Capacitation induces changes in metabolic pathways supporting motility of epididymal and ejaculated sperm.

Mammalian sperm require sufficient energy to support motility and capacitation for successful fertilization. Previous studies cataloging the changes to metabolism in sperm explored ejaculated human sperm or dormant mouse sperm surgically extracted from the cauda epididymis. Due to the differences in methods of collection, it remains unclear whether any observed differences between mouse and human sperm represent species differences or reflect the distinct maturation states of the sperm under study. Here we compare the metabolic changes during capacitation of epididymal versus ejaculated mouse sperm and relate these changes to ejaculated human sperm. Using extracellular flux analysis and targeted metabolic profiling, we show that capacitation-induced changes lead to increased flux through both glycolysis and oxidative phosphorylation in mouse and human sperm. Ejaculation leads to greater flexibility in the ability to use different carbon sources. While epididymal sperm are dependent upon glucose, ejaculated mouse and human sperm gain the ability to also leverage non-glycolytic energy sources such as pyruvate and citrate.

Corrigendum: Assessing potency and binding kinetics of soluble adenylyl cyclase (sAC) inhibitors to maximize therapeutic potential.

[This corrects the article DOI: 10.3389/fphys.2022.1013845.].

On-demand male contraception via acute inhibition of soluble adenylyl cyclase.

Nearly half of all pregnancies are unintended; thus, existing family planning options are inadequate. For men, the only choices are condoms and vasectomy, and most current efforts to develop new contraceptives for men impact sperm development, meaning that contraception requires months of continuous pretreatment. Here, we provide proof-of-concept for an innovative strategy for on-demand contraception, where a man would take a birth control pill shortly before sex, only as needed. Soluble adenylyl cyclase (sAC) is essential for sperm motility and maturation. We show a single dose of a safe, acutely-acting sAC inhibitor with long residence time renders male mice temporarily infertile. Mice exhibit normal mating behavior, and full fertility returns the next day. These studies define sAC inhibitors as leads for on-demand contraceptives for men, and they provide in vivo proof-of-concept for previously untested paradigms in contraception; on-demand contraception after just a single dose and pharmacological contraception for men.

Design, Synthesis, and Pharmacological Evaluation of Second-Generation Soluble Adenylyl Cyclase (sAC, ADCY10) Inhibitors with Slow Dissociation Rates.

Soluble adenylyl cyclase (sAC: ADCY10) is an enzyme involved in intracellular signaling. Inhibition of sAC has potential therapeutic utility in a number of areas. For example, sAC is integral to successful male fertility: sAC activation is required for sperm motility and ability to undergo the acrosome reaction, two processes central to oocyte fertilization. Pharmacologic evaluation of existing sAC inhibitors for utility as on-demand, nonhormonal male contraceptives suggested that both high intrinsic potency, fast on and slow dissociation rates are essential design elements for successful male contraceptive applications. During the course of the medicinal chemistry campaign described here, we identified sAC inhibitors that fulfill these criteria and are suitable for in vivo evaluation of diverse sAC pharmacology.

Assessing potency and binding kinetics of soluble adenylyl cyclase (sAC) inhibitors to maximize therapeutic potential.

In mammalian cells, 10 different adenylyl cyclases produce the ubiquitous second messenger, cyclic adenosine monophosphate (cAMP). Amongst these cAMP-generating enzymes, bicarbonate (HCO3 -)-regulated soluble adenylyl cyclase (sAC; ADCY10) is uniquely essential in sperm for reproduction. For this reason, sAC has been proposed as a potential therapeutic target for non-hormonal contraceptives for men. Here, we describe key sAC-focused in vitro assays to identify and characterize sAC inhibitors for therapeutic use. The affinity and binding kinetics of an inhibitor can greatly influence in vivo efficacy, therefore, we developed improved assays for assessing these efficacy defining features.

Soluble adenylyl cyclase inhibition prevents human sperm functions essential for fertilization.

Soluble adenylyl cyclase (sAC: ADCY10) has been genetically confirmed to be essential for male fertility in mice and humans. In mice, ex vivo studies of dormant, caudal epididymal sperm demonstrated that sAC is required for initiating capacitation and activating motility. We now use an improved sAC inhibitor, TDI-10229, for a comprehensive analysis of sAC function in mouse and human sperm. In contrast to caudal epididymal mouse sperm, human sperm are collected post-ejaculation, after sAC activity has already been stimulated. In addition to preventing the capacitation-induced stimulation of sAC and protein kinase A activities, tyrosine phosphorylation, alkalinization, beat frequency and acrosome reaction in dormant mouse sperm, sAC inhibitors interrupt each of these capacitation-induced changes in ejaculated human sperm. Furthermore, we show for the first time that sAC is required during acrosomal exocytosis in mouse and human sperm. These data define sAC inhibitors as candidates for non-hormonal, on-demand contraceptives suitable for delivery via intravaginal devices in women.

