A modular system to evaluate the efficacy of protease inhibitors against HIV-2

Antiretroviral Treatment of HIV-2 Infection: Available Drugs, Resistance Pathways, and Promising New Compounds

Currently, it is estimated that 1-2 million people worldwide are infected with HIV-2, accounting for 3-5% of the global burden of HIV. The course of HIV-2 infection is longer compared to HIV-1 infection, but without effective antiretroviral therapy (ART), a substantial proportion of infected patients will progress to AIDS and die. Antiretroviral drugs in clinical use were designed for HIV-1 and, unfortunately, some do not work as well, or do not work at all, for HIV-2. This is the case for non-nucleoside reverse transcriptase inhibitors (NNRTIs), the fusion inhibitor enfuvirtide (T-20), most protease inhibitors (PIs), the attachment inhibitor fostemsavir and most broadly neutralizing antibodies. Integrase inhibitors work well against HIV-2 and are included in first-line therapeutic regimens for HIV-2-infected patients. However, rapid emergence of drug resistance and cross-resistance within each drug class dramatically reduces second-line treatment options. New drugs are needed to treat infection with drug-resistant isolates. Here, we review the therapeutic armamentarium available to treat HIV-2-infected patients, as well as promising drugs in development. We also review HIV-2 drug resistance mutations and resistance pathways that develop in HIV-2-infected patients under treatment.

Cellular Proteo-Transcriptomic Changes in the Immediate Early-Phase of Lentiviral Transduction

Lentivirus-based vectors derived from human immunodeficiency viruses type 1 and 2 (HIV-1 and 2) are widely used tools in research and may also be utilized in clinical settings. Like their parental virions, they are known to depend on the cellular machinery for successful gene delivery and integration. While most of the studies on cellular proteomic and transcriptomic changes have focused on the late phase of the transduction, studies of those changes in early time-points, especially in the case of HIV-2 based vectors, are widely lacking. Using second generation HIV-1 and 2 vesicular stomatitis virus G protein (VSV-G) pseudotyped lentiviral vectors, we transduced HEK-293T human embryonic kidney cells and carried out transcriptomic profiling at 0 and 2 h time points, with accompanying proteomic analysis at 2 h following transduction. Significant variations were observed in gene expression profile between HIV-1 and HIV-2 transduced samples. Thrombospondin 1 (THBS1), collagens (COL1A2, COL3A1), and eukaryotic translation factors (EIF3CL) in addition to various genes coding for long non-coding RNA (lncRNA) were significantly upregulated 2 h after HIV-2 transduction compared to HIV-1. Label-free quantification mass spectrometry (MS) indicated that seven proteins involved in RNA binding, mRNA transport, and chaperoning were significantly downregulated. The identification of cellular protein targets of lentiviral vectors and their effect on the cellular transcriptome will undoubtedly shed more light on their complex life cycle and may be utilized against infection by their parental lentiviruses. Furthermore, characterizing the early phase of HIV-2 infection may aid in the understanding of its pathomechanism and long incubation period.

Y44A Mutation in the Acidic Domain of HIV-2 Tat Impairs Viral Reverse Transcription and LTR-Transactivation

HIV transactivator protein (Tat) plays a pivotal role in viral replication through modulation of cellular transcription factors and transactivation of viral genomic transcription. The effect of HIV-1 Tat on reverse transcription has long been described in the literature, however, that of HIV-2 is understudied. Sequence homology between Tat proteins of HIV-1 and 2 is estimated to be less than 30%, and the main difference lies within their N-terminal region. Here, we describe Y44A-inactivating mutation of HIV-2 Tat, studying its effect on capsid production, reverse transcription, and the efficiency of proviral transcription. Investigation of the mutation was performed using sequence- and structure-based in silico analysis and in vitro experiments. Our results indicate that the Y44A mutant HIV-2 Tat inhibited the activity and expression of RT (reverse transcriptase), in addition to diminishing Tat-dependent LTR (long terminal repeat) transactivation. These findings highlight the functional importance of the acidic domain of HIV-2 Tat in the regulation of reverse transcription and transactivation of the integrated provirions.

Inhibitory Effects of HIV-2 Vpx on Replication of HIV-1

Human immunodeficiency virus type 1 (HIV-1) and HIV-2 share a striking genomic resemblance; however, variability in the genetic sequence accounts for the presence of unique accessory genes, such as the viral protein X (vpx) gene in HIV-2. Dual infection with both viruses has long been described in the literature, yet the molecular mechanism of how dually infected patients tend to do better than those who are monoinfected with HIV-1 has not yet been explored. We hypothesized that in addition to extracellular mechanisms, an HIV-2 accessory gene is the culprit, and interference at the viral accessory/regulatory protein level is perhaps responsible for the attenuated pathogenicity of HIV-1 observed in dually infected patients. Following simulation of dual infection in cell culture experiments, we found that pretransduction of cells with HIV-2 significantly protects against HIV-1 transduction. Importantly, we have found that this dampening of the infectivity of HIV-1 was a result of interviral interference carried out by viral protein X of HIV-2, resulting in a severe hindrance to the replication dynamics of HIV-1, influencing both its early and late phases of the viral life cycle. Our findings shed light on potential intracellular interactions between the two viruses and broaden our understanding of the observed clinical spectrum in dually infected patients, highlighting HIV-2 Vpx as a potential candidate worth exploring in the fight against HIV-1.IMPORTANCE Dual infection with human immunodeficiency virus types 1 and 2 is relatively common in areas of endemicity. For as-yet-unclarified reasons, patients who are dually infected were shown to have lower viral loads and generally a lower rate of progression to AIDS than those who are monoinfected. We aimed to explore dual infection in cell culture, to elucidate possible mechanisms by which HIV-2 may be able to exert such an effect. Our results indicate that on the cellular level, pretransduction of cells with HIV-2 significantly protects against HIV-1 transduction, which was found to be a result of interviral interference carried out by viral protein X of HIV-2. These findings broaden our knowledge of interviral interactions on the cellular level and may provide an explanation for the decreased pathogenicity of HIV-1 in dually infected patients, highlighting HIV-2 Vpx as a potential candidate worth exploring in the fight against HIV.

Inhibition Profiling of Retroviral Protease Inhibitors Using an HIV-2 Modular System

Retroviral protease inhibitors (PIs) are fundamental pillars in the treatment of HIV infection and acquired immunodeficiency syndrome (AIDS). Currently used PIs are designed against HIV-1, and their effect on HIV-2 is understudied. Using a modular HIV-2 protease cassette system, inhibition profiling assays were carried out for protease inhibitors both in enzymatic and cell culture assays. Moreover, the treatment-associated resistance mutations (I54M, L90M) were introduced into the modular system, and comparative inhibition assays were performed to determine their effect on the susceptibility of the protease. Our results indicate that darunavir, saquinavir, indinavir and lopinavir were very effective HIV-2 protease inhibitors, while tipranavir, nelfinavir and amprenavir showed a decreased efficacy. I54M, L90M double mutation resulted in a significant reduction in the susceptibility to most of the inhibitors with the exception of tipranavir. To our knowledge, this modular system constitutes a novel approach in the field of HIV-2 protease characterization and susceptibility testing.