of this review is to summarize the current knowledge regarding the epidemiology, the clinical implications and the trends in the research field of TDR. Until now, there have been different approaches for monitoring TDR, however, the surveillance drug resistance-associated mutations list seems fairly advantageous for TDR surveillance compared with other methods. The prevalence of TDR is approximately 10% in Europe and North America among recently or newly infected individuals sampled over the last few years. TDR was found to be higher among patients infected in Europe and North America compared with those in geographic areas with a high prevalence of HIV-1, reflecting the differences in the access to HAART in the two populations. Resistant viruses show different reversal rates to wild-type depending on the fitness cost of particular mutations. TDR in treatment-naive individuals is of major importance in HIV clinical practice and for this reason British–European and USA guideline panels recommend drug-resistance testing prior to treatment.

Neuropsychological functioning and antiretroviral treatment in HIV/AIDS: a review

This article presents a review of studies that have investigated the neuropsychological effects of antiretroviral treatment (ART) for HIV-1 infection. It provides a brief overview of the era of monotherapy, dual-therapy, and an extended overview of the current era of combination antiretroviral therapy (CART). This review highlights that while CART has had a dramatic effect on the incidence and the severity of HIV-associated neurocognitive disorders (HAND), HAND, in its mild form, still remains prevalent. New causes of this sustained prevalence are poor CNS penetration of some antiretroviral agents, drug resistance, poor adherence, potential neurotoxicity, co-morbidities such as the long-term CART side effects in relation to cardio-vascular disease, and chronic HIV brain infection that may facilitate the expression of new forms of neurodegenerative processes. The review emphasizes the need to address methodological limitations of published studies and the need for large and representative cross-disciplinary longitudinal investigations across the HIV illness span.

Primary HIV drug resistance and efficacy of first-line antiretroviral therapy guided by resistance testing

BACKGROUND

Primary HIV drug resistance has been associated with poor treatment outcome of first-line highly active antiretroviral therapy (HAART) in several trials. The aim of the study was to assess the efficacy of first-line HAART guided by resistance testing.

METHODS

In a prospective multicenter study in the state of Nordrhein-Westfalen, Germany, chronically HIV-infected patients underwent genotypic resistance testing and were monitored for 48 weeks after initiation of HAART.

RESULTS

Primary drug resistance was found in 30 of 269 patients entering the study between January 2001 and December 2003 [11.2%; 95% confidence interval, 7.4-14.9]. In intent-to-treat analysis, the proportion of patients with viral load below 50 copies/mL after 24 and 48 weeks was 70.0% and 66.7%, respectively, in patients with resistance and 74.1% and 73.6%, respectively, in patients without (P = 0.66 and 0.51). In on-treatment analysis, the proportions were 80.8% and 83.3%, respectively, in patients with resistance and 81.9% and 85.0%, respectively, in patients without (P= 0.79 and 0.77). These results were also valid considering a detection limit of 400 copies/mL.

CONCLUSIONS

The prevalence of primary drug resistance was 11.2% in chronically HIV-infected patients. HAART guided by resistance testing had similar efficacy in patients with primary drug resistance as compared with patients with wild-type virus. Based on these facts, resistance-adapted first-line HAART is suggested as routine practice.

High sequence conservation of human immunodeficiency virus type 1 reverse transcriptase under drug pressure despite the continuous appearance of mutations

To define the extent of sequence conservation in human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) in vivo, the first 320 amino acids of RT obtained from 2,236 plasma-derived samples from a well-defined cohort of 1,704 HIV-1-infected individuals (457 drug naïve and 1,247 drug treated) were analyzed and examined in structural terms. In naïve patients, 233 out of these 320 residues (73%) were conserved (<1% variability). The majority of invariant amino acids clustered into defined regions comprising between 5 and 29 consecutive residues. Of the nine longest invariant regions identified, some contained residues and domains critical for enzyme stability and function. In patients treated with RT inhibitors, despite profound drug pressure and the appearance of mutations primarily associated with resistance, 202 amino acids (63%) remained highly conserved and appeared mostly distributed in regions of variable length. This finding suggests that participation of consecutive residues in structural domains is strictly required for cooperative functions and sustainability of HIV-1 RT activity. Besides confirming the conservation of amino acids that are already known to be important for catalytic activity, stability of the heterodimer interface, and/or primer/template binding, the other 62 new invariable residues are now identified and mapped onto the three-dimensional structure of the enzyme. This new knowledge could be of help in the structure-based design of novel resistance-evading drugs.

