Multidrug-resistant Virus Research Articles

Design and expeditious synthesis of organosilanes as potent antivirals targeting multidrug-resistant influenza A viruses

The efficacy of current influenza vaccines and small molecule antiviral drugs is curtailed by the emerging of multidrug-resistant influenza viruses. As resistance to the only FDA-approved oral influenza antiviral, oseltamivir (Tamiflu), continues to rise, there is a clear need to develop the next-generation of antiviral drugs. Since more than 95% of current circulating influenza A viruses carry the S31N mutation in their M2 genes, the AM2-S31N mutant proton channel represents an attractive target for the development of broad-spectrum antivirals. In this study we report the design and synthesis of the first class of organosilanes that have potent antiviral activity against a panel of human clinical isolates of influenza A viruses, including viruses that are resistant to amantadine, oseltamivir, or both.

Expeditious Lead Optimization of Isoxazole-Containing Influenza A Virus M2-S31N Inhibitors Using the Suzuki-Miyaura Cross-Coupling Reaction.

The existence of multidrug-resistant influenza viruses, coupled with the continuously antigenic shift and antigenic drift of influenza viruses, necessitates the development of the next-generation of influenza antivirals. As the AM2-S31N mutant persists in more than 95% of current circulating influenza A viruses, targeting the AM2-S31N proton channel appears to be a logical and valid approach to combating drug resistance. Starting from compound 1, an isoxazole compound with potent AM2-S31N channel blockage and antiviral activity, in this study we report an expeditious synthetic strategy that allows us to promptly explore the structure-activity relationships of isoxazole-containing AM2-S31N inhibitors. Propelled by the convenient synthesis, the lead optimization effort yielded a number of potent antivirals with submicromolar efficacy against several human clinical isolates of influenza A viruses, including both oseltamivir-sensitive and -resistant strains.

A recombinant vesicular stomatitis virus encoding CCR5-tropic HIV-1 receptors targets HIV-1-infected cells and controls HIV-1 infection

Anti-retroviral therapy is useful to treat human immunodeficiency virus type 1 (HIV-1)-infected individuals, but has some major problems, such as the generation of multidrug-resistant viruses. To develop a novel supplemental or alternative therapeutic for CCR5-tropic (R5) HIV-1 infection, we generated a recombinant vesicular stomatitis virus (rVSV) in which the gene encoding its envelope glycoprotein (G) was replaced with the genes encoding R5 HIV-1 receptors (human CD4 and CCR5), designated VSVΔG-CC5. Our present data demonstrate that this rVSV specifically infects cells that are transiently expressing R5 HIV-1 envelope glycoproteins, but does not infect those expressing CXCR4-tropic HIV-1 envelope glycoproteins. Notably, after a CD4+CCR5+ T cell line or primary cells initially infected with R5 HIV-1 were inoculated with G-complemented VSVΔG-CC5, the rVSV significantly reduced the number of HIV-1-infected cells, probably through direct targeting of the rVSV and VSV-mediated cytolysis and/or through syncytium formation- or cell–cell fusion-dependent killing, and markedly inhibited HIV-1 production. Furthermore, G-complemented VSVΔG-CC5 also efficiently inhibited HIV-1 infection in R5 HIV-1-infected humanized immunodeficient mice. Taken together, our findings indicate that a cytolytic rVSV that targets and eliminates R5 HIV-1-infected cells potentially has therapeutic value for controlling R5 HIV-1 infection.

Trends and predictors of HIV-1 acquired drug resistance in Minas Gerais, Brazil: 2002–2012

