PRESTIGIO RING "a 59-year-old man with multidrug resistant HIV-1 infection failing a regimen including dolutegravir, rilpivirine, atazanavir/cobicistat: successful treatment tailoring based on genotypic and phenotypic resistance tests".

Management of virological failure in heavily treatment-experienced people with multidrug-resistant (MDR) HIV infection is a serious clinical challenge. New drugs with novel mechanisms of action have recently been approved, and their use has improved the outcome of subjects with limited treatment options (LTO). In this setting, the choice of antiretroviral therapy (ART) should be tailored based on the pattern of resistance, treatment history and patients' individual characteristics. While genotypic resistance testing is the reference method for analysing residual drug susceptibility, phenotypic resistance testing can provide additional support when facing LTO. Herein, we present the case of a patient with MDR HIV-1 infection on virological failure enrolled in the PRESTIGIO Registry. The salvage ART regimen, which included drugs with novel mechanisms of action (MoA), was tailored to the patient's clinical characteristics and on the resistance pattern explored with genotypic and phenotypic investigation, allowing the achievement of viro-immunological success. The use of recently approved drugs with novel MoA, combined with an optimized background regimen, may also achieve virological suppression in people with LTO.

In Vitro Combinatorial Activity of Direct Acting Antivirals and Monoclonal Antibodies against the Ancestral B.1 and BQ.1.1 SARS-CoV-2 Viral Variants.

Combination antiviral therapy may be helpful in the treatment of SARS-CoV-2 infection; however, no clinical trial data are available, and combined use of direct-acting antivirals (DAA) and monoclonal antibodies (mAb) has been reported only anecdotally. To assess the cooperative effects of dual drug combinations in vitro, we used a VERO E6 cell-based in vitro system with the ancestral B.1 or the highly divergent BQ.1.1 virus to test pairwise combinations of the licensed DAA, including nirmatrelvir (NRM), remdesivir (RDV) and the active metabolite of molnupiravir (EIDD-1931) as well the combination of RDV with four licensed mAbs (sotrovimab, bebtelovimab, cilgavimab, tixagevimab; tested only with the susceptible B.1 virus). According to SynergyFinder 3.0 summary and weighted scores, all the combinations had an additive effect. Within DAA/DAA combinations, paired scores with the B.1 and BQ.1.1 variants were comparable. In the post hoc analysis weighting synergy by concentrations, several cases of highly synergistic scores were detected at specific drug concentrations, both for DAA/DAA and for RDV/mAb combinations. This was supported by in vitro confirmation experiments showing a more than a linear shift of a drug-effective concentration (IC50) at increasing concentrations of the companion drug, although the effect was prominent with DAA/DAA combinations and minimal or null with RDV/mAb combinations. These results support the cooperative effects of dual drug combinations in vitro, which should be further investigated in animal models before introduction into the clinic.

Prevalence and phenotypic susceptibility to doravirine of the HIV-1 reverse transcriptase V106I polymorphism in B and non-B subtypes.

AIM: To evaluate the prevalence and in vitro susceptibility to doravirine of RT-V106I polymorphism detected in samples collected from drug-naïve subjects. METHODS: Doravirine susceptibility was measured in site-directed mutants (SDMs) containing V106I, V106A, V106 M and Y188L mutations in subtype B (NL4-3, HXB2) and CRF02_AG background and in recombinant viruses with RT harboring V106I alone derived from 50 PLWH. RESULTS: HIV-1 B subtype was detected in 1523/2705 cases. Prevalence of V106I was 3.2% in B and 2.5% in non-B subtypes, and was higher in subtype F (8.1%), and D (14.3%). Fold-changes (FC) in susceptibility for SDMs were below doravirine biological cutoff (3.0) for V106I, but not for V106A, V106 M, and Y188L. Clinically-derived viruses tested included 22 B (median FC 1.2 [IQR 0.9-1.6]) and 28 non-B subtypes (median FC 1.8 [IQR 0.9-3.0]). Nine (18%) viruses showed FC values equal or higher than the doravirine biological FC cutoff. CONCLUSIONS: The prevalence of the HIV-1 RT-V106I polymorphism in MeditRes HIV consortium remains low, but significantly more prevalent in subtypes D and F. V106I minimally decreased the susceptibility to doravirine in SDMs and most clinical isolates. Reduced susceptibility seems to occur at increased frequency in subtype F1, however the clinical impact remains to be investigated.