Evolutionary Pathways to Persistence of Highly Fit and Resistant Hepatitis C Virus Protease Inhibitor Escape Variants.

Protease inhibitors (PIs) are important components of treatment regimens for patients with chronic hepatitis C virus (HCV) infection. However, emergence and persistence of antiviral resistance could reduce their efficacy. Thus, defining resistance determinants is highly relevant for efforts to control HCV. Here, we investigated patterns of PI resistance-associated substitutions (RASs) for the major HCV genotypes and viral determinants for persistence of key RASs. We identified protease position 156 as a RAS hotspot for genotype 1-4, but not 5 and 6, escape variants by resistance profiling using PIs grazoprevir and paritaprevir in infectious cell culture systems. However, except for genotype 3, engineered 156-RASs were not maintained. For genotypes 1 and 2, persistence of 156-RASs depended on genome-wide substitution networks, co-selected under continued PI treatment and identified by next-generation sequencing with substitution linkage and haplotype reconstruction. Persistence of A156T for genotype 1 relied on compensatory substitutions increasing replication and assembly. For genotype 2, initial selection of A156V facilitated transition to 156L, persisting without compensatory substitutions. The developed genotype 1, 2, and 3 variants with persistent 156-RASs had exceptionally high fitness and resistance to grazoprevir, paritaprevir, glecaprevir, and voxilaprevir. A156T dominated in genotype 1 glecaprevir and voxilaprevir escape variants, and pre-existing A156T facilitated genotype 1 escape from clinically relevant combination treatments with grazoprevir/elbasvir and glecaprevir/pibrentasvir. In genotype 1 infected patients with treatment failure and 156-RASs, we observed genome-wide selection of substitutions under treatment. Conclusion: Comprehensive PI resistance profiling for HCV genotypes 1-6 revealed 156-RASs as key determinants of high-level resistance across clinically relevant PIs. We obtained in vitro proof of concept for persistence of highly fit genotype 1-3 156-variants, which might pose a threat to clinically relevant combination treatments.

HCV genotype 1-6 NS3 residue 80 substitutions impact protease inhibitor activity and promote viral escape.

BACKGROUND & AIMS: Protease inhibitors (PIs) are of central importance in the treatment of patients with chronic hepatitis C virus (HCV) infection. HCV NS3 protease (NS3P) position 80 displays polymorphisms associated with resistance to the PI simeprevir for HCV genotype 1a. We investigated the effects of position-80-substitutions on fitness and PI-resistance for HCV genotypes 1-6, and analyzed evolutionary mechanisms underlying viral escape mediated by pre-existing Q80K. METHODS: The fitness of infectious NS3P recombinants of HCV genotypes 1-6, with engineered position-80-substitutions, was studied by comparison of viral spread kinetics in Huh-7.5 cells in culture. Median effective concentration (EC50) and fold resistance for PIs simeprevir, asunaprevir, paritaprevir, grazoprevir, glecaprevir and voxilaprevir were determined in short-term treatment assays. Viral escape was studied by long-term treatment of genotype 1a recombinants with simeprevir, grazoprevir, glecaprevir and voxilaprevir and of genotype 3a recombinants with glecaprevir and voxilaprevir, next generation sequencing, NS3P substitution linkage and haplotype analysis. RESULTS: Among tested PIs, only glecaprevir and voxilaprevir showed pan-genotypic activity against the original genotype 1-6 culture viruses. Variants with position-80-substitutions were all viable, but fitness depended on the specific substitution and the HCV isolate. Q80K conferred resistance to simeprevir across genotypes but had only minor effects on the activity of the remaining PIs. For genotype 1a, pre-existing Q80K mediated accelerated escape from simeprevir, grazoprevir and to a lesser extent glecaprevir, but not voxilaprevir. For genotype 3a, Q80K mediated accelerated escape from glecaprevir and voxilaprevir. Escape was mediated by rapid and genotype-, PI- and PI-concentration-dependent co-selection of clinically relevant resistance associated substitutions. CONCLUSIONS: Position-80-substitutions had relatively low fitness cost and the potential to promote HCV escape from clinically relevant PIs in vitro, despite having a minor impact on results in classical short-term resistance assays. LAY SUMMARY: Among all clinically relevant hepatitis C virus protease inhibitors, voxilaprevir and glecaprevir showed the highest and most uniform activity against cell culture infectious hepatitis C virus with genotype 1-6 proteases. Naturally occurring amino acid changes at protease position 80 had low fitness cost and influenced sensitivity to simeprevir, but not to other protease inhibitors in short-term treatment assays. Nevertheless, the pre-existing change Q80K had the potential to promote viral escape from protease inhibitors during long-term treatment by rapid co-selection of additional resistance changes, detected by next generation sequencing.

