Brief report: primary infection with zidovudine-resistant human immunodeficiency virus type 1

Detection of antiretroviral resistance in HIV-1

Resistance testing should be readily available to every clinician who specializes in HIV/AIDS. Based in part on requests we receive in our laboratory, we believe that the use of resistance testing is expanding. However, selecting an initial antiretroviral treatment regimen or changing a failing one according to the test results is complex and inexact and requires knowledgeable interpretation to maximize the clinical benefit. Future studies about viral fitness and other viral, host, and pharmacologic factors responsible for disease progression likely will facilitate more precise application of resistance testing to the clinical setting.

Primary HIV infection

Primary HIV infection is a critical and highly dynamic time period in the course of HIV infection. The initial pathologic processes are important in determining long-term disease progression. In the absence of our ability to eradicate the virus, identifying individuals during primary HIV infection and performing interventions that optimize outcome are important to provide adequate care to a newly infected patient and, from a public health perspective, to identify sexual networks and provide a platform to reduce HIV exposures during a time of high viremia.

Genotypic resistance of antiretroviral drugs among drug-naive HIV type 1 patients with the background of long-term access-easy zidovudine therapy

The prevalence of transmitted resistance to antiretroviral drugs varies geographically, with little known about this effect in Asia. In Korea, zidovudine has been widely administered, without charge, through the National AIDS program since the early 1990s; with other potent antiretroviral agents also being introduced in the late 1990s. An analysis of the drug susceptibility to antiretroviral drugs was performed by genotyping of the drug-resistant mutations in HIV on plasma samples from 50 HIV-infected patients who had received no treatment, between February 1998 and November 2002, which was interpreted according to the consensus guidelines of the International AIDS Society-USA panel. The median CD4 cell count was 100 cells/mm3; the mean plasma RNA level was (5.19 +/- 0.56) log copies per milliliter. Of the 50 subjects tested 4 (8.0%) had one or more major drug-resistance mutation. The prevalence of resistance to multiple classes of drugs was 2.0%. No mutations, associated with resistance to non nucleoside reverse transcriptase inhibitors, were identified. Resistant mutations of the reverse-transcriptase gene were found at codons 67, 70, 118, 215, and 219, and a resistant mutation of the protease gene was found only at codon 46 (2.6%, 1 of 39). There was an 8.0% prevalence of primary drug resistance to antiretroviral drugs in Korean patients infected with HIV-1.

Stability of adherence to highly active antiretroviral therapy over time among clients enrolled in the treatment adherence demonstration project

Adherence to antiretroviral medications is essential to therapeutic success. Many published studies have investigated the degree of adherence or nonadherence, but sample sizes have generally been small, and adherence has seldom been viewed as a longitudinal process. This paper investigates the stability of adherence over time among HIV-infected individuals attending adherence support programs in New York State. The study cohort consists of 435 clients who were on HAART at baseline and who completed at least 2 follow-up interviews. Although cross-sectional nonadherence did not exceed 35%, nonadherence reached 54% when considered across all 3 interviews. Analysis of transition matricies revealed moderate stability in adherence over time (e.g., first follow-up adherence was 81.0% for clients adherent at baseline, compared with 58.3% for clients nonadherent at baseline). Second-order transition matricies offered additional predictive utility. Multivariate results indicated that, for some, it was the transition from a desirable to an undesirable state (e.g., from no illicit drug use to illicit drug use) that increased the likelihood of nonadherence, rather than the presence of these characteristics over time. Findings illustrate the importance of multiple, periodic assessments of adherence and the need to consider strategies to increase stability in the factors affecting adherence to HAART.

Postexposure prophylaxis in children and adolescents for nonoccupational exposure to human immunodeficiency virus

Exposure to human immunodeficiency virus (HIV) can occur in a number of situations unique to, or more common among, children and adolescents. Guidelines for postexposure prophylaxis (PEP) for occupational and nonoccupational (eg, sexual, needle-sharing) exposures to HIV have been published by the US Public Health Service, but they do not directly address nonoccupational HIV exposures unique to children (such as accidental exposure to human milk from a woman infected with HIV or a puncture wound from a discarded needle on a playground), and they do not provide antiretroviral drug information relevant to PEP in children. This clinical report reviews issues of potential exposure of children and adolescents to HIV and gives recommendations for PEP in those situations. The risk of HIV transmission from nonoccupational, nonperinatal exposure is generally low. Transmission risk is modified by factors related to the source and extent of exposure. Determination of the HIV infection status of the exposure source may not be possible, and data on transmission risk by exposure type may not exist. Except in the setting of perinatal transmission, no studies have demonstrated the safety and efficacy of postexposure use of antiretroviral drugs for the prevention of HIV transmission in nonoccupational settings. Antiretroviral therapy used for PEP is associated with significant toxicity. The decision to initiate prophylaxis needs to be made in consultation with the patient, the family, and a clinician with experience in treatment of persons with HIV infection. If instituted, therapy should be started as soon as possible after an exposure-no later than 72 hours-and continued for 28 days. Many clinicians would use 3 drugs for PEP regimens, although 2 drugs may be considered in certain circumstances. Instruction for avoiding secondary transmission should be given. Careful follow-up is needed for psychologic support, encouragement of medication adherence, toxicity monitoring, and serial HIV antibody testing.

Antiretroviral-drug resistance among patients recently infected with HIV

BACKGROUND

Among persons in North America who are newly infected with the human immunodeficiency virus (HIV), the prevalence of transmitted resistance to antiretroviral drugs has been estimated at 1 to 11 percent.

METHODS

We performed a retrospective analysis of susceptibility to antiretroviral drugs before treatment and drug-resistance mutations in HIV in plasma samples from 377 subjects with primary HIV infection who had not yet received treatment and who were identified between May 1995 and June 2000 in 10 North American cities. Responses to treatment could be evaluated in 202 subjects.