Cohort Profile: A European Multidisciplinary Network for the Fight against HIV Drug Resistance (EuResist Network).

The EuResist cohort was established in 2006 with the purpose of developing a clinical decision-support tool predicting the most effective antiretroviral therapy (ART) for persons living with HIV (PLWH), based on their clinical and virological data. Further to continuous extensive data collection from several European countries, the EuResist cohort later widened its activity to the more general area of antiretroviral treatment resistance with a focus on virus evolution. The EuResist cohort has retrospectively enrolled PLWH, both treatment-naïve and treatment-experienced, under clinical follow-up from 1998, in nine national cohorts across Europe and beyond, and this article is an overview of its achievement. A clinically oriented treatment-response prediction system was released and made available online in 2008. Clinical and virological data have been collected from more than one hundred thousand PLWH, allowing for a number of studies on the response to treatment, selection and spread of resistance-associated mutations and the circulation of viral subtypes. Drawing from its interdisciplinary vocation, EuResist will continue to investigate clinical response to antiretroviral treatment against HIV and monitor the development and circulation of HIV drug resistance in clinical settings, along with the development of novel drugs and the introduction of new treatment strategies. The support of artificial intelligence in these activities is essential.

Potential role of doravirine for the treatment of HIV-1-infected persons with transmitted drug resistance.

BACKGROUND: Doravirine has a unique resistance profile but how this profile might increase its usefulness beyond first-line therapy in persons with susceptible viruses has not been well studied. We sought to determine scenarios in which doravirine would retain activity against isolates from ART-naïve persons with transmitted drug resistance (TDR) and to identify gaps in available doravirine susceptibility data. METHODS: We analyzed published in vitro doravirine susceptibility data and applied the results to 42,535 RT sequences from ART-naïve persons published between 2017 and 2021. NNRTI drug resistance mutations (DRMs) were defined as those with a Stanford HIV Drug Resistance Database doravirine penalty score either alone or in combination with other mutations. RESULTS: V106A, Y188L, F227C/L, M230L, and Y318F were associated with the greatest reductions in doravirine susceptibility. However, several NNRTI DRMs and DRM combinations lacking these canonical resistance mutations had > tenfold reduced susceptibility including G190E, one isolate with G190S, three isolates with L100I + K103N, one isolate with K103N + P225H, and isolates with L100I + K103N + V108I and K101E + Y181C + G190A. Of the 42,535 ART-naïve sequences, 3,374 (7.9%) contained a NNRTI DRM of which 2,788 (82.6%) contained 1 DRM (n = 33 distinct mutations), 426 (12.6%) contained 2 DRMs (79 distinct pairs of mutations), and 143 (4.2%) contained ≥ 3 DRMs (86 distinct mutation patterns). Among the 2,788 sequences with one DRM, 112 (4.0%) were associated with ≥ 3.0-fold reduced doravirine susceptibility while 2,625 (94.2%) were associated with < 3.0-fold reduced susceptibility. Data were not available for individual NNRTI DRMs in 51 sequences (1.8%). Among the 426 sequences with two NNRTI DRMs, 180 (42.3%) were associated with ≥ 3.0 fold reduced doravirine susceptibility while just 32 (7.5%) had < 3.0 fold reduced susceptibility. Data were not available for 214 (50.2%) sequences containing two NNRTI DRMs. CONCLUSIONS: First-line therapy containing doravirine plus two NRTIs is expected to be effective in treating most persons with TDR as more than 80% of TDR sequences had a single NNRTI DRM and as more than 90% with a single DRM were expected to be susceptible to doravirine. However, caution is required for the use of doravirine in persons with more than one NNRTI DRM even if none of the DRMs are canonical doravirine-resistance mutations.

