HIV-1 drug resistance in newly infected individuals

Guidelines for the management of HIV infection in pregnant women and the prevention of mother-to-child transmission

AIMS OF THE GUIDELINES: These guidelines, drawn up by a multidisciplinary group of clinicians and lay workers active in the management of pregnant women infected with HIV, aim to give up-to-date information on interventions to reduce the risk of mother to child transmission of the virus. The evidence on the use of interventions to prevent mother to child transmission of HIV has been graded according to the strength of the data as per the definitions of the US Agency for Health Care Policy and Research [1]. Weighted evidence on the use of combination antiretroviral therapy (ART) for the treatment of HIV infection per se is presented in the BHIVA guidelines for adults [2,3]. The highest level evidence (i.e. randomised controlled trials (RCTs) or large, well conducted meta-analyses) is only available for formula feeding, prelabour caesarean section and zidovudine monotherapy. The need to treat mothers for HIV infection has led to the widespread use of ART in pregnancy which in turn results in new questions such as how to deliver when the mother, on therapy, has no detectable plasma viraemia with the most sensitive assays. In addressing many common and/or difficult clinical scenarios in the absence of 'best evidence' the guidelines rely heavily on 'expert opinion'. Recommendations for management are given in the section on clinical scenarios, and summarized in Table 3. An expanded version of these guidelines with an appendix on safety and toxicity data is available on the BHIVA website http://www.bhiva.org. The authors are available to discuss individual cases.

Prevalence of resistance mutations in antiretroviral-naive chronically HIV-infected patients in 1998: a French nationwide study

OBJECTIVE

To estimate the prevalence of resistance-conferring mutations to antiretroviral drugs in previously untreated patients with chronic HIV-1 infection as a basis for French recommendations on viral genotyping before antiretroviral treatment initiation.

DESIGN

Resistance mutations were sought in samples from 404 patients seen in 23 specialized centres throughout metropolitan France in 1998.

METHODS

The protease and reverse transcriptase (RT) genes of plasma virions were sequenced. Primary and secondary protease and RT gene mutations were identified from the International AIDS Society resistance testing - USA panel.

RESULTS

The prevalence of patients with primary and secondary mutations were 3.7% (95% CI 1.7-5.7) and 50.3% (95% CI 45.0-55.6), respectively. The prevalence of patients with mutations associated with resistance to nucleoside RT inhibitors (NRTI) and non-nucleoside RT inhibitors was 3.3% (95% CI 1.5-5.1) and 0.8% (95% CI 0.0-1.7), respectively. The prevalence of patients with NRTI primary mutations differed according to whether seropositivity had been diagnosed more or less than one year previously (0.2 versus 2.2% P = 0.023). Primary mutations associated with protease inhibitor resistance occurred at a prevalence of 1.9% (95% CI 0.5-3.4) with no difference according to the duration of known seropositivity.

CONCLUSION

In France, in 1998, the prevalence of patients with primary mutations associated with resistance to antiretroviral drugs was low. Genotyping before the initiation of therapy was not recommended in chronically HIV-1-infected naive patients. A national sentinel survey of resistance in this clinical setting is performed regularly to update the recommendations for resistance testing.

World-wide variation in HIV-1 phenotypic susceptibility in untreated individuals: biologically relevant values for resistance testing

OBJECTIVES

To examine the natural phenotypic variability in drug susceptibility among recombinant HIV-1 isolates from a large number of untreated HIV-positive individuals from wide-ranging geographic locations, and to use this information to establish biologically relevant cut-off values for phenotypic antiretroviral susceptibility testing.

METHODS

Phenotypic susceptibility to 14 antiretroviral agents was determined for HIV-1 samples from > 1000 treatment-naive individuals in seven clinical trials. Samples were from the USA (n = 351), Germany (n = 306), Canada (n = 265), and South Africa (n = 358). Geometric mean fold-resistance and confidence intervals were determined relative to a standard laboratory wild-type virus.

RESULTS

Baseline fold-resistance was approximately log-normally distributed for all antiretroviral agents examined. There was no evidence of large geographical differences in average antiviral susceptibility. Geometric mean fold-resistance for each of 14 antiviral agents was similar (+/- 0.5-fold) for samples derived from the USA, Canada, Germany, or South Africa. The non-nucleoside reverse transcriptase inhibitors (NNRTI) exhibited the broadest distribution of susceptibility; approximately 97.5% of all isolates had < 2.5-4.0, < 3.0-4.5, and < 5-10 fold-decrease in susceptibility to five protease inhibitors, six nucleoside analogues, and three NNRTI, respectively. No consistent geographic pattern or clade effect (B versus C) in either the mean or the distribution of baseline antiretroviral susceptibility was observed.

