Comparison of G-to-A mutation frequencies induced by APOBEC3 proteins in H9 cells and peripheral blood mononuclear cells in the context of impaired processivities of drug-resistant HIV-1 reverse transcriptase variants

University of Erlangen-Nuremberg, Institute of Clinical and Molecular Virology, Erlangen, Germany; and NEPRC, Harvard Medical School, Boston, Massachusetts, USA

^* To whom correspondence should be addressed. Email: Karin.metzner{at}viro.med.uni-erlangen.de.

	Abstract

APOBEC3 proteins can inhibit HIV-1 replication by inducing G-to-A mutations in newly synthesized viral DNA. However, HIV-1 is able to overcome the antiretroviral activity of some of those enzymes by the viral protein Vif. We investigated the impact of different processivities of HIV-1 reverse transcriptases (RT) on the frequencies of G-to-A mutations introduced by APOBEC3 proteins. Wild-type RT or the M184V-, M184I- and K65R/M184V- RT-variants, which are increasingly impaired in their processivities, were used in the context of a vif-deficient molecular HIV-1 clone to infect H9 cells and peripheral blood mononuclear cells (PBMCs). After two rounds of infection, a part of the HIV-1 env gene was amplified, cloned, and sequenced. The M184V mutation led to similar G-to-A mutation frequencies compared to the wild-type RT in H9 cells and PBMCs. The frequencies of G-to-A mutations were increased after infection with the M184I virus variant. This effect was augmented using the K65R+M184V virus variant (p<0.001). Overall, the G-to-A mutation frequencies were lower in PBMCs compared to H9 cells. Remarkably, 38±18% of the env clones derived from PBMCs did not harbor any G-to-A mutation. This was rarely observed in H9 cells (3±3%). Our data imply that the frequency of G-to-A mutations induced by APOBEC3 proteins can be influenced by the processivities of HIV-1 RT-variants. The high number of non-mutated clones derived from PBMCs leads to several hypotheses including that additional antiretroviral mechanisms of APOBEC3 proteins other than their deamination activity might be involved in the inhibition of vif-deficient viruses.