Complementation can maintain a quasispecies of drug sensitive and resistant HIV

The goal of this study was to determine how an HIV quasispecies is maintained in the face of selection. We deep sequenced the HIV provirus from cell populations as well as single cells at different time points from in vitro evolution experiments and found that when a less fit and more fit infect the same cell, they share components (complmentation) and therefore allow the less fit to perpetuate. We reproduced a quasispecies to an HIV reverse transcriptase inhibitor. The drug resistant genotype never completely supplanted the drug sensitive genotype, which stabilized at about 20% of viral sequences. Single-cell sequencing showed that resistant genotype frequency plateaued when cells were co-infected with sensitive and resistant genotypes, suggesting a sharing of viral proteins in co-infected cells (complementation), masking genotypic differences. To test if complementation can confer phenotypic drug resistance, we co-transfected fluorescently labelled molecular clones of sensitive and resistant HIV and observed drug resistance in genotypically sensitive virus from co-transfected cells. Resistant virus preferentially co-infected cells with drug sensitive HIV, explaining initiation of co-infections. Modelling showed that a stable quasispecies could form at the experimental multiplicities of infection. Conclusions: Complementation can lead to a quasispecies in infection environments where multiple infections per cell are common Sequencing of Reverse transcriptase region of HIV proviral DNA from infected cell populations (3 independent experiments) as well as single cells (either 30 or 60 cells from each time point)