RESULTS

Over the five-year period, the frequency of transmitted drug resistance increased significantly. The frequency of high-level resistance to one or more drugs (indicated by a value of more than 10 for the ratio of the 50 percent inhibitory concentration [IC50] for the subject's virus to the IC50 for a drug-sensitive reference virus) increased from 3.4 percent during the period from 1995 to 1998 to 12.4 percent during the period from 1999 to 2000 (P=0.002), and the frequency of multidrug resistance increased from 1.1 percent to 6.2 percent (P=0.01). The frequency of resistance mutations detected by sequence analysis increased from 8.0 percent to 22.7 percent (P<0.001), and the frequency of multidrug resistance detected by sequence analysis increased from 3.8 percent to 10.2 percent (P=0.05). Among subjects infected with drug-resistant virus, the time to viral suppression after the initiation of antiretroviral therapy was longer (P=0.05), and the time to virologic failure was shorter (P=0.05).

CONCLUSIONS

The proportion of new HIV infections that involve drug-resistant virus is increasing in North America. Initial antiretroviral therapy is more likely to fail in patients who are infected with drug-resistant virus. Testing for resistance to drugs before therapy begins is now indicated even for recently infected patients.

Zidovudine use during pregnancy among HIV-infected women on Medicaid

OBJECTIVES

This study estimates the rate of zidovudine (ZDV) use during pregnancy among HIV-infected women receiving Medicaid. The rates of ZDV use during pregnancy are compared before (preperiod) and after (postperiod) the 1994 publication of US Public Service Task Force guidelines, recommending use of ZDV during pregnancy. The authors also compare and contrast the correlates of ZDV use during pregnancy in each of the preguideline and postguideline periods.

METHODS

New Jersey AIDS/HIV surveillance data and paid Medicaid claims data between 1992 and 1996 were merged to examine ZDV use during pregnancy. Among ZDV users, the authors also examined persistence of ZDV use during the 3 months preceding delivery. In these analyses, the authors examined care received during pregnancy and differentiated routine medical care from pregnancy-specific care. Correlates of intrapregnancy ZDV use were examined using chi2 analysis and robust regression techniques that correct for correlation among repeated observations.

RESULTS

Use of ZDV during pregnancy steadily increased from 13% in 1992 to 70% in 1996, with the upward trend beginning before the release of the guidelines. Averaged over the full preperiod (1992-1994), the rate was 29%, increasing to 57% during the full postperiod (1995-1996). Women with no health care during pregnancy did not receive any ZDV prophylaxis. Women who had some health care contacts, but did not receive pregnancy-specific care, had low rates of ZDV use that did not increase after the promulgation of the guidelines (21% in preperiod and 27% in postperiod). Women who received pregnancy-specific care, whether from obstetrician-gynecologists (OB-GYNs) or other providers, substantially increased their use of ZDV in the postguideline period (from 37% to 63% for those who saw OB-GYNS, and from 20% to 59% for those who received pregnancy-specific care from other providers). However, among users of ZDV, only a minority (24%) used ZDV persistently during the 3 months preceding delivery. African American women were less likely to be persistent ZDV users, even after controlling for other factors.

CONCLUSIONS

The study highlights the underutilization of ZDV by women who did not receive pregnancy-related care, even after the publication of guidelines. Lack of pregnancy-specific medical care during pregnancy is an important barrier to ZDV prophylaxis. This study confirms that the receipt of prenatal care during pregnancy is a key intervening variable in the real world application of the PHS guidelines and underscores the importance of proactive efforts to provide prenatal care to pregnant women with HIV.

Antiretroviral prophylaxis of perinatal HIV-1 transmission and the potential impact of antiretroviral resistance

Since 1994, trials of zidovudine, zidovudine and lamivudine, and nevirapine have demonstrated that these antiretroviral drugs can substantially reduce the risk of perinatal HIV-1 transmission. With reductions in drug price, identification of simple, effective antiretroviral regimens to prevent perinatal HIV-1 transmission, and an increasing international commitment to support health care infrastructure, antiretrovirals for both perinatal HIV-1 prevention and HIV-1 treatment will likely become more widely available to HIV-1-infected persons in resource-limited countries. In the United States, widespread antiretroviral usage has been associated with increased antiretroviral drug resistance. This raises concern that drug resistance may reduce the effectiveness of perinatal antiretroviral prophylaxis as well as therapeutic intervention strategies. The purpose of this article is to review what is known about resistance and risk of perinatal HIV transmission, assess the interaction between antiretroviral resistance and the prevention of perinatal HIV-1 transmission, and discuss implications for current global prevention and treatment strategies.

Mutations associated with genotypic resistance to antiretroviral therapy in treatment naïve HIV-1 infected patients in Greece

The widespread use of antiviral drugs against HIV has increased the prevalence of HIV-1 resistant strains among naïve individuals due to transmission of resistant strains. The purpose of this study was to investigate the presence of HIV-1 strains harboring resistance mutations in naïve patients in Greece. Blood samples were collected from 25 individuals. The DNA sequence of protease and partial reverse transcriptase regions (codons 41-223) were obtained by direct sequencing. Our results showed the absence of any primary resistance mutations in the study population. However, we were able to identify high prevalence of sequence polymorphisms at positions in reverse transcriptase region associated mainly with resistance to NNRTIs. Moreover, in protease region several secondary mutations were detected, suggesting the higher genetic variability of this region. The clinical significance of the polymorphisms associated with reduced susceptibility to NNRTIs remains to be clarified.

[Mutations of resistance of HIV-1 in previously untreated patients at penitentiary centers of the Autonomous Community of Valencia, Spain. REPRICOVA study]

BACKGROUND

Our purpose was to determine the prevalence of mutations of resistance to nucleoside inhibitors of reverse transcriptase (NIRT) and protease inhibitors (PI) in the HIV-1 genotype of naïve infected subjects in the prisons of the Autonomous Community of Valencia, Spain.

PATIENTS AND METHOD

Multicentric, descriptive, cross-sectional study of prevalence including a systematic stratified and randomised sampling by centres. Demographic, clinical, virological and immunological data were collected. The HIV gene of protease and transcriptase was studied in peripheral blood plasma samples by means of double PCR amplification and subsequent automatic sequence. Reference: wild strain HXB2.

