Conference 2021 Live Talk
Elucidating mechanisms by which mutations in Env contribute to broad, multi-class HIV-1 drug resistance
Authors and Affiliations
Rachel Van Duyne1, Phuong Pham1, Jon Spindler2, Mary Kearney2, Eric O. Freed1
1. Virus-Cell Interaction Section, HIV Dynamics and Replication Program, NCI-Frederick, Frederick, MD
2. Translational Research Unit, HIV Dynamics and Replication Program, NCI-Frederick, Frederick, MD
We have previously characterized mutations within the HIV-1 envelope (Env) glycoprotein that arise in response to defective viruses which confer a broad replication advantage. In the presence of an antiretroviral (ARV) inhibitor, Dolutegravir (DTG), we also identified escape mutants containing substitutions in Env, instead of within the target gene. The goal of this study was to determine the breadth of this observation by characterizing Env mutations selected in the presence of all classes of ARVs and exploring the mechanism of escape by these mutant Env glycoproteins.
We propagated HIV-1 in T-cell lines and measured virus replication kinetics in the presence or absence of low concentrations of ARVs, testing at least one compound per class of inhibitor. We selected for viral escape mutants exhibiting at least partial resistance to ARVs as indicated by efficient replication in the presence of the inhibitors.
Long-term passage of wild-type (WT) virus in the presence of ARVs led to the selection of ARV-escape mutants greatly lacking changes in the target gene, but instead containing substitutions in Env. We have now identified a panel of Env mutants which arose in the presence of protease, RT, and integrase inhibitors in two different T-cell lines and two different viral subtypes. Nearly all of the ARV-resistant Env mutants exhibit at least partial resistance, which raises the possibility that acquisition of these mutations represents a stepping stone towards developing HIV-1 drug resistance in the target gene. In support of this, replication of an ARV-resistant mutant at high concentrations of inhibitor forced selection of additional Env mutations. One of the de novo selected DTG-resistant Env mutants, A539V, also exhibits markedly reduced sensitivity to at least two other classes of ARVs at drug concentrations that block or delay WT virus replication. Using a GFP-expressing virus, we observed a higher percentage and a brighter population of GFP+ cells with the A539V virus compared to WT suggesting the Env mutants bypass inhibition by increasing the MOI. We are currently measuring the number of proviruses present per infected cell in the presence and absence of DTG.
These results provide insights into escape from ARVs and demonstrate that mutations in Env can contribute to HIV drug resistance in vitro. We are currently investigating the implications of these findings for HIV drug resistance in patients.