Developing a method to measure bioavailable phosphorus in river water via simultaneous multisample ultrasonic extraction.

To reduce aquatic eutrophication, measurements of bioavailable phosphorus (BAP) rather than total phosphorus (TP) are deemed critical. However, current methods require much time to separate sediments from river water, which limits the routine measurement of BAP in rivers. Therefore, in this study, a simultaneous multisample ultrasonic extraction method is proposed to directly measure total BAP (TBAP) in river water without the separation of sediment and water. Spike-and-recovery assessments showed that at least three extractions are required to maintain efficiency. A process including 2-min extraction time and three extractions was suggested. The concentrations of TBAP extracted by this process showed no significant differences with the spike calculations. Furthermore, river water TBAP was quantified using the conventional and proposed method to examine the practicality of using the proposed method for simultaneous multisample ultrasonic extraction and to evaluate its adaptability to actual river water analysis. The extracted concentrations matched those obtained using the conventional method, in which total BAP is calculated as the sum of dissolved BAP and particulate BAP; no significant difference was observed between the concentrations. Ultrasonic extraction was considerably less time-consuming than the conventional method because more samples could be analyzed during a single run. Therefore, the simultaneous multisample ultrasonic extraction method proposed in this study can be used to directly quantify total BAP in river water.

Enhancing ECG readability in LVAD patients: A comparative analysis of Denoising techniques with an emphasis on discrete wavelet transform.

BACKGROUND: Electrocardiograms (ECGs) are vital for diagnosing cardiac conditions but obtaining clean signals in Left Ventricular Assist Device (LVAD) patients is hindered by electromagnetic interference (EMI). Traditional filters have limited efficacy. There is a current need for an easy and effective method. METHODS: Raw ECG data obtained from 5 patients with LVADs. LVAD types included HeartMate II, III at multiple impeller speeds, and a case with HeartMate III and a ProtekDuo. ECG spectral profiles were examined ensuring the presence of diverse types of EMI in the study. ECGs were then processed with four denoising techniques: Moving Average Filter, Finite Impulse Response Filter, Fast Fourier Transform, and Discrete Wavelet Transform. RESULTS: Discrete Wavelet Transform proved as the most promising method. It offered a one solution fits all, enabling automatic processing with minimal user input while preserving crucial high-frequency components and reducing LVAD EMI artifacts. CONCLUSION: Our study demonstrates the practicality and efficiency of Discrete Wavelet Transform in obtaining high-fidelity ECGs in LVAD patients. This method could enhance clinical diagnosis and monitoring.

Predicting drought stress under climate change in the Southern Central Highlands of Vietnam.

In the Southern Central Highlands of Vietnam, droughts occur more frequently, causing significant damage and impacting the region's socio-economic development. During the dry season, rivers, streams, and reservoirs often face limited water availability, exacerbated in recent years by increasing drought severity. Recognizing the escalating severity of droughts, the study offers a novel contribution by conducting a comprehensive analysis of surface water resource distribution in Lam Dong province, focusing on assessing water demand for agricultural production, a crucial factor in ensuring sustainable crop growth. Two scenarios, Current-2020 (SC1) and Climate Change-2025 (SC2), are simulated, with SC2 based on climate change and sea level rise scenarios provided by the Ministry of Natural Resources and Environment (MONRE). These scenarios are integrated into the MIKE-NAM and MIKE-HYDRO basin models, allowing for a thorough assessment of the water balance of Lam Dong province. Furthermore, the study utilizes the Keetch-Byram Drought Index (KBDI) to measure drought severity, revealing prevalent dry and moderately droughty conditions in highland districts with rainfall frequency ranging from 50 to 85%. Severe drought conditions occur with a rainfall frequency of 95%, indicating an increased frequency and geographic scope of severe droughts. Additionally, the study highlights that under abnormally dry conditions, water demand for the winter-spring crop is consistently met at 100%, decreasing to 85%, 80%, and less than 75% for moderate, severe, and extreme droughts, respectively. These findings offer insights into future drought conditions in the Lam Dong province and their potential impact on irrigation capacity, crucial for adaptation strategies.

Mitigating machine learning bias between high income and low-middle income countries for enhanced model fairness and generalizability.