RESULTS

Plasma was obtained from 133 individuals (119 men and 14 women). 117 samples were selected and the rest did not have enough copies for transcription. With regard to NIRT, 7 samples (5.2% of total) showed some mutation of resistance: M41L, D67N, L210W and K219Q, all them secondary to and associated with resistance to zidovudine, abacavir as well as group B multinucleoside-resistance. With regard to PI, only one sample showed a primary mutation, M46I, which was associated with resistance to indinavir. Moreover, a further 41 samples were found to express some secondary mutation.

CONCLUSIONS

In our series, there was a low number of primary mutations of resistance. These results allow us to exclude the systematic use of resistance tests before an initiation antiretroviral therapy.

Increasing prevalence of resistance mutations in antiretroviral-naïve individuals with established HIV-1 infection from 1996-2001 in St. Louis

BACKGROUND

Transmission of drug-resistant virus in HIV-1 infected individuals is well documented, particularly in patients with primary infection. Prevalence in chronically infected antiretroviral-naïve patients is reportedly low. Routine genotyping in this population is not recommended.

PURPOSE

The purpose of this study was to evaluate resistance profiles in patients with established HIV infection in St. Louis.

METHOD

We selected specimens from drug-naïve individuals (CD4 >300 cells/mL and VL >1000 copies/mL) with established HIV infection between 1996-2001. 62 of 75 specimens were available for genotyping. We excluded patients with evidence of acute HIV infection and long-term nonprogressors.

RESULTS

The overall prevalence of resistance was 11% (7/62). From 1996 to 1998, a prevalence of 4% was observed (1/27 individuals). During the subsequent period from 1999 to 2001, the frequency increased to 17% (6/35 participants; p =.08; 95% CI 5-29%).

CONCLUSION

The results suggest that the prevalence of primary resistance is increasing in our region to the point that it justifies genotypic testing in all individuals before the initiation of antiretroviral therapy. This has to be considered when designing antiretroviral clinical trials.

The effects of antiretroviral therapy on HIV-1 RNA loads in seminal plasma in HIV-positive patients with and without urethritis

BACKGROUND

High seminal plasma HIV-1 RNA loads (SVL) have been reported during gonococcal, non-gonococcal and chlamydial urethritis in patients not taking antiretroviral therapy.

OBJECTIVE

To examine if urethritis leads to increased SVL in HIV-positive patients taking antiretroviral therapy.

METHODS

Men who had been taking therapy for at least 3 months were recruited: 24 had urethitis (PWU) and 16 were without urethritis (controls). At three visits, 1 week apart, blood plasma viral load (BVL) and SVL were assayed by quantitative polymerase chain reaction or the NASBA assay.

RESULTS

Most subjects had undetectable SVL (18 PWU, 13 controls). Among those with undetectable BVL prior to first study visit, virus was undetectable in semen in 5/5 episodes of chlamydial urethritis, 6/7 episodes of non-gonococcal urethritis and 4/5 cases of gonococcal urethritis. Two PWU with undetectable BVL just prior to the first study visit had low to moderate SVL, which became undetectable by visit 2 following treatment. Of nine subjects with detectable SVL, eight had detectable BVL (3/3 controls and 5/6 PWU). Of these, 1/3 controls and 4/5 PWU (all with gonococcal urethritis) had poorly controlled BVL just prior to the first study visit. These four PWU had high SVL and one had higher levels in semen than in blood. This patient's SVL was reduced more than 20-fold following treatment for gonococcal urethritis.

CONCLUSIONS

Effective antiretroviral therapy appeared to limit the effect of urethritis on SVL. When BVL was poorly controlled by antiretroviral therapy, high SVL occurred during gonococcal urethritis, increasing the potential risk of transmitting both wild type and drug resistant strains of HIV-1.

Use of the sensitive/less-sensitive (detuned) EIA strategy for targeting genetic analysis of HIV-1 to recently infected blood donors

OBJECTIVE

To corroborate the validity of the recently developed sensitive/less sensitive (S/LS) dual enzyme immunoassay (EIA) strategy for the detection of recently infected individuals and to genetically analyze recently transmitted strains of HIV-1 in a US blood donor population.

DESIGN

The S/LS EIA strategy was used to identify 33 recently infected subjects among 281 enrolled HIV-1 seropositive blood donors (from a total of 410 HIV-1 infected subjects identified from 5 230 463 blood donations screened by participating US blood centers in 1995-1996).

METHODS

We analysed three host response and viral characteristics were associated with recent HIV-1 infection: rapidly increasing EIA optical density (OD) values, genetically homogeneous env gene quasispecies, and putative non-syncytium inducing env V3 loop sequences. The drug resistance genotypes of the recently transmitted strains were determined by DNA sequencing.

RESULTS

Increasing EIA OD values, clonal HIV-1 quasispecies and V3 loop sequences with inferred NSI phenotypes were generally detected in LS EIA non-reactive samples. Thirty-two subtype B and one CRF02_AG recombinant HIV-1 were detected. Genetic evidence for drug resistance to zidovudine (K70R) and non-nucleoside analog reverse transcriptase inhibitors (V108I) was detected in one strain each, and three other strains showed the presence of accessory protease inhibitor resistance mutations.

CONCLUSIONS

Immunologic and virologic results further substantiate the validity of the S/LS EIA strategy for the detection of recent infections and illustrate its use for targeting molecular and epidemiological investigations to incident cases identified from large cross-sectional screening programs, rather than the more costly and logistically difficult longitudinal studies.