Several studies show that the prevalence of multidrug-resistant HIV-1 virus is declining over time. A retrospective cohort study was carried out to evaluate the trends of drug resistance in antiretroviral treatment-exposed individuals in a state of a middle-income country, Minas Gerais, southeast region of Brazil. We analyzed 2115 HIV-1 sequences from 2002 up to 2012, from 52 cities of Minas Gerais. The groups were analyzed according to the definitions: “IAS – 3 class mutations”, if ≥1 drug resistance mutation from IAS 2015 list (DRM) was present in each class; “No fully susceptible drugs” as the absence of any fully susceptible drug in Stanford algorithm; and “GSS≥2″, when a maximum calculated GSS (genotypic susceptibility score) was ≥2 or ≥3, counting only drugs available in Brazil and USA at given calendar years. Time trends of resistance were analyzed by Cochran–Armitage test. We observed a decrease in the rate resistance mutations for PI, NRTI, “IAS – 3 class mutations”, and “No fully susceptible drugs” over these 11 years, from 69.2% to 20.7%, 92.3% to 90.2%, 46.2% to 22.5%, and 12.8% to 5.7%, respectively (p<0.05). Resistance to NNRTI increased from 74.4% to 81.6%, mainly because of K103N mutation. The GSS score ≥2 increased during the years from 35.9% to 87.3% (p<0.001). We demonstrate that resistance to PI and to the three main classes simultaneously are declining, although the number of patients on of antiretroviral therapy has doubled in the last ten years in Brazil (125,000 in 2002 to 400,000 in 2014). Broader resistance testing and the availability of more therapeutic options might have influenced this decline. The increase in NNRTI resistance can limit this class as first line treatment in Brazil in the future.

Increasing prevalence of K65K and K66K in HIV-1 subtype B reverse transcriptase.

Synonymous substitutions K65K/K66K in HIV-1 reverse transcriptase alleviate fitness and fidelity defects in HIV-1 molecular clones harboring thymidine analogue mutations (TAMs); however, their potential for transmission and persistence is unknown. Here, we investigated the temporal appearance of K65K/K66K relative to TAMs in a HIV-1 cohort, their prevalence over time, and their impact on viral fitness in the context of patient-derived reverse transcriptase sequences. Retrospective analyses of the temporal appearance and longitudinal prevalence of synonymous substitutions and drug resistance mutations were performed using the British Columbia Centre for Excellence in HIV/AIDS Drug Treatment Program (DTP) database. Plasma-derived HIV-1 from the DTP was used to generate infectious molecular clones. Growth competition assays were performed to determine viral fitness. The prevalence of K65K/K66K in drug-naïve individuals tripled from 11% in 1997 to 37% in 2014 (P < 0.0001, n = 5221), with K66K mainly accounting for the increase. These mutations emerged in drug-treated individuals without TAMs in 14% of the cohort and conferred a fitness advantage in the context of patient-derived multidrug-resistant (MDR) virus in the absence of drug. The appearance of K65K/K66K in drug-treated individuals was largely independent of TAMs, suggesting alternative factors are likely associated with their emergence. The increasing K65K/K66K prevalence to over a third of treatment-naïve individuals in the mostly subtype B DTP cohort and their ability to confer a fitness advantage to multidrug-resistant virus might explain the transmission and persistence of virus harbouring K65K/K66K in untreated individuals, and highlights their role in adaptive HIV-1 evolution.

Resistance to Mutant Group 2 Influenza Virus Neuraminidases of an Oseltamivir-Zanamivir Hybrid Inhibitor.

Oseltamivir and zanamivir are the two major antiviral drugs available for the treatment of influenza virus infections. However, multidrug-resistant viruses have emerged in clinical cases, which pose a challenge for the development of new drugs. N1 and N2 subtypes exist in the viruses which cause seasonal epidemics and past pandemics. Although N1 drug resistance is well characterized, the molecular mechanisms underlying N2 drug resistance are unknown. A previous report showed that an N2 E119V/I222L dual mutant conferred drug resistance to seasonal influenza virus. Here, we confirm that these substitutions result in multidrug resistance and dramatically reduced sensitivity to NAI. We further elucidate the molecular mechanism underlying N2 drug resistance by solving crystal structures of the N2 E119V and I222L mutants and the dual mutant. Most importantly, we found that a novel oseltamivir-zanamivir hybrid inhibitor, MS-257, remains more effective against drug-resistant N2 and is a promising candidate as a next-generation anti-influenza virus drug.

Role of Public-Private Partnerships in Meeting Healthcare Challenges in Africa: A Perspective From the Public Sector.

