Maria Antonia Papathanasopoulos

Islatravir is a novel nucleoside reverse transcriptase translocation inhibitor recently approved for the treatment of HIV-1 infection in virologically suppressed PLWH. While we previously documented high-level phenotypic resistance to islatravir (ISL) in HIV-1 subtype C variants harboring combinations of type 2 thymidine analogue mutations (TAM2) along with the M184V resistance-associated mutation, the primary contributor to the observed phenotype remains unclear. This report dissects the relative contribution of M184V to ISL resistance in the context of TAM2-containing variants through systematic reversion analysis. We show that reverting mutant 184V to wildtype M184 resulted in substantial sensitization to ISL, with fold-change reductions ranging from 8.1 to 13.4-fold across three TAM2 genetic backgrounds. Contrary to the well-documented antagonism between M184V and TAMs in zidovudine resistance, these two resistance pathways exhibit cooperative rather than antagonistic interactions in the context of ISL resistance. These findings provide critical evidence for refinement of genotypic resistance interpretation algorithms for ISL and have direct implications for the future clinical management of ISL-based antiretroviral therapy in people living with HIV. Importantly, elucidating the mechanistic basis of M184V-TAM2 cooperation would establish a more predictive framework for understanding how complex resistance mutation patterns impact ISL susceptibility and guide treatment decisions in virologically experienced individuals. Considering the diminished use of TAM2-seletive antiretroviral drugs in contemporary ART regimens, islatravir is likely to be an effective treatment option.

Islatravir is a novel nucleoside reverse transcriptase translocation inhibitor under clinical investigation for the treatment of HIV-1 infection. While we previously documented high-level phenotypic resistance to islatravir (ISL) in HIV-1 subtype C variants harboring combinations of type 2 thymidine analogue mutations (TAM2) along with the M184V resistance-associated mutation, the primary contributor to the observed phenotype remained unclear. This report dissects the relative contribution of M184V to ISL resistance in the context of TAM2-containing variants through systematic reversion analysis. We show that reverting mutant 184V to wildtype M184 resulted in substantial sensitization to ISL, with fold-change reductions ranging from 8.1 to 13.4-fold across three TAM2 genetic backgrounds. Contrary to the well-documented antagonism between M184V and TAMs in zidovudine resistance, these two resistance pathways exhibit cooperative rather than antagonistic interactions in the context of ISL resistance. These findings provide critical evidence for refinement of genotypic resistance interpretation algorithms for ISL and have direct implications for the future clinical management of ISL-based antiretroviral therapy in people living with HIV. Importantly, elucidating the mechanistic basis of M184V-TAM2 cooperation would establish a more predictive framework for understanding how complex resistance mutation patterns impact ISL susceptibility and guide treatment decisions in virologically experienced individuals.

Background: Mortality among people living with HIV (PLWH) in developing settings remains elevated, despite high coverage with antiretroviral therapy (ART), with 70% – 80% being virally suppressed (VS). Objectives: This study aimed to determine cause-specific mortality in PLWH in South Africa. Method: An autopsy study with detailed medical record review was undertaken in PLWH dying in hospital. Minimally invasive autopsies were performed on 38 VS and 21 unsuppressed PLWH (≥ 18 years) dying in hospital between May 2018 and April 2022. We assessed clinical and histological findings to determine underlying, contributing, and immediate causes of death (CODs). Results: Median CD4 counts were 180 and 42 cells/mm3 in patients with and without VS respectively. Leading immediate CODs in both VS and unsuppressed PLWH were respiratory failure, sepsis, and septic shock; leading contributing CODs in decreasing order of frequency in both groups were acute kidney injury (AKI), bacterial pneumonia, immunological failure, gastroenteritis and current tuberculosis. Leading underlying CODs in both groups were hypertension, current tuberculosis, malignancies, and chronic obstructive pulmonary disease. VS was associated with lower risk of septic shock and AKI. Conclusion: VS on ART appeared to reduce risk of death from specific pathologies. However, infections, multi-organ failure, non-AIDS-defining malignancies, and metabolic diseases remain important CODs. Incomplete immune reconstitution appears to be a key contributor to premature death.

Islatravir (ISL) is the first-in-class nucleoside reverse transcriptase translocation inhibitor (NRTtI) with novel modes of action. Data on ISL resistance are currently limited, particularly to HIV-1 non-B subtypes. This study aimed to assess prevalent nucleos(t)ide reverse transcriptase inhibitor (NRTI)-resistant mutations in HIV-1 subtype C for their phenotypic resistance to ISL. Prevalent single and combinations of NRTI-resistant mutations were selected from a routine HIV-1 genotypic drug resistance testing database and introduced into HIV-1 subtype C-like pseudoviruses, which were then tested for ISL susceptibility. Single NRTI-resistant mutations were susceptible or showed only a low level of resistance to ISL. This included thymidine analogue mutations (TAMs, i.e., M41L, D67N, K70R, T215FY, and K219EQ) and non-TAMs (i.e., A62V, K65R, K70ET, L74IV, A114S, Y115F, and M184V). Combinations of M184V with one or more additional NRTI-resistant mutations generally displayed reduced ISL susceptibilities. This was more prominent for combinations that included M184V+TAMs, and particularly M184V+TAM-2 mutations. Combinations that included M184V+K65R did not impact significantly on ISL susceptibility. Our study suggests that ISL would be effective in treating people living with HIV (PLWH) failing tenofovir disoproxil fumarate (TDF)/lamivudine (3TC) or TDF/emtricitabine (FTC)-containing regimens, but would be less effective in PLH failing zidovudine (AZT) with 3TC or FTC-containing regimens.