Increased ability for selection of zidovudine resistance in a distinct class of wild-type HIV-1 from drug-naive persons

Transmission of HIV-1 with reduced susceptibility to antiretroviral drugs raises public health concerns. Through surveillance of drug-resistant HIV-1 in 603 treatment-naive, recently diagnosed HIV-1-infected persons, we identified a distinct group of viruses that have mutations at codon 215 of the reverse transcriptase (RT) gene that are different from either the wild-type (WT) T or the zidovudine (AZT)-selected T215Y/F. These mutations included 215D/C/S and were found in 20 patients (3.3%). The 215D, 215C, and 215S mutations differ from 215Y by a 1-nt change compared with 2 nt for the WT T215 and likely represent revertants of 215Y. These viruses all were found to have WT susceptibility to AZT, and all replicated efficiently as WT HIV-1(T215). However, differences in fitness among HIV-1(215D), HIV-1(215C), and HIV-1(215S) were seen when RT backgrounds were changed, demonstrating a role of the RT background in the selection of these revertants. In vitro selection with AZT showed that HIV-1(215D) and HIV-1(215C) acquired 215Y more rapidly than did WT HIV-1(T215), likely reflecting the need for only 1-nt change to evolve to 215Y. Our study demonstrates that HIV-1 with unusual mutations at codon 215 replicate efficiently, have WT susceptibility, and are commonly found in treatment-naive persons. The increased ability for selecting resistance mutations defines this class of WT HIV-1 and highlights the higher potential of these viruses to compromise the efficacy of antiretroviral therapy.

The Biology and Evolution of HIV

▪ Abstract  This review examines the current state of knowledge about HIV/AIDS in terms of its origins, pathogenesis, genetic variation, and evolutionary biology. The HIV virus damages the host's immune system, resulting in AIDS, which is characterized by immunodeficiency, opportunistic infections, neoplasms, and neurological problems. HIV is a complex retrovirus with a high mutation rate. This mutation rate allows the virus to evade host immune responses, and evidence indicates that selection favors more virulent strains with rapid replication. While a number of controversial theories attempt to explain the origin of HIV/AIDS, phylogenetic evidence suggests a zoonotic transmission of HIV to humans and implicates the chimpanzee (Pan troglodytes troglodytes) as the source of HIV-1 infection and the sooty mangabey as the source of HIV-2 infection in human populations. New therapies provide hope for increased longevity among people living with AIDS, but the biology of HIV presents significant obstacles to finding a cure and/or vaccine. HIV continues to be a threat to the global population because of its fast mutation rate, recombinogenic effect, and its use of human defenses to replicate itself.

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.

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.

HIV protease and reverse transcriptase variation and therapy outcome in antiretroviral-naive individuals from a large North American cohort

OBJECTIVE

To assess the effect of baseline HIV reverse transcriptase (RT) and protease sequence variation on virologic outcomes in a large cohort of antiretroviral-naive patients in British Columbia, Canada.

METHODS

Population sequencing of RT and protease was performed on baseline viral RNA of all antiretroviral-naive patients first seeking treatment in British Columbia between June 1997 and August 1998 (n = 479). Relative risks of virological failure associated with genotypic differences from a 'standard' HIV strain (HXB2) were assessed for up to 18 months.

RESULTS

The prevalence of key baseline mutations known to confer resistance to RT and protease inhibitors (PI) was 3.4 and 3.8%, respectively. No statistically significant impact on virologic outcomes could be established for these patients. However, the data suggest that some individuals (harboring a M184V mutation in RT or a V82I in protease) may have benefited from pre-therapy resistance tests. 'Secondary' mutations in the protease associated with resistance (e.g. codons 10, 36 or 63) were common, but the presence of these secondary mutations, either alone or in combination, did not appear to result in early loss of therapeutic virological suppression. Preliminary analyses suggest that an amino acid change at codon 35 in the protease may be associated with early treatment failure.

CONCLUSIONS

The results suggest that routine genotyping of naive patients about to start antiretroviral therapy would be of benefit to a relatively small proportion of the population. Secondary mutations associated with resistance to PI alone were not found to affect virologic outcomes significantly.

Anti-HIV type 1 activity of 3'-fluoro-3'-deoxythymidine for several different multidrug-resistant mutants

The objective of this work was to test the antiviral activity of a potent nucleoside reverse transcriptase inhibitor, 3'-fluoro-3'-deoxythymidine (FLT), on both a wild-type human immunodeficiency virus (HIV-1) isolate and multidrug-resistant HIV-1 patient isolates. Drug-resistant viral isolates were selected on the basis of four different categories of well-characterized and representative multidrug-resistant mutants. The isolates included three variants containing 151M alone or in combination; three variants containing 215Y and 41L, 67N, 184V, 210W, and 219N in combination; two insertion mutant viruses (69 + EA and 69 + SA); and two deletion mutant viruses (del67NG and del67GS), the latter two groups both also containing other significant mutations. The activity of FLT and AZT against these isolates was determined by drug susceptibility assays and by measuring viral antigen p24 by ELISA. The cytotoxicity of FLT and AZT was assessed in PHA-stimulated PBMCs. Development of resistant mutants under FLT pressure was attempted by passaging HIV-1 isolates in SupT1 cells and stepwise increasing the concentration of FLT. The multidrug-resistant mutant HIV-1 isolates exhibited 7-fold to >100-fold increased resistance to AZT, but showed IC(50) values for FLT of 0.0014-0.0168 microM, which were lower than or similar to that of wild type (0.0075 microM). The cellular cytotoxicities of FLT and AZT fell into a similar range in PBMCs. The development of HIV mutants resistant to FLT appeared to be slower than for other RT inhibitors. HIV isolates with mutations resulting in multidrug resistance had no evidence of resistance to FLT. FLT may be useful in salvage therapies for patients harboring resistant strains and a reassessment of its therapeutic potential seems required.

International perspectives on antiretroviral resistance. Nonnucleoside reverse transcriptase inhibitor resistance

Although understanding of nonnucleoside reverse transcriptase inhibitor (NNRTI) resistance is less clearly established than that of other classes of antiretroviral drugs, certain facts have been established. The treatment-associated genetic mutation profiles of the available NNRTIs have been mapped, and resistance has been found to develop rapidly after initiation of NNRTI therapy. Despite the chemical diversity of the NNRTIs, cross-resistance among agents of this class is nearly universal. Although the viral replicative capacity ("fitness") of NNRTI-induced viral variants has not been extensively studied, available data suggest that NNRTI-selected mutations confer little damage to viral fitness, and thus a single point mutation produces a strain that is both resistant and fit. Furthermore, with continued therapy, viral evolution persists, creating species with greater numbers of mutations and higher level phenotypic resistance. Taken together, these facts suggest that continued use of NNRTIs after emergence of resistance will produce variants of complex mutational patterns that limit future treatment options, and, therefore, strong consideration should be given to discontinuing NNRTIs after virologic failure is confirmed. This article describes the scientific literature establishing the efficacy and limitations of NNRTI therapy and attempts to define a role for this class of drug in the long-term treatment of HIV-1 disease.