CONCLUSIONS

Phenotypic drug susceptibility of HIV-1 in untreated individuals varies markedly from drug to drug, with broadly similar patterns world-wide. These results have important implications in defining the 'normal range' of phenotypic susceptibility to antiretroviral agents and establish biologically relevant cut-off values for this phenotypic drug susceptibility test.

Randomized salvage therapy with saquinavir-ritonavir versus saquinavir-nelfinavir for highly protease inhibitor-experienced HIV-infected patients

PURPOSE

To compare saquinavir + ritonavir and saquinavir + nelfinavir with nucleoside recycling in patients with multiple failures of highly active antiretroviral therapy (HAART).

METHOD

This was a prospective, multicenter, randomized open trial. Inclusion criteria were the following: consent, age > 18, previous protease inhibitor (PI) exposure > 6 months, unchanged HAART > 3 months, and viral load > 3 log. The treatments compared were ritonavir 200 mg bid + saquinavir 600 mg bid (Rito-Saq), and nelfinavir 1,000 mg bid + saquinavir 600 mg bid (Nelf-Saq). Nucleoside analogues were recycled, and nonnucleoside inhibitors were not permitted. Trough levels of the three drugs were measured by high-performance liquid chromatography at the month 3 visit. After the study had been completed, genotyping analysis was done on the first serum at entry.

RESULTS

The study was interrupted due to the availability of new anti-HIV drugs. A random sample of 31 (16 Rito-Saq and 15 Nelf-Saq) patients was divided into two groups, which were comparable in terms of demographic data and previous history of HIV infection. Mean CD4 cell count and plasma viral load (pVL) were 316 +/- 169 and 3.89 +/- 0.87 for Rito-Saq and 448 +/- 238 and 3.85 +/- 0.32 for Nelf-Saq. Previous duration of PI exposure was 31 months for both groups. The mean number of protease gene mutations was 3.8 (range, 2-7) and 4.4 (range, 2-9), respectively. On intention-to-treat (ITT) analysis at month 6, pVL stabilization or decrease >/= 0.5 log was observed in 18 patients (58%): 10 for Rito-Saq and 8 for Nelf-Saq. In a multivariate logistic regression analysis, virological success at month 3 was inversely correlated to baseline viral load (R = 0.14; 95% CI 0.03-2.9; p =.01); and at month 6, virological success was inversely associated to the number of mutations in the protease gene (R = 2.2; 95% CI 0.73-6.53; p =.06).

CONCLUSION

Nelf-Saq and Rito-Saq combinations can be proposed in case of multiple HAART failures. The fact that the virological response was inversely correlated to baseline viral load makes the case for an early switch after a HAART failure.

HIV type 1 genetic diversity and genotypic drug susceptibility in the Republic of Moldova

HIV-1 genetic diversity and, for the first time, genotypic drug susceptibility was investigated for strains circulating in the Republic of Moldova (of the former Soviet Union). Eighty-three samples from adults recently infected by intravenous drug use (IDU) (n = 60), heterosexual contact (n = 8), and from blood donors (n = 15) that tested positive from 1997 to 1998, and originating from different regions of Moldova were serotyped. By group-specific and subtype-specific peptide ELISA, patients were infected by serotype A (n = 65), serotype B (n = 1), or were nontypable (n = 17). Heteroduplex mobility assay (HMA) confirmed 11 subtype A and the one subtype B infection. Analyses of pol and env sequences for six of the IDUs confirmed that they were infected with subtype A strain. These strains clustered tightly with subtype A strains isolated from the former Soviet Union in phylogenetic analysis. No mutations associated with drug resistance were detected. The Republic of Moldova is culturally more closely related to Romania (where subtype F dominates the epidemic), but depends economically on Russia (where subtype A is established among IDUs). Thus, our results suggest that the spread of HIV in this region is driven by drug networks rather than being due to cultural similarities.

Piperazine-based CCR5 antagonists as HIV-1 inhibitors. I: 2(S)-methyl piperazine as a key pharmacophore element

Optimization of the piperidino-piperazines 1 and 2 provided early leads 3 and 4, which showed good activity in the CCR5-RANTES binding assay and in antiviral assays. A systematic study around these structures showed that the 2(S)-methyl piperazine is essential for CCR5 affinity, which is further enhanced by forming the 2,6-dimethyl benzamide of the piperidine.

Comparison of different treatment regimens for the emergence of new resistance under therapy

OBJECTIVE

To compare the effects of different therapy regimens on the probability of emergence of new resistant mutants during therapy.