The antiretroviral rollout and drug-resistant HIV in Africa: insights from empirical data and theoretical models

The U.S. Government has pledged to spend $15 billion in Africa and the Caribbean on AIDS. A central focus of this plan is to provide antiretroviral treatment (ART) to millions. Here, we evaluate whether the plan to rollout ART in Africa is likely to generate an epidemic of drug-resistant strains of HIV. We review what has occurred as a result of high usage of ART in developed countries in terms of changes in risky behavior, and the emergence and transmission of drug-resistant HIV. We also review how mathematical models have been used to predict the evolution of drug-resistant HIV epidemics. We then show how models can be used to predict the likely impact of the ART rollout on the evolution of drug-resistant HIV in Africa. At currently planned levels of treatment coverage, we predict that (over the next decade) in Africa: (i) the impact of ART on reducing HIV transmission (and prevalence) is likely to be undetectable (unless accompanied by substantial changes in behavior), (ii) the transmission rate of drug-resistant HIV will be below the WHO surveillance threshold of 5%, and (ii) the majority of cases of drug-resistant HIV that will occur will be due to acquired (and not transmitted) resistance. For the next decade, large-scale surveillance for detecting transmitted resistance in Africa is unnecessary. Instead, we recommend that patients should be closely monitored for acquired resistance, and sentinel surveillance (in a few urban centers) should be used to monitor transmitted resistance.

Identification of the minimal conserved structure of HIV-1 protease in the presence and absence of drug pressure

OBJECTIVE

To define the extent of amino acid protease (PR) conservation in vivo in the absence and presence of pharmacological pressure in a large patient cohort.

METHODS

Plasma-derived complete protein PR sequences from a well-defined cohort of 1096 HIV-1 infected individuals (457 drug-naive and 639 under antiretroviral therapy including PR-inhibitors) were obtained and analysed, and are discussed in a structural context.

RESULTS

In naive patients, the PR sequence showed conservation (< 1% variability) in 68 out of 99 (69%) residues. Five large conserved regions were observed, one (P1-P9) at the N-terminal site, another (E21-V32) comprised the catalytic active-site, a third (P44-V56) contained the flap, a fourth contained the region G78-N88, and another (G94-F99) contained the C-terminal site. In PR-inhibitor treated patients, the appearance of mutations primarily associated with drug resistance determined a decrease of amino acid invariance to 45 out of 99 residues (45% conservation). The overall degree of enzyme conservation, when compared to the PR sequences in drug-naive patients, was preserved at the N- and C-terminal regions, whereas the other large conserved areas decreased to smaller domains containing, respectively, the active-site residues D25-D29, the tip of the flap G49-G52, and the G78-P81 and G86-R87 turns.

CONCLUSIONS

Amino acid conservation in HIV PR can be minimally present in 45 residues out of 99. Identification of these invariable residues, with crucial roles in dimer stability, protein flexibility and catalytic activity, and their mapping on the three-dimensional structure of the enzyme will help guide the design of novel resistance-evading drugs.

Limited transmission of drug-resistant HIV type 1 in 100 Swedish newly detected and drug-naive patients infected with subtypes A, B, C, D, G, U, and CRF01_AE

The prevalence of genetic drug resistance in newly diagnosed HIV-1 cases and potential subtype-specific mutation patterns were studied. Samples from 100 newly diagnosed patients were randomly chosen from three HIV clinics in Sweden, prospectively collected during the period June 1998 to August 2001. Viral RNA was extracted from plasma and an approximately 2000-bp fragment covering the protease (PR) and reverse transcriptase (RT) genes was sequenced. Subtypes A, B, C, D, G, U, and CRF01_AE were found. All 100 sequences had mutations reported to be involved in some drug resistance, revealing naturally occurring subtype-specific amino acid patterns. Such patterns may be important to consider when treating patients infected with nonsubtype B viruses. While many drug resistance mutations seem to be naturally occurring, 9% of the newly detected patients in Sweden may have been infected with virus from antiviral-treated patients. Among the individuals infected with resistant virus, the majority were infected with subtype B virus and belonged to the homosexual risk group. It may be important to routinely test for resistance in newly infected cases to improve the choice of drugs for treatment because the virus may revert and resistant forms can become latent.

Rates of transmission of antiretroviral drug resistant strains of HIV-1

BACKGROUND

It is clear that transmission of drug resistant HIV-1 is possible and occurs regularly. However, there is a lack of clarity concerning the true rate of this transmission in a given population, the impact of combination therapies on this rate, and the contribution of transmitted resistant virus to treatment failure either in an individual or on a population basis.

