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

[HIV drug resistance: past and current trends]

HIV infection is incurable, but effective antiretroviral therapy (ART) makes it possible to achieve an undetectable viral load (VL), to preserve the function of the immune system and to prevent the patient's health. Due to the constant increase in the use of ART and the high variability of HIV, especially in patients receiving so-called suboptimal therapy for various reasons, the incidence of drug resistance (DR) is increasing. In turn, the presence of DR in an HIV-infected patient affects the effectiveness of therapy, which leads to a limited choice and an increase in the cost of treatment regimens, disease progression and, consequently, an increased risk of death, as well as transmission of infection to partners. The main problems of drug resistance, its types and causes, as well as factors associated with its development are considered. The main drug resistance mutations for each of the drug classes are described.

Trends in practice: attitudes and challenges in the diagnosis, treatment and management of HIV infection in Australia

As life expectancy for people living with human immunodeficiency virus (HIV) (PLWHIV) increases, management models for HIV infection are changing. To understand approaches to practice within this shifting climate and across different medical settings, in 2017 we conducted a baseline survey among the main medical practitioner groups responsible for HIV-infection care in Australia: hospital-based physicians (HBP), sexual health physicians (SHP) and 'accredited general practitioners' (referred to in 2017 study as 's100 GPs'), who are GPs authorised to prescribe HIV therapies after completing accredited national training. The follow-up survey presented here explores any changes in approaches, attitudes and challenges associated with HIV-infection management among the same practitioner groups: 17 HBP, 15 SHP and 69 accredited GP (referred to throughout as GP; includes those with sexual health diploma). Analysis of survey results showed practices remained largely similar between surveys, with a few notable exceptions. Greater consistency in attitudes, knowledge and approaches was observed between the practitioner specialty groups, with only small differences between modes of practice. A trend towards earlier initiation of HIV treatment was also identified, with a higher proportion of practitioners than baseline reporting they were comfortable beginning therapy on the day of HIV diagnosis. The impact of the introduction of two-drug therapy in Australia was also explored. Although the majority of survey respondents (and SHP in particular) expressed greater preference for three-drug compared with two-drug regimens, interest in two-drug regimens appears to be growing and may influence future prescribing practices. Addressing mental health issues for PLWHIV was again highlighted as a major priority, with practitioners overwhelmingly reporting mental health management as among their most difficult clinical challenges. Reduction in stigma/discrimination and better access to substance dependency programmes were also identified as unmet needs for this patient cohort. Consistent with our baseline survey, it appears targeted interventions and supports appropriate to this population are still required to improve overall wellbeing for PLWHIV.

Avoiding Drug Resistance in HIV Reverse Transcriptase

HIV reverse transcriptase (RT) is an enzyme that plays a major role in the replication cycle of HIV and has been a key target of anti-HIV drug development efforts. Because of the high genetic diversity of the virus, mutations in RT can impart resistance to various RT inhibitors. As the prevalence of drug resistance mutations is on the rise, it is necessary to design strategies that will lead to drugs less susceptible to resistance. Here we provide an in-depth review of HIV reverse transcriptase, current RT inhibitors, novel RT inhibitors, and mechanisms of drug resistance. We also present novel strategies that can be useful to overcome RT's ability to escape therapies through drug resistance. While resistance may not be completely avoidable, designing drugs based on the strategies and principles discussed in this review could decrease the prevalence of drug resistance.

HIV in practice: current approaches and challenges in the diagnosis, treatment and management of HIV infection in Australia

As treatment improves, people living with HIV (PLWHIV) can now expect to live longer, which means that the foci of HIV-related care for them and their medical practitioners continue to change. With an increasingly older cohort of patients with HIV infection, practitioners' key considerations are shifting from issues of acute treatment and patient survival to multiple comorbidities, toxicities associated with chronic therapy, and ongoing health maintenance. Within this context, this paper explores the current standard of practice for the management of HIV infection in Australia. We surveyed 56 Australian practitioners currently involved in managing HIV infection: 'HIV section 100' (HIV therapy-prescribing) general practitioners (s100 GPs; n = 26), sexual health physicians (SHPs; n = 24) and hospital-based physicians (HBPs; n = 6). Survey results for practice approaches and challenges were broadly consistent across the three practitioner specialties, apart from a few key areas. s100 GPs reported less prophylaxis use among patients whom they deemed at risk of HIV infection in comparison with SHPs, which may reflect differences in patient populations. Further, a higher proportion of s100 GPs nominated older HIV treatment regimens as their preferred therapy choices compared with the other specialties. In contrast with SHPs, s100 GPs were less likely to switch HIV therapies to simplify the treatment protocol, and to immediately initiate treatment upon patient request in those newly diagnosed with HIV infection. Considerably lower levels of satisfaction with current HIV practice guidelines were also reported by s100 GPs. It appears that greater support for s100 GPs may be needed to address these identified challenges and enhance approaches to HIV practice. Across all specialties, increasing access to mental health services for patients with HIV infection was reported as a key management issue. A renewed focus on providing improved mental health and wellbeing supports is recommended, particularly in the face of an ageing HIV-infected population.