Residual phenotypic susceptibility to doravirine in multidrug-resistant HIV-1 from subjects enrolled in the PRESTIGIO Registry.

OBJECTIVES: Doravirine shows a rather distinct resistance profile within the nonnucleoside reverse transcriptase inhibitor (NNRTI) class. This study aimed to evaluate the phenotypic susceptibility to doravirine, rilpivirine and etravirine in a panel of multidrug-resistant (MDR) HIV-1 isolates collected from people living with HIV (PLWH) enrolled in the PRESTIGIO Registry. METHODS: Recombinant viruses expressing PLWH-derived protease, reverse transcriptase coding regions were generated from plasma samples at virological failure with documented resistance to protease inhibitors, nucleoside reverse transcriptase inhibitors, NNRTIs and integrase strand transfer inhibitors. In vitro susceptibility was assessed through a phenotypic assay measuring fold-change values with respect to the reference NL4-3 virus. Genotypic susceptibility was computed by the Stanford HIVdb algorithm 8.9-1. RESULTS: Plasma samples were collected from 22 PLWH: 20 (91%) were male, median age 55 years (IQR 50-58), time since HIV-1 diagnosis 27 years (23-31) and time on antiretroviral treatment 23 years (22-26). Median doravirine, etravirine and rilpivirine fold-change values were 9.8 (2.9-40.4), 42.9 (3.1-100.0) and 100.0 (17.9-100.0), respectively. According to the fold-change cut-offs, full susceptibility was observed in five (23%), four (18%) and one (5%) cases with doravirine, etravirine and rilpivirine, respectively. Irrespective of the presence of specific doravirine mutations, higher numbers of NNRTI mutations correlated with higher fold-change values for doravirine. By comparing the distribution of fold-change values with the Stanford HIVdb predicted susceptibility, a significant correlation was detected for doravirine and rilpivirine but not etravirine. CONCLUSION: Despite extensive cross-resistance among NNRTIs, doravirine can be a valid option in a proportion of PLWH with MDR HIV-1. Doravirine activity appeared to be inferred with fair accuracy by the HIVdb algorithm.

Molecular Epidemiology of HIV-1 in Eastern Europe and Russia.

The HIV epidemic in Eastern Europe and Russia is large and not well-controlled. To describe the more recent molecular epidemiology of HIV-1, transmitted drug resistance, and the relationship between the epidemics in this region, we sequenced the protease and reverse transcriptase genes of HIV-1 from 812 people living with HIV from Ukraine (n = 191), Georgia (n = 201), and Russia (n = 420) before the initiation of antiretroviral therapy. In 190 Ukrainian patients, the integrase gene sequence was also determined. The most reported route of transmission was heterosexual contact, followed by intravenous drug use, and men having sex with men (MSM). Several pre-existing drug resistance mutations were found against non-nucleoside reverse transcriptase inhibitors (RTIs) (n = 103), protease inhibitors (n = 11), and nucleoside analogue RTIs (n = 12), mostly polymorphic mutations or revertants. In the integrase gene, four strains with accessory integrase strand transfer inhibitor mutations were identified. Sub-subtype A6 caused most of the infections (713/812; 87.8%) in all three countries, including in MSM. In contrast to earlier studies, no clear clusters related to the route of transmission were identified, indicating that, within the region, the exchange of viruses among the different risk groups may occur more often than earlier reported.

Dynamics of Total and Intact HIV-1 DNA in Virologically Suppressed Patients Switching to DTG-Based or ATV-Based Dual Therapy.