METHODS

We developed a stochastic model of infection and treatment to calculate the probability of de novo resistance during therapy. We simulated diverse treatment regimens, with different efficacy in controlling HIV replication. We studied the use of genotypic testing to choose treatment protocols specifically tailored against the wild type.

RESULTS

The probability of emergence of a previously nonexisting drug-resistant mutant during therapy depends crucially on the drug regimen used. In particular, therapy protocols targeting the wild-type strain may lead to a higher probability of treatment failure due to resistance. Conversely, targeting the minority strains in the population, which readily mutate into the resistant variety, significantly lowers the probability of a new resistant emerging under therapy.

CONCLUSIONS

Use of genotypic testing may lead to wrong decisions in the choice of therapy if the population dynamics of production of new resistant mutants is not taken into account.

Using HIV-1 sequence variability to explore virus biology

Human immunodeficiency virus type 1 (HIV-1) only recently established an epidemic world-wide infection in the human population. The virus persists in the human host through active replication and is able to avoid clearance by the immune system. Active replication is an important component of the rapid evolutionary potential of HIV-1, a potential which manifests itself in the evolution of immune escape variants, drug resistant variants, and variants with the ability to use different cell surface coreceptors in conjunction with CD4. Multiple zoonotic introductions, compartmentalization of virus replication in the body, and genetic bottlenecks associated with sampling during transmission, antiretroviral therapy, and geographic and/or host population isolation further contribute to the range of sequences present in extant viruses. The sum of the history of all of these phenomena is reflected in HIV-1 sequence variability, and most of these phenomena are ongoing today. Here we review the use of HIV-1 sequence variability to explore its underlying biology.

Phenotypic analysis of the sensitivity of HIV-1 to inhibitors of the reverse transcriptase, protease, and integrase using a self-inactivating virus vector system

Conventional phenotypic analysis of resistance of the human immunodeficiency virus (HIV) to antiviral therapy is time-consuming and requires culture of infectious virus. Although phenotypic analyses may be desirable, rapid generation of test results and decentralized availability of the test system will be important to achieve utility in the clinical practice. This study describes the design of an alternative phenotypic resistance test using replication incompetent viral vectors. Chimeric HIV vectors containing a marker gene were generated. The env and most of the regulatory and accessory genes of HIV were removed. In addition, the 3'U3 region was deleted to obtain a self-inactivating construct. Cotransfection of the plasmid with a plasmid that provided the vesicular stomatitis virus glycoprotein resulted in the production of replication-incompetent virus vectors. Infection of susceptible cells with the vectors led to marker gene expression. Vector production in the presence of protease (PR) inhibitors, or infection in the presence of reverse transcriptase (RT) or integrase (IN) inhibitors reduced marker gene expression in a dose-dependent manner. Marker gene activity was preserved at higher drug levels if vectors contained RT and PR genes from resistant virus isolates. Sensitivity to nucleoside and non-nucleoside RT inhibitors, protease and integrase inhibitors could be determined in 10 working days. The phenotypic drug resistance test using replication-incompetent HIV vectors significantly speeds up drug resistance measurements and allows testing at reduced biosafety levels. This will make clinical use of phenotypic assessment of antiviral resistance more feasible.

The Serostatus Approach to Fighting the HIV Epidemic: prevention strategies for infected individuals

In the United States, HIV prevention programs have historically tailored activities for specific groups primarily on the basis of behavioral risk factors and demographic characteristics. Through the Serostatus Approach to Fighting the Epidemic (SAFE), the Centers for Disease Control and Prevention is now expanding prevention programs, especially for individuals with HIV, to reduce the risk of transmission as a supplement to current programs that primarily focus on reducing the risk of acquisition of the virus. For individuals with HIV, SAFE comprises action steps that focus on diagnosing all HIV-infected persons, linking them to appropriate high-quality care and prevention services, helping them adhere to treatment regimens, and supporting them in adopting and sustaining HIV risk reduction behavior. SAFE couple a traditional infectious disease control focus on the infected person with behavioral interventions that have been standard for HIV prevention programs.

Prevalence of the T215Y mutation in human immunodeficiency virus type 1-infected pregnant women in a New York cohort, 1995--1999

From 1997 through 1999, the prevalence of the zidovudine resistance mutation T215Y was 9.7% among pregnant women, and the human immunodeficiency virus type 1 (HIV-1) load in those with resistant virus was higher than that measured in women with wild-type HIV-1. All mutations were noted in women with zidovudine experience, which suggests that monotherapy may not be adequate prophylaxis for vertical transmission of HIV-1 infection in the current era.