HIV-1 subtype diversity, transmitted drug resistance and phylogenetics in Australia

Australia has maintained a low prevalence of HIV, with a mainly concentrated epidemic and successful public health response. With the widespread availability of HIV genotyping for resistance testing, and development of phylogenetic methodologies, the field of molecular epidemiology has evolved a deeper understanding of diversity and transmission dynamics of HIV. Studies combining HIV genotype with epidemiological data have allowed insights to be gained into the changing subtype diversity, rates of transmitted drug resistance and transmission networks of HIV in Australia. This review provides an overview of HIV molecular epidemiology studies in Australia.

[Comparative analysis of genetic variants of the HIV-1 circulating in the Irkutsk region in 1999 and 2012]

The pol and env genome regions of the HIV-1 genetic variants circulating in the irkutsk region of russia in 1999 and 2012 were compared. The results of this work showed the dominance of the HIV-1 subtype a IDU-A genetic variant (100%) in this region. No primary resistance mutations in the pol gene in the treatment-naive patients were found. The heterogeneity of the viral population was found to be significantly increased based on the pol and env analysis among HIV-variants isolated in 2012 (12.88% and 2.16%) from the intravenous drug users as compared to HIV-variants that caused the outbreak of the HIV infection in 1999 (1.64% and 0.47%). In addition, the comparison of genetic distances of the pol and env gene sequences in the viruses isolated in 2012 from the HIV-positive persons infected through heterosexual intercourse and intravenous drug use demonstrated that the transmission route influenced the variability of the virus population. Among the viruses of IDU-A variant circulating in the area in 2012 the prevalence of X4-tropic variants was 24.7%.

Comparisons of Primary HIV-1 Drug Resistance between Recent and Chronic HIV-1 Infection within a Sub-Regional Cohort of Asian Patients

Background

The emergence and transmission of HIV-1 drug resistance (HIVDR) has raised concerns after rapid global antiretroviral therapy (ART) scale-up. There are limited data on the epidemiology of primary HIVDR in resource-limited settings in Asia. We aimed to determine the prevalence and compare the distribution of HIVDR in a cohort of ART-naïve Asian patients with recent and chronic HIV-1 infection.

Methods

Multicenter prospective study was conducted in ART-naïve patients between 2007 and 2010. Resistance-associated mutations (RAMs) were assessed using the World Health Organization 2009 list for surveillance of primary HIVDR.

Results

A total of 458 patients with recent and 1,340 patients with chronic HIV-1 infection were included in the analysis. The overall prevalence of primary HIVDR was 4.6%. Recently infected patients had a higher prevalence of primary HIVDR (6.1% vs. 4.0%, p = 0.065) and frequencies of RAMs to protease inhibitors (PIs; 3.9% vs. 1.0%, p<0.001). Among those with recent infection, the most common RAMs to nucleoside reverse transcriptase inhibitors (NRTIs) were M184I/V and T215D/E/F/I/S/Y (1.1%), to non-NRTIs was Y181C (1.3%), and to PIs was M46I (1.5%). Of patients with chronic infection, T215D/E/F/I/S/Y (0.8%; NRTI), Y181C (0.5%; non-NRTI), and M46I (0.4%; PI) were the most common RAMs. K70R (p = 0.016) and M46I (p = 0.026) were found more frequently among recently infected patients. In multivariate logistic regression analysis in patients with chronic infection, heterosexual contact as a risk factor for HIV-1 infection was less likely to be associated with primary HIVDR compared to other risk categories (odds ratio 0.34, 95% confidence interval 0.20–0.59, p<0.001).

Conclusions

The prevalence of primary HIVDR was higher among patients with recent than chronic HIV-1 infection in our cohort, but of borderline statistical significance. Chronically infected patients with non-heterosexual risks for HIV were more likely to have primary HIVDR.

Mechanism of HIV antiretroviral drugs progress toward drug resistance

The rapid replication rate of HIV-1 RNA and its inherent genetic variation have led to the production of many HIV-1 variants with decreased drug susceptibility. The capacity of HIV to develop drug resistance mutations is a major obstacle to long-term effective anti-HIV therapy. Incomplete suppression of viral replication with an initial drug regimen diminishes the clinical benefit to the patient and may promote the development of broader drug resistance that may cause subsequent treatment regimens to be ineffective. The increased clinical use of combination antiretroviral treatment for HIV-1 infection has led to the selection of viral strains resistant to multiple drugs, including strains resistant to all licensed nucleoside analog RT inhibitors and protease inhibitors. Therefore, it is important to understand the influence of such mutations on viral properties such as replicative fitness, fidelity, and mutation rates. Although research continues to improve our understanding of resistance, leading to refined treatment strategies and, in some cases, improved outcome, resistance to antiretroviral therapy remains a major cause of treatment failure among patients living with HIV-1.

Characteristics of HIV epidemics driven by men who have sex with men and people who inject drugs

PURPOSE OF REVIEW

To highlight the latest developments in mathematical transmission modelling of HIV epidemics among men who have sex with men (MSM) and people who inject drugs (PWID).