OBJECTIVES

To provide a review of our current understanding of rates of transmission of drug resistant HIV-1 in various populations and to report the results of a study conducted to determine this rate in Sydney, Australia in the years 1992-2000.

STUDY DESIGN

A review of the literature combined with a prospective study of antiretroviral drug resistance in 130 individuals who were diagnosed with symptomatic primary infection at St. Vincent's Hospital, Sydney, Australia between 1992 and 2000. Sequencing of reverse transcriptase (RT) and protease (PR) was performed by the TruGene HIV-1 genotyping kit (Visible Genetics Inc.).

RESULTS

The results found in the Sydney population contrast with much of the literature. The prevalence of mutations that conferred primary resistance to protease inhibitors (PIs) was only 0.8% at position V82I. Secondary mutations/polymorphisms were seen in the PR at position L10I/V, K20R, M36I, L63P, A71T/V, or V77I in 60%. L63P was the most frequently found mutation (46.3%). The incidence of protease-resistant strains of HIV in primary HIV-1 infection did not change after the introduction of PIs in 1996. The distribution of the most common resistance mutations in the RT was as follows; M41L (8.5%) and T215Y (8.5%) and K70R (4.8%). The frequency of mutations associated with NRTI resistance was significantly lower in the post 1995 samples (43.9 vs. 19.1%, P < 0.05). Moreover, both M41L and K70R, but not T215Y, occurred with significantly decreased frequency in the post 1995 samples.

CONCLUSIONS

In contrast to other studies we found no increase in the rate of PR resistance and a decrease in the rate of RT resistance in recently transmitted virus over the period 1992-2000. The reasons for the differences between these results and those reported from elsewhere may relate to treatment regimens used in the transmitting population and may have implications for treatment policies in this country.

Nonnucleoside reverse transcriptase inhibitor resistance among antiretroviral-naive HIV-positive pregnant women

From 1999 to 2001, the overall prevalence of resistance in the antiretroviral (ART)-naive population in St. Louis, Missouri, was 17%. We sought to determine if resistance testing in ART-naive HIV-positive pregnant women identified resistant mutations, which would modify our initial choice of therapy. A retrospective chart review was performed on all HIV-positive pregnant women seen from January 2000 to December 2001 at a university hospital. There were 72 pregnancies. Twenty-seven of 72 patients were ART naive. Genotype testing was performed in 18 of 27 naive patients. Three of 18 ART-naive patients (17%) had primary resistance (95% CI: 4%-41%) by genotype to NNRTIs. The primary mutation, G190S, conferring resistance to NNRTIs was present in 1 patient. Another had the K103N mutation. One had the K103R mutation, which conferred phenotypic resistance to NNRTIs by 8.3-fold, warranting a change in the initial regimen. In our community, resistance testing in ART-naive pregnant patients is warranted. Switching later to a more complex regimen during pregnancy may adversely affect adherence, resulting in virologic failure. Strategies to avoid prescribing a suboptimal regimen include waiting to initiate ART until the resistance testing results are available and/or beginning ART with a protease inhibitor-based regimen if the patient is already in the third trimester of pregnancy at the time of her initial clinic presentation.

[Genotypic resistance of human immunodeficiency virus in patients with virologic failure]

BACKGROUND

The aim of the present study is to asses the prevalence of resistances in a group of patients with virological failure establishing the relationship between the appearance of mutations and the given antiretroviral therapy along with other variables used in these patients follow-up.

PATIENTS AND METHOD

Samples belonging to 88 patients were selected either with viral load levels above 30.000 copies/ml after reaching undetectable viral load levels, or with persistently detectable levels above 1.000 copies/ml. Resistances were tested by means of Line Probe Assay (LiPA). The history of patients' antiretroviral treatments was reviewed.

RESULTS

Mutations were observed in 52,6% of cases for reverse transcriptase (RT) an in 81,8% for the protease genes, being T215Y and V82A the most frequently detected ones. Mutations coferring resistance to the given antiretrovirals appeared in 33 cases. No statistical significance was observed between the presence of mutations and the administered therapy. In the multivariate analysis we found for LiPA RT a greater risk of appearance of mutations according to patient motility (OR = 4,0).

CONCLUSIONS

the prevalence of resistance mutations in patients with virologic failure is placed around 50% in both genes. A consensus in the definition of virologic failure in HIV infected patients is urged.

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.