Are we headed for a resurgence of the HIV epidemic among men who have sex with men?

HIV remains a critical health issue for men who have sex with men (MSM). In the United States, an estimated 365,000 to 535,000 MSM are living with HIV, and 42% of new HIV infections occur in this population. Recent data on sexually transmitted diseases and on sexual behavior indicate the potential for a resurgence in HIV infections among MSM. Outbreaks of gonorrhea and syphilis have been reported in a growing number of cities, and several studies have observed an increase in unprotected anal intercourse among MSM. These increases in HIV risk behavior may be attributed to several factors that have affected the sexual practices of MSM, including changes in beliefs regarding the severity of HIV disease. These emerging data have implications for surveillance and intervention research activities and indicate a need to reevaluate, refocus, and reinvigorate HIV prevention efforts for MSM. Our recommendations for addressing the HIV prevention needs of MSM include the need to consider HIV-related issues within the broader context of the physical, mental, and sexual health of MSM.

Women's HIV transmission risk perceptions and behaviors in the era of potent antiretroviral therapies

The availability of potent antiretroviral medications has raised new concerns regarding continued HIV transmission risk behavior among seropositive persons. Relatively little is known about how women with HIV perceive secondary transmission risk in the context of HIV treatment advances. This study describes sexual risk perceptions and behaviors of 80 women enrolled in HIV outpatient care in 1999. Participants completed structured interviews assessing sexual risk perceptions, attitudes regarding severity of HIV disease, sources of HIV prevention information, and sexual practices during the previous 6 months. Medical histories including 6-month cumulative incidence of sexually transmitted diseases (STDs) were obtained from a clinic database. Thirty-five percent of the sample had engaged in unprotected intercourse or had been diagnosed with an STD in the past 6 months. Only 5% of women believed that medication-related reductions in viral load signify safer sex is unimportant, but 15% indicated they practice safer sex less often since the advent of new HIV treatments and 40% believed AIDS is now a less serious threat. These data suggest women's perceptions of diminished disease severity may be more influential than beliefs regarding diminished infectivity. Study results have implications for framing prevention messages for women and suggest that close integration of secondary prevention and clinical HIV services may be beneficial.

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.

The Emergence and Epidemiology of Resistance in the Nucleoside-Experienced HIV-Infected Population

HIV drug resistance remains one of the most important influences on long-term therapeutic prospects. Resistance and therapeutic failure arises out of the selection and preservation of randomly generated genomic mutations that confer a replicative advantage in the presence of one or more antiretrovirals. The primary correlate to the time to emergence of a drug-resistant HIV variant is the extent of residual replication under selecting drug pressure, emphasizing the importance of full virological suppression to long-term therapy. Further contributions to the time to emergence are the degree of selective pressure exerted by a given drug, whereby greater potency forces earlier selection of mutant strains in balance with the extent of residual replication, and the degree of reduced drug susceptibility afforded by a particular mutation. Once evolved, drug-resistant strains can persist indefinitely as minority viral populations or archived genomes in latently infected CD4 cells, despite long-term withdrawal of the selecting drugs, to re-emerge rapidly on rechallenge with those or any cross-resistant drug. Variable adherence to medication in the routine clinical setting has given rise to resistance mutations being observed in some 50–60% of those with detectable viral loads on therapy in countries where anti-retroviral therapy has been widely available. Nucleoside reverse transcriptase inhibitor-associated mutations form the majority of these, and the long and almost universal use of zidovudine and stavudine has led to mutations selected by these drugs being the most common observed, along with the primary lamivudine resistance mutation M184V. Transmission of drug-resistant HIV in cases of new infection has also been widely studied, and although the extent is considerably lower than that in the treated population (typically 4–10% outside certain geographic areas), early data suggest that it is rising over time as the infected source population becomes more therapy-experienced. Once again, mutations from zidovudine or, to a lesser extent, stavudine exposure form the majority of mutations observed in cases of primary transmission. These data are a cause for concern, and imply that, as things stand, the use of a drug resistance test may become as important to the design of an effective first-line highly active antiretroviral therapy regimen as they have become for selecting new drugs on therapeutic failure.

Clinical use of genotypic and phenotypic drug resistance testing to monitor antiretroviral chemotherapy

Assays that detect antiretroviral drug resistance in human immunodeficiency virus have recently become available to clinicians. Phenotypic assays measure the drug susceptibility of the virus by determining the concentration of drug that inhibits viral replication in tissue culture. Genotypic assays determine the presence of mutations that are known to confer decreased drug susceptibility. Although each type of assay has specific advantages, limitations associated with these tests often complicate the interpretation of results. Several retrospective clinical trials have suggested that resistance testing may be useful in the assessment of the success of salvage antiretroviral therapy. Prospective, controlled trials have demonstrated that resistance testing improves short-term virological response. Resistance testing is currently recommended to help guide the choice of new drugs for patients after treatment has failed and for pregnant women. Resistance testing should also be considered for treatment-naïve patients, to detect transmission of resistant virus.