Collaborative efforts in artificial intelligence (AI) are increasingly common between high-income countries (HICs) and low- to middle-income countries (LMICs). Given the resource limitations often encountered by LMICs, collaboration becomes crucial for pooling resources, expertise, and knowledge. Despite the apparent advantages, ensuring the fairness and equity of these collaborative models is essential, especially considering the distinct differences between LMIC and HIC hospitals. In this study, we show that collaborative AI approaches can lead to divergent performance outcomes across HIC and LMIC settings, particularly in the presence of data imbalances. Through a real-world COVID-19 screening case study, we demonstrate that implementing algorithmic-level bias mitigation methods significantly improves outcome fairness between HIC and LMIC sites while maintaining high diagnostic sensitivity. We compare our results against previous benchmarks, utilizing datasets from four independent United Kingdom Hospitals and one Vietnamese hospital, representing HIC and LMIC settings, respectively.

Morphological Evolution of an Intertidal Mudflat in Relation to Mangrove Growth: Implications for Future Erosion Control.

There is limited information regarding the influence of mangrove growth on the morphological evolution of intertidal mudflats. In this study, Tan Phu Dong district, Tien Giang Province, Vietnam, was selected for investigating how mangrove growth influenced the morphological evolution of an intertidal mudflat. The authors analyzed a series of satellite images (from 1995 and 2022), calculated the enhanced vegetation index (EVI), and documented field visits and observations in pursuit of the objective of the study. The findings revealed that fine-grained sediment accumulated as unconsolidated substratum (US) in the first step of the morphological evolution of the intertidal mudflat, with sediment accumulation of 910 ha in 1995. The US provided favorable conditions for mangroves to grow, while mangrove growth helped compact the US into a compact substratum (CS) in addition to promoting continuous sediment accumulation, increased the vegetation cover of the island, and elevated the substrate density of the remaining areas. As a result, the US and CS decreased steadily between 1995 and 2020, from 910 ha in 1995 to 401 ha in 2020 and from 433 ha in 2005 to 111 ha in 2020, respectively. Meanwhile, the low-vegetation area (LVA), medium-vegetation area (MVA), and high vegetation area (HVA) gradually increased between 1995 and 2015, from 0 ha in 1995 to 104 ha in 2015, from 0 ha in 1995 to 96 ha in 2015, and from 0 ha in 1995 to 114 ha in 2015, respectively. However, the LVA decreased slightly between 2015 and 2020 due to significant sand accumulation, which significantly killed the mangrove trees. In contrast, the MVA and HVA steadily increased between 2015 and 2020, from 96 ha in 2015 to 116 ha in 2020 and from 114 ha in 2015 to 221 ha in 2020, respectively. In 2022, there was a steady increase in HVA (298 ha in 2022), although the date of the 2022 satellite retrieval was 28 January 2022. This study recommends that the technical design of the existing coastal protection works should be revised or adapted to take account of sediment accumulation as the first step in the morphological evolution of the examined intertidal mudflat, rather than mangrove growth.

Optimization of Multiplex-PCR Technique To Determine Azf Deletions in infertility Male Patients.

Background: To optimize the multiplex polymerase chain reaction (M-PCR) technique to diagnose microdeletions of azoospermia factors (AZF) on the Y chromosome and initially apply the technique to diagnose male patients with sperm density less than 5×106 million sperm/mL was assigned to do a test to check for AZF microdeletions on the Y chromosome. Methods: Based on the positive control samples which belong to male subjects who have had 2 healthy children without any assisted reproductive technologies, the M-PCR method was developed to detect simultaneously and accurately AZF microdeletions on 32 male patients with sperm densities below 5×106 million sperm/mL of semen at the Department of Biology and Medical Genetics - Vietnam Military Medical University. Results: Successful optimization of the M-PCR technique including 7 reactions arranged according to each AZFabc region using 24 STS/gene on the Y chromosome. Initial application to diagnose AZF deletion on 32 azoospermic and oligospermic men reveals that AZFa deletion accounts for 6.25% (2/32); deletion of all 3 regions AZFa,b,c with 18.75% (6/32 cases); The combined deletion rate of AZFb,c is highest, accounting for 56.24% (18/32 patients). Conclusion: Successfully optimized the M-PCR technique in identifying AZF microdeletions using 24 sequence tagged sites (STS)/gene for azoospermic and oligozoospermic men. The M-PCR technique has great potential in the application of AZF deletion diagnosis.

Traditional Uses, Phytochemistry, and Pharmacological Activities of Vernonia cinerea (L.) Less.: An Updated Review.

