Broad-Spectrum Small-Molecule Inhibitors Targeting the SAM-Binding Site of Flavivirus NS5 Methyltransferase.

Flavivirus infections, such as those caused by dengue virus (DENV), West Nile virus (WNV), yellow fever virus (YFV), and Zika virus (ZIKV), pose a rising threat to global health. There are no FDA-approved drugs for flaviviruses, although a small number of flaviviruses have vaccines. For flaviviruses or unknown viruses that may appear in the future, it is particularly desirable to identify broad-spectrum inhibitors. The NS5 protein is regarded as one of the most promising flavivirus drug targets because it is conserved across flaviviruses. In this study, we used FL-NAH, a fluorescent analog of the methyl donor S-adenosyl methionine (SAM), to develop a fluorescence polarization (FP)-based high throughput screening (HTS) assay to specifically target methyltransferase (MTase), a vital enzyme for flaviviruses that methylates the N7 and 2'-O positions of the viral 5'-RNA cap. Pilot screening identified two candidate MTase inhibitors, NSC 111552 and 288387. The two compounds inhibited the FL-NAH binding to the DENV3 MTase with low micromolar IC50. Functional assays verified the inhibitory potency of these molecules for the flavivirus MTase activity. Binding studies indicated that these molecules are bound directly to the DENV3 MTase with similar low micromolar affinity. Furthermore, we showed that these compounds greatly reduced ZIKV replication in cell-based experiments at dosages that did not cause cytotoxicity. Finally, docking studies revealed that these molecules bind to the SAM-binding region on the DENV3 MTase, and further mutagenesis studies verified residues important for the binding of these compounds. Overall, these compounds are innovative and attractive candidates for the development of broad-spectrum inhibitors for the treatment of flavivirus infections.

Calcimycin Inhibits Cryptococcus neoformans In Vitro and In Vivo by Targeting the Prp8 Intein Splicing.

Drug resistance is a significant concern in the treatment of diseases, including cryptococcosis caused by Cryptococcus neoformans (Cne) and Cryptococcus gattii (Cga). Alternative drug targets are necessary to overcome drug resistance before it attains a critical stage. Splicing of inteins from pro-protein precursors is crucial for activities of essential proteins hosting intein elements in many organisms, including human pathogens such as Cne and Cga. Through a high-throughput screening, we identified calcimycin (CMN) as a potent Prp8 intein splicing inhibitor with a minimum inhibitory concentration (MIC) of 1.5 µg/mL against the wild-type Cne-H99 (Cne-WT or Cne). In contrast, CMN inhibited the intein-less mutant strain (Cne-Mut) with a 16-fold higher MIC. Interestingly, Aspergillus fumigatus and a few Candida species were resistant to CMN. Further studies indicated that CMN reduced virulence factors such as urease activity, melanin production, and biofilm formation in Cne. CMN also inhibited Cne intracellular infection in macrophages. In a target-specific split nanoluciferase assay, the IC50 of CMN was 4.6 µg/mL. Binding of CMN to recombinant Prp8 intein was demonstrated by thermal shift assay and microscale thermophoresis. Treating Cne cells with CMN reduced intein splicing. CMN was fungistatic and showed a synergistic effect with the known antifungal drug amphotericin B. Finally, CMN treatment at 20 mg/kg body weight led to 60% reduction in lung fungal load in a cryptococcal pulmonary infection mouse model. Overall, CMN represents a potent antifungal with a novel mechanism of action to treat Cne and possibly Cga infections.

Inteins as Drug Targets and Therapeutic Tools.

Multidrug-resistant pathogens are of significant concern in recent years. Hence new antifungal and anti-bacterial drug targets are urgently needed before the situation goes beyond control. Inteins are polypeptides that self-splice from exteins without the need for cofactors or external energy, resulting in joining of extein fragments. Inteins are present in many organisms, including human pathogens such as Mycobacterium tuberculosis, Cryptococcus neoformans, C. gattii, and Aspergillus fumigatus. Because intein elements are not present in human genes, they are attractive drug targets to develop antifungals and antibiotics. Thus far, a few inhibitors of intein splicing have been reported. Metal-ions such as Zn2+ and Cu2+, and platinum-containing compound cisplatin inhibit intein splicing in M. tuberculosis and C. neoformans by binding to the active site cysteines. A small-molecule inhibitor 6G-318S and its derivative 6G-319S are found to inhibit intein splicing in C. neoformans and C. gattii with a MIC in nanomolar concentrations. Inteins have also been used in many other applications. Intein can be used in activating a protein inside a cell using small molecules. Moreover, split intein can be used to deliver large genes in experimental gene therapy and to kill selected species in a mixed population of microbes by taking advantage of the toxin-antitoxin system. Furthermore, split inteins are used in synthesizing cyclic peptides and in developing cell culture model to study infectious viruses including SARS-CoV-2 in the biosafety level (BSL) 2 facility. This mini-review discusses the recent research developments of inteins in drug discovery and therapeutic research.