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.

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.

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.

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.

Reduced susceptibility of human immunodeficiency virus type 1 (HIV-1) from patients with primary HIV infection to nonnucleoside reverse transcriptase inhibitors is associated with variation at novel amino acid sites

Recently, significant numbers of individuals with primary human immunodeficiency virus (HIV) infection have been found to harbor viral strains with reduced susceptibility to antiretroviral drugs. In one study, HIV from 16% of such antiretroviral-naive individuals was shown to have a susceptibility to nonnucleoside reverse transcriptase (RT) inhibitors (NNRTIs) between 2.5- and 10-fold lower than that of a wild-type control. Mutations in the RT domain that had previously been associated with antiretroviral resistance were not shared by these strains. We have analyzed by logistic regression 46 variable amino acid sites in RT for their effect on susceptibility and have identified two novel sites influencing susceptibility to NNRTIs: amino acids 135 and 283 in RT. Eight different combinations of amino acids at these sites were observed among these patients. These combinations showed a 14-fold range in mean susceptibility to both nevirapine and delavirdine. In vitro mutagenesis of the control strain combined with a phenotypic assay confirmed the significance of amino acid variation at these sites for susceptibility to NNRTIs.

Shift in HIV resistance genotype after treatment interruption and short-term antiviral effect following a new salvage regimen

OBJECTIVE

To investigate the changes in genotypic drug-resistance pattern, plasma HIV RNA and CD4 cell count after treatment interruption and assess the short-term antiviral effect of a new salvage regimen.

DESIGN

Prospective study of 38 patients with multiple failing regimens who had completely stopped all medication for 3 months before a three to five-drug regimen was reintroduced according to clinical guidelines.

METHODS

Patients were tested for HIV resistance before and after treatment interruption by population-based sequencing and clonal analysis of selected patients.

RESULTS

Discontinuation of therapy for 3 months was associated with a median increase in HIV RNA of 0.4 log10 and a median decrease in CD4 cell count of 43 x 10(6)/l. Sixty-one per cent of patients had a shift from the drug-resistant genotype to a predominantly wild-type genotype. The patients significantly likely to show genotype reversion were those in Centers for Disease Control groups A or B, who had been exposed to few drugs, had a low plasma HIV RNA, or a high CD4 cell count. The only independent factor predicting genotype reversion was the clinical stage. The median change in plasma HIV RNA at month 3 after treatment reintroduction was -2.3 log10 copies/ml in patients who had genotype reversion compared with -0.6 log10 copies/ml in patients without genotype reversion (P = 0.004).

CONCLUSION

Suspending treatment for 3 months after multiple failures could be a suitable strategy for optimizing salvage therapy provided it is instituted early, before the HIV disease becomes too advanced.

Risk and management of blood-borne infections in health care workers

Exposure to blood-borne pathogens poses a serious risk to health care workers (HCWs). We review the risk and management of human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV) infections in HCWs and also discuss current methods for preventing exposures and recommendations for postexposure prophylaxis. In the health care setting, blood-borne pathogen transmission occurs predominantly by percutaneous or mucosal exposure of workers to the blood or body fluids of infected patients. Prospective studies of HCWs have estimated that the average risk for HIV transmission after a percutaneous exposure is approximately 0.3%, the risk of HBV transmission is 6 to 30%, and the risk of HCV transmission is approximately 1.8%. To minimize the risk of blood-borne pathogen transmission from HCWs to patients, all HCWs should adhere to standard precautions, including the appropriate use of hand washing, protective barriers, and care in the use and disposal of needles and other sharp instruments. Employers should have in place a system that includes written protocols for prompt reporting, evaluation, counseling, treatment, and follow-up of occupational exposures that may place a worker at risk of blood-borne pathogen infection. A sustained commitment to the occupational health of all HCWs will ensure maximum protection for HCWs and patients and the availability of optimal medical care for all who need it.

Semen and serum pharmacokinetics of zidovudine and zidovudine-glucuronide in men with HIV-1 infection

STUDY OBJECTIVE

To characterize the concentration-time profiles of zidovudine and zidovudine-glucuronide in semen and serum of men infected with the human immunodeficiency-1 virus (HIV-1).

DESIGN

Open-label observational study.

SETTING

University-affiliated teaching hospital and research center.

PATIENTS

Four asymptomatic HIV-1-infected men.

INTERVENTIONS

Zidovudine administration was followed by an 8-hour intensive pharmacokinetic study on day 1. Over the next 8 days, a dose administration and timed single-sample strategy was employed to determine serum and semen concentration time profiles simultaneously.

MEASUREMENTS AND MAIN RESULTS

Zidovudine and zidovudine-glucuronide concentrations were uniformly higher in semen than in serum except at 1 hour after the dose. The median area under the curve ratio (semen AUC0-48:serum AUC0-infinity) was 3.31 for zidovudine and 15.04 for zidovudine-glucuronide.

CONCLUSION

Zidovudine and zidovudine-glucuronide reach high levels in seminal plasma relative to serum. The virologic, pharmacodynamic, and public health implications of distribution to this compartment require further study.

Incidence and impact of resistance against approved antiretroviral drugs

More than 15 antiretroviral drugs are now available for clinical use, and have led to significant reductions in morbidity and mortality for HIV infected individuals. Nevertheless, antiviral drug resistance emerges to all these drugs, which limits their benefit. This review addresses the biological basis of antiretroviral drug resistance, and the prevalence of specific drug resistance associated mutations in patients treated with the three currently available classes of agents, namely nucleoside analogue reverse transcriptase inhibitors, non nucleoside reverse transcriptase inhibitors and protease inhibitors. In addition, data on prevalence of HIV drug resistance in untreated individuals published to date are summarised, and the implications of potential transmission of drug resistant HIV is discussed.