Efficacy of NS5A Inhibitors Against Hepatitis C Virus Genotypes 1-7 and Escape Variants.

BACKGROUND & AIMS: Inhibitors of the hepatitis C virus (HCV) NS5A protein are a key component of effective treatment regimens, but the genetic heterogeneity of HCV has limited the efficacy of these agents and mutations lead to resistance. We directly compared the efficacy of all clinically relevant NS5A inhibitors against HCV genotype 1-7 prototype isolates and resistant escape variants, and investigated the effects of pre-existing resistance-associated substitutions (RAS) on HCV escape from treatment. METHODS: We measured the efficacy of different concentrations of daclatasvir, ledipasvir, ombitasvir, elbasvir, ruzasvir, velpatasvir, and pibrentasvir in cultured cells infected with HCV recombinants expressing genotype 1-7 NS5A proteins with or without RAS. We engineered HCV variants that included RAS identified in escape experiments, using recombinants with or without T/Y93H and daclatasvir, or that contained RAS previously reported from patients. RESULTS: NS5A inhibitors had varying levels of efficacy against original and resistant viruses. Only velpatasvir and pibrentasvir had uniform high activity against all HCV genotypes tested. RAS hotspots in NS5A were found at amino acids 28, 30, 31, and 93. Engineered escape variants had high levels of fitness. Pibrentasvir had the highest level of efficacy against variants; viruses with RAS at amino acids 28, 30, or 31 had no apparent resistance to pibrentasvir, and HCV with RAS at amino acid 93 had a low level of resistance to this drug. However, specific combinations of RAS and deletion of amino acid 32 led to significant resistance to pibrentasvir. For the remaining NS5A inhibitors tested, RAS at amino acids 28 and 93 led to high levels of resistance. Among these inhibitors, velpatasvir was more effective against variants with RAS at amino acid 30 and some variants with RAS at amino acid 31 than the other agents. Variants with the pre-existing RAS T/Y93H acquired additional NS5A changes during escape experiments, resulting in HCV variants with specific combinations of RAS, showing high fitness and high resistance. CONCLUSIONS: We performed a comprehensive comparison of the efficacy of the 7 clinically relevant inhibitors of HCV NS5A and identified variants associated with resistance to each agent. These findings could improve treatment of patients with HCV infection.

Hepatitis C Virus Genotype 1 to 6 Protease Inhibitor Escape Variants: In Vitro Selection, Fitness, and Resistance Patterns in the Context of the Infectious Viral Life Cycle.

Hepatitis C virus (HCV) NS3 protease inhibitors (PIs) are important components of novel HCV therapy regimens. Studies of PI resistance initially focused on genotype 1. Therefore, knowledge about the determinants of PI resistance for the highly prevalent genotypes 2 to 6 remains limited. Using Huh7.5 cell culture-infectious HCV recombinants with genotype 1 to 6 NS3 protease, we identified protease positions 54, 155, and 156 as hot spots for the selection of resistance substitutions under treatment with the first licensed PIs, telaprevir and boceprevir. Treatment of a genotype 2 isolate with the newer PIs vaniprevir, faldaprevir, simeprevir, grazoprevir, paritaprevir, and deldeprevir identified positions 156 and 168 as hot spots for resistance; the Y56H substitution emerged for three newer PIs. Substitution selection also depended on the specific recombinant. The substitutions identified conferred cross-resistance to several PIs; however, most substitutions selected under telaprevir or boceprevir treatment conferred less resistance to certain newer PIs. In a single-cycle production assay, across genotypes, PI treatment primarily decreased viral replication, which was rescued by PI resistance substitutions. The substitutions identified resulted in differential effects on viral fitness, depending on the original recombinant and the substitution. Across genotypes, fitness impairment induced by resistance substitutions was due primarily to decreased replication. Most combinations of substitutions that were identified increased resistance or fitness. Combinations of resistance substitutions with fitness-compensating substitutions either rescued replication or compensated for decreased replication by increasing assembly. This comprehensive study provides insight into the selection patterns and effects of PI resistance substitutions for HCV genotypes 1 to 6 in the context of the infectious viral life cycle, which is of interest for clinical and virological HCV research.