RECENT FINDINGS

Mathematical approaches have been applied to a wide range of topics in recent HIV research. Epidemiological models have evaluated past and forecasted future trends in prevalence and incidence, evaluated innovative behaviour modification strategies and public health programmes aimed at minimizing risk, and explored the potential impact of various biomedical interventions. MSM have developed new risk reduction strategies which models have deemed to be effective at a population level only in certain settings, such as when there are high rates of HIV testing. Modelling has also indicated that persistent circulation of drug-resistant HIV strains is likely to become an inevitable public health issue in the near future in resource-rich settings among MSM. Models have also recently been used to demonstrate that needle and syringe programmes for harm reduction among PWID are effective and cost-effective.

SUMMARY

Mathematical modelling is particularly amenable to single population groups of concentrated HIV epidemics, such as among MSM and PWID. Models have been utilized to evaluate innovative areas in clinical, biomedical and public health research that cannot be conducted in other population groups. Future directions are likely to include evaluation of specific public health programmes and providing understanding of the importance of specific treatment regimens and incidence and interaction of comorbid conditions associated with HIV.

HIV-1 drug resistance mutations among antiretroviral-naive HIV-1-infected patients in Asia: results from the TREAT Asia Studies to Evaluate Resistance-Monitoring Study

Of 682 antiretroviral-naïve patients initiating antiretroviral therapy in a prospective, multicenter human immunodeficiency virus type 1 (HIV-1) drug resistance monitoring study involving 8 sites in Hong Kong, Malaysia, and Thailand, the prevalence of patients with ≥1 drug resistance mutation was 13.8%. Primary HIV drug resistance is emerging after rapid scaling-up of antiretroviral therapy use in Asia.

Co-lethality studied as an asset against viral drug escape: the HIV protease case

BACKGROUND

Co-lethality, or synthetic lethality is the documented genetic situation where two, separately non-lethal mutations, become lethal when combined in one genome. Each mutation is called a "synthetic lethal" (SL) or a co-lethal. Like invariant positions, SL sets (SL linked couples) are choice targets for drug design against fast-escaping RNA viruses: mutational viral escape by loss of affinity to the drug may induce (synthetic) lethality.

RESULTS

From an amino acid sequence alignment of the HIV protease, we detected the potential SL couples, potential SL sets, and invariant positions. From the 3D structure of the same protein we focused on the ones that were close to each other and accessible on the protein surface, to possibly bind putative drugs. We aligned 24,155 HIV protease amino acid sequences and identified 290 potential SL couples and 25 invariant positions. After applying the distance and accessibility filter, three candidate drug design targets of respectively 7 (under the flap), 4 (in the cantilever) and 5 (in the fulcrum) amino acid positions were found.

CONCLUSIONS

These three replication-critical targets, located outside of the active site, are key to our anti-escape strategy. Indeed, biological evidence shows that 2/3 of those target positions perform essential biological functions. Their mutational variations to escape antiviral medication could be lethal, thus limiting the apparition of drug-resistant strains.

REVIEWERS

This article was reviewed by Arcady Mushegian, Shamil Sunyaev and Claus Wilke.

Primary drug resistance in antiretroviral-naïve injection drug users

OBJECTIVES

We evaluated the prevalence of primary HIV drug resistance in a population of 128 injection drug users (48 female) prior to initiating antiretroviral therapy.

METHODS

Genotypic and phenotypic profiles were obtained retrospectively for the period June 1996 to February 2007. Genotypic drug resistance was defined as the presence of a major mutation (IAS-USA table, 2007 revision), adding revertants at reverse transcriptase (RT) codon 215. Phenotypic drug resistance was defined as the fold change associated with >or=80% loss of the wild type virologic response due to viral resistance based on virtual phenotype analysis.

RESULTS

Genotypic drug resistance was uncommon, and was only identified in six (4.7%) cases, all in the RT gene (L100I, K103N, Y181C, M184V, Y188L, and T215D). There were no cases of multi-class or protease inhibitor (PI) resistance. However, polymorphisms in the protease and RT genes were extremely common. Phenotypic drug resistance was also identified in six (4.7%) patients, four in the RT gene (in patients with mutations K103N, Y181C, M184V and Y188L) and two the protease gene (in two patients with minor PI mutations). In addition, 25 (19.5%) of the patients had reduced susceptibility to PIs, defined as resistance>20% but <80% of the wild type virologic response, with no primary PI mutations detected in all these patients.

CONCLUSION

The prevalence of primary HIV drug resistance was low in this population of injection drug users.

Darunavir: a nonpeptidic antiretroviral protease inhibitor

BACKGROUND

Protease inhibitors were a major therapeutic breakthrough in the mid-1990s for the treatment of HIV infection, which resulted in improved life expectancy for patients who had failed previous therapies. With time and evolution of the virus, however, there is a new population of patients with treatment-resistant disease and few treatment options. Darunavir is a synthetic nonpeptidic analogue of amprenavir with enhanced activity against resistant virus that became available in 2006.

OBJECTIVES

The purpose of this review was to describe the clinical pharmacology, pharmacokinetic and pharmacodynamic properties, and clinical efficacy of darunavir. Also discussed are the published clinical experience with darunavir, its adverse events, drug interactions, pharmacoeconomics, and dosing and administration.