In vitro evolution of the human immunodeficiency virus type 1 gag-protease region and maintenance of reverse transcriptase resistance following prolonged drug exposure

We studied the human immunodeficiency virus type 1 phenotypic and genotypic profiles of a dual drug-resistant isolate (isolate 14aPost-DR) selected for zidovudine (ZDV) and lamivudine (3TC) resistance and then cultured in the presence of 3TC and a protease inhibitor: indinavir (IDV), ritonavir, or KNI-272. The IDV-treated virus was highly resistant to 3TC, ZDV, and IDV and accumulated protease mutations at positions M46I and V82F. A change from alanine to valine was observed in 4 of 10 clones in the P2 position of the p7-p1 Gag-protease cleavage site, linked to position M46I in the dominant viral quasispecies. Previous 3TC resistance did not impair the development of additional mutations in the protease and Gag-protease cleavage regions.

International perspectives on antiretroviral resistance. Clinical utility of resistance testing: retrospective and prospective data supporting use and current recommendations

Data from retrospective and prospective studies support use of genotypic and phenotypic resistance assays to guide treatment changes when initial or subsequent antiretroviral regimens fail. Several retrospective studies have shown that response to antiretroviral therapy can be predicted based on genotypic analysis of HIV, with baseline genotypic evidence of resistance predicting virologic failure. Other retrospective analyses demonstrated that phenotypic drug sensitivity correlates with increased viral load suppression, particularly when virus remains sensitive to two or three drugs at initiation of the regimen. Furthermore, prospective studies such as VIRADAPT and Genotype-Assisted Antiretroviral Resistance Testing (GART) have substantiated that drug selection based on genotypic assay results yield superior viral suppression compared with empiric treatment assignment. One additional study suggested significant improvement in short-term virologic outcome when phenotypic testing was used to guide treatment selection. Based on these findings, resistance testing is currently recommended for patients with acute HIV infection, those who have failed one or more antiretroviral regimens, and pregnant women. Although these tests move toward becoming a standard of care, several research questions remain: the long-term benefit of resistance testing is not yet certain, the interpretation of specific genotypic resistance patterns needs to be better defined, and clinical cut-off points for phenotypic resistance need to be established. As these issues continue to be studied, resistance testing likely will prove a reliable tool to help plan successful ART strategies.

Frequency of genotypic and phenotypic drug-resistant HIV-1 among therapy-naive patients of the German Seroconverter Study

Genotypic and phenotypic resistance of viral reverse transcriptase (RT) and protease (PR) was determined for 64 therapy-naive, HIV-1-infected seroconverters of the German Seroconverter Study coordinated by the Robert Koch-Institut, Berlin. The date of seroconversion of patients and the laboratory, clinical, and therapeutic follow-up data were documented. Samples were collected between 1996 and 1999. Phenotypic resistant HIV-1 were found in 8 (13%) seroconverters; in most cases resistance was weak and mainly directed against RT inhibitors (4 nucleoside reverse transcriptase inhibitors [NRTIs], 2 nonnucleoside reverse transcriptase inhibitors [NNRTIs], 1 combination NRTI/NNRTI). Only one infection with a weak PR inhibitor resistance was identified. Transmission of multidrug-resistant HIV-1 has not yet been observed. Frequently at least one or more amino acid mutations associated with antiretroviral drug resistance were detected by genotypic analysis. The mean number of resistance-associated mutations in the RT of the transmitted virus has increased significantly since 1996. Studies have shown the improved benefit of initial antiretroviral therapy if based on genotypic resistance data. In view of the considerably high level of transmission of resistant HIV-1 in Germany, which is also seen in other studies in Europe and the United States, we suggest determining the genotypic resistance pattern before starting therapy of newly HIV-1-infected patients.