BACKGROUND: Clinical trials have demonstrated noninferior viral suppression rates of selected 2-drug regimens (2DRs) over standard 3-drug regimens (3DRs). However, the effect of simplification to 2DRs on HIV-1 reservoir remains to be fully assessed. SETTING: Retrospective analyses of samples of virologically suppressed people living with HIV remaining on the same 3DRs or switching to DTG + 3TC or ATV/r + 3TC 2DRs. METHODS: Whole blood samples were collected at enrollment and after 48 weeks. Total HIV-1 DNA (tDNA) and intact HIV-1 DNA (iDNA) were quantified by droplet digital polymerase chain reaction and intact proviral DNA assay, respectively. Statistical analysis was performed to identify associations among variables, and multiple linear regression was used to analyze potential predictors of tDNA and iDNA changes over time. RESULTS: Forty-seven individuals were switched to DTG + 3TC 2DR (N = 23) and ATV/r + 3TC 2DR (N = 24), while 18 remained on 3DRs. tDNA did not change either in the overall population or in the 3DR and 2DR groups. iDNA decreased significantly in the whole data set and in the overall 3DR and 2DR groups ( P = 0.001, P = 0.039 and P = 0.009, respectively). iDNA, but not tDNA, was inversely correlated with the time of viral suppression ( P = 0.002) and time under antiretroviral therapy ( P = 0.006). Higher nadir CD4 + T-cell counts ( P = 0.001) and lower zenith viral load ( P = 0.02) showed an association with the decrease of iDNA, but not with tDNA. CONCLUSIONS: Both tDNA and iDNA dynamics supported noninferior efficacy of 2DRs over 3DRs. iDNA could be more informative than tDNA in analyzing the dynamics of the HIV-1 reservoir under different treatment strategies.

Early versus delayed antiretroviral therapy based on genotypic resistance test: Results from a large retrospective cohort study.

Rapid start of antiretroviral therapy (ART) pending genotypic resistance test (GRT) has been recently proposed, but the effectiveness of this strategy is still debated. The rate of virological success (VS), defined as HIV-RNA < 50 copies/ml, with and without GRT was compared in drug-naïve individuals enrolled in the Italian ARCA cohort who started ART between 2015 and 2018. 521 individuals started ART: 397 without GRT (pre-GRT group) and 124 following GRT (post-GRT group). Overall, 398 (76%) were males and 30 (6%) were diagnosed with AIDS. In the pre-GRT group, baseline CD4+ cell counts were lower (p < 0.001), and viral load was higher (p < 0.001) than in the post-GRT group. The estimated probability of VS in pre-GRT versus post-GRT group was 72.54% (CI95 : 67.78-76.60) versus 66.94% (CI95 : 57.53-74.26) at Week 24 and 92.40% (CI95 : 89.26-94.62) versus 92.92% (CI95 : 86.35-96.33) at Week 48, respectively (p = 0.434). At Week 48, VS was less frequent among individuals with baseline CD4+ cell counts <200 versus >500 (90.33% vs. 97.33%), log viral load <5.00 versus >5.70 log10 cps/ml (97.17% vs 78.16%; p < 0.001), and those treated with protease inhibitors or non-nucleoside reverse transcriptase inhibitors versus those treated with integrase strand transfer inhibitors (p < 0.001). The rate of VS does not seem to be affected by an early ART initiation pending GRT results, but it could be influenced by the composition of the ART regimen, as well as immuno-virological parameters.

External quality assessment of HIV-1 DNA quantification assays used in the clinical setting in Italy.

Total cell-associated HIV-1 DNA is a surrogate marker of the HIV-1 reservoir, however, certified systems for its quantification are not available. The Italian HIV DNA Network was launched to validate HIV-1 DNA quantification methods in use at University and Hospital labs. A quality control panel including HIV-1 DNA standards, reconstructed blood samples (RBSs) and DNA from different HIV-1 subtypes was blindly tested by 12 participating labs by quantitative real-time PCR (n = 6), droplet digital PCR (n = 3) or both (n = 3). The median 95% hit rate was 4.6 (3.7-5.5) copies per test and linearity in the tested range was excellent (R2 = 1.000 [1.000-1.000]). The median values obtained across labs were 3,370 (2,287-4,245), 445 (299-498), 59 (40-81) and 7 (6-11) HIV-1 DNA copies, for the 3,584, 448, 56 and 7-copy standards, respectively. With RBSs, measured values were within twofold with respect to the median in two thirds of cases. HIV-1 subtypes were missed (CRF01_AE by 3 labs) or underestimated by > 1 log (subtypes A, C, D, F by one lab; CRF01_AE by one lab; CRF02_AG by one lab). The overall performance was excellent with HIV-1 DNA standards, however detection of different HIV-1 subtypes must be improved.