METHODS

A MEDLINE and EMBASE search (English-language only) was performed from January 1996 through April 2007 using the key words darunavir and TMC114. Abstracts from relevant scientific meetings were searched for the years 2000 through 2007. Additionally, the US Food and Drug Administration Web site was accessed to review the new drug application summary and data presented therein.

RESULTS

Darunavir was found to maintain antiretroviral activity against HIV with protease inhibitor mutations in 6 studies. Clinical efficacy and safety data are limited to 4 controlled and 2 uncontrolled trials. In 2 large Phase IIb clinical studies, viral suppression at 48 weeks to undetectable levels in heavily pretreated patients was achieved in 45% of patients compared with 10% of patients in the control group (P < 0.001). The addition of enfuvirtide enhanced this response rate to 58% compared with 11% of the patients who did not receive enfuvirtide (P < 0.001). Gastrointestinal symptoms, nausea, and headache were the most commonly reported events.

CONCLUSIONS

Darunavir has improved activity against resistant HIV isolates in patients with few treatment choices, particularly when enfuvirtide is added. The safety profile of darunavir is comparable to other protease inhibitors based on early data.

In vitro antiviral activity of the novel, tyrosyl-based human immunodeficiency virus (HIV) type 1 protease inhibitor brecanavir (GW640385) in combination with other antiretrovirals and against a panel of protease inhibitor-resistant HIV

Brecanavir, a novel tyrosyl-based arylsulfonamide, high-affinity, human immunodeficiency virus type 1 (HIV-1) protease inhibitor (PI), has been evaluated for anti-HIV activity in several in vitro assays. Preclinical assessment of brecanavir indicated that this compound potently inhibited HIV-1 in cell culture assays with 50% effective concentrations (EC(50)s) of 0.2 to 0.53 nM and was equally active against HIV strains utilizing either the CXCR4 or CCR5 coreceptor, as was found with other PIs. The presence of up to 40% human serum decreased the anti-HIV-1 activity of brecanavir by 5.2-fold, but under these conditions the compound retained single-digit nanomolar EC(50)s. When brecanavir was tested in combination with nucleoside reverse transcriptase inhibitors, the antiviral activity of brecanavir was synergistic with the effects of stavudine and additive to the effects of zidovudine, tenofovir, dideoxycytidine, didanosine, adefovir, abacavir, lamivudine, and emtricitabine. Brecanavir was synergistic with the nonnucleoside reverse transcriptase inhibitor nevirapine or delavirdine and was additive to the effects of efavirenz. In combination with other PIs, brecanavir was additive to the activities of indinavir, lopinavir, nelfinavir, ritonavir, amprenavir, saquinavir, and atazanavir. Clinical HIV isolates from PI-experienced patients were evaluated for sensitivity to brecanavir and other PIs in a recombinant virus assay. Brecanavir had a <5-fold increase in EC(50)s against 80% of patient isolates tested and had a greater mean in vitro potency than amprenavir, indinavir, lopinavir, atazanavir, tipranavir, and darunavir. Brecanavir is by a substantial margin the most potent and broadly active antiviral agent among the PIs tested in vitro.

Transmitted drug-resistant HIV-1 in primary HIV-1 infection; incidence, evolution and impact on response to antiretroviral therapy

OBJECTIVES

The aim of the study was to determine the incidence and persistence of transmitted drug-resistant HIV-1 in an incident cohort between 2000 and 2004, and to investigate the impact of transmitted drug-resistant HIV-1 on the response to antiretroviral therapy (ART).

METHODS

A prospective, nonrandomized study was carried out on 140 individuals identified with primary HIV-1 infection (PHI). PHI was defined as an HIV-positive antibody test with an HIV antibody-negative result in the prior 6 months (n = 69); positive HIV DNA in the absence of antibody (n = 30); an evolving titre positive HIV antibody test (n = 23), or an incident 'detuned' assay (B clade viruses only) (n = 18). Genotypic resistance testing was performed at baseline, following ART and annually over a 4-year period.

RESULTS

The prevalence of transmitted drug-resistant HIV-1 infection between January 2000 and June 2004 was nine in 140 (6.0%) and the annual incidence was stable. Seven of these nine patients had a single point mutation conferring single-class drug resistance and the other two patients had multiple mutations conferring multiclass drug resistance (MDR). In eight of the nine cases, mutations conferring drug resistance persisted for more than 12 months off therapy. In contrast to transmitted MDR HIV-1, the virological response to initial ART and CD4 decline were comparable in those with wild-type virus, virus with 'polymorphisms' (secondary mutations) and virus with single drug-resistance mutations.

CONCLUSIONS

The incidence of transmitted drug-resistant HIV remained stable and low over a 4-year period. Although MDR remains rare, its presence significantly affects the response to first-line ART, predisposes towards the accumulation of new resistance mutations and is associated with a more rapid CD4 decline.

Prevalence of primary genotypic resistance in a UK centre: Comparison of primary HIV-1 and newly diagnosed treatment-naive individuals

The worrying finding that up to 19% of newly diagnosed HIV-1 cases in the UK have genotypic evidence of transmitted drug-resistant HIV-1 (TrDR-HIV-1) does not concur with levels observed in one London centre. A study of the prevalence of resistance in primary HIV infection and newly diagnosed antiretroviral-naive individuals demonstrated significantly lower levels of TrDR-HIV-1 than previously reported. Variations in the prevalence of TrDR-HIV-1 may reflect the heterogeneity of methodologies and definitions used for resistance.