Clinical and laboratory guidelines for the use of HIV-1 drug resistance testing as part of treatment management: recommendations for the European setting. The EuroGUidelines Group for HIV resistance

Viral drug susceptibility is associated with virologic response to new treatments. Standardized drug resistance tests are now available, and data from some clinical trials suggest that the use of drug resistance testing may be associated with improved virologic outcome. However, drug resistance testing is complex in terms of performance, interpretation and clinical application. HIV-1 drug resistance testing is used across Europe in patient management, but not in a consistent manner. This is due to differences in the national approaches to treatment, treatment management and reimbursement, as well as availability of tests. National guidelines only exist in some countries. In addition, the laboratory quality assurance and quality control standards are not applied uniformly. The EuroGuidelines Group was established to formulate clinical as well as laboratory guidelines for the use of HIV-1 drug resistance testing that are specific for the European setting. The group is comprised of academic clinicians and virologists, scientist from the industry and representatives of the patient community. The panel of experts will review these guidelines and update them on a yearly basis as new scientific evidence becomes available.

Antiretroviral drug concentrations in semen of HIV-1 infected men

Because semen is a major vehicle for the sexual transmission of HIV-1, control of viral replication within the sanctuary of the male genital tract should be a goal of antiretroviral therapy. Local immune responses, virus specific factors, and the degree of viral and cellular trafficking all appear to be important in controlling viral replication and evolution. However, the most important factor influencing viral replication and evolution within the male genital tract may be the disposition of antiretroviral agents into genital tissues and fluids. This review proposes possible mechanisms of antiretroviral distribution into the male genital tract by using other sanctuary barriers; such as the placenta, renal tubules, and blood-brain barrier; as models. In addition, this review summarises recent clinical studies regarding the disposition of currently available antiretroviral drugs into the seminal plasma and discusses some of the difficulties in interpreting drug concentration in the genital tract.

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.

Determinants of heterogeneous adherence to HIV-antiretroviral therapies in the Multicenter AIDS Cohort Study

Assessment of adherence to HIV antiretroviral therapy (ART) is required for studying therapeutic effectiveness and identifying subgroups needing focused education. The study's goals were to describe the level of ART adherence using self-reported recall over a 4-day period and to characterize determinants of lower adherence. The interaction between adherence and drug holidays on level of HIV RNA also was investigated. Perfect self-reported adherence was defined as taking all doses and numbers of pills as prescribed for current HIV medications. Independent predictors of <100% adherence were determined using multivariate logistic regression. Among 539 men, 419 (77.7%) were 100% adherent by the algorithm using self-reported data. HIV-1 RNA was <50 copies/ml in 48.2% of the adherent group versus 33.7% in the less adherent group (p = .015). This proportion dropped to 28% if a drug holiday was reported in addition to lower adherence. A drug holiday was not virologically detrimental if the participant was otherwise adherent. Determinants of lower adherence included African American race (odds ratio [OR], 2.4; p = .008), income <U.S.$50,000 (OR, 2.2; p = .002), no outpatient visits (OR, 3.6; p = .003) and increasing numbers of ART medications (OR, 4.5; p = .001). These data support the validity of using a questionnaire to assess adherence in observational studies. Identification of individuals with characteristics associated with lower adherence provides the basis for interventions to enhance adherence and optimize effective therapies.

Resistance Profiles to Antiretroviral Drugs in HIV-1 Drug-Naive Patients in Argentina

The drug resistance profile of treatment-naive HIV-infected individuals living in Buenos Aires, Argentina, was studied. Samples taken from 94 drug-naive individuals with established HIV infection and 13 patients with primary HIV infection were assessed by nucleotide sequencing and LiPA. The prevalence of drug-associated primary mutations in individuals with established infection was very low. In the viral protease region, 1/86 (1.2%) individuals carried the D30N mutation, whereas 1/85 (1.2%) had the M41L mutation in the reverse transcriptase (RT) region. Secondary mutations in both the protease and RT regions were found in almost 90% of the individuals. In individuals with primary infection, primary mutations were detected in 2/13 (15.4%) patients, one of them carrying M46I mutation in the protease while the other patient had a mutation at codon 184 of the RT. In accordance with current drug resistance testing guidelines, the results of this study suggest that susceptibility tests need not be performed at this time prior to initiation of antiretroviral therapy in HIV-1-infected people in Argentina. However, the public health implications of this subject warrant follow-up studies that will examine a larger number of drug-naive patients, not only in Buenos Aires but also in other major Argentinian cities and in rural areas.

Prevalence of Genotypic Resistance among Antiretroviral Drug-Naive HIV-1-Infected Patients in Belgium

Objectives

To estimate the prevalence and the evolution over time (1995–1998) of genotypic resistance to antiviral drugs in antiretroviral drug-naive HIV-1-infected patients in Belgium.

Design

Belgian Aids Reference Laboratories provided retrospective samples and clinical data from antiretroviral drug-naive HIV-1-infected patients who visited the hospital for the first time in 1995 ( n=45), 1997 ( n=75) and 1998 ( n=111). Genotypic resistance to the three available classes of drugs was monitored using the Line Probe Assay (Innogenetics, Gent, Belgium). Additionally, ARMS-151 was performed for scoring multinucleoside resistance.