Risk and management of blood-borne infections in health care workers

Exposure to blood-borne pathogens poses a serious risk to health care workers (HCWs). We review the risk and management of human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV) infections in HCWs and also discuss current methods for preventing exposures and recommendations for postexposure prophylaxis. In the health care setting, blood-borne pathogen transmission occurs predominantly by percutaneous or mucosal exposure of workers to the blood or body fluids of infected patients. Prospective studies of HCWs have estimated that the average risk for HIV transmission after a percutaneous exposure is approximately 0.3%, the risk of HBV transmission is 6 to 30%, and the risk of HCV transmission is approximately 1.8%. To minimize the risk of blood-borne pathogen transmission from HCWs to patients, all HCWs should adhere to standard precautions, including the appropriate use of hand washing, protective barriers, and care in the use and disposal of needles and other sharp instruments. Employers should have in place a system that includes written protocols for prompt reporting, evaluation, counseling, treatment, and follow-up of occupational exposures that may place a worker at risk of blood-borne pathogen infection. A sustained commitment to the occupational health of all HCWs will ensure maximum protection for HCWs and patients and the availability of optimal medical care for all who need it.

A randomized study of antiretroviral management based on plasma genotypic antiretroviral resistance testing in patients failing therapy. CPCRA 046 Study Team for the Terry Beirn Community Programs for Clinical Research on AIDS

OBJECTIVE

To determine the short-term effects of using genotypic antiretroviral resistance testing (GART) with expert advice in the management of patients failing on a protease inhibitor and two nucleoside reverse transcriptase inhibitors.

DESIGN

Prospective randomized controlled trial.

SETTING

Multicenter community-based clinical trials network.

PATIENTS

One-hundred and fifty-three HIV-infected adults with a threefold or greater rise in plasma HIV-1 RNA on at least 16 weeks of combination antiretroviral therapy.

INTERVENTIONS

Randomization was either to a GART group, where genotype interpretation and suggested regimens were provided to clinicians, or to a no-GART group, where treatment choices were made without such input.

MAIN OUTCOMES MEASURES

Plasma HIV-1 RNA levels and CD4 cell counts were measured at 4, 8, and 12 weeks following randomization. The primary endpoint was change in HIV-1 RNA levels from baseline to the average of the 4 and 8 week levels.

RESULTS

The average baseline CD4 cell count was 230 x 10(6) cells/l and the median HIV-1 RNA was 28,085 copies/ml. At entry, 82 patients were failing on regimens containing indinavir, 51 on nelfinavir, 11 on ritonavir, and nine on saquinavir. HIV-1 RNA, averaged at 4 and 8 weeks, decreased by 1.19 log10 for the 78 GART patients and -0.61 log10 for the 75 no-GART patients (treatment difference: -0.53 log, 95% confidence interval, -0.77 to -0.29; P = 0.00001). Overall, the best virologic responses occurred in patients who received three or more drugs to which their HIV-1 appeared to be susceptible.

CONCLUSION

In patients failing triple drug therapy, GART with expert advice was superior to no-GART as measured by short-term viral load responses.

Prevalence of drug resistant mutants and virological response to combination therapy in patients with primary HIV-1 infection

Baseline genotype resistance analysis was carried out in 48 adults with primary HIV-1 infection between 1995 and 1998 before starting early combination therapy. Seventeen percent (8/48) of the isolates displayed key mutations conferring resistance to reverse transcriptase (RT) inhibitors such as amino acid substitutions 215Y/F (5/48,10%), 70R (3/48, 6%), 184V (2%). Two percent (1/48) had a major mutation associated with resistance to protease inhibitors (D30N). Other mutations at positions 10, 15, 20, 33, 36, 46, 63, 71, 77, 82, 93 of the protease gene were frequent (73%). Among the 46 patients who were given antiretroviral combination therapy and who responded durably to treatment after 6 and 12 months, there was no significant difference between those harboring RT mutant strains (Group I) and those with wild-type isolates (Group II). No significant difference was found at months 6 and 12 between the two groups in terms of CD4+ cell counts. These findings suggest that the presence of drug-resistant strains at the time of primary HIV-1 infection does not necessarily predict drug failure. Other factors, such as adherence to treatment, tolerance and pharmacokinetics parameters are probably major determinants of virological response in patients with early therapeutic intervention.

Clinical utility of testing human immunodeficiency virus for drug resistance

Human immunodeficiency virus (HIV) type 1 drug-resistance testing is quickly moving from the research laboratory to the clinic as data defining its utility as a prognostic indicator of response to therapy become available. In July 1998, a panel of the International AIDS Society-USA did not recommend the widespread application of resistance testing, but by May 2000 this panel endorsed and recommended the incorporation of resistance testing in patient-care management. Considerable data supporting the use of drug-resistance testing have now been published or presented at international conferences. These data strongly suggest that drug-resistance testing is of considerable value in many clinical settings. Prospective trials of resistance testing as a clinical management tool are still ongoing, and the long-term benefits still need to be evaluated. Nevertheless, early results from several studies showed a significantly better virological response when treatment regimens were based on resistance-testing data, rather than on the standard of care. HIV drug-resistance testing is also useful as a tool for new antiretroviral drug design and development, as well as for monitoring the spread of primary HIV drug resistance.

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

OBJECTIVE

While transmission of drug-resistant HIV-1 has been reported, estimates of prevalence of resistance in drug-naïve populations are incomplete. We investigated the prevalence of genotypic mutations and phenotypic antiretroviral resistance in a cohort of HIV-1 infected U.S. military personnel prior to the institution of antiretroviral therapy.

DESIGN

Cross-sectional cohort study.

METHODS

Plasma was obtained from 114 recently HIV-1 infected subjects enrolled in an epidemiological study. Genotypic resistance was determined by consensus sequencing of a PCR product from the HIV-1 pol gene. Sequences were interpreted by a phenotypic-genotypic correlative database. Resistance phenotypes were determined by a recombinant virus cell culture assay.

