Characterization and frequency of a newly identified HIV-1 BF1 intersubtype circulating recombinant form in São Paulo, Brazil.
BACKGROUND
HIV circulating recombinant forms (CRFs) play an important role in the global and regional HIV epidemics, particularly in regions where multiple subtypes are circulating. To date, several (>40) CRFs are recognized worldwide with five currently circulating in Brazil. Here, we report the characterization of near full-length genome sequences (NFLG) of six phylogenetically related HIV-1 BF1 intersubtype recombinants (five from this study and one from other published sequences) representing CRF46_BF1.


METHODS
Initially, we selected 36 samples from 888 adult patients residing in São Paulo who had previously been diagnosed as being infected with subclade F1 based on pol subgenomic fragment sequencing. Proviral DNA integrated in peripheral blood mononuclear cells (PBMC) was amplified from the purified genomic DNA of all 36-blood samples by five overlapping PCR fragments followed by direct sequencing. Sequence data were obtained from the five fragments that showed identical genomic structure and phylogenetic trees were constructed and compared with previously published sequences. Genuine subclade F1 sequences and any other sequences that exhibited unique mosaic structures were omitted from further analysis


RESULTS
Of the 36 samples analyzed, only six sequences, inferred from the pol region as subclade F1, displayed BF1 identical mosaic genomes with a single intersubtype breakpoint identified at the nef-U3 overlap (HXB2 position 9347-9365; LTR region). Five of these isolates formed a rigid cluster in phylogentic trees from different subclade F1 fragment regions, which we can now designate as CRF46_BF1. According to our estimate, the new CRF accounts for 0.56% of the HIV-1 circulating strains in São Paulo. Comparison with previously published sequences revealed an additional five isolates that share an identical mosaic structure with those reported in our study. Despite sharing a similar recombinant structure, only one sequence appeared to originate from the same CRF46_BF1 ancestor.


CONCLUSIONS
We identified a new circulating recombinant form with a single intersubtype breakpoint identified at the nef-LTR U3 overlap and designated CRF46_BF1. Given the biological importance of the LTR U3 region, intersubtype recombination in this region could play an important role in HIV evolution with critical consequences for the development of efficient genetic vaccines.
Sanabani
Sabri Saeed
SS
Fundação Pro-Sangue, Hemocentro, São Paulo, Brazil. sabyem_63@yahoo.com
Pastena
Evelyn Regina de Souza
ER
Neto
Walter Kleine
WK
Martinez
Vanessa Pouza
VP
Sabino
Ester Cerdeira
EC
D000328:Adult; D001938:Brazil / Q000453:epidemiology; D016000:Cluster Analysis; D004279:DNA, Viral / Q000235:genetics*; D005260:Female; D016679:Genome, Viral; D005838:Genotype; D015658:HIV Infections / Q000453:epidemiology* / Q000821:virology*; D015497:HIV-1 / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D011533:Proviruses / Q000235:genetics*; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D054302:pol Gene Products, Human Immunodeficiency Virus
D004279:DNA, Viral; D054302:pol Gene Products, Human Immunodeficiency Virus
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