Differential Sensitivities of Retroviruses to Integrase Strand Transfer Inhibitors

Abstract

Integrase inhibitors are emerging anti-human immunodeficiency virus (HIV) drugs, and multiple retroviruses and transposable elements were evaluated here for susceptibilities to raltegravir (RAL) and elvitegravir (EVG). All viruses, including primate and nonprimate lentiviruses, a Betaretrovirus, a Gammaretrovirus, and the Alpharetrovirus Rous sarcoma virus (RSV), were susceptible to inhibition by RAL. EVG potently inhibited all lentiviruses and intermediately inhibited Betaretrovirus and Gammaretrovirus infections yet was basically ineffective against RSV. Substitutions based on HIV type 1 (HIV-1) resistance changes revealed that integrase residue Ser150 contributed significantly to the resistance of RSV. The drugs intermediately inhibited intracisternal A-particle retrotransposition but were inactive against Sleeping Beauty transposition and long interspersed nucleotide element 1 (LINE-1) retrotransposition.Reverse transcription of retroviral RNA yields linear viral DNA (vDNA) containing a copy of the long terminal repeat (LTR) at each end. Integrase (IN) is an essential retroviral enzyme that catalyzes two reactions to insert the vDNA into cellular chromosomal DNA. IN prepares the LTR ends by hydrolyzing phosphodiester bonds adjacent to invariant CA dinucleotides, yielding reactive 3Ј deoxyadenylate (dA OH ) termini. In the nucleus, IN catalyzes DNA strand transfer by using the 3Ј OHs to cut the chromosome in a staggered fashion, concomitantly joining the vDNA ends to 5Ј phosphates. Hostmediated repair of the resulting DNA recombination intermediate completes the integration process. See reference 8 for an overview of retroviral reverse transcription and integration.IN belongs to the polynucleotidyl transferase superfamily of nucleic acid-metabolizing enzymes (7). Conserved amino acid residues (typically Asp and Glu [32]) arranged commonly on an RNase H structural fold comprise active sites that coordinate divalent metal ions for in-line nucleophilic attack of phosphodiester bonds. Due to its critical role in replication, human immunodeficiency virus type 1 (HIV-1) IN has long been targeted for drug development, and the first-in-class inhibitor raltegravir (RAL) was licensed in 2007 (45). Because RAL and related compounds preferentially inhibit DNA strand transfer activity, the drugs are referred to as IN strand transfer inhibitors (INSTIs) (24). Elvitegravir (EVG) is another well-studied INSTI (41). Recently determined X-ray crystal structures revealed that the drugs work by ejecting the 3Ј dA and its associated OH nucleophile from the IN active site (10,

ComprehensiveIn VitroAnalysis of Simian Retrovirus Type 4 Susceptibility to Antiretroviral Agents

“…We next evaluated the inhibitory effect of RAL, the first INSTI approved for clinical use, on SRV-4 infection. RAL has potent anti-HIV-1 activity in addition to a broad antiviral spectrum including simian immunodeficiency virus (SIV) (33), MLV (34), XMRV (11), and SRV-3 (19). We also observed that RAL inhibited HIV-1 and MoMLV infections (Table 1).…”

“…Reportedly, SRV-3 also contains amino acids corresponding to N155H and F121Y, which are other INSTI resistance mutations; however, SRV-3 shows complete susceptibility to RAL (19). In contrast, bovine immunodeficiency virus (BIV) reportedly showed 23-fold resistance to RAL compared to wild-type HIV-1, although BIV contains a histidine (H) residue at the position corresponding to N155 (19), as seen in SRV-4, indicating that N155H is not a determinant of RAL susceptibility in retroviruses other than HIV. Although in the present study, FIV showed less susceptibility to RAL than the other retroviruses/lentiviruses tested (Table 1), FIV does not contain major INSTI resistance mutations.…”

“…Rosenblum et al reported that anti-SRV-1 and anti-SRV-2 activities of several NRTIs were relatively comparable with anti-HIV-1 activity (18). Furthermore, elvitegravir (EVG) and raltegravir (RAL), which are HIV-1 integrase strand transfer inhibitors (INSTIs), efficiently block SRV-3 (also known as Mason-Pfizer monkey virus) infection at nanomolar concentrations (19). Thus, some NRTIs and INSTIs exhibit anti-SRV/D activity; however, whether these drugs are active against SRV-4 infection remains unclear.…”

Enhanced Autointegration in Hyperstable Simian Immunodeficiency Virus Capsid Mutants Blocked after Reverse Transcription

“…As a negative control, viruses were heat inactivated at 56°C for 1 h, and 100 M AZT was added to the target cells throughout the experiment. As an additional control, one subset of infected cells was treated with 1 M (10ϫ the reported 95% effective concentration [EC 95 ]) raltegravir, an active-site inhibitor of retroviral integrases (41,42). The infection levels achieved for the experimental and control assays are shown in Fig.…”

Retroviral Integrase Structure and DNA Recombination Mechanism

“…7, blue). INSTIs display generally broad-spectrum antiretroviral activity (56,205,206), and co-crystallization with the PFV CI accordingly revealed critical aspects of the mechanism of INSTI action (94,207,208). As predicted from prior solution-based measures (201), the co-planar oxygen atoms engage the divalent metal ions at the integrase active site.…”