Towards the design of combination therapy for the treatment of enterovirus infections

Enterovirus 71 (EV-A71) is a major causative pathogen of hand, foot, and mouth disease (HFMD) epidemics. No antiviral therapies are currently available for treating EV-A71 infections. Here, we selected five reported enterovirus inhibitors (suramin, itraconazole [ITZ], GW5074, rupintrivir, and favipiravir) with different mechanisms of action to test their abilities to inhibit EV-A71 replication alone and in combination. All selected compounds have anti-EV-A71 activities in cell culture. The combination of rupintrivir and ITZ or favipiravir was synergistic, while the combination of rupintrivir and suramin was additive. The combination of suramin and favipiravir exerted a strong synergistic antiviral effect. The observed synergy was not due to cytotoxicity, as there was no significant increase in cytotoxicity when compounds were used in combinations at the tested doses. To investigate the potential inhibitory mechanism of favipiravir against enterovirus, two favipiravir-resistant EV-A71 variants were independently selected, and both of them carried an S121N mutation in the finger subdomain of the 3D polymerase. Reverse engineering of this 3D S121N mutation into an infectious clone of EV-A71 confirmed the resistant phenotype. Moreover, viruses resistant to ITZ or favipiravir remained susceptible to other inhibitors. Most notably, combined with ITZ, rupintrivir prevented the development of ITZ-resistant variants. Taken together, these results provide a rational basis for the design of combination regimens for use in the treatment of EV-A71 infections.

Section: Discussionmentioning

confidence: 99%

In Vitro Assessment of Combinations of Enterovirus Inhibitors against Enterovirus 71

Wang

Yuan

et al. 2016

“…In one study, antiviral activity of pleconaril was reported in EV71-infected mice (20). Other studies, however, reported a lack of in vitro anti-EV71 activity of pleconaril (21)(22)(23). Moreover, inconsistent data on the potential efficacy of pleconaril in the treatment of enteroviral infections in humans have been reported (24)(25)(26).…”

mentioning

confidence: 93%

The Capsid Binder Vapendavir and the Novel Protease Inhibitor SG85 Inhibit Enterovirus 71 Replication

Tijsma

Franco

Tucker³

et al. 2014

Self Cite

c Antivirals against enterovirus 71 (EV71) are urgently needed. We demonstrate that the novel enteroviral protease inhibitor (PI) SG85 and capsid binder (CB) vapendavir efficiently inhibit the in vitro replication of 21 EV71 strains/isolates that are representative of the different genogroups A, B, and C. The PI rupintrivir, the CB pirodavir, and the host-targeting compound enviroxime, which were included as reference compounds, also inhibited the replication of all isolates. Remarkably, the CB compound pleconaril was devoid of any anti-EV71 activity. An in silico docking study revealed that pleconaril-unlike vapendavir and pirodavir-lacks essential binding interactions with the viral capsid. Vapendavir and SG85 (or analogues) should be further explored for the treatment of EV71 infections. The data presented here may serve as a reference when developing yet-novel inhibitors.

“…Data were analyzed with the MacSynergy II template at the 95% confidence level (22 (22)(23)(24). Infectious virus yield assay.…”

Section: Methodsmentioning

confidence: 99%

Ribavirin Inhibits In Vitro Hepatitis E Virus Replication through Depletion of Cellular GTP Pools and Is Moderately Synergistic with Alpha Interferon

Debing

Emerson

Wang

et al. 2014

Self Cite

134

123

c Hepatitis E virus (HEV) is a common cause of acute hepatitis that results in high mortality in pregnant women and may establish chronic infections in immunocompromised patients. We demonstrate for the first time that alpha interferon (IFN-␣) and ribavirin inhibit in vitro HEV replication in both a subgenomic replicon and an infectious culture system based on a genotype 3 strain. IFN-␣ showed a moderate but significant synergism with ribavirin. These findings corroborate the reported clinical effectiveness of both drugs. In addition, the antiviral activity of ribavirin against wild-type genotype 1, 2, and 3 strains was confirmed by immunofluorescence staining. Furthermore, the in vitro activity of ribavirin depends on depletion of intracellular GTP pools, which is evident from the facts that (i) other GTP-depleting agents (5-ethynyl-1-␤-D-ribofuranosylimidazole-4-carboxamide [EICAR] and mycophenolic acid) inhibit viral replication, (ii) exogenously added guanosine reverses the antiviral effects, and (iii) a strong correlation (R 2 ‫؍‬ 0.9998) exists between the antiviral activity and GTP depletion of ribavirin and other GTP-depleting agents.H epatitis E virus (HEV) is a positive-sense, single-stranded RNA virus and is classified as the sole member of the Hepevirus genus in the Hepeviridae family (1, 2). HEV is usually transmitted feco-orally and may cause self-limiting acute hepatitis. At least four genotypes are currently recognized: genotypes 1 and 2 seem to infect only humans and are endemic in developing regions, with an estimated 70,000 deaths annually (3), while genotypes 3 and 4 are zoonotic agents, with domestic pigs as their main reservoir (1, 2). The latter two genotypes cause sporadic autochthonous infections in both developing and industrialized parts of the world, e.g., through consumption of undercooked pig meat (1, 2). In addition, related viruses have been found in several animal species, including chickens (avian HEV) (4), rats (5), rabbits (6), ferrets (7), bats (8), and trout (cutthroat trout virus [CTV]) (9).Infections with HEV are often severe in pregnant women infected with genotype 1, with up to 25% mortality (1, 10). In addition, genotype 3 can cause chronic infections, particularly in immunocompromised individuals (11). The first consideration in treating chronic hepatitis E, especially in transplant patients, is lowering immunosuppressive therapy, which induces clearance in over 30% of cases (12). An additional course of pegylated alpha interferon (IFN-␣) for 3 months or longer proved successful in most cases described (13), but ribavirin (RBV) monotherapy is probably the most frequently used option for chronic hepatitis E (11), and it also seems effective in severe acute infections (14, 15).Research on HEV has long been hampered by a lack of efficient cell culture models; however, in vitro cultures have been established in recent years (16,17). By employing a replicon, an infectious virus yield assay, and immunofluorescence staining, we investigated the antiviral activities of both IF...