RESULTS

Genotypic mutations and phenotypic resistance were found at a higher than expected frequency. Resistance to non-nucleoside reverse transcriptase inhibitors was most common, with a prevalence of 15% of 95 subjects by genotype and 26% of 91 subjects by phenotype. Genotypic and phenotypic resistance respectively were found in 4% and 8% of subjects for nucleoside reverse transcriptase inhibitors and in 10% and 1% for protease inhibitors. One subject harbored virus with resistance to all three drug classes.

CONCLUSIONS

A substantial frequency of resistance to antiretroviral drugs was identified in a therapy-naïve U.S. cohort. In most cases, the genotypic and phenotypic assays yielded similar results, although the genotypic assay could detect some protease inhibitor resistance-associated mutations in the absence of phenotypic resistance. These data suggest the need for optimization of treatment guidelines based on current estimates of the prevalence of drug resistance in HIV-1 seroconverters.

The case for more cautious, patient-focused antiretroviral therapy

Many clinicians who care for patients with HIV infection are dissatisfied with the existing recommendations on antiretroviral therapy. Current practice focuses on the early suppression of viremia, yet the outcome of that approach may not be in the best interest of individual patients or populations. The major goal of HIV therapy is to maintain the long-term health of the patient while avoiding drug-related toxicity and preserving viable future treatment options. Recent studies have challenged the principles on which recommendations for early, aggressive treatment were based. Key studies that lead to licensure of antiretroviral medications usually involve short-term results in treatment-naive patients; it is difficult to apply these results to long-term management of therapy-experienced patients. Early, aggressive therapy often prematurely exposes patients to risks for medication-related side effects and resistance. A more cautious, patient-focused, long-term approach to therapy would help foster studies of alternate strategies, such as delayed initiation of therapy, protease-sparing therapy, class-sparing therapy, planned drug interruptions, switches in therapy, and immune-based therapy. It is time for clinicians to rethink their approach to the treatment of HIV infection.

Prophylactic and therapeutic benefits of short-term 9-[2-(R)-(phosphonomethoxy)propyl]adenine (PMPA) administration to newborn macaques following oral inoculation with simian immunodeficiency virus with reduced susceptibility to PMPA

Simian immunodeficiency virus (SIV) infection of newborn macaques is a useful animal model of human pediatric AIDS to study pathogenesis and to develop intervention strategies aimed at preventing infection or delaying disease progression. In previous studies, we demonstrated that 9-¿2-(R)-(phosphonomethoxy)propylădenine (PMPA; tenofovir) was highly effective in protecting newborn macaques against infection with virulent wild-type (i.e., drug-susceptible) SIVmac251. In the present study, we determined how reduced drug susceptibility of the virus inoculum affects the chemoprophylactic success. SIVmac055 is a virulent isolate that has a fivefold-reduced in vitro susceptibility to PMPA, associated with a K65R mutation and additional amino acid changes (N69T, R82K, A158S, S211N) in reverse transcriptase (RT). Eight newborn macaques were inoculated orally with SIVmac055. The three untreated control animals became SIVmac055 infected; these animals had persistently high viremia and developed fatal immunodeficiency within 3 months. Five animals were treated once daily with PMPA (at 30 mg/kg of body weight) for 4 weeks, starting 24 h prior to oral SIVmac055 inoculation. Two of the five PMPA-treated animals had no evidence of infection. The other three PMPA-treated infant macaques became infected but had a delayed viremia, enhanced antiviral antibody responses, and a slower disease course (AIDS in 5 to 15 months). No reversion to wild-type susceptibility or loss of the K65R mutation was detected in virus isolates from any of the PMPA-treated or untreated SIVmac055-infected animals. Several additional amino acid changes developed in RT, but they were not exclusively associated with PMPA therapy. The results of this study suggest that prophylactic administration of PMPA to human newborns and to adults following exposure to human immunodeficiency virus will still be beneficial even in the presence of viral variants with reduced susceptibility to PMPA.

Prevalence of HIV-1 resistant to antiretroviral drugs in 81 individuals newly infected by sexual contact or injecting drug use. Investigators of the Quebec Primary Infection Study

OBJECTIVE

Prolonged treatment with antiretroviral drugs results in the selection of HIV-1 variants with mutations conferring resistance to nucleoside and non-nucleoside reverse transcriptase inhibitors (NRTI and NNRTI) or to protease inhibitors (PI). There is serious concern about transmission of resistant viruses to newly infected persons. This study monitored the prevalence of resistant viruses in individuals undergoing primary HIV infection.

DESIGN

Resistance testing was performed on 81 individuals infected between 1997 and 1999 by injecting drug use (n =21), sexual (n = 56), or unknown (n = 4) transmission.

METHODS

Automated sequencing was used to genotype the reverse transcriptase (RT) and protease regions of virus isolated from patients' plasma. The phenotypic susceptibility of stimulated peripheral blood mononuclear cells to antiretroviral drugs was assayed. Line probe assays detected quasispecies variations in wild-type and mutated RT codons.

RESULTS

A high prevalence of PI and RT genotypic variants, associated with high-level resistance to antiretroviral drugs, was observed in individuals newly infected by injecting drug use (PI = 24%, RT = 24%) or sexual transmission (PI = 12%, RT = 22%). The PI mutations, L101, V82A, and L90M, were found in 10.5, 3 and 4% of cases, respectively; whereas for RT, primary mutations at positions T215Y (zidovudine), M184V (lamivudine), T69D/A (zalcitabine), and K103N (multi-NNRTI) were present in 8, 5, 4, and 4% of subjects, respectively. Resistance to NRTI was demonstrated by phenotypic, genotypic, and line probe analyses. Transmission of multidrug (NRTI/NNRTI/PI) resistance in eight subjects (9.9%) was confirmed by showing that source partners possessed viruses of similar genotype.

CONCLUSIONS

The transmission of drug-resistant HIV is a serious problem that merits further attention by public health officials as well as virologists and clinicians.