Predictors of Virological Failure Among People Living with HIV Switching from an Effective First-Line Antiretroviral Regimen.

Aim of this study was to assess the predictors of virological failure (VF) among patients living with HIV (PLWHIV) switching from an effective first-line antiretroviral therapy (ART) regimen, and to evaluate the emergence of resistance-associated mutations. All adult patients enrolled in the Antiviral Response Cohort Analysis cohort who started ART after 2010, with at least 6 months of virological suppression (VS) before ART switch and with an available genotypic resistance test (GRT) at baseline were included. Thirty-two patients out of the 607 PLWHIV included (5.3%) experienced VF after a median of 11 months from ART switch. Younger age (adjusted Hazard Ratio [aHR] 0.96, 95% confidence interval [CI] 0.92-0.99, p = .023), being male who have sex with male (aHR 0.15, 95% CI 0.03-0.69, p = .014), and longer time from VS to ART switch (aHR 0.97, 95% CI 0.95-1.00, p = .021) resulted protective toward VF, while receiving a first-line regimen containing a backbone other than ABC/3TC or TXF/FTC (aHR 3.61, 95% CI 1.00-13.1, p = .050) and a boosted protease inhibitor as anchor drug (aHR 3.34, 95% CI 1.20-9.28, p = .021) were associated with higher risk of VF. GRT at the moment of VF was available only for 13 patients (40.6%). ART switch in patients with stable control of HIV infection is a safe practice, even if particular attention should be paid in certain cases of patients switching from regimens containing low-performance backbones or protease inhibitors.

In Vitro Anti-SARS-CoV-2 Activity of Selected Metal Compounds and Potential Molecular Basis for Their Actions Based on Computational Study.

Metal-based drugs represent a rich source of chemical substances of potential interest for the treatment of COVID-19. To this end, we have developed a small but representative panel of nine metal compounds, including both synthesized and commercially available complexes, suitable for medical application and tested them in vitro against the SARS-CoV-2 virus. The screening revealed that three compounds from the panel, i.e., the organogold(III) compound Aubipyc, the ruthenium(III) complex KP1019, and antimony trichloride (SbCl3), are endowed with notable antiviral properties and an acceptable cytotoxicity profile. These initial findings prompted us to perform a computational study to unveil the likely molecular basis of their antiviral actions. Calculations evidenced that the metalation of nucleophile sites in SARS-CoV-2 proteins or nucleobase strands, induced by Aubipyc, SbCl3, and KP1019, is likely to occur. Remarkably, we found that only the deprotonated forms of Cys and Sec residues can react favorably with these metallodrugs. The mechanistic implications of these findings are discussed.

Sofosbuvir Selects for Drug-Resistant Amino Acid Variants in the Zika Virus RNA-Dependent RNA-Polymerase Complex In Vitro.

The nucleotide analog sofosbuvir, licensed for the treatment of hepatitis C, recently revealed activity against the Zika virus (ZIKV) in vitro and in animal models. However, the ZIKV genetic barrier to sofosbuvir has not yet been characterized. In this study, in vitro selection experiments were performed in infected human hepatoma cell lines. Increasing drug pressure significantly delayed viral breakthrough (p = 0.029). A double mutant in the NS5 gene (V360L/V607I) emerged in 3 independent experiments at 40-80 µM sofosbuvir resulting in a 3.9 ± 0.9-fold half- maximal inhibitory concentration (IC50) shift with respect to the wild type (WT) virus. A triple mutant (C269Y/V360L/V607I), detected in one experiment at 80 µM, conferred a 6.8-fold IC50 shift with respect to the WT. Molecular dynamics simulations confirmed that the double mutant V360L/V607I impacts the binding mode of sofosbuvir, supporting its role in sofosbuvir resistance. Due to the distance from the catalytic site and to the lack of reliable structural data, the contribution of C269Y was not investigated in silico. By a combination of sequence analysis, phenotypic susceptibility testing, and molecular modeling, we characterized a double ZIKV NS5 mutant with decreased sofosbuvir susceptibility. These data add important information to the profile of sofosbuvir as a possible lead for anti-ZIKV drug development.

