Sepsis among Neonates Admitted to a Neonatal Intensive Care Unit in a Tertiary Care Centre.

Introduction: Neonatal sepsis is a condition that carries a high risk for mortality as neonates rapidly transition to extra-uterine life and are subjected to various risk factors. Sepsis prevalence can be reduced by good antenatal care, early detection and treatment of risk factors. The study aimed to find out the prevalence of sepsis among neonates admitted to a neonatal intensive care unit in a tertiary care centre. Methods: This is a descriptive cross-sectional study conducted among neonates admitted to the neonatal care unit of a tertiary care centre after obtaining ethical approval from the Institutional Review Committee. Data of patients admitted from 12 December 2022 to 30 June 2023 was collected from hospital records. Symptomatic patients admitted to the neonatal intensive care unit were included and those with incomplete data were excluded from the study. A convenience sampling method was used. The point estimate was calculated at a 95% Confidence Interval. Results: Among 379 neonates, the prevalence of sepsis was 138 (36.41%) (28.38-44.44, 95% Confidence Interval). A total of 98 (71.01%) had early-onset neonatal sepsis and 40 (28.99%) had late-onset neonatal sepsis. Conclusions: The prevalence of neonatal sepsis was found to be lower than other studies done in similar settings. Keywords: neonate; neonatal sepsis; prematurity; prevalence.

Structure-Based Discovery of Inhibitors of the SARS-CoV-2 Nsp14 N7-Methyltransferase.

An under-explored target for SARS-CoV-2 is the S-adenosyl methionine (SAM)-dependent methyltransferase Nsp14, which methylates the N7-guanosine of viral RNA at the 5'-end, allowing the virus to evade host immune response. We sought new Nsp14 inhibitors with three large library docking strategies. First, up to 1.1 billion lead-like molecules were docked against the enzyme's SAM site, leading to three inhibitors with IC50 values from 6 to 50 µM. Second, docking a library of 16 million fragments revealed 9 new inhibitors with IC50 values from 12 to 341 µM. Third, docking a library of 25 million electrophiles to covalently modify Cys387 revealed 7 inhibitors with IC50 values from 3.5 to 39 µM. Overall, 32 inhibitors encompassing 11 chemotypes had IC50 values < 50 µM and 5 inhibitors in 4 chemotypes had IC50 values < 10 µM. These molecules are among the first non-SAM-like inhibitors of Nsp14, providing starting points for future optimization.

Probing the SAM Binding Site of SARS-CoV-2 Nsp14 In Vitro Using SAM Competitive Inhibitors Guides Developing Selective Bisubstrate Inhibitors.

The COVID-19 pandemic has clearly brought the healthcare systems worldwide to a breaking point, along with devastating socioeconomic consequences. The SARS-CoV-2 virus, which causes the disease, uses RNA capping to evade the human immune system. Nonstructural protein (nsp) 14 is one of the 16 nsps in SARS-CoV-2 and catalyzes the methylation of the viral RNA at N7-guanosine in the cap formation process. To discover small-molecule inhibitors of nsp14 methyltransferase (MTase) activity, we developed and employed a radiometric MTase assay to screen a library of 161 in-house synthesized S-adenosylmethionine (SAM) competitive MTase inhibitors and SAM analogs. Among six identified screening hits, SS148 inhibited nsp14 MTase activity with an IC50 value of 70 ± 6 nM and was selective against 20 human protein lysine MTases, indicating significant differences in SAM binding sites. Interestingly, DS0464 with an IC50 value of 1.1 ± 0.2 µM showed a bisubstrate competitive inhibitor mechanism of action. DS0464 was also selective against 28 out of 33 RNA, DNA, and protein MTases. The structure-activity relationship provided by these compounds should guide the optimization of selective bisubstrate nsp14 inhibitors and may provide a path toward a novel class of antivirals against COVID-19, and possibly other coronaviruses.

The Structure-Based Design of SARS-CoV-2 nsp14 Methyltransferase Ligands Yields Nanomolar Inhibitors.