Public-private partnerships (PPPs) align public and private needs around mutual goals to move vital projects forward. When PPPs work to strengthen the critical link in the healthcare system, such aslaboratorynetworks,as demonstrated inthissupplementbyauthors from the International Laboratory Branch at the Centers for Disease Control and Prevention (CDC), in-country officials from therespectiveCDCandMinistriesofHealth,implementingpartners, and Becton, Dickinson, and Company (BD), they significantly change the landscape of healthcare and patient outcomes. The laboratory networks in African countries supported by a PPP between BD and US President’s Emergency Plan for AIDS Relief are achieving a positive transformation. Over the years, thePPPhasdemonstratedsignificantcontributionsindeveloping a more competent laboratory workforce, reinforced laboratory systems, and improved treatment efficiencies by significantly reducing turnaround time to provide accurate laboratory results to patients afflicted by deadly diseases, such as multidrug resistant tuberculosis and human immunodeficiency virus (HIV). This PPP has not just improved efficiencies in the countries where they exist, it has also provided a successful model for other low-income countries to consider. The effort needed to meet the UNAIDS 90-90-90 treatment goals to help end the AIDS epidemic by 2020 is tremendous, and neither governments nor the private sector can do it alone. These goals, which state that, by 2020, all people living with HIV will know their HIV status, 90% of all people with diagnosed HIV infection will receive sustained antiretroviral therapy, and 90% of all people receiving antiretroviral therapy will have viral suppression, are being significantly advanced as a result of this collaboration. We encourage more entities—public, private, health ministries, and nongovernmental organizations— to consider PPPs as an opportunity to efficiently and synergistically meet the needs of people living with HIV/AIDS and of their caregivers.

The end of the line? A case of drug resistance to third-line antiretroviral therapy

HIV drug resistance has been described in all antiretroviral drug classes and threatens the long-term success of HIV treatment. Here, we describe the first reported case of acquired resistance to the integrase strand transfer inhibitors in South Africa. This case illustrates the dilemma of treatment in the context of inadequate adherence and poor psychosocial support and highlights the potential risk of transmission of multidrug-resistant virus. Keywords: HIV drug resistance; third line

Synthesis of a Vpr-Binding Derivative for Use as a Novel HIV-1 Inhibitor.

The emergence of multidrug-resistant viruses compromises the efficacy of anti-human immunodeficiency virus type 1 (HIV-1) therapy and limits treatment options. Therefore, new targets that can be used to develop novel antiviral agents need to be identified. We previously identified a potential parent compound, hematoxylin, which suppresses the nuclear import of HIV-1 via the Vpr-importin α interaction and inhibits HIV-1 replication in a Vpr-dependent manner by blocking nuclear import of the pre-integration complex. However, it was unstable. Here, we synthesized a stable derivative of hematoxylin that bound specifically and stably to Vpr and inhibited HIV-1 replication in macrophages. Furthermore, like hematoxylin, the derivative inhibited nuclear import of Vpr in an in vitro nuclear import assay, but had no effect on Vpr-induced G2/M phase cell cycle arrest or caspase activity. Interestingly, this derivative bound strongly to amino acid residues 54–74 within the C-terminal α-helical domain (αH3) of Vpr. These residues are highly conserved among different HIV strains, indicating that this region is a potential target for drug-resistant HIV-1 infection. Thus, we succeeded in developing a stable hematoxylin derivative that bound directly to Vpr, suggesting that specific inhibitors of the interaction between cells and viral accessory proteins may provide a new strategy for the treatment of HIV-1 infection.

Treatment outcomes in multidrug resistant tuberculosis-human immunodeficiency virus Co-infected patients on anti-retroviral therapy at Sizwe Tropical Disease Hospital Johannesburg, South Africa.