Vernonia cinerea (L.) Less. is a perennial herbaceous plant found mainly in tropical areas, particularly in Southeast Asia, South America, and India. Various parts of V. cinerea have traditionally been used in folk medicine to treat several diseases, such as malaria, fever, and liver diseases. V. cinerea has so far yielded about 92 secondary metabolites. The majority of these are sesquiterpene lactones, but triterpenes, flavonoids, steroids, phenolics, and other compounds are present as well. V. cinerea crude extracts reportedly exhibit anti-inflammatory, antiprotozoal, antidiabetic, anticancer, antimicrobial, antioxidant, and renoprotective activities. This study aims to provide the latest up-to-date information on the botanical characterization, distribution, traditional uses, phytochemistry, and pharmacological activity of V. cinerea. Information on V. cinerea was thoroughly reviewed. The literature published between 1950 and 2024 was compiled through online bibliographic databases, including SciFinder, Web of Science, Google Scholar, PubMed, ScienceDirect, Springer Link, Wiley, and the MDPI online library. The keywords used for the literature search included Vernonia cinerea (L.) Less. and the synonyms Cyanthillium cinereum (L.) H.Rob., Conyza cinerea L., and various others.

Preimplantation Genetic Diagnosis of Androgen Resistance Syndrome Caused by Mutation on the AR Gene in Vietnam.

Background: Androgen resistance syndrome or androgen insensitivity syndrome (AIS - Androgen Insensitivity Syndrome, OMIM 300068) is an X-linked recessive genetic syndrome causing disorders of sexual development in males. This disease is caused by mutations in the AR gene located on the X chromosome, which encodes the protein that structures the androgen receptor, with the role of receiving androgens. Mutation of the AR gene causes complete or partial loss of androgen receptor function, thereby androgen not being obtained and exerting its effect on target organs, resulting in abnormalities of the male reproductive system due to this organ system, differentiating towards feminization under the influence of estrogen. Disease prevention can be achieved by using pre-implantation genetic diagnosis, which enables couples carrying the mutation to have healthy offspring. Aim: To carry out preimplantation genetic diagnosis of androgen resistance syndrome. Methods: Sanger sequencing was used to detect the mutation in the blood samples of the couple, their son, and 01 embryo that were biopsied on the fifth day based on the findings of next-generation sequencing (NGS) of the affected son. We combined Sanger sequencing and linkage analysis using short tandem repeats (STR) to provide diagnostic results. Results: We performed preimplantation genetic diagnosis for AIS on an embryo from a couple who had previously had an affected son. Consequently, one healthy embryo was diagnosed without the variant NM_000044: c.796del (p.Asp266IlefsTer30). Conclusion: We report on a novel variant (NM_000044: c.796del (p.Asp266IlefsTer30)) in the AR gene discovered in Vietnam. The developed protocol was helpful for the preimplantation genetic diagnosis process to help families with the monogenic disease of AIS but wish to have healthy children.

Endothelial and inflammatory pathophysiology in dengue shock: New insights from a prospective cohort study in Vietnam.

Dengue shock (DS) is the most severe complication of dengue infection; endothelial hyperpermeability leads to profound plasma leakage, hypovolaemia and extravascular fluid accumulation. At present, the only treatment is supportive with intravenous fluid, but targeted endothelial stabilising therapies and host immune modulators are needed. With the aim of prioritising potential therapeutics, we conducted a prospective observational study of adults (≥16 years) with DS in Vietnam from 2019-2022, comparing the pathophysiology underlying circulatory failure with patients with septic shock (SS), and investigating the association of biomarkers with clinical severity (SOFA score, ICU admission, mortality) and pulmonary vascular leak (daily lung ultrasound for interstitial and pleural fluid). Plasma was collected at enrolment, 48 hours later and hospital discharge. We measured biomarkers of inflammation (IL-6, ferritin), endothelial activation (Ang-1, Ang-2, sTie-2, VCAM-1) and endothelial glycocalyx breakdown (hyaluronan, heparan sulfate, endocan, syndecan-1). We enrolled 135 patients with DS (median age 26, median SOFA score 7, 34 required ICU admission, 5 deaths), together with 37 patients with SS and 25 healthy controls. Within the DS group, IL-6 and ferritin were associated with admission SOFA score (IL-6: ßeta0.70, p<0.001 & ferritin: ßeta0.45, p<0.001), ICU admission (IL-6: OR 2.6, p<0.001 & ferritin: OR 1.55, p<0.001) and mortality (IL-6: OR 4.49, p = 0.005 & ferritin: OR 13.8, p = 0.02); both biomarkers discriminated survivors and non-survivors at 48 hours and all patients who died from DS had pre-mortem ferritin ≥100,000ng/ml. IL-6 most strongly correlated with severity of pulmonary vascular leakage (R = 0.41, p<0.001). Ang-2 correlated with pulmonary vascular leak (R = 0.33, p<0.001) and associated with SOFA score (ß 0.81, p<0.001) and mortality (OR 8.06, p = 0.002). Ang-1 was associated with ICU admission (OR 1.6, p = 0.005) and mortality (OR 3.62, p = 0.006). All 4 glycocalyx biomarkers were positively associated with SOFA score, but only syndecan-1 was associated with ICU admission (OR 2.02, p<0.001) and mortality (OR 6.51, p<0.001). This study highlights the central role of hyperinflammation in determining outcomes from DS; the data suggest that anti-IL-1 and anti-IL-6 immune modulators and Tie2 agonists may be considered as candidates for therapeutic trials in severe dengue.