In this study, we have focused on the structure-based design of the inhibitors of one of the two SARS-CoV-2 methyltransferases (MTases), nsp14. This MTase catalyzes the transfer of the methyl group from S-adenosyl-l-methionine (SAM) to cap the guanosine triphosphate moiety of the newly synthesized viral RNA, yielding the methylated capped RNA and S-adenosyl-l-homocysteine (SAH). As the crystal structure of SARS-CoV-2 nsp14 is unknown, we have taken advantage of its high homology to SARS-CoV nsp14 and prepared its homology model, which has allowed us to identify novel SAH derivatives modified at the adenine nucleobase as inhibitors of this important viral target. We have synthesized and tested the designed compounds in vitro and shown that these derivatives exert unprecedented inhibitory activity against this crucial enzyme. The docking studies nicely explain the contribution of an aromatic part attached by a linker to the position 7 of the 7-deaza analogues of SAH.

A High-Throughput Radioactivity-Based Assay for Screening SARS-CoV-2 nsp10-nsp16 Complex.

Frequent outbreaks of novel coronaviruses (CoVs), highlighted by the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, necessitate the development of therapeutics that could be easily and effectively administered worldwide. The conserved mRNA-capping process enables CoVs to evade their host immune system and is a target for antiviral development. Nonstructural protein (nsp) 16 in complex with nsp10 catalyzes the final step of coronaviral mRNA capping through its 2'-O-methylation activity. Like other methyltransferases, the SARS-CoV-2 nsp10-nsp16 complex is druggable. However, the availability of an optimized assay for high-throughput screening (HTS) is an unmet need. Here, we report the development of a radioactivity-based assay for the methyltransferase activity of the nsp10-nsp16 complex in a 384-well format, kinetic characterization, and optimization of the assay for HTS (Z' factor = 0.83). Considering the high conservation of nsp16 across known CoV species, the potential inhibitors targeting the SARS-CoV-2 nsp10-nsp16 complex may also be effective against other emerging pathogenic CoVs.

Probing the SAM Binding Site of SARS-CoV-2 nsp14 in vitro Using SAM Competitive Inhibitors Guides Developing Selective bi-substrate Inhibitors.

The COVID-19 pandemic has clearly brought the healthcare systems world-wide to a breaking point along with devastating socioeconomic consequences. The SARS-CoV-2 virus which causes the disease uses RNA capping to evade the human immune system. Non-structural protein (nsp) 14 is one of the 16 nsps in SARS-CoV-2 and catalyzes the methylation of the viral RNA at N7-guanosine in the cap formation process. To discover small molecule inhibitors of nsp14 methyltransferase (MT) activity, we developed and employed a radiometric MT assay to screen a library of 161 in house synthesized S-adenosylmethionine (SAM) competitive methyltransferase inhibitors and SAM analogs. Among seven identified screening hits, SS148 inhibited nsp14 MT activity with an IC 50 value of 70 ± 6 nM and was selective against 20 human protein lysine methyltransferases indicating significant differences in SAM binding sites. Interestingly, DS0464 with IC 50 value of 1.1 ± 0.2 µM showed a bi-substrate competitive inhibitor mechanism of action. Modeling the binding of this compound to nsp14 suggests that the terminal phenyl group extends into the RNA binding site. DS0464 was also selective against 28 out of 33 RNA, DNA, and protein methyltransferases. The structure-activity relationship provided by these compounds should guide the optimization of selective bi-substrate nsp14 inhibitors and may provide a path towards a novel class of antivirals against COVID-19, and possibly other coronaviruses.

A High-Throughput RNA Displacement Assay for Screening SARS-CoV-2 nsp10-nsp16 Complex toward Developing Therapeutics for COVID-19.

SARS-CoV-2, the coronavirus that causes COVID-19, evades the human immune system by capping its RNA. This process protects the viral RNA and is essential for its replication. Multiple viral proteins are involved in this RNA capping process, including the nonstructural protein 16 (nsp16), which is an S-adenosyl-l-methionine (SAM)-dependent 2'-O-methyltransferase. Nsp16 is significantly active when in complex with another nonstructural protein, nsp10, which plays a key role in its stability and activity. Here we report the development of a fluorescence polarization (FP)-based RNA displacement assay for nsp10-nsp16 complex in a 384-well format with a Z' factor of 0.6, suitable for high-throughput screening. In this process, we purified the nsp10-nsp16 complex to higher than 95% purity and confirmed its binding to the methyl donor SAM, the product of the reaction, S-adenosyl-l-homocysteine (SAH), and a common methyltransferase inhibitor, sinefungin, using isothermal titration calorimetry (ITC). The assay was further validated by screening a library of 1124 drug-like compounds. This assay provides a cost-effective high-throughput method for screening the nsp10-nsp16 complex for RNA competitive inhibitors toward developing COVID-19 therapeutics.