BackgroundMultidrug resistant-tuberculosis (MDR-TB) is a threat to global tuberculosis control which is worsened by human immune-deficiency virus (HIV) co-infection. There is however paucity of data on the effects of antiretroviral treatment (ART) before or after starting MDR-TB treatment. This study determined predictors of mortality and treatment failure among HIV co-infected MDR-TB patients on ART.MethodsA retrospective medical record review of 1200 HIV co-infected MDR-TB patients admitted at Sizwe Tropical Disease Hospital, Johannesburg from 2007 to 2010 was performed. Chi-square test was used to determine treatment outcomes in HIV co-infected MDR-TB patients on ART. Multivariable logistic regression and Poisson models were used to determine predictors of mortality and treatment failure respectively.ResultsMortality was higher (21.8 % vs. 15.4 %) among patients who started ART before initiating MDR-TB treatment compared with patients initiated on ART after commencing MDR-TB treatment (p = 0.013). Factors significantly associated with mortality included: the use of ART before starting MDR-TB treatment (OR 1.65, 95 % CI 1.02–2.73), severely-underweight (OR 3.71, 95 % CI 1.89–7.29) and underweight (OR 2.35, 95 % CI 1.30–4.26), cavities on chest x-rays at baseline (OR 1.76, 95 % CI 1.08–2.94), presence of other opportunistic infections (OR 1.80, 95 % CI 1.10–2.94) and presence of other co-morbidities (OR 2.26, 95 % CI 1.20–4.21). Factors predicting failure were severe anaemia (IRR (OR 4.72, 95 % CI 1.47–15), other co-morbidities (OR 2.39, 95 % CI 1.05–5.43) and modified individualised regimen at baseline (OR 2.15, 95 % CI 0.98–4.71).ConclusionsHigh mortality among patients already on ART before initiating MDR-TB treatment is a worrisome development. Management of adverse-events, opportunistic infections and co-morbidities in these patients is important if the protective benefits of being on ART are to be maximized. There is the need to intensify intervention programmes targeted at early identification of MDR-TB, treatment initiation, drug monitoring and increasing adherence among HIV co-infected MDR-TB patients.

Viral envelope is a major determinant of enhanced fitness of a multidrug-resistant HIV-1 variant.

Multidrug-resistant (MDR) HIV-1 viruses are thought to be less pathogenic than wild-type viruses because of the fitness costs of drug-resistance mutations. However, we identified an individual infected with MDR virus associated with rapid disease progression referred to as MDR-1. To study the contribution of virologic factors to rapid disease progression, we constructed molecular clones that demonstrated high replication fitness and cytopathicity. To dissect determinants of enhanced fitness of a cytopathic clone, pMDR-1c, we divided its genome into 2 parts: the envelope (gp160) and the remaining backbone genome, and constructed mutual chimeric viruses with a reference, wild-type virus clone, pNL4-3. The growth competition assay indicated that pMDR-1c has high fitness (1.62), although its envelope confers remarkably enhanced fitness (2.29) and its backbone confers reduced fitness (0.56) as compared with pNL4-3. We also performed a similar study with a less cytopathic pMDR-5a, a molecular clone derived from another subject MDR-5, infected with MDR HIV-1, and associated with slower clinical progression. The results indicated that pMDR-5a has reduced fitness (0.82), although its envelope confers enhanced fitness (1.64) and its backbone confers reduced fitness (0.49), a fitness pattern compatible with envelope-mediated fitness compensation. These results suggest that the viral envelope may be a major determinant of the enhanced fitness of the MDR HIV-1 variant isolated from a patient with rapid disease progression. Furthermore, we speculate that compensation conferred by envelope may be a mechanism by which MDR HIV-1 maintains overall fitness despite the presence of changes in pol, which reduce replication capacity.

In vitro drug combination studies of Letermovir (AIC246, MK-8228) with approved anti-human cytomegalovirus (HCMV) and anti-HIV compounds in inhibition of HCMV and HIV replication.

Despite modern prevention and treatment strategies, human cytomegalovirus (HCMV) remains a common opportunistic pathogen associated with serious morbidity and mortality in immunocompromised individuals, such as transplant recipients and AIDS patients. All drugs currently licensed for the treatment of HCMV infection target the viral DNA polymerase and are associated with severe toxicity issues and the emergence of drug resistance. Letermovir (AIC246, MK-8228) is a new anti-HCMV agent in clinical development that acts via a novel mode of action and has demonstrated anti-HCMV activity in vitro and in vivo. For the future, drug combination therapies, including letermovir, might be indicated under special medical conditions, such as the emergence of multidrug-resistant virus strains in transplant recipients or in HCMV-HIV-coinfected patients. Accordingly, knowledge of the compatibility of letermovir with other HCMV or HIV antivirals is of medical importance. Here, we evaluated the inhibition of HCMV replication by letermovir in combination with all currently approved HCMV antivirals using cell culture checkerboard assays. In addition, the effects of letermovir on the antiviral activities of selected HIV drugs, and vice versa, were analyzed. Using two different mathematical techniques to analyze the experimental data, (i) additive effects were observed for the combination of letermovir with anti-HCMV drugs and (ii) no interaction was found between letermovir and anti-HIV drugs. Since none of the tested drug combinations significantly antagonized letermovir efficacy (or vice versa), our findings suggest that letermovir may offer the potential for combination therapy with the tested HCMV and HIV drugs.