Ring substituent effects on biological activity of vinyl sulfones as inhibitors of HIV-1

In a previous study, we prepared a small library of chicoric acid analogs that possessed both potent anti-integrase and antiviral activity. It was also shown that active compounds fell into one of two groups: those that inhibited an early stage in viral replication and those that inhibited at a later stage. In this study, a series of vinyl geminal disulfone-containing compounds possessing a range of ring substituents has been synthesized to probe the impact of structure on inhibitory mechanisms. Four active compounds were identified using HIV drug susceptibility assays. Three of the inhibitors possessing either no substituents or electron-withdrawing substituents on the aromatic rings led to high levels of cytotoxicity and antiviral activity. Intrigued by the potential implications of electronic effects on activity, we probed whether the active compounds could be nonspecifically reacting via 1,4-addition. To investigate this hypothesis, the compounds were incubated with glutathione and upon LC/MS analysis, molecular ion peaks corresponding to both mono and double addition adducts were identified. Second, we synthesized analogs lacking the ability to participate in 1,4-addition and tested them for antiviral activity and cytotoxicity, and found the compounds inactive for both activities. Taken together, the studies reported herein suggest that compounds lacking electron-donating substituents on the aromatic ring are promiscuous acceptors of biological nucleophiles, whereas compounds possessing electron-donating substituents seem to resist addition or at least be more selective and significantly less toxic.

Declining Prevalence of HIV-Infected Individuals at Risk of Transmitting Drug-Resistant HIV in Denmark during 1997–2004

Background

Transmission of drug-resistant HIV is a potential threat to the substantial clinical benefit of highly active antiretroviral therapy (HAART). To explore the background for the low rates of drug resistance transmission (2–5%) in our population, we estimated acquisition of HIV drug resistance and examined temporal trends in the prevalence of patients at risk of transmitting drug-resistant HIV.

Methods

The study population included all 4,025 patients from The Danish HIV Cohort Study seen during the period 1995–2004. Virological failure to a given drug class was defined as a viral load (VL) >1,000 copies/ml for 120 days while on a HAART regimen including that drug class. In addition, receiving nucleoside reverse transcriptase inhibitors (NRTIs) for 180 days before HAART counted as NRTI failure irrespective of VL. Having experienced failure was considered a proxy for harbouring drug-resistant virus in subsequent observation time. Patients with a current VL >1,000 copies/ml were considered at risk of transmitting HIV.

Results

We found a decrease from 1997 to 2004 in the prevalence of potential transmitters of drug-resistant HIV. The number of these patients with previous NRTI failure decreased from 429 (24% of all patients) in 1998 to 213 (8.0% of all patients) in 2004. Previous protease inhibitor (PI) failure peaked at 279 (14%) in 1999, declining to 142 (5.3%) in 2004. Previous NNRTI failure peaked at 121 patients (4.7%) in 2002, and occurred in 113 patients (4.2%) in 2004. Of all 686 potential transmitters in 2004, 31% had previously experienced NRTI failure, 21% PI failure, and 16% non-NRTI failure.

Conclusion

In the population of HIV-infected individuals in Denmark with complete follow-up, the number at risk of transmitting drug-resistant virus declined over time.

HIV-1 genetic diversity and genotypic drug susceptibility in the Republic of Georgia

The genetic diversity and genotypic drug susceptibility of HIV-1 strains circulating in the Republic of Georgia, formerly part of the Soviet Union, were investigated for first time. Forty-eight HIV-positive drug-naive Georgian individuals contributed PBMC DNA between 1998 and 2003. On the basis of phylogenetic analyses of partial pol sequences, the predominant HIV-1 genetic forms were subtype A (70%), followed by subtype B (26%); both genetic forms were carried by injecting drug users and heterosexuals. There was also one subtype C (2%) and one CRF18_cpx (2%). The Georgian subtype A strains clustered with subtype A from Russia, designated A(FSU). Twelve of the subtype A strains (25%) contained the secondary protease inhibitor mutation V77I and 9 also had two other silent mutations. This "V77I haplotype" marks one particular genetic lineage of the epidemic in the former Soviet Union. Two strains (4%) carried antiretroviral (ARV) drug resistance mutations. Nearly full-length genome sequences of five Georgian strains were also completed. Two, 98GEMZ011 (subtype A) and 98GEMZ003 (subtype B), closely resembled the parental strains that recombined to create CRF03_AB. The use of these parental strains in the analysis revealed an additional segment of subtype A in CRF03_AB. Thus, the HIV-1 epidemic in Georgia was composed of a mixture of subtype A(FSU) and subtype B.

Immunological cross-reactivity against a drug mutated HIV-1 protease epitope after DNA multi-CTL epitope construct immunization

Epitopes in HIV polymerase were analyzed by peptide binding to human leukocyte antigen (HLA) A0201 molecules, the most frequent HLA class in the Caucasian population. We found that HIV-1 protease peptides representing both the wild type and anticipated drug resistance variants of the sequence bound well to HLA-A0201. We also found that wild type as well as a double mutated variant of the epitope was strongly immunogenic in HLA-A0201 transgenic mice, either as individual peptides or encoded in DNA multi-CTL epitope constructs. Immunological cross-reactivity between different variants of the peptide could be seen, suggesting that it may be possible to induce a broad immune response by immunizing with drug resistance-mutated epitopes. This may be of advantage for HIV-1 infected patients since such a response may cause a better outcome of an anti-retroviral drug therapy.