Adapted J6/JFH1-based Hepatitis C virus recombinants with genotype-specific NS4A show similar efficacies against lead protease inhibitors, alpha interferon, and a putative NS4A inhibitor.

To facilitate studies of hepatitis C virus (HCV) NS4A, we aimed at developing J6/JFH1-based recombinants with genotype 1- to 7-specific NS4A proteins. We developed efficient culture systems expressing NS4A proteins of genotypes (isolates) 1a (H77 and TN), 1b (J4), 2a (J6), 4a (ED43), 5a (SA13), 6a (HK6a), and 7a (QC69), with peak infectivity titers of ∼3.5 to 4.5 log10 focus-forming units per ml. Except for genotype 2a (J6), growth depended on adaptive mutations identified in long-term culture. Genotype 1a, 1b, and 4a recombinants were adapted by amino acid substitutions F772S (p7) and V1663A (NS4A), while 5a, 6a, and 7a recombinants required additional substitutions in the NS3 protease and/or NS4A. We demonstrated applicability of the developed recombinants for study of antivirals. Genotype 1 to 7 NS4A recombinants showed similar responses to the protease inhibitors telaprevir (VX-950), boceprevir (Sch503034), simeprevir (TMC435350), danoprevir (ITMN-191), and vaniprevir (MK-7009), to alpha interferon 2b, and to the putative NS4A inhibitor ACH-806. The efficacy of ACH-806 was lower than that of protease inhibitors and was not influenced by changes at amino acids 1042 and 1065 (in the NS3 protease), which have been suggested to mediate resistance to ACH-806 in replicons. Genotype 1a, 1b, and 2a recombinants showed viral spread under long-term treatment with ACH-806, without acquisition of resistance mutations in the NS3-NS4A region. Relatively high concentrations of ACH-806 inhibited viral assembly, but not replication, in a single-cycle production assay. The developed HCV culture systems will facilitate studies benefitting from expression of genotype-specific NS4A in a constant backbone in the context of the complete viral replication cycle, including functional studies and evaluations of the efficacy of antivirals.

Combination treatment with hepatitis C virus protease and NS5A inhibitors is effective against recombinant genotype 1a, 2a, and 3a viruses.

With the development of directly acting antivirals, hepatitis C virus (HCV) therapy entered a new era. However, rapid selection of resistance mutations necessitates combination therapy. To study combination therapy in infectious culture systems, we aimed at developing HCV semi-full-length (semi-FL) recombinants relying only on the JFH1 NS3 helicase, NS5B, and the 3' untranslated region. With identified adaptive mutations, semi-FL recombinants of genotypes(isolates) 1a(TN) and 3a(S52) produced supernatant infectivity titers of ~4 log(10) focus-forming units/ml in Huh7.5 cells. Genotype 1a(TN) adaptive mutations allowed generation of 1a(H77) semi-FL virus. Concentration-response profiles revealed the higher efficacy of the NS3 protease inhibitor asunaprevir (BMS-650032) and the NS5A inhibitor daclatasvir (BMS-790052) against 1a(TN and H77) than 3a(S52) viruses. Asunaprevir had intermediate efficacy against previously developed 2a recombinants J6/JFH1 and J6cc. Daclatasvir had intermediate efficacy against J6/JFH1, while low sensitivity was confirmed against J6cc. Using a cross-titration scheme, infected cultures were treated until viral escape or on-treatment virologic suppression occurred. Compared to single-drug treatment, combination treatment with relatively low concentrations of asunaprevir and daclatasvir suppressed infection with all five recombinants. Escaped viruses primarily had substitutions at amino acids in the NS3 protease and NS5A domain I reported to be genotype 1 resistance mutations. Inhibitors showed synergism at drug concentrations reported in vivo. In summary, semi-FL HCV recombinants, including the most advanced reported genotype 3a infectious culture system, permitted genotype-specific analysis of combination treatment in the context of the complete viral life cycle. Despite differential sensitivity to lead compound NS3 protease and NS5A inhibitors, genotype 1a, 2a, and 3a viruses were suppressed by combination treatment with relatively low concentrations.