Peptide Inhibitors of the α-Cobratoxin-Nicotinic Acetylcholine Receptor Interaction.

Venomous snakebites cause >100 000 deaths every year, in many cases via potent depression of human neuromuscular signaling by snake α-neurotoxins. Emergency therapy still relies on antibody-based antivenom, hampered by poor access, frequent adverse reactions, and cumbersome production/purification. Combining high-throughput discovery and subsequent structure-function characterization, we present simple peptides that bind α-cobratoxin (α-Cbtx) and prevent its inhibition of nicotinic acetylcholine receptors (nAChRs) as a lead for the development of alternative antivenoms. Candidate peptides were identified by phage display and deep sequencing, and hits were characterized by electrophysiological recordings, leading to an 8-mer peptide that prevented α-Cbtx inhibition of nAChRs. We also solved the peptide:α-Cbtx cocrystal structure, revealing that the peptide, although of unique primary sequence, binds to α-Cbtx by mimicking structural features of the nAChR binding pocket. This demonstrates the potential of small peptides to neutralize lethal snake toxins in vitro, establishing a potential route to simple, synthetic, low-cost antivenoms.

Synthesis and Characterisation of Substrate-Based Peptides as Inhibitors of Histone Demethylase KDM4C.

The design and synthesis of modified pentapeptides based on a truncated version of the substrate for KDM4C, a histone lysine demethylase (KDM), and investigation of their inhibitory activity at KDM4C is reported. By modifying the lysine residue corresponding to lysine 9 at histone 3 (H3K9), three different series of peptides were designed and synthesized. One series contained N-acylated H3K9 and two series introduced triazoles in this position via click chemistry to enable facile variation of headgroups. The click reaction is compatible with free amino acids and this was performed on an azido containing deprotected pentapeptide demonstrating a highly facile and convergent synthetic strategy for making substrate-based inhibitors. One of the 14 peptides showed inhibitory activity at KDM4C demonstrating the need for an iron chelator in the pentapeptide series.

A fluorescence resonance energy transfer-based method for histone methyltransferases.

A simple dye-quencher fluorescence resonance energy transfer (FRET)-based assay for methyltransferases was developed and used to determine kinetic parameters and inhibitory activity at EHMT1 and EHMT2. Peptides mimicking the truncated histone H3 tail were functionalized in each end with a dye and a quencher, respectively. When lysine-9 residues in the peptides were methylated, they were protected from cleavage by endoproteinase-EndoLysC, whereas unmethylated peptides were cleaved, resulting in an increase in fluorescent intensity.

Analogues of the Natural Product Sinefungin as Inhibitors of EHMT1 and EHMT2.

A series of analogues of the natural product sinefungin lacking the amino acid moiety was synthesized and probed for their ability to inhibit EHMT1 and EHMT2. This study led to inhibitors 3b and 4d of methyltransferase activity of EHMT1 and EHMT2 and it demonstrates that such analogues constitute an interesting scaffold to develop selective methyltransferase inhibitors. Surprisingly, the inhibition was not competitive toward AdoMet.

A substrate-optimized electrophoretic mobility shift assay for ADAM12.

ADAM12 belongs to the A disintegrin and metalloprotease (ADAM) family of secreted sheddases activating extracellular growth factors such as epidermal growth factor receptor (EGFR) ligands and tumor necrosis factor-alpha (TNF-α). ADAM proteases, most notably ADAM17 (TNF-α-converting enzyme), have long been investigated as pharmaceutical drug targets; however, due to lack of potency and in vivo side effects, none of the small-molecule inhibitors discovered so far has made it beyond clinical testing. Ongoing research on novel selective inhibitors of ADAMs requires reliable biochemical assays to validate molecular probes from large-scale screening efforts. Here we describe an electrophoretic mobility shift assay for ADAM12 based on the identification of an optimized peptide substrate that is characterized by excellent performance and reproducibility.