Current trends of HIV disease of the mouth

HIV infection affects residents of all countries of the world, but the greater majority of affected individuals reside in the developing world. In the past decade there have been substantial changes in the management of HIV disease, particularly the introduction of highly active antiretroviral therapy (HAART). Such agents have reduced significantly the morbidity and mortality associated with HIV disease, however, they are not available for most HIV-infected individuals in the developing world. There is now considerable understanding of the molecular epidemiology, transmission and therapy of the common opportunistic oral infections of HIV disease, and as a consequence of improved anti-HIV strategies, the frequency and severity of oral disease associated with HIV infection have reduced considerably, although HAART may predispose to human papilloma virus infection of the mouth and potentially increase the risk of later oral squamous cell carcinoma. Despite advances in clinical care the majority of individuals with HIV disease worldwide will continue to develop oral disease, as they are resident in the developing world and do not have ready access to even simple therapies.

The use of a triple nucleoside-nucleotide regimen for nonoccupational HIV post-exposure prophylaxis

OBJECTIVES

Nonoccupational post-exposure prophylaxis (NPEP) for HIV is recommended after high-risk sexual exposure. Because of the high incidence of intolerable side effects observed with protease inhibitor- and zidovudine-based NPEP regimens, our unit changed standard NPEP treatment to 28 days of tenofovir-lamivudine-stavudine (TDF-3TC-d4T). The aim of this study was to compare side effects and numbers of individuals completing NPEP before and after this change.

METHODS

Parameters were compared amongst individuals commencing the following NPEP regimens: zidovudine-lamivudine (ZDV-3TC), zidovudine-lamivudine-nelfinavir (ZDV-3TC-NFV) and TDF-3TC-d4T.

RESULTS

A total of 385 individuals received ZDV-3TC (n = 36), ZDV-3TC-NFV (n = 225) or TDF-3TC-d4T (n = 137) as NPEP for the first time between June 1999 and November 2003. Noncompletion rates were 25%, 32% and 15%, respectively (P = 0.001), with odds ratios for noncompletion being 2.0 [95% confidence interval (CI) 0.8-4.8] and 2.7 (95% CI 1.6-4.8) in the first two groups compared with the TDF-3TC-d4T group (P = 0.008). Adverse events were less common in the TDF-3TC-d4T group, with significantly lower rates of nausea and headache, but significantly higher rates of peripheral neuropathy and asymptomatic raised transaminases. There was no HIV seroconversion in any group.

CONCLUSIONS

TDF-3TC-d4T is significantly better tolerated than ZDV-3TC or ZDV-3TC-NFV as NPEP and results in greater numbers of individuals completing 28 days of treatment.

Frequency of Drug-Resistant Variants of HIV-1 Coexistent With Wild-Type in Treatment-Naive Patients of India

Context

Over the past few years, reports of emergence and transmission of drug-resistant strains of HIV have increased, especially in western countries. In the context of increased widespread use of zidovudine- and lamivudine-based combinations in India, coupled with the genetic diversity of HIV, it is essential to generate preliminary data on the frequency of zidovudine- and lamivudine-resistant variants of HIV-1 in North India.

Objectives

In the present study, the authors screened for mutations in the pol gene of HIV-1 associated with resistance to zidovudine and lamivudine in HIV-infected treatment-naive patients from North India.

Design and Patients

The mutations were screened at codons 70 and 215 (conferring resistance to zidovudine) and at codon 184 (conferring resistance to lamivudine) by using a nested amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) approach from the proviral DNA of 60 patients.

Results

Most of the patients showed a mixture of both wild-type and mutant virus. In all but 1 patient, wild-type virus was observed with respect to each codon. Mutant variants were also observed in many patients, especially at codon 70 (48 patients [80%]) and codon 184 (19 patients [31.67%]). In contrast, the frequency of mutation at codon 215 was found to be very low (1 patient [1.67%]).

Conclusion

In this sample of treatment-naive HIV-1-infected patients in North India, a high proportion of mutant variants harbored mutations in the pol gene at codons- 70 and 184 coexisting with wild-type HIV-1.

Molecular characteristics of HIV type 1 circulating in São Paulo, Brazil

Partial sequences of HIV-1 polymerase from 185 patients, 141 ARV experienced and 44 naive, of gag (p24) and env (C2V3) from a subset of naive cases were evaluated in São Paulo, Brazil. Antiretroviral resistance mutations were detected in 4% of 26 recently (<2 years) infected patients. Polymorphisms at the protease gene were common both in contemporary and pre-HAART era isolates, some significantly associated with the viral clade. HIV-1 clade B was preponderant, in 79%, with 11% clade F and one case of HIV-1 C. Recently infected women had a significantly higher proportion of non-B clade HIV-1. A mosaic pol was observed in 9%, all B/F except for one G mosaic. A CRF-12-BF structure, observed in 20% of B/F pol mosaics, provides evidence for an epidemic relationship in the major South American metropolitan areas.

