Performance of Affinity-Improved DARPin Targeting HIV Capsid Domain in Interference of Viral Progeny Production

Previously, a designed ankyrin repeat protein, AnkGAG1D4, was generated for intracellular targeting of the HIV-1 capsid domain. The efficiency was satisfactory in interfering with the HIV assembly process. Consequently, improved AnkGAG1D4 binding affinity was introduced by substituting tyrosine (Y) for serine (S) at position 45. However, the intracellular anti-HIV-1 activity of AnkGAG1D4-S45Y has not yet been validated. In this study, the performance of AnkGAG1D4 and AnkGAG1D4-S45Y in inhibiting wild-type HIV-1 and HIV-1 maturation inhibitor-resistant replication in SupT1 cells was evaluated. HIV-1 p24 and viral load assays were used to verify the biological activity of AnkGAG1D4 and AnkGAG1D4-S45Y as assembly inhibitors. In addition, retardation of syncytium formation in infected SupT1 cells was observed. Of note, the defense mechanism of both ankyrins did not induce the mutation of target amino acids in the capsid domain. The present data show that the potency of AnkGAG1D4-S45Y was superior to AnkGAG1D4 in interrupting either HIV-1 wild-type or the HIV maturation inhibitor-resistant strain.

Derivation and characterization of an HIV-1 mutant that rescues IP6 binding deficiency

Background A critical step in the HIV-1 replication cycle is the assembly of Gag proteins to form virions at the plasma membrane. Virion assembly and maturation are facilitated by the cellular polyanion inositol hexaphosphate (IP6), which is proposed to stabilize both the immature Gag lattice and the mature capsid lattice by binding to rings of primary amines at the center of Gag or capsid protein (CA) hexamers. The amino acids comprising these rings are critical for proper virion formation and their substitution results in assembly deficits or impaired infectiousness. To better understand the nature of the deficits that accompany IP6 binding deficiency, we passaged HIV-1 mutants that had substitutions in IP6 coordinating residues to select for compensatory mutations. Results We found a mutation, a threonine to isoleucine substitution at position 371 (T371I) in Gag, that restored replication competence to an IP6-binding-deficient HIV-1 mutant. Notably, unlike wild-type HIV-1, the assembly and infectiousness of resulting virus was not impaired when IP6 biosynthetic enzymes were genetically ablated. Surprisingly, we also found that the maturation inhibitor Bevirimat (BVM) could restore the assembly and replication of an IP6-binding deficient mutant. Moreover, using BVM-dependent mutants we were able to image BVM-induced assembly of individual HIV-1 particles assembly in living cells. Conclusions Overall these results suggest that IP6-Gag and Gag-Gag contacts are finely tuned to generate a Gag lattice of optimal stability, and that under certain conditions BVM can rescue IP6 deficiency. Additionally, our work identifies an inducible virion assembly system that can be utilized to visualize HIV-1 assembly events using live cell microscopy.

A Phase I Evaluation of the Pharmacokinetics and Tolerability of the HIV-1 Maturation Inhibitor GSK3640254 and Tenofovir Alafenamide/Emtricitabine in Healthy Participants

Introduction: GSK3640254 is a next-generation maturation inhibitor that would likely be combined with standard antiretroviral agents to form a regimen of ≥2 fully active classes. Methods: This phase I, open-label, 2-period, 1-way study assessed potential pharmacokinetic (PK) interactions between GSK3640254 and tenofovir alafenamide/emtricitabine (TAF/FTC; including the metabolite tenofovir [TFV]) in healthy volunteers. Eligible participants received TAF/FTC 25/200 mg once daily (QD) on Days 1 through 21 with a moderate-fat meal; GSK3640254 200 mg QD was added on Days 15 through 21. Geometric least squares mean ratios (GMRs) and 90% CIs were derived using linear mixed-effect models. Adverse events (AEs) and laboratory, electrocardiogram, and vital sign parameters were monitored. Results: Sixteen participants, all male, received treatment; one withdrew because of treatment-related grade 1 urticaria. After TAF/FTC + GSK3640254 coadministration, TAF steady-state area under the plasma concentration-time curve from time 0 to the end of the dosing interval and maximum observed concentration were 11% and 13% lower than when TAF/FTC was administered alone, with GMR (90% CI) of 0.886 (0.75-1.04) and 0.874 (0.68-1.12), respectively. Steady-state PK of TFV and FTC was similar when TAF/FTC was administered alone or with GSK3640254. No clinically significant trends in tolerability or safety were observed. Conclusions: GSK3640254 200 mg QD did not meaningfully affect the steady-state PK of TAF, TFV, or FTC in healthy participants under fed conditions and was not associated with major tolerability or safety findings. These data support the further investigation of GSK3640254 for coadministration with TAF/FTC for the treatment of HIV (ClinicalTrials.gov, NCT03836729).

The Broad Role of Nkx3.2 in the Development of the Zebrafish Axial Skeleton

The transcription factor Nkx3.2 (Bapx1) is an important chondrocyte maturation inhibitor. Previous Nkx3.2 knock-down and overexpression studies in non-mammalian gnathostomes have focused on its role in primary jaw joint development, while little is known about the function of this gene in broader skeletal development. We generated CRISPR/Cas9 knockout of nkx3.2 in zebrafish and applied a range of techniques to characterize skeletal phenotypes at developmental stages from larva to adult, revealing fusions in bones of the occiput, the loss or deformation of bony elements derived from basiventral cartilages of the vertebrae, and an increased length of the proximal radials of the dorsal and anal fins. These phenotypes are reminiscent of Nkx3.2 knockout phenotypes in mammals, suggesting that the function of this gene in axial skeletal development is ancestral to osteichthyans. Our results highlight the broad role of nkx3.2 in zebrafish skeletal development and its context-specific functions in different skeletal elements.

QSAR-Based Design of The More Potent Betulinic Acid Derivatives as HIV Maturation Inhibitor

In this study, we make QSAR models from 29 of BA derivatives’ HIV maturation inhibition activities against their 3D descriptors. The best model involve 5 descriptors as follows: 1/log EC50 = -462.275 + (69.213 × TDB6u) + (723.745 × TDB6e) + (-0.576 × FPSA-3) + (0.849 × RDF140u) + (0.302 × RDF80e) r2 training = 0.7918; Q2 test = 0.9644; r2test = 0.9798; and r2m-test = 0.9445 TDB6u and TDB6e are the 3d topological distance-based autocorrelation-lag 6 /unweighted and weighted by Sanderson electronegati-vities, respectively. FPSA-3 is the value of charge weighted partial positive surface area / total molecular surface area. RDF140u is radial distribution function-140 / unweighted. RDF80e is radial distribution function-080/weighted by relative Sanderson electronegativities. The QSAR model was then used to design and predict some of the new BA derivatives’ HIV maturation activities. The best predicted compound had pEC50 value of -0.838 and EC50 value of 0.064 nM with the chemical IUPAC name of 4‐[(1R, 3aR, 5aR, 5bR, 7aS, 11aR, 11bS, 13aS,13bS)‐5a, 5b, 8, 8, 11b pentamethyl‐1‐(prop‐1‐en‐2‐yl)‐3a[({2‐[4‐(pyrimidin2yl)piperazin-1-yl]ethyl}amino) methyl]‐icosahydro‐1H-cyclopenta[a]chrysen‐9‐yl]benzoic acid. We also suggest the synthetic route to the proposed compound.