Background:  The nucleotide sequence of HIV-1 gp41 encodes, by RNA-splicing, for the II exon of Rev and contains the Rev responsive elements (RRE). This unique RNA element binds Rev and allows the transport of mRNA out of the nucleus (an essential step for HIV-1 life cycle). The goal of this study is to investigate whether fusion inhibitor T-20 can induce mutations in Rev, and correlate them with the classical T-20 resistance mutations in gp41 and with viro-immunological parameters.

Methods:  We analyzed 181 sequences of HIV-1 gp41 and clinical follow-up from 88 T-20-treated patients at baseline and monthly until week 48. The association of mutations with T-20 treatment was assessed by χ² test. Co-variation φanalysis was based on binomial correlation coefficient (φ) and hierarchical clustering. Association of mutations with viremia and CD4 cell count was assessed by Mann-Whitney test.

Results:  Specific mutations (E57A, L78I, N86S) in Rev are positively associated (p <0.05) with T-20 treatment (prevalence, 14.8%, 10.2%, 52.3%, respectively) and significantly correlate in pairs and in cluster with known T-20-resistance mutations in gp41. In particular, a strong cluster was observed for the Rev mutations E57A and N86S with the T-20-resistance mutations Q40H and L45M in gp41 (bootstrap = 0.78, p <0.05). Q40H and L45M derive from nucleotide substitutions, GAC to CAC, and CUG to AUG, respectively, that lie near with each other in RRE secondary structure in a key region involved in Rev binding. The presence at week 48 of the Rev mutation E57A (independently from the presence of gp41 mutations) correlates with an increase of viremia from BL to week 48 (+0.40 log/mL with vs –0.65 log/mL without E57A, p = 0.006), and with a loss of CD4 cell count from baseline to week 48 (–72 cell/µL with vs +41cell/µL without E57A, p = 0.04). In addition, the presence of the Rev N86S at baseline is the only mutations (in gp41 or Rev) predictive of the on treatment development of the T-20-resistance mutations Q40H+L45M (p = 0.01).  

Conclusions:  T-20 pressure can affect also Rev-RRE interactions. Mutations in Rev might drive the evolution of T-20 resistance. This highlights the importance of the correct interplay between the different HIV-1 genes and proteins during the HIV-1 life cycle, and the multiple role of T-20 (and perhaps other entry inhibitors) in modulating HIV replication and cytopathic effect by acting at different steps at both protein and RNA levels.