Islatravir (ISL) is the first-in-class nucleoside reverse transcriptase translocation inhibitor (NRTtI) with novel modes of action. Data on ISL resistance is currently limited, particularly to HIV-1 non-B subtypes. This study aimed to assess prevalent nucleos(t)ide reverse transcriptase inhibitor (NRTI) resistance mutations in HIV-1 subtype C for phenotypic resistance to ISL. Prevalent single and combinations of NRTI resistance mutations were selected from a routine HIV-1 genotypic drug resistance testing database and introduced into HIV-1 subtype C-like pseudoviruses, which were then tested for ISL susceptibility. Single NRTI resistance mutations were susceptible or showed only a low level of resistance to ISL. This included thymidine analogue mutations (TAMs, i.e., M41L, D67N, K70R, T215FY, K219EQ) and non-TAMs (i.e., A62V, K65R, K70ET, L74IV, A114S, Y115F, M184V). Combinations of M184V with one or more additional NRTI resistance mutations generally displayed reduced ISL susceptibilities. This was more prominent for combinations that included M184V+TAMs, and particularly M184V+TAM-2 mutations. Combinations that included M184V+K65R did not impact significantly on ISL susceptibility. Our study suggests that ISL would be effective in treating people living with HIV (PLWH) failing tenofovir disoproxil fumarate (TDF)/lamivudine (3TC) or TDF/emtricitabine (FTC)-containing regimens but would be less effective in PLH failing zidovudine (AZT) with 3TC or FTC-containing regimens.

Doravirine (DOR) is a non-nucleoside reverse transcriptase inhibitor (NNRTI) with efficacy against some NNRTI-resistant mutants. Although DOR resistance mutations are established for HIV-1 subtype B, it is less clear for non-B subtypes. This study investigated prevalent NNRTI resistance mutations on DOR susceptibility in HIV-1 subtype C. Prevalent drug resistance mutations were identified from a South African genotypic drug resistance testing database. Mutations, single or in combination, were introduced into replication-defective pseudoviruses and assessed for DOR susceptibility in vitro. The single V106M and Y188L mutations caused high-level resistance while others did not significantly impact DOR susceptibility. We observed an agreement between our in vitro and the Stanford HIVdb predicted susceptibilities. However, the F227L mutation was predicted to cause high-level DOR resistance but was susceptible in vitro. Combinations of mutations containing K103N, V106M or Y188L caused high-level resistance, in agreement with the predictions. These mutations are frequently observed in patients failing efavirenz- or nevirapine-based first-line regimens. However, they are also observed in those failing a protease inhibitor-based second-line regimen, as we have observed in our database. Genotypic drug resistance testing is therefore vital prior to the initiation of DOR-based treatment for those previously exposed to efavirenz or nevirapine.

Doravirine (DOR) is a non-nucleoside reverse transcriptase inhibitor (NNRTI) with efficacy against some NNRTI resistant mutants. Although DOR resistance mutations are established for HIV-1 subtype B, it is less clear for non-B subtypes. This study investigated prevalent NNRTI resistance mutations on DOR susceptibility in HIV-1 subtype C. Prevalent drug resistance mutations were identified from a South African genotypic drug resistance testing database. Mutations, single or in combination, were introduced into replication defective pseudoviruses and assessed for DOR susceptibility in vitro. The single V106M and Y188L mutations caused high-level resistance while others didn’t significantly impact DOR susceptibility. We observed agreement between our in vitro and the Stanford HIVdb predicted susceptibilities. However, the F227L mutation was predicted to cause high-level DOR resistance but was susceptible in vitro. Combinations of mutations containing K103N, V106M or Y188L caused high-level resistance, in agreement with the predictions. These mutations are frequently observed in patients failing efavirenz or nevirapine-based first-line regimens. However, they are also observed in those failing a protease inhibitor-based second-line regimen, as we have observed in our database. Genotypic drug resistance testing is therefore vital prior to initiation on DOR-based treatment for those previously exposed to efavirenz or nevirapine.

Background: Liver disease is the leading cause of non-AIDS-related mortality in people living with HIV (PLWH). Steatotic liver disease (SLD) is increasingly recognised as an important aetiological factor in liver dysfunction in PLWH. Objectives: This study aimed to determine the post-mortem prevalence and severity of SLD and determine HIV- and non-HIV-related risk factors associated with it. Method: We conducted a retrospective cross-sectional study in which liver histology from 59 deceased people who were infected with HIV was assessed for steatosis, and findings correlated with clinical, epidemiological, and biochemical data. Results: Decedents were predominantly men (33/59); 63% (37/59) were virologically supressed. Median CD4+ T-cell count was 139 cells/µL (interquartile range [IQR]: 47–344). Steatosis was present in 39% (23/59) of decedents: 74% mild, 9% moderate, and 17% severe steatosis. There were no cases of steatohepatitis, and one case with mild fibrosis. Factors associated with SLD were: CD4 T-lymphocyte count > 200 cells/µL (odds ratio [OR]: 3.69; 95% confidence interval [CI]: 1.19–11.44), female sex (OR: 8.5; 95% CI: 2.57–28.17), hypertension (OR: 6.5; 95% CI: 2.05–21.00), and being normal or overweight (OR: 6.75; 95% CI: 1.12–40.56). Virological suppression and duration of antiretroviral drug use were not associated with steatosis. Conclusion: We found a high proportion of SLD with heterogeneous causes in deceased people who were infected with HIV, exceeding previously reported prevalences from elsewhere in Africa. A preserved CD4 count and being female conferred the highest risk for steatosis, underscoring the need for screening in this subgroup and further research to delineate risks in a Southern African population.