Induction of T-cell immunity to antiretroviral drug-resistant human immunodeficiency virus type 1

Antiretroviral drug-resistant human immunodeficiency virus type 1 (HIV-1) is a major, growing, public health problem. Immune responses targeting epitopes spanning drug resistance sites could ameliorate development of drug resistance. We studied 25 individuals harboring multidrug-resistant HIV-1 for T-cell immunity to HIV-1 proteins and peptides spanning all common drug resistance mutations. CD8 T cells targeting epitopes spanning drug-induced mutations were detected but only in the 3 individuals with robust HIV-specific T-cell activity. Novel CD8 T-cell responses were detected against the common L63P and L10I protease inhibitor fitness mutations. Induction of T-cell immunity to drug-resistant variants was demonstrated in simian human immunodeficiency virus-infected macaques, where both CD8 and CD4 T-cell immune responses to reverse transcriptase and protease antiretroviral mutations were elicited using a novel peptide-based immunotherapy. T-cell responses to antiretroviral resistance mutations were strongest in the most immunocompetent animals. This study suggests feasible strategies to further evaluate the potential of limiting antiretroviral drug resistance through induction of T-cell immunity.

Prevalence of Antiretroviral Drug Resistance Mutations in Chronically HIV-Infected, Treatment-Naive Patients: Implications for Routine Resistance Screening before Initiation of Antiretroviral Therapy

BACKGROUND

The prevalence of drug resistance among persons with newly acquired human immunodeficiency virus (HIV) infection is well documented. However, it is unclear to what extent these mutations persist in chronically infected, treatment-naive patients.

METHODS

Prevalence of and factors associated with genotypic drug resistance were analyzed retrospectively in a subset of 491 chronically HIV-infected, antiretroviral-naive patients enrolled at 25 cities in the Terry Beirn Community Programs for Clinical Research on Acquired Immune Deficiency Syndrome (AIDS) Flexible Initial Retrovirus Suppressive Therapies trial during 1999-2001. Resistance was defined on the basis of the International AIDS Society 2003 definition, as well as the presence of additional mutations at codons 215 (C/D/E/S) and 69 (A/N/S) in the pol gene. Prevalence of mutations was estimated by use of techniques for stratified random samples. Logistic regression models were used to determine factors associated with resistance.

RESULTS

Among the 491 chronically HIV-infected patients (mean CD4 cell count, 269 cells/mm(3); 31% of patients had a prior AIDS diagnosis), 57 (11.6%) had >or=1 resistance mutation, resulting in an estimated prevalence for the cohort of 10.8% (95% confidence interval [CI], 9.5%-12.1%). The prevalence was 8.8% if the 118I mutation was excluded. By drug class, the estimated prevalence of mutations conferring resistance to nucleoside reverse-transcriptase inhibitors was 7.8%, and the prevalence was 3.0% for nonnucleoside reverse-transcriptase inhibitors and 0.7% for protease inhibitors. In a multiple logistic regression analysis, non-Hispanic white subjects were twice as likely than African American subjects to have resistance (odds ratio [OR], 2.1; 95% CI, 1.1-4.1; P=.03), and there was a 40% increase per year in prevalence of mutations by later year of enrollment (OR, 1.4; 95% CI, 1.0-2.1; P=.05).

CONCLUSIONS

These results demonstrate the persistence of drug resistance mutations in chronically HIV-infected patients and an increasing prevalence of resistance over time, and they support genotyping of virus at baseline for chronically HIV-infected patients.

Diversity of human immunodeficiency virus type 1 subtype A and CRF03_AB protease in Eastern Europe: selection of the V77I variant and its rapid spread in injecting drug user populations

To characterize polymorphisms of the subtype A protease in the former Soviet Union, proviral DNA samples were obtained, with informed consent, from 119 human immunodeficiency virus type 1 (HIV-1)-positive untreated injecting drug users (IDUs) from 16 regions. All individuals studied have never been treated with antiretroviral drugs. The isolates were defined as IDU-A (n = 115) and CRF03_AB (n = 4) by using gag/env HMA/sequencing. The pro region was analyzed by using sequencing and original HIV-ProteaseChip hybridization technology. The mean of pairwise nucleotide distance between 27 pro sequences (23 IDU-A and 4 CRF03_AB) was low (1.38 +/- 0.79; range, 0.00 to 3.23). All sequences contained no primary resistance mutations. However, 13 of 23 (56.5%) subtype A isolates bore the V77I substitution known as the secondary protease mutation. V77I was associated with two synonymous substitutions in triplets 31 and 78, suggesting that all V77I-bearing viruses evolved from a single source in 1997. Hybridization analysis showed that 55 of 115 (47.8%) HIV-1 isolates contained V77I, but this variant was not found in any of 31 DNA samples taken from regions, where the HIV-1 epidemic among IDUs started earlier 1997, as well as in any of four CRF03_AB isolates. The results of analysis of 12 additional samples derived from epidemiologically linked subjects showed that in all four epidemiological clusters the genotype of the donor and the recipients was the same irrespective of the route of transmission. This finding demonstrates the transmission of the V77I mutant variant, which is spreading rapidly within the circulating viral pool in Russia and Kazakhstan. The continued molecular epidemiological and virological monitoring of HIV-1 worldwide thus remains of great importance.