A review of the presentation and outcome of sarcoidosis in coronavirus disease 2019.

BACKGROUND: In the setting of the current pandemic, concerns have arisen regarding the multisystemic involvement of sarcoidosis and the possible exacerbations in response to the exposure to severe acute respiratory syndrome coronavirus 2. AIM: This study aims to compare the differences in clinical presentation, management, and outcome of coronavirus disease 2019 (COVID-19) between patients with sarcoidosis and those in the general population. METHODS: A literature search was conducted by reviewing original research articles such as case reports, case series, observational studies, and questionnaire-based surveys published in PubMed/Medline, Web of Science, and Google scholar. Data from individual patients in case series and case reports have been pooled to create a data set that was compared with larger such cohorts obtained from several other observational studies. RESULTS: Twenty-seven patients were identified from 14 original articles. No significant differences were found in the clinical manifestations of patients with sarcoidosis presenting with COVID-19 as compared to the general population. The rate of hospitalization in our study was found to be 48.1%. The overall mortality in our study was 7.4%, which is higher than the global average of 2.1%. CONCLUSION: Our observations have reinforced the hypothesis that the presence of additional medical comorbidities is associated with a higher risk of intensive care unit admission. Furthermore, the presence of moderate to a severe limitation in pulmonary functions is an additional risk factor associated with increased hospital admissions and mortality in sarcoidosis. However, neither the diagnosis of sarcoidosis nor ongoing treatment with steroids, methotrexate, or other immunosuppressants was associated with a poorer prognosis in patients with sarcoidosis. RELEVANCE FOR PATIENTS: Patients with sarcoidosis must take added precautions to mitigate the risk of acquiring COVID-19 infection in view of the COVID-19-related mortality rate in this group of patients. Specifically, immunocompromised patients (on immunomodulator drugs and high dose steroids) have been found to have an increased risk of contracting COVID-19. Overall impact on prognostication and outcome in cases requiring hospitalization remains yet to be determined.

Small-molecule inhibitors for the Prp8 intein as antifungal agents.

Self-splicing proteins, called inteins, are present in many human pathogens, including the emerging fungal threats Cryptococcus neoformans (Cne) and Cryptococcus gattii (Cga), the causative agents of cryptococcosis. Inhibition of protein splicing in Cryptococcus sp. interferes with activity of the only intein-containing protein, Prp8, an essential intron splicing factor. Here, we screened a small-molecule library to find addititonal, potent inhibitors of the Cne Prp8 intein using a split-GFP splicing assay. This revealed the compound 6G-318S, with IC50 values in the low micromolar range in the split-GFP assay and in a complementary split-luciferase system. A fluoride derivative of the compound 6G-318S displayed improved cytotoxicity in human lung carcinoma cells, although there was a slight reduction in the inhibition of splicing. 6G-318S and its derivative inhibited splicing of the Cne Prp8 intein in vivo in Escherichia coli and in C. neoformans Moreover, the compounds repressed growth of WT C. neoformans and C. gattii In contrast, the inhibitors were less potent at inhibiting growth of the inteinless Candida albicans Drug resistance was observed when the Prp8 intein was overexpressed in C. neoformans, indicating specificity of this molecule toward the target. No off-target activity was observed, such as inhibition of serine/cysteine proteases. The inhibitors bound covalently to the Prp8 intein and binding was reduced when the active-site residue Cys1 was mutated. 6G-318S showed a synergistic effect with amphotericin B and additive to indifferent effects with a few other clinically used antimycotics. Overall, the identification of these small-molecule intein-splicing inhibitors opens up prospects for a new class of antifungals.

A review of the presentation and outcome of left ventricular thrombus in coronavirus disease 2019 infection.

