Holsey, J. | Search bioRxiv

bioRxiv2023

Rev-Rev Response Element Activity Selection Bias at the HIV Transmission Bottleneck

HIV is not efficiently transmitted between hosts, and selection of viral variants occurs during the process of sexual transmission. The factors that confer selective advantage at the transmission bottleneck remain incompletely understood. We explored whether differences in the Rev-Rev Response Element (RRE) regulatory axis of HIV affect transmission fitness, since functional variation in the Rev-RRE axis in different viral isolates has been shown to affect replication kinetics and relative expression of many HIV proteins. Single genome HIV sequences were identified from nine linked subject pairs near the time of female-to-male transmission. Using a rapid flow-cytometric assay, we found that the functional Rev-RRE activity varied significantly between isolates. Moreover, it was generally lower in recipients viruses compared to the corresponding donor viruses. In six of nine transmission events, recipient virus Rev-RRE activity clustered at the extreme low end of the range of donor virus activity. Rev-RRE pair activity was an unpredictable product of component Rev and RRE activity variation. These data indicate selection pressure on the Rev-RRE axis during female-to-male sexual transmission. Variation in the activity of the Rev-RRE axis may permit viral adaptation to different fitness landscapes and could play an important role in HIV pathogenesis.

microbiology↗

bioRxiv2022

HIV-1 Rev-RRE Functional Activity in Primary Isolates is Highly Dependent on Minimal Context-Dependent Changes in Rev

During HIV infection, intron-containing viral mRNAs have to be exported efficiently from the host cell nucleus to the cytoplasm in order to complete the replication cycle. To overcome cellular restrictions to export incompletely spliced transcripts, HIV encodes a protein, Rev, that is constitutively expressed from a completely spliced transcript. Rev is then imported into the nucleus where it binds to an RNA structure on intron-containing viral mRNAs called the Rev Response Element (RRE). Bound Rev multimerizes and recruits cellular factors that permit the nuclear export of the resulting ribonucleoprotein complex. Primary HIV isolates display substantial variation in the functional activity of the Rev-RRE axis, which may permit viral adaptation to differing immune environments. We describe two subtype G primary isolates with disparate Rev activity. Rev activity was correlated with in vitro fitness of replication-competent viral constructs. Amino acid differences within the oligomerziation domain, but not within the arginine-rich motif or nuclear export signal, determined the different levels of Rev activity. Two specific amino acid substitutions were demonstrated to be able to alter the low-activity Rev to a high-activity phenotype. However, introducing the original amino acids from the the low activity Rev into high activity Rev in this position did not result in significant alterations in activity, highlighting the importance of the broader sequence context for functional activity. These results demonstrate that studies of Rev and RRE activity variation, which may have broader implications for HIV transmission and pathogenesis, should include sequences from primary isolates, as findings using only laboratory-adapted strains cannot be generalized.

microbiology↗