Emerging viral infections

"Emerging infections" have been defined as infections that have newly appeared, that have appeared previously but are expanding in incidence and geographic range, or that threaten to increase in the near future. This article focuses on nine emerging viral infectious agents. These viruses illustrate how such agents emerge: by encroaching on previously unvisited habitats (eg, hantaviruses), by air travel (eg, SARS), and by accidental importation (eg, monkeypox). Additionally, the example of SARS demonstrates not only how quickly emerging viral infections can spread but also how quickly they can be identified and contained with motivated cooperation.

Transmission of HIV-1 drug resistance

BACKGROUND

The use of highly-active anti-retroviral therapy (HAART) for treating HIV infections is increasing. Recent studies have demonstrated that HAART is improving both the length and quality of life in HIV-infected patients. Resistant strains of HIV arise when drug adherence is poor. This can lead to the transmission of drug-resistant strains of HIV to susceptible individuals. This can lead to suboptimal first-line therapy, if the resistance profile of the transmitted virus is unknown.

OBJECTIVES

To review the mechanisms of how drug resistance arises; the methods used to characterise drug resistance; the problems arising with compliance leading to the development of drug-resistant HIV strains; the evidence for the incidence, prevalence and trends in the transmission of resistant HIV strains in different risk groups; and the evidence of suboptimal response to first-line therapy where transmission of a resistant HIV strain has occurred. On the basis of this, a case is presented for the routine resistance testing of all newly diagnosed HIV-infected individuals.

STUDY DESIGN

Literature review.

RESULTS AND CONCLUSIONS

There is evidence, though limited at present, that transmission of drug-resistant HIV strains can lead to suboptimal response to first-line therapy in newly diagnosed HIV-infected individuals. As the use of HAART can only increase in the future, and compliance will always be a problem in such HAART-treated patients, baseline resistance testing should become a routine part of their management.

The Influence of Protease Inhibitor Resistance Profiles on Selection of HIV Therapy in Treatment-Naive Patients

Although protease inhibitors (PIs) have dramatically improved outcomes in HIV-infected patients, half still fail treatment with PI-based combination therapy. Genetic pressure from incomplete viral suppression rapidly selects for HIV variants with protease gene mutations that confer reduced susceptibility to PI drugs. A number of specific amino acid substitutions have been associated with PI resistance. However, high-level resistance to individual PIs requires the accumulation of several primary and secondary mutations, developing along drug-specific, step-wise pathways. HIV variants resistant to saquinavir and ritonavir usually contain L90M and V82A substitutions, respectively. Indinavir resistance may be linked to substitutions at positions 46 or 82. Resistance to nelfinavir is primarily associated with D30N but may alternatively be found with L90M. Resistance during exposure to amprenavir can follow development of I50V, which also may confer resistance to lopinavir. Failure during treatment with atazanavir is closely linked to I50L. The overlapping of these pathways can lead to multiple-PI resistance, limiting therapeutic options in antiretroviral-experienced patients. Reduced susceptibility to more than one PI is most likely to be associated with amino acid substitutions at six positions: 10, 46, 54, 82, 84 and 90. Other mutations (D30N, G48V, I50V or I50L) are relatively specific for particular PIs and are less likely to produce cross resistance. Certain resistance mutations selected by exposure to one PI may actually increase susceptibility to others. Patients newly diagnosed with HIV infection are increasingly found to harbour virus that is resistant to the more commonly used drugs. Newer PIs may select for mutations that result in less cross resistance with older agents.

HIV-1 pol gene variation is sufficient for reconstruction of transmissions in the era of antiretroviral therapy

OBJECTIVES

We wished to assess the potential of using HIV-1 pol gene for the identification of transmissions events by phylogenetic means in the era of antiretroviral drug selective pressure.

DESIGN

The relatedness of the viruses within a large database of pol sequences generated from HIV-1 infected individuals from the UK was reconstructed by phylogenetic analyses.

METHODS

A total of 140 pol sequences were selected out of the 2500 database entries, on the basis of a pairwise genetic distance higher than 95%. Neighbour Joining and Maximum Likelihood trees were implemented. Trees were reconstructed after exclusion of codon positions associated with drug resistance from the original pol alignment. Trees based on the corresponding env and gag genes were implemented to confirm the linkages.

RESULTS

Up to 23 transmission clusters were identified, supported by high bootstrap values (> 99), congruent epidemiological data and/or similar drug resistance motifs. The topology of the tree was consistent after exclusion of the drug resistance associated codons. Identical topologies were obtained in trees implemented from gag and env genes alignments.

CONCLUSIONS

Despite its genetic conservation, the HIV-1 pol gene holds sufficient variability to permit the phylogenetic reconstruction of transmissions. Identical clusters were obtained whichever of the three principal genes is considered and no bias was induced by the presence of drug resistance mutations. These findings demonstrate the important epidemiological information inherent within routinely collected laboratory data, which can assist in estimating rates of recent HIV-1 transmission within a population.