Dolutegravir-based antiretroviral therapy in a severely overweight child with a multidrug-resistant human immunodeficiency virus infection. Acase report and review.

The management of multidrug-resistant human immunodeficiency virus (MDR HIV) infections in children is particularly challenging due to the lack of experience with new drugs. Dolutegravir, combined with an optimized antiretroviral background therapy, is promising for the treatment of MDR HIV and has been approved recently for adults and adolescents. Data for children are extremely limited. We describe the efficacy, safety and plasmatic levels of a dolutegravir-based, complex active antiretroviral treatment regimen in a severely overweight 11-year-old child infected with an MDR HIV strain.

Treatment outcomes in multidrug resistant tuberculosis-human immunodeficiency virus Co-infected patients on anti-retroviral therapy at Sizwe Tropical Disease Hospital Johannesburg, South Africa

Treatment outcomes in multidrug resistant tuberculosis-human immunodeficiency virus Co-infected patients on anti-retroviral therapy at Sizwe Tropical Disease Hospital Johannesburg, South Africa

Structure-activity relationships of a novel capsid targeted inhibitor of HIV-1 replication.

Despite the considerable successes of highly active antiretroviral therapy (HAART) for the treatment of HIV/AIDS, cumulative drug toxicities and the development of multidrug-resistant virus necessitate the search for new classes of antiretroviral agents with novel modes of action. The HIV-1 capsid (CA) protein has been structurally and functionally characterized as a druggable target. We have recently designed a novel small molecule inhibitor I-XW-053 using the hybrid structure based method to block the interface between CA N-terminal domains (NTD–NTD interface) with micromolar affinity. In an effort to optimize and improve the efficacy of I-XW-053, we have developed the structure activity relationship of I-XW-053 compound series using ligand efficiency methods. Fifty-six analogues of I-XW-053 were designed that could be subclassified into four different core domains based on their ligand efficiency values computed as the ratio of binding efficiency (BEI) and surface efficiency (SEI) indices. Compound 34 belonging to subcore-3 showed an 11-fold improvement over I-XW-053 in blocking HIV-1 replication in primary human peripheral blood mononuclear cells (PBMCs). Surface plasmon resonance experiments confirmed the binding of compound 34 to purified HIV-1 CA protein. Molecular docking studies on compound 34 and I-XW-053 to HIV-1 CA protein suggested that they both bind to NTD–NTD interface region but with different binding modes, which was further validated using site-directed mutagenesis studies.

Profiling and characterization of influenza virus N1 strains potentially resistant to multiple neuraminidase inhibitors.

Neuraminidase inhibitors (NAIs) have been widely used to control influenza virus infection, but their increased use could promote the global emergence of resistant variants. Although various mutations associated with NAI resistance have been identified, the amino acid substitutions that confer multidrug resistance with undiminished viral fitness remain poorly understood. We therefore screened a known mutation(s) that could confer multidrug resistance to the currently approved NAIs oseltamivir, zanamivir, and peramivir by assessing recombinant viruses with mutant NA-encoding genes (catalytic residues R152K and R292K, framework residues E119A/D/G, D198N, H274Y, and N294S) in the backbones of the 2009 pandemic H1N1 (pH1N1) and highly pathogenic avian influenza (HPAI) H5N1 viruses. Of the 14 single and double mutant viruses recovered in the backbone of pH1N1, four variants (E119D, E119A/D/G-H274Y) exhibited reduced inhibition by all of the NAIs and two variants (E119D and E119D-H274Y) retained the overall properties of gene stability, replicative efficiency, pathogenicity, and transmissibility in vitro and in vivo. Of the nine recombinant H5N1 viruses, four variants (E119D, E119A/D/G-H274Y) also showed reduced inhibition by all of the NAIs, though their overall viral fitness was impaired in vitro and/or in vivo. Thus, single mutations or certain combination of the established mutations could confer potential multidrug resistance on pH1N1 or HPAI H5N1 viruses. Our findings emphasize the urgency of developing alternative drugs against influenza virus infection. There has been a widespread emergence of influenza virus strains with reduced susceptibility to neuraminidase inhibitors (NAIs). We screened multidrug-resistant viruses by studying the viral fitness of neuraminidase mutants in vitro and in vivo. We found that recombinant E119D and E119A/D/G/-H274Y mutant viruses demonstrated reduced inhibition by all of the NAIs tested in both the backbone of the 2009 H1N1 pandemic (pH1N1) and highly pathogenic avian influenza H5N1 viruses. Furthermore, E119D and E119D-H274Y mutants in the pH1N1 background maintained overall fitness properties in vitro and in vivo. Our study highlights the importance of vigilance and continued surveillance of potential NAI multidrug-resistant influenza virus variants, as well as the development of alternative therapeutics.