Results

The prevalence of genotypic resistance at baseline to nucleoside analogue reverse transcriptase inhibitors (NRTIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs) were each between 10% and 20% for 1995, 1997 and 1998 without an increasing trend over time. For NRTIs, resistance mutations were mainly related to zidovudine in 1995, whereas in 1997 and 1998 baseline resistance was scored for zidovudine, lamivudine or for both drugs simultaneously. No patients displayed the multi-nucleoside resistance Q151M mutation. Baseline resistance mutations to protease inhibitors (PIs) did not rise significantly: 4.4% in 1995, 8% in 1997 and 9.9% in 1998. When scoring any resistance-related mutation, 26.6% displayed genotypic baseline resistance in 1995, 26.6% in 1997 and 31.5% in 1998.

Discussion

The prevalence of genotypic baseline resistance to any drug, as scored with LiPA, in naive HIV-1 patients in Belgium is 29%, with baseline resistance mutations to one or several drugs from all available classes of antiviral drugs. The ability of LiPA to pick up minor variants could be an explanation for the higher overall prevalence we observe, when compared to recent estimates in other countries of 16.3% and 22%, which were based on sequencing methods. According to the European guidelines for resistance testing, resistance testing in Belgium before starting antiviral therapy should be considered.

Factors influencing physicians' judgments of adherence and treatment decisions for patients with HIV disease

New medications for HIV reduce mortality and morbidity but require strict adherence. Thus, physicians treating HIV-positive patients must weigh both disease severity and likelihood of adherence when deciding whether to start patients on treatment. A national sample of 495 physicians surveyed via mail responded to clinical scenarios depicting HIV-positive patients and indicated whether they would start patients on medication (response rate = 53%). Scenarios varied on the patient characteristics of gender, disease severity, ethnicity, and risk group. Physicians predicted that patients with less severe disease, former injection drug users, and African American men would be less likely to adhere. Perceived adherence and disease severity influenced treatment decisions. Results are discussed in the context of attitudes about minority groups and injection drug users, which may influence adherence judgments in practice settings. Psychological research to identify better methods of predicting medication adherence may serve to inform medical decision making.

Resistance to antiretroviral drugs in patients with primary HIV-1 infection. Investigators of the Quebec Primary Infection Study

The widespread use of antiretroviral agents (ARVs) and the growing occurrence of HIV strains resistant to these drugs have given rise to serious concerns regarding the transmission of resistant viruses to newly infected persons. Plasma viral RNA from 80 individuals newly infected between 1997 and 1999 was genotyped by automated sequencing to analyze the profile of viruses resistant to nucleoside and non-nucleoside reverse transcriptase inhibitors (NRTIs and NNRTIs) and to protease inhibitors (PIs). The prevalence of mutations that conferred primary resistance to PIs (L10I, D30Y, V82A, L90M) was 15% of the cohort. RT genotypic variants, associated with high-level resistance to ARVs, were observed in 21% of individuals, including NRTI, NNRTI and multidrug (MDR) resistance in 6, 5, and 10% of cases, respectively. The phenotypic susceptibility of viral isolates to ARVs was also assayed and showed transmission of high-level resistance to ZDV, 3TC, and PIs in those individuals with MDR. The transmission of drug-resistant HIV genotypic variants is a serious problem that merits further attention by public health officials, virologists, and clinicians.

Biologic approaches to the prevention of sexual transmission of human immunodeficiency virus