SARS-CoV-2 RNA-dependent RNA polymerase as a therapeutic target for COVID-19.

Introduction: The current SARS-CoV-2 pandemic urgently demands for both prevention and treatment strategies. RNA-dependent RNA-polymerase (RdRp), which has no counterpart in human cells, is an excellent target for drug development. Given the time-consuming process of drug development, repurposing drugs approved for other indications or at least successfully tested in terms of safety and tolerability, is an attractive strategy to rapidly provide an effective medication for severe COVID-19 cases.Areas covered: The currently available data and upcominSg studies on RdRp which can be repurposed to halt SARS-CoV-2 replication, are reviewed.Expert opinion: Drug repurposing and design of novel compounds are proceeding in parallel to provide a quick response and new specific drugs, respectively. Notably, the proofreading SARS-CoV-2 exonuclease activity could limit the potential for drugs designed as immediate chain terminators and favor the development of compounds acting through delayed termination. While vaccination is awaited to curb the SARS-CoV-2 epidemic, even partially effective drugs from repurposing strategies can be of help to treat severe cases of disease. Considering the high conservation of RdRp among coronaviruses, an improved knowledge of its activity in vitro can provide useful information for drug development or drug repurposing to combat SARS-CoV-2 as well as future pandemics.

Maraviroc as a potential HIV-1 latency-reversing agent in cell line models and ex vivo CD4 T cells.

Recent studies have suggested that the CCR5 antagonist maraviroc (MVC) may exert an HIV-1 latency reversal effect. This study aimed at defining MVC-mediated induction of HIV-1 in three cell line latency models and in ex vivo CD4 T cells from six patients with suppressed viraemia. HIV-1 induction was evaluated in TZM-bl cells by measuring HIV-1 LTR-driven luciferase expression, and in ACH-2 and U1 latently infected cell lines by measuring cell-free (CFR) and cell-associated (CAR) HIV-1 RNA by qPCR. NF-κB p65 was quantified in nuclear extracts by immunodetection. In ex vivo CD4 T cells, CAR, CFR and cell-associated DNA (CAD) were quantified at baseline and 1-7-14 days post-induction (T1, T7, T14). At T7 and T14, the infectivity of the CD4 T cells co-cultured with MOLT-4/CCR5 target cells was evaluated in the TZM-bl assay (TZA). Results were expressed as fold activation (FA) with respect to untreated cells. No LTR activation was observed in TZM-bl cells at any MVC concentration. NF-κB activation was only modestly upregulated (1.6±0.4) in TZM-bl cells with 5 µM MVC. Significant FA of HIV-1 expression was only detected at 80 µM MVC, namely on HIV-1 CFR in U1 (3.1±0.9; P=0.034) and ACH-2 cells (3.9±1.4; P=0.037). CFR was only weakly stimulated at 20 µM in ACH-2 (1.7±1.0 FA) cells and at 5 µM in U1 cells (1.9±0.5 FA). Although no consistent pattern of MVC-mediated activation was observed in ex vivo experiments, substantial FA values were detected sparsely on individual samples with different parameters. Notably, in one sample, MVC stimulated all parameters at T7 (2.3±0.2 CAD, 6.8±3.7 CAR, 18.7±16.7 CFR, 7.3±0.2 TZA). In conclusion, MVC variably induces HIV-1 production in some cell line models not previously used to test its latency reversal potential. In ex vivo CD4 T cells, MVC may exert patient-specific HIV-1 induction; however, clinically relevant patterns, if any, remain to be defined.