Molecular docking studies of chromone derivatives against wild type and mutant strains of HIV-1 protease

Developing a new HIV-1 protease (HIV-1 PR) inhibitor is still a challenging task to overcome the drug resistance mutations in the HIV-PR. In this study, docking simulations of chromone derivatives against wild type and eleven mutant variants HIV-1 PR were investigated using GOLD and Autodock programs. From both GOLD and Autodock results, chromone 3, the experimentally observed highly potent HIV-1 PR inhibitor, showed stronger binding affinity against every studied mutant strain (2AVS, 2AVO, 2AVV, 1MES, 1MET, 1MEU, 1SDU, 1SDV, 1C6Y, 2F8O, and 1SH9) than the wild-type enzyme (1AJX). Chromone 32, another potent inhibitor as well as chromones 33, 34, 37, and 47 also showed high binding interaction with several mutant-type enzymes. The coherent picture of the interactions at the active sites of mutant PR should facilitate the further design and development of new potent inhibitor against multidrug-resistant virus.

Cost-Effectiveness of Newer Antiretroviral Drugs in Treatment-Experienced Patients With Multidrug-Resistant HIV Disease

Newer antiretroviral drugs provide substantial benefits but are expensive. The cost-effectiveness of using antiretroviral drugs in combination for patients with multidrug-resistant HIV disease was determined. A cohort state-transition model was built representing treatment-experienced patients with low CD4 counts, high viral load levels, and multidrug-resistant virus. The effectiveness of newer drugs (those approved in 2005 or later) was estimated from published randomized trials. Other parameters were estimated from a randomized trial and from the literature. The model had a lifetime time horizon and used the perspective of an ideal insurer in the United States. The interventions were combination antiretroviral therapy, consisting of 2 newer drugs and 1 conventional drug, compared with 3 conventional drugs. Outcome measures were life-years, quality-adjusted life-years (QALYs), costs, and incremental cost-effectiveness. Substituting newer antiretroviral drugs increased expected survival by 3.9 years in advanced HIV disease. The incremental cost-effectiveness ratio of newer, compared with conventional, antiretroviral drugs was $75,556/QALY gained. Sensitivity analyses showed that substituting only one newer antiretroviral drug cost $54,559 to $68,732/QALY, depending on assumptions about efficacy. Substituting 3 newer drugs cost $105,956 to $117,477/QALY. Cost-effectiveness ratios were higher if conventional drugs were not discontinued. In treatment-experienced patients with advanced HIV disease, use of newer antiretroviral agents can be cost-effective, given a cost-effectiveness threshold in the range of $50,000 to $75,000 per QALY gained. Newer antiretroviral agents should be used in carefully selected patients for whom less expensive options are clearly inferior.

