SC-28 Evaluation of HIV-1 drug resistance in newly diagnosed individuals in Italy according to subtype over the period 2017–2023

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Background HIV drug resistance (DR) in newly diagnosed individuals is still a critical aspect for the management of individuals living with HIV-1. Thus, its evaluation is crucial to optimize HIV care. An increase of HIV-1 non-B diagnoses has been observed in Italy from 2005. According to these considerations we aimed at evaluating the prevalence of DR from 2017 to 2023 according to subtype. Materials and Methods 1,188 genotypic resistance tests (GRT) obtained from naive people with HIV (PWH) between 2017 and 2023 and collected in the ARCA database were analyzed. All the mutations (such as major, accessory, and other polymorphic) reported in the Stanford database algorithm (version 9.5.1) for the evaluation of the genotypic susceptibility score (GSS) have been considered for the analysis. Potential differences in the prevalence of DR were evaluated by Chi-squared test for trend. Maximum likelihood approach implemented in MEGA11 and IqTree programs was used to assign the subtype and define transmission clusters (TCs, containing at least 3 sequences). Results Most individuals were males (74.9%), with a median age of 40 (interquartile range IQR: 30–50) and Italian (table 1). HIV-1 B subtypes accounted for 56.1% of the overall population (table 1), and significantly decreased over time (58.2% in 2017–2019 vs 51.4% in 2020–2023; p=0.029). The most prevalent non-B subtypes were CRF02_AG (10.7%), F (6.7%), A (6.6%), C (3.5%). Phylogeny showed a presence of 95 TCs involving 740 PLWH (76.3% of analyzed strains); 23/95 (24.2%) were considered large TCs involving at least 10 individuals. A similar proportion of strains collected in the 2017–2019 and 2020–2023 were observed in TCs (76.4%, 528/691 and 76.0%, 212/279, respectively). DR to any drug class was 29.0% and showed a stable trend over time (figure 1A). A similar trend was observed by considering HIV-1 B and non-B subtypes (figure 1B & 1C). DR was mainly due to the presence of NNRTI mutations. A deeper analysis focused on major NNRTI-DR mutations (11.8%) showed a stable trend (p= 0.702) (table 2). When we considered all mutations, we observed a stable trend during the 7 years for the other classes (INSTI-DR: 5.1%; NRTI-DR: 4.7%; PI-DR: 4.4%). The sub-analysis that considered just major mutations showed an overall prevalence of 15.8% (major INSTI-DR: 0.7%; major NRTI-DR: 4.6%; major PI-DR 1.7%) (table 2). Conclusions The prevalence of DR in newly diagnosed individuals in Italy remains stable over the period 2017–2023 overall and in PWH carrying B or non-B subtypes. DR was higher than that observed in recent studies, which generally included just surveillance mutations. Future analysis will need to focus on the DR prevalence in non-B subtypes, which are characterized by a solid increasing trend in recent years, and on TCs regardless of subtype.

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