Marked decrease in acquired resistance to antiretrovirals in latest years in Italy.

OBJECTIVES: The aim of this study was to evaluate acquired drug resistance in Italy in the 2009-2018 period. METHODS: We analysed 3094 patients from the Italian ARCA database who had failed antiretroviral treatment and who had received a genotypic test after 6 months of treatment. Drug resistance mutations were identified using International AIDS Society (IAS)-USA tables and the Stanford HIVdb algorithm. The global burden of acquired resistance was calculated among all subjects with antiretroviral failure. Time trends and correlates of resistance were analysed using standard statistical tests. RESULTS: Patients of non-European origin and non-B subtypes increased significantly from 11.5% (103/896) to 19.2% (33/172) and from 13.1% (141/1079) to 23.8% (53/223), respectively, over time. Overall, 14.5% (448/3094), 12.1% (374/3094) and 37.8% (1169/3094) of patients failed first, second and later lines, respectively. According to both IAS and HIVdb, in the study period resistance to any class, nucleoside reverse inhibitor, non-nucleoside reverse inhibitor, and protease inhibitors (PIs) declined significantly. Integrase strand transfer inhibitor (INSTI) resistance declined significantly from 31% (36/116) to 20.8% (41/197) according to HIVdb but not to IAS. Divergent data were highlighted regarding the proportion of non-European patients carrying any, PI and INSTI resistance using IAS tables compared with the Stanford HIVdb algorithm, as the former failed to detect a decrease in resistance while the latter indicates a reduction of 1.6-, 5- and 1.8-fold resistance for such drug classes. In the multivariate analysis, the risk of resistance increased in patients with a larger number of treatment lines and higher viraemia and decreased in those starting therapy in the last biennium of the study. DISCUSSION: A marked reduction in drug resistance was observed over 10 years, compatible with higher genetic barrier and potency of new antiretrovirals. Nonetheless, concerns remain for subjects with non-B subtypes when using mutation lists instead of interpretation systems because of the extensive polymorphism of the protease region.

Prevalence and factors associated with HIV-1 multi-drug resistance over the past two decades in the Italian ARCA database.

Despite successful antiretroviral therapy (ART), patients infected with human immunodeficiency virus (HIV) can develop multi-class drug resistance (MDR). This retrospective study aimed to explore the prevalence of HIV-1 drug resistance over the past two decades by focusing on HIV-MDR and its predictors. ART-experienced patients with HIV with results from at least one plasma genotypic resistance test (GRT) from 1998 to 2018, from the Antiviral Response Cohort Analysis database, were included in this study. The temporal trend of resistance to any drug class was evaluated by considering all GRTs. Prevalence and predictors of HIV-MDR were analysed by consideration of cumulative GRTs. Among 15 628 isolates from 6802 patients, resistance to at least one drug class decreased sharply from 1998 to 2010 (1998-2001: 78%; 2008-2010: 59%; P<0.001) and then remained relatively constant at approximately 50% from 2011 to 2018, with the proportion of isolates with HIV-MDR also stable (approximately 9%). By evaluating factors associated with cumulative HIV-MDR, the following factors were found to be associated with increased risk of HIV-MDR on multi-variate analysis: male gender; sexual and vertical transmission; number of previous protease inhibitors, nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) and non-NRTIs; previous exposure to integrase strand transfer inhibitors, enfuvirtide and maraviroc; and co-infection with hepatitis B virus. In contrast, a nadir CD4 cell count ≥200 cells/mm3, starting first-line ART in 2008 or later and co-infection with hepatitis C virus were associated with lower risk of HIV-MDR. In conclusion, this study revealed that HIV-1 drug resistance has been stable since 2011 despite its dramatic decrease over the past two decades. HIV-MDR is still present, although at a lower rate, suggesting the need for continuous surveillance and accurate management of ART-experienced patients with HIV.