“Test-and-Treat” Strategy for Control of HIV and AIDS Can Lead to a Decrease, Not an Increase, of Multidrug-Resistant Viruses

To the Editor—Sood et al modeled the effects of a “test-and-treat” program for the men who have sex with men population in Los Angeles [1]. Relative to the status quo, this deterministic epidemiologic model predicted that “test-and-treat” could lead to a 34% reduction in new human immunodeficiency virus (HIV) infections, a 19% reduction in deaths, and a 39% reduction in new AIDS cases. However, it also predicted that the benefits from this expansion of HIV therapy would be counterbalanced by an 89% increase (from 4.79% to 9.06%) in the prevalence of multidrug resistance (MDR) over 10 years. They conclude that the risks of developing widespread MDR may exceed the benefits derived from “test and treat,” but that much of the benefit could derive from larger-scale testing alone. However, actual data collected during 12 years of province-wide follow-up in British Columbia, Canada, during a period of treatment expansion [2] do not support the model's conclusions regarding drug resistance (Figure 1). On the contrary, we now observe a much lower proportion of MDR in 2012 in comparison to 2000, despite the number of patients on therapy expanding from 4755 to >7700 during the same period. Figure 1. In 2012, 88% of British Columbia Drug Treatment Program (BC DTP) patients had either undetectable viremia (<50 copies/mL) or wild-type human immunodeficiency virus (HIV). Individuals with resistance to 2 or more antiretroviral (ARV) drug categories ... Part of the discordance between our data and Sood et al's model may be due to the parameters used for resistance development and the definition of “MDR” used [1, 3], both of which may be outdated. The rates of development and the clinical significance of HIV resistance have both declined as more and better HIV medications have led to improved rates of HIV suppression [4]. Furthermore, the definition of “MDR” used and its estimated rate of development appear to consist of resistance to >1 drug or drug class—for example, resistance to merely lamivudine/emtricitabine and/or nonnucleoside reverse transcriptase inhibitors [1, 3], rather than pandrug resistance. Obviously any resistance is of concern, but some levels of resistance are less clinically threatening. More than 25 approved antiretrovirals in 6 classes exist, and regimens with fully active drugs can be constructed even for patients harboring MDR strains resistant to 2 or more drug classes. Currently, few patients in British Columbia harbor strains with 3-drug-class resistance, let alone to all drugs from all 6 classes. In addition, even if the estimates of Sood et al for MDR in their model were correct and the proportion of cases of MDR would increase, the total number of cases of MDR would increase only slightly. The relatively small increase in the number of cases of MDR would be a very small price to pay for preventing approximately 18 000 new infections and 15 000 deaths. “Test-and-treat” remains a very promising strategy for the control of HIV and AIDS. The whole point of developing the array of effective antiretrovirals now available was to have a variety of options to treat the vast majority of HIV-infected patients who require these therapies for their own individual health benefit (and reap the secondary societal benefits described by Sood et al), rather than reserve these therapies due to a theoretical, possibly overemphasized, concern about the future effectiveness of the medications.

Highly multidrug-resistant HIV: clonal analysis and therapeutic strategies

There are today HIV-infected patients in therapeutic impasses because of highly multidrug-resistant (HMDR) viruses. We studied the distribution of resistance mutations at clonal level, and we analysed the therapeutic strategies used in such cases to achieve undetectable viraemia. The HMDR profile was defined as a genotypic sensitivity score (GSS) ≤ 1.5 for etravirine and raltegravir with full resistance to darunavir. About 30 clones per gene and per patient were sequenced. Virtual phenotypes were determined. Efficacy of therapeutic strategies was evaluated by follow-up of viral loads, CD4 cell counts and trough concentrations of drugs. Among 1310 patients on treatment and with genotypic resistance testing, 25 (2%) were resistant to darunavir and 11 (0.8%) had an HMDR profile. Five-hundred clones could be analysed for four of them. HMDR profiles were harboured by the great majority of clones and all resistance mutations were located on the same strains for all genes. Despite this and a regimen with a GSS <2.0 in three patients, they achieved a viraemia <20 copies/mL. These results were obtained using different strategies: high doses of drugs; combination of antiretrovirals with full or intermediate susceptibility, such as tipranavir, etravirine or maraviroc; and use of alternative compounds, such as foscarnet or interferon. Patients with HMDR HIV were uncommon, but, in such cases, all resistance mutations were borne on the same majority strains. In this study, tipranavir was the only protease inhibitor with full or intermediate susceptibility. Despite very limited therapeutic options, an undetectable viraemia can be achieved by combining different strategies.