BACKGROUND: Cardiovascular complications of the coronavirus disease 2019 (COVID-19), which is caused by the severe acute respiratory syndrome coronavirus 2 (SARS- CoV-2), have been documented both in the acute phase and in convalescence. One such complication is the formation of the left ventricular (LV) thrombus. There is a lack of clarity regarding the incidence, risk factors, and management of this complication. AIM: The aim of the study is to identify the clinical presentation, risk factors and outcome of COVID-19 patients with left ventricular thrombus (LVT). METHODS: A literature search was conducted to identify all case reports of COVID-19 with LVT in PubMed/Medline, Embase, Web of Science, and Google Scholar. RESULTS: Among the 65 patients identified, 60 had LVT, either at admission, or during the acute phase of the illness. Six patients with mild symptoms during the acute phase of viral illness had only the COVID-19 antibody test positivity at the time LV thrombus was detected. Few of the patients (23.1%) had no comorbidities. The mean age of the patients was 52.8 years, and the youngest patient was 4 years old. This suggests that LVT formation can occur in young COVID-19 patients with no co-morbid conditions. Most of the patients (69.2%) had more than one site of thrombosis. A mortality rate of 23.1% was observed in our review, and ST-elevation myocardial infarction (STEMI) was diagnosed in 33.3% of those who died. CONCLUSIONS: A high degree of suspicion for LVT must be maintained in patients with known cardiac disease and those with new-onset arterial or venous thromboembolism, and such patients may benefit from a screening echocardiography at admission. RELEVANCE FOR PATIENTS: The patients with preexisting cardiovascular disease must take added precautions to prevent acquiring COVID-19 infection as there is a higher risk of developing LV thrombus. In patients who develop LVT in COVID-19, mortality rate is higher.

Targeting Crucial Host Factors of SARS-CoV-2.

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread worldwide since its first incidence in Wuhan, China, in December 2019. Although the case fatality rate of COVID-19 appears to be lower than that of SARS and Middle East respiratory syndrome (MERS), the higher transmissibility of SARS-CoV-2 has caused the total fatality to surpass other viral diseases, reaching more than 1 million globally as of October 6, 2020. The rate at which the disease is spreading calls for a therapy that is useful for treating a large population. Multiple intersecting viral and host factor targets involved in the life cycle of the virus are being explored. Because of the frequent mutations, many coronaviruses gain zoonotic potential, which is dependent on the presence of cell receptors and proteases, and therefore the targeting of the viral proteins has some drawbacks, as strain-specific drug resistance can occur. Moreover, the limited number of proteins in a virus makes the number of available targets small. Although SARS-CoV and SARS-CoV-2 share common mechanisms of entry and replication, there are substantial differences in viral proteins such as the spike (S) protein. In contrast, targeting cellular factors may result in a broader range of therapies, reducing the chances of developing drug resistance. In this Review, we discuss the role of primary host factors such as the cell receptor angiotensin-converting enzyme 2 (ACE2), cellular proteases of S protein priming, post-translational modifiers, kinases, inflammatory cells, and their pharmacological intervention in the infection of SARS-CoV-2 and related viruses.

Emetine inhibits Zika and Ebola virus infections through two molecular mechanisms: inhibiting viral replication and decreasing viral entry.

The re-emergence of Zika virus (ZIKV) and Ebola virus (EBOV) poses serious and continued threats to the global public health. Effective therapeutics for these maladies is an unmet need. Here, we show that emetine, an anti-protozoal agent, potently inhibits ZIKV and EBOV infection with a low nanomolar half maximal inhibitory concentration (IC50) in vitro and potent activity in vivo. Two mechanisms of action for emetine are identified: the inhibition of ZIKV NS5 polymerase activity and disruption of lysosomal function. Emetine also inhibits EBOV entry. Cephaeline, a desmethyl analog of emetine, which may be better tolerated in patients than emetine, exhibits a similar efficacy against both ZIKV and EBOV infections. Hence, emetine and cephaeline offer pharmaceutical therapies against both ZIKV and EBOV infection.

Coronary angiography and angioplasty using the aberrant radial artery as an access site.

OBJECTIVE: To study the suitability of the aberrant radial artery (ARA) as an access site for coronary angiography and angioplasty. BACKGROUND: In certain situations, the radial artery operator finds that the right radial artery in its usual location is unsuitable for a transradial procedure (TRP). In such cases, the ARA should be considered as an alternate access site. METHODS: Between January 2002 and December 2004, all patients considered suitable for a TRP with a clinically absent radial artery, or a small radial artery and a palpable ARA, underwent a TRP using this vessel as an access site. We describe the technical aspects and the differences that this approach entails, in comparison to the standard radial artery approach to TRPs. RESULTS: Of the 3,610 patients considered suitable for a TRP, 22 patients underwent 29 procedures using the ARA as an access site [22 angiograms and 7 percutaneous transluminal coronary angioplasty procedures (PTCAs)]. The median age of the patients was 55 years, with 19 males and 3 females. All procedures using the aberrant radial artery were successful. None of the patients developed spasm or an access site complication. The mean fluoroscopy time for angiography in the right radial artery group was 4.6 minutes, and 4.8 minutes for the ARA group. The procedure timed were 24 minutes and 32 minutes, respectively. CONCLUSION: The aberrant radial artery can be used as a safe alternate access site for coronary angiography and angioplasty when the right radial artery at the usual site is not suitable.