The Human Immunodeficiency Virus 1 (HIV-1) is characterized by high rates of genetic diversity, being classified into groups, subtypes and recombinant forms. To date, 14 Circulating Recombinant Forms (CRFs) of subtypes B and C have been identified, three of them in 2021: CRF108_BC in Spain, CRF110_BC and CRF118_BC in China. This study investigated the genetic diversity among circulating BC recombinant viruses. Near-Full Length Genomes (NFLG) of 225 BC strains were retrieved from the Los Alamos database. Recombination and phylogenetic analysis were conducted using bioinformatics tools. Sequences were obtained from 17 countries between 1992 and 2018. Fourteen CRFs and 82 distinct Unique Recombinant Forms (URFs) recombination patterns were identified. Preferential recombination points were found in pol (66.7%) and env (62.5%) genes, while subtype C is the predominant genetic form in gag, vif, vpr, tat, rev, tat2, rev2, nef and 3'-LTR genomic regions. Specific positions in pol and env genes maintain the B subtype, which may be related to the acquisition of adaptive advantage over subtype C.

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BACKGROUND The human immunodeficiency virus type 1, F1 sub-subtype (HIV-1 F1) circulates in three continents: Africa, Europe, and South America. In Brazil, this sub-subtype co-circulates with subtypes B and C and several recombinant forms, mainly BF1 variants. OBJECTIVES This study aimed to reconstruct the dynamic history of HIV-1 F1 in Brazil. METHODS HIV-1 near full-length genome and pol gene nucleotide sequences available in public databases were assembled in two datasets (POL671 and NFLG53) to cover the largest number of F1 sub-subtype sequences. Phylodynamic and temporal analyses were performed. FINDINGS Two main strains of the F1 sub-subtype are circulating worldwide. The first (F1.I) was found among Brazilian samples (75%) and the second (F1.II) among Romanian (62%) and other European and African isolates. The F1 subtype epidemic in Brazil originated from a single entry into the country around 1970. This ancestral sample is related to samples isolated in European countries (France, Finland, and Belgium), which are possibly of African origin. Moreover, further migration (1998 CI: 1994-2003) of strains from Brazil to Europe (Spain and the UK) was observed. Interestingly, all different recombinant BF patterns found, even those from outside Brazil, present the same F1 lineage (F1.I) as an ancestor, which could be related to the acquisition of adaptive advantages for the recombinant progenies. MAIN CONCLUSIONS These findings are important for the understanding of the origin and dynamics of the F1 sub-subtype and a consequent better and greater understanding of the HIV-1 F1 and BF epidemic that still spreads from Brazil to other countries.