{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,20]],"date-time":"2026-05-20T10:07:27Z","timestamp":1779271647749,"version":"3.51.4"},"reference-count":38,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2026,5,12]],"date-time":"2026-05-12T00:00:00Z","timestamp":1778544000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Viruses"],"abstract":"<jats:p>The international spread of HIV-1 sub-subtype A6 raises concerns due to its association with contraindications for long-acting injectable formulations of cabotegravir (LA-CAB) and rilpivirine (LA-RPV). This study investigated its increasing proportion in Belgium, assessing transmission dynamics and potential migration links. Additionally, genotypic drug resistance in the Belgian HIV-1 sub-subtype A6 population were analyzed and four automatic subtyping tools were compared. A dataset of 4764 HIV-1 protease and reverse transcriptase (RT) sequences from newly diagnosed, treatment-na\u00efve individuals in Belgium (2013\u20132022) was analyzed. A combination of phylogenetic analysis and online subtyping tools identified 136 sub-subtype A6 sequences. The increase in the proportion of HIV-1 sub-subtype A6 observed in Belgium since 2020 reflects changing transmission patterns, especially among Belgium-born men having sex with men, and cannot be solely linked to the recent influx of Ukrainian migrants. Of these sub-subtype A6 sequences, less than 10% showed LA-CAB + LA-RPV resistance, mainly due to E138A within RT. HIVdb and ANRS reliably assessed resistance in this therapy-na\u00efve cohort, and HIVdb, COMET, and SmartGene\u00ae produced concordant subtyping results. While algorithm choice has little impact at low resistance prevalence, further research is necessary and HIVdb and ANRS remain more suitable for ongoing clinical and research use.<\/jats:p>","DOI":"10.3390\/v18050554","type":"journal-article","created":{"date-parts":[[2026,5,19]],"date-time":"2026-05-19T16:07:26Z","timestamp":1779206846000},"page":"554","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Emerging Trends in HIV-1 Sub-Subtype A6 in Belgium: Transmission Dynamics, Drug Resistance, and Subtyping Tool Evaluation"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9376-8910","authenticated-orcid":false,"given":"Virginie","family":"Mortier","sequence":"first","affiliation":[{"name":"AIDS Reference Laboratory, Department of Diagnostic Sciences, Ghent University, 9000 Ghent, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Laurent","family":"Debaisieux","sequence":"additional","affiliation":[{"name":"AIDS Reference Laboratory, Universit\u00e9 Libre de Bruxelles (ULB), H\u00f4pital Universitaire de Bruxelles (H.U.B), CUB H\u00f4pital Erasme, 1070 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Deborah","family":"De Geyter","sequence":"additional","affiliation":[{"name":"AIDS Reference Laboratory, Vrije Universiteit Brussel VUB, 1090 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Marie-Luce","family":"Delforge","sequence":"additional","affiliation":[{"name":"AIDS Reference Laboratory, Universit\u00e9 Libre de Bruxelles (ULB), H\u00f4pital Universitaire de Bruxelles (H.U.B), CUB H\u00f4pital Erasme, 1070 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Melissa","family":"Depypere","sequence":"additional","affiliation":[{"name":"Department of Microbiology, Immunology and Transplantation, KU Leuven, 3000 Leuven, Belgium"},{"name":"AIDS Reference Laboratory, University Hospitals Leuven, 3000 Leuven, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8598-3226","authenticated-orcid":false,"given":"G\u00e9raldine","family":"Dessilly","sequence":"additional","affiliation":[{"name":"AIDS Reference Laboratory, Medical Microbiology Unit, Universit\u00e9 Catholique de Louvain, 1200 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Beno\u00eet","family":"Kabamba-Mukadi","sequence":"additional","affiliation":[{"name":"AIDS Reference Laboratory, Medical Microbiology Unit, Universit\u00e9 Catholique de Louvain, 1200 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0009-3317-377X","authenticated-orcid":false,"given":"Khalid","family":"El Moussaoui","sequence":"additional","affiliation":[{"name":"AIDS Reference Laboratory, University Hospital of Liege, 4000 Liege, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Samy","family":"Mzougui","sequence":"additional","affiliation":[{"name":"AIDS Reference Laboratory, University Hospital of Liege, 4000 Liege, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ben","family":"Serrien","sequence":"additional","affiliation":[{"name":"Department of Epidemiology and Public Health, Sciensano, 1050 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0738-6343","authenticated-orcid":false,"given":"Karolien","family":"Stoffels","sequence":"additional","affiliation":[{"name":"AIDS Reference Laboratory, Centre Hospitalier Universitaire St. Pierre, 1000 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0821-2756","authenticated-orcid":false,"given":"Dominique","family":"Van Beckhoven","sequence":"additional","affiliation":[{"name":"Department of Epidemiology and Public Health, Sciensano, 1050 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ellen","family":"Van Cutsem","sequence":"additional","affiliation":[{"name":"AIDS Reference Laboratory, Vrije Universiteit Brussel VUB, 1090 Brussels, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7545-4360","authenticated-orcid":false,"given":"Dorien","family":"Van den Bossche","sequence":"additional","affiliation":[{"name":"AIDS Reference Laboratory, Department of Clinical Sciences, Institute of Tropical Medicine, 2000 Antwerp, Belgium"},{"name":"Clinical Reference Laboratory, Department of Clinical 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