Differential efficacy of protease inhibitors against HCV genotypes 2a, 3a, 5a, and 6a NS3/4A protease recombinant viruses.

BACKGROUND & AIMS: The hepatitis C virus (HCV) genotype influences efficacy of interferon (IFN)-based therapy. HCV protease inhibitors are being licensed for treatment of genotype 1 infection. Because there are limited or no data on efficacy against HCV genotypes 2-7, we aimed at developing recombinant infectious cell culture systems expressing genotype-specific nonstructural (NS) protein 3 protease (NS3P). METHODS: Viability of J6/JFH1-based recombinants with genotypes 1-7 NS3P/NS4A was evaluated in Huh7.5 human hepatoma cells. Adaptive mutations were identified in reverse genetic studies. Efficacy of lead compound linear protease inhibitors VX-950 (telaprevir) and SCH503034 (boceprevir) and macrocyclic inhibitors TMC435350, ITMN-191 (danoprevir), and MK-7009 (vaniprevir) was determined in high-throughput infection assays. RESULTS: For genotype(isolate) 2a(J6), 3a(S52), 5a(SA13), and 6a(HK6a), we developed culture systems producing supernatant infectivity titers of 3.5-4.0 log10 focus forming units/mL. Against 2a(J6), 5a(SA13), and 6a(HK6a), all inhibitors showed similar efficacy; macrocyclic inhibitors had ~10-fold greater potency than linear inhibitors. However, compared with 2a recombinant J6/JFH1, efficacy against 3a(S52) was 16- to 70-fold lower for macrocyclic inhibitors and 2- to 7-fold lower for linear inhibitors. Testing of additional genotype 2a and 3a isolates showed that these differences were genotype specific. The resistance of 3a isolates was similar to J6/JFH1 with engineered resistance mutations originally observed for genotype 1 patients. In contrast, we found similar efficacy of NS5A inhibitor BMS-790052 and interferon-alfa2. CONCLUSIONS: Novel HCV culture systems with genotype specific NS3P/NS4A revealed similar efficacy of protease inhibitors against genotypes 2a, 5a, and 6a and comparatively low but varying efficacy against genotype 3a isolates. These systems will facilitate genotype-specific studies of HCV protease inhibitors and of viral resistance.

Development and application of hepatitis C reporter viruses with genotype 1 to 7 core-nonstructural protein 2 (NS2) expressing fluorescent proteins or luciferase in modified JFH1 NS5A.

To facilitate genotype-specific high-throughput studies of hepatitis C virus (HCV), we have developed reporter viruses using JFH1-based recombinants expressing core-nonstructural protein 2 (NS2) of genotype 1 to 7 prototype isolates. We introduced enhanced green fluorescent protein (EGFP) into NS5A domain III of the genotype 2a virus J6/JFH1 [2a(J6)]. During Huh7.5 cell culture adaptation, 2a(J6)-EGFP acquired a 40-amino-acid (aa) (Δ40) or 25-aa (Δ25) deletion in NS5A domain II, rescuing the impairment of viral assembly caused by the EGFP insertion. Δ40 conferred efficient growth characteristics to 2a(J6) tagged with EGFP, DsRed-Express2, mCherry, or Renilla luciferase (RLuc), yielding peak supernatant infectivity titers of 4 to 5 log(10) focus-forming units (FFU)/ml. 2a(J6) with Δ40 or Δ25 was fully viable in Huh7.5 cells. In human liver chimeric mice, 2a(J6)-EGFPΔ40 acquired various deletions in EGFP, while 2a(J6)Δ40 did not show an impaired viability. We further developed panels of JFH1-based genotype 1 to 7 core-NS2 recombinants expressing EGFP- or RLuc-NS5AΔ40 fusion proteins. In cell culture, the different EGFP recombinants showed growth characteristics comparable to those of the nontagged recombinants, with peak infectivity titers of 4 to 5 log(10) FFU/ml. RLuc recombinants showed slightly less efficient growth characteristics, with peak infectivity titers up to 10-fold lower. Overall, the EGFP and RLuc recombinants were genetically stable after one viral passage. The usefulness of these reporter viruses for high-throughput fluorescence- and luminescence-based studies of HCV-receptor interactions and serum-neutralizing antibodies was demonstrated. Finally, using RLuc viruses, we showed that the genotype-specific core-NS2 sequence did not influence the response to alfa-2b interferon (IFN-alfa-2b) and that genotype 1 to 7 viruses all responded to treatment with p7 ion channel inhibitors.