Prevalence of Transmitted Nucleoside Analogue-Resistant HIV-1 Strains and Pre-Existing Mutations in Pol Reverse Transcriptase and Protease Region: Outcome after Treatment in Recently Infected Individuals

We retrospectively studied 38 Italian recently HIV-1-infected subjects who seroconverted from 1994 to 1997 to investigate: (i) the prevalence of nucleoside reverse transcriptase inhibitors (NRTI)-related mutations at primary infection; (ii) the proportion of naturally occurring mutations in reverse transcriptase (RT) and protease regions of patients naive for non-nucleoside RT inhibitors (NNRTIs) and protease inhibitors (PIs); (iii) the drug-susceptibility to NRTIs and PIs in subjects with NRTI-and/or PI-related mutations; and (iv) the outcome of seroconverters treated with various NRTIs or NRTI/PI regimens. Baseline HIV-1 plasma viraemia and absolute CD4 count at baseline could not be used to distinguish patients with NRTI- and/or PI-related pre-existing mutations from those with wild-type virus ( P=0.693 and P=0.542, respectively). The frequency of zidovudine-related mutations was 21% in the study period. The response to treatment was not significantly different in subjects with or without genotypic zidovudine-related mutations at primary infection ( P=0.744 for HIV-1 RNA and P=0.102 for CD4 cells). Some natural variation (2.6%) was present within regions 98–108 and 179–190 of RT involved in NNRTI resistance. The high natural polymorphism in the protease region present in our patients was similar to that reported by others. In our study some PI-associated substitutions, thought to be compensatory in protease enzymatic function, could confer intermediate to high PI-resistance. As discrepancies between genotypic and phenotypic results may exist in recent seroconverters, our data suggest that the role of transmitted NRTI- and PI-resistant variants remain to be fully elucidated in vivo.

Transmission and Prevalence of HIV Resistance among Treatment-Naive Subjects

Recent reports demonstrate the transmission of drug-resistant HIV-1 variants to newly infected individuals, although estimates of the prevalence of drug resistance among populations from different geographic regions are highly varied. The interpretation and comparison of available study results are confounded by the lack of consensus regarding the nomenclature and reporting of antiviral resistance. This report re-evaluates previously presented and published data using uniform criteria for genotypic and phenotypic drug resistance. Treatment-inexperienced and recently or chronically infected populations are reviewed. The prevalence of transmitted drug resistance ranges from 1% to 11% among recently infected persons using these criteria. Programmes to monitor and characterize drug resistance among newly infected persons and their source partners are essential to evaluate the selection processes that influence the transmission of certain genetic variants of HIV. Temporal trends in the prevalence of transmitted drug resistance among diverse populations are necessary to evaluate the potential need for selective and generalized drug resistance screening programmes among newly infected, treatment-naive patients.

Drug resistance mutations among HIV-1 strains from antiretroviral-naive patients in Martinique, French West Indies

We report on the frequency of genetic mutations associated with drug resistance in antiretroviral treatment-naive patients from Martinique (French West Indies), where zidovudine (ZDV) has been available since 1987 and where combination therapy developed simultaneously with its use in continental France. Genotypic resistance was studied in plasma HIV RNA from samples collected between 1988 and 1998 from 70 antiretroviral-naive study subjects, half presenting with either primary infection or documented seroconversion. A line probe assay (LIPA) was used to detect substitutions on the reverse transcriptase (RT) codons 41, 69, 70, 74, 184, and 215. Direct sequencing was used to complete the data for RT codons which were uninterpretable by LIPA. Of these patients, 17 harbored mutated viruses with one or more mutations in the RT gene codons analyzed. ZDV resistance mutations T215Y/F, M41L, and K70R were found in 2, 5, and 12 individuals, respectively. Mutant strains L74V (didanosine [ddI] and dideoxycytidine [ddC]) were detected in 3 patients and M184V (lamivudine/ddI/ddC) in 4 patients. However, pure mutant results at one or more codons of interest were observed in only 5 (7%; 95% confidence interval [CI], 1%-13%) patients, all involving ZDV resistance. One carried both mutations T215Y and M41L known to confer a high degree of phenotypic resistance to ZDV. Among a subgroup of 28 patients with a timepoint of infection after 1995, 24 [86%; approximately 95% CI, 73%-99%) presented with a wild-type pattern. The significance of the high prevalence of mixed patterns observed in drug-naive patients remains unclear. However, the frequency of primary mutant genotypes associated with high levels of drug resistance is low in Martinique and in this study we did not observe any currently increased tendency in this frequency.

Strategies of antiretroviral therapy in adults

Recent progress in antiretroviral treatment has led to dramatic improvements in HIV-related morbidity and mortality. These improvements have been fostered by advances in our understanding of HIV-related pathogenesis, the use of plasma HIV RNA levels to monitor patients, and the availability of 13 licensed antiretroviral drugs. Numerous drug combinations, especially those containing three or more agents, can suppress plasma HIV RNA levels below the lower limit of detection in the majority of treated patients. Urologists should be familiar with the limitations of this therapeutic response: patient adherence, drug resistance, a residual burden of chronically infected cells which are refractory to treatment, an unknown impact on HIV in genital secretions, and potential transmissibility through sexual contact.

Viral dynamics of acute HIV-1 infection

Viral dynamics were intensively investigated in eight patients with acute HIV infection to define the earliest rates of change in plasma HIV RNA before and after the start of antiretroviral therapy. We report the first estimates of the basic reproductive number (R(0)), the number of cells infected by the progeny of an infected cell during its lifetime when target cells are not depleted. The mean initial viral doubling time was 10 h, and the peak of viremia occurred 21 d after reported HIV exposure. The spontaneous rate of decline (alpha) was highly variable among individuals. The phase 1 viral decay rate (delta(I) = 0.3/day) in subjects initiating potent antiretroviral therapy during acute HIV infection was similar to estimates from treated subjects with chronic HIV infection. The doubling time in two subjects who discontinued antiretroviral therapy was almost five times slower than during acute infection. The mean basic reproductive number (R(0)) of 19.3 during the logarithmic growth phase of primary HIV infection suggested that a vaccine or postexposure prophylaxis of at least 95% efficacy would be needed to extinguish productive viral infection in the absence of drug resistance or viral latency. These measurements provide a basis for comparison of vaccine and other strategies and support the validity of the simian immunodeficiency virus macaque model of acute HIV infection.