Difficulties in classifying a/g recombinants: methodological problems or genetic variability?

Thirty pol gene plasma-derived sequences clustering with the circulating recombinant form (CRF) 02_AG (IbNG) (bootstrap 100%) were evaluated to analyze the genomic composition. Subtype assignment was also phylogenetically confirmed by C2–V3 region analysis for 18/21 sequences evaluated. Thereafter, we compared the genomic recombination of the CRF02_AG/IbNG prototype as predicted by bootscanning and Jumping HMMER software (jpHMM) to that of our strains. With these methods, 27% and 50%, respectively, of our clinical sequences demonstrated the same pol structure as the prototype CRF02_A/G-IbNG. However, in subtrees built for each segment predicted by jpHMM (with a bootstrap value of more than 75%), all fragments clustered with IbNG and were distinct from A and G clades. Overall, our sequences resulted in true members of CRF02_AG–IbNG, which, however, appeared to be a subtype phylogenetically separate from A or G, at least with regard to the pol gene.