HIV prevention science has made progress, especially in Thailand and some sub-Saharan African countries. New cases of HIV in the United States, however, have not diminished and explosive epidemics in India and the People's Republic of China seem inevitable. Therefore, HIV prevention activities must move forward in parallel. Funding for biologic and behavioral research efforts must be balanced. Behavioral research must inform biologic strategies. In addition, HIV prevention efforts have been distorted by forces that require further consideration. First, the stigmatization associated with a diagnosis of HIV infection led to prevention efforts that virtually ignore the index case. Focusing entirely on the susceptible population puts intense and unrealistic pressure on behavior change and vaccine development. Although development of an HIV vaccine is desirable, there is no evidence that this goal can be achieved in the near future. Blind faith in vaccine technology detracts from pursuit of alternative aspects of prevention science. Vaccine development is but one of several key components to a broad-based prevention strategy. The history of control of infectious diseases has shown the need for targeting index cases. This certainly will prove important in HIV over the next few years. In developed countries, antiretroviral therapy for established HIV infection has become the standard of care. Increased knowledge of the biology of transmission of HIV suggests use of ART to prevent transmission. Such intervention must be accompanied by safer sex behavior in the index cases, and ultimately could lead to some form of monitoring and directly observed therapy. At this time, the latter approach seems unrealistic in developing countries, where the expense of drugs renders them unavailable. But there is every reason to believe that cheaper, more appropriate drugs will be developed before an effective vaccine. Furthermore, targeted use of ART might have disproportionate benefits in some countries. Women are the fastest growing HIV risk group. Several issues, both biologic and social, make this trend a concern. Increases in the number of HIV-infected women will lead to greater vertical transmission. Women possibly have different risk factors for acquisition and transmission than men. Information about the effects of vaginal ecology, specifically, the role of bacterial vaginosis, in the acquisition of HIV is essential because bacterial vaginosis can be reversed, at least transiently. To allow women to take an active role in HIV prevention methods, development of a topical microbicide is vital and may prove easier than a vaccine. Finally, HIV prevention efforts require knowledgeable, central leadership. All prevention efforts should be developed and implemented in parallel, to gain a synergistic result. Few vaccine experts are enthusiastic about microbicides, and HIV caregivers only rarely focus on the public health considerations of their patients. Stopping the spread of HIV requires a coordinated, concerted efforts using "all the tools in the toolbox."

Clinical monitoring of HIV-1 infection in the ERA of antiretroviral resistance testing

Viral replication of HIV-1 in the human body is a dynamic process. Incomplete suppression of replication during antiretroviral therapy ultimately selects for resistance that imparts an adaptive advantage to HIV-1. Therefore, the goal of antiretroviral therapy is complete suppression of viral replication. Viral suppression to below the lowest possible limits of detection has been associated with an optimal clinical response and delay of drug resistance. An ultrasensitive viral load assay with a very low threshold of detection remains our best laboratory tool to monitor the response to therapy. Patients may fail HAART for many reasons. Only when other potential causes of treatment failure are excluded should antiretroviral resistance testing be considered. Genotypic and phenotypic assays for assessing resistance are now available, and recent retrospective and prospective data support their use in clinical management as an adjunct to helping to choose among different antiretroviral drugs. Despite the growing enthusiasm for these tests, improvements in sensitivity, turnaround time, and quality control are still needed. A practitioner's decision about when to initiate or change therapy in an HIV-infected patient should depend primarily on viral load results, and not on antiretroviral resistance test results. Moreover, resistance testing is no substitute for a thorough clinical and drug history. As we approach the third decade of the HIV epidemic, we will learn how to use antiretroviral resistance tests in conjunction with (not in lieu of) proven clinical and laboratory tools.

Progress in HIV therapeutics and the challenges of adherence to antiretroviral therapy

The impressive and gratifying advances in antiretroviral therapy have benefited many with HIV disease who are fortunate to have access to these complicated and expensive regimens. It is still early in the era of HAART, and the future of therapeutics is not clear. No other infectious disease has required lifelong therapy, and the challenges of equitable treatment of this chronic infectious disease are daunting; not the least among them is lifelong adherence to medications. To maximize the potential of each drug and drug combination, targeted efforts to increase and maintain excellent adherence in the real-world clinical setting are essential, and are second in importance only to the more widespread availability of HAART and continued development of new and more potent agents. The theoretical basis for improving adherence exists, but more substantial research is required. The aim of providing and maintaining therapeutic benefit necessitates that clinicians develop and employ practical and relevant strategies to support antiretroviral adherence. The marriage of biology and behavior that characterizes clinical care in HIV disease is nowhere more challenging for clinicians than in the issue of adherence, but also nowhere more gratifying.

Antiretroviral Resistance: Mechanisms, Detection and Clinical Implications

Widespread use of antiretroviral agents and the epidemic of human immunodeficiency virus (HIV) strains resistant to these drugs have raised a lot of issues including the biology and clinical implications of HIV resistance, reliability of resistant assays and their role in clinical practice. In May 2000, the International AIDS panel endorsed and recommended the use of antiretroviral drug resistance testing in patients. Considerable data on HIV drug resistance testing that strongly suggest that utility of these assays may be of great value have been published and presented at major meetings. Although the genotypic and phenotypic assays are available for antiretroviral drug resistance testing, the testing has certain limitations. The role of these resistance assays is not clearly defined in clinical practice. Prospective studies are needed to define the long-term benefits of these assays. HIV drug resistance testing in the near future may become an important tool and standard of practice for patients infected with HIV. Clinicians caring for HIV-positive patients should be familiar with the antiretroviral drug resistant assays.