Acetylcholinesterase inhibition studies of alkaloid components from Crinum asiaticum var. sinicum: in vitro assessments by molecular docking and molecular dynamics simulations.

Alkaloids are among the most important and best-known secondary metabolites as sources of new drugs from medicinal plants and marine organisms. A phytochemical investigation of the whole plant of Crinum asiaticum var. sinicum resulted in the isolation of seven alkaloids (1-7), including one new dimeric compound, bis-(-)-8-demethylmaritidine (1). Their structures were elucidated using NMR and HR-ESI-MS. The absolute configuration of new compound 1 was established by circular dichroism spectroscopy. All isolated compounds were evaluated for their inhibitory effects on acetylcholinesterase (AChE) activity in vitro. Among them, compound 1 exhibited the most potent AChE inhibition. Moreover, molecular docking and molecular dynamics simulations were carried out for the most active compound to investigate their binding interactions and dynamics behavior of the AChE protein-ligand complex. Therefore, compound 1 may be a potential candidate for effectively treating Alzheimer's disease.

Genome evolution of dengue virus serotype 1 under selection by Wolbachia pipientis in Aedes aegypti mosquitoes.

The introgression of antiviral strains of Wolbachia into Aedes aegypti mosquito populations is a public health intervention for the control of dengue. Plausibly, dengue virus (DENV) could evolve to bypass the antiviral effects of Wolbachia and undermine this approach. Here, we established a serial-passage system to investigate the evolution of DENV in Ae. aegypti mosquitoes infected with the wMel strain of Wolbachia. Using this system, we report on virus genetic outcomes after twenty passages of serotype 1 of DENV (DENV-1). An amino acid substitution, E203K, in the DENV-1 envelope protein was more frequently detected in the consensus sequence of virus populations passaged in wMel-infected Ae. aegypti than wild-type counterparts. Positive selection at residue 203 was reproducible; it occurred in passaged virus populations from independent DENV-1-infected patients and also in a second, independent experimental system. In wild-type mosquitoes and human cells, the 203K variant was rapidly replaced by the progenitor sequence. These findings provide proof of concept that wMel-associated selection of virus populations can occur in experimental conditions. Field-based studies are needed to explore whether wMel imparts selective pressure on DENV evolution in locations where wMel is established.

Insights into the inhibitory activities of neolignans and diarylnonanoid derivatives from nutmeg (Myristica fragrans Houtt.) seeds on soluble epoxide hydrolase using in vitro and in silico approaches.

Two new neolignans, myrifralignans F-G (14 and 18), four new diarylnonanoid derivatives, myrifragranones A-D (21-24), and 18 known compounds were isolated and structurally elucidated from nutmeg (Myristica fragrans Houtt.) seeds. The absolute configurations of these secondary metabolites were determined using the electronic circular dichroism technique. The inhibitory potential of these isolated compounds on soluble epoxide hydrolase (sEH) was investigated for the first time. Among them, malabaricones B and C (19 and 20) and four new compounds 21-24 displayed inhibitory activities against sEH, with IC50 values ranging from 14.24 to 46.35 µM. Additionally, the binding mechanism, key binding interactions, stability, and dynamic behaviour of the active compounds with the sEH enzyme were analysed using in silico molecular docking and dynamics simulations. Our findings suggest that nutmeg could become a promising natural source for discovering and developing new sEH inhibitors.

Single versus Double Coffee-Ring Effect Patterns in Thin-Layer Chromatography Coupled with Surface-Enhanced Raman Spectroscopic Analysis of Anti-Diabetic Drugs Adulterated in Herbal Products.

In thin-layer chromatography coupled with surface-enhanced Raman spectroscopy (TLC-SERS), the coffee ring effect (CRE) describes the formation of a ring-shape spot (blank in the middle and darker on the edge) caused by the aggregation of silver nanoparticles (Ag NPs), alone (single CRE) or with the analytes (double CRE). In this work, the SCRE and DCRE were investigated in two anti-diabetic drugs, hydrophobic glibenclamide (GLB) and more hydrophilic metformin (MET). The SCRE occurred in GLB analysis, as opposed to the DCRE that occurred in MET. It was proven that for optimization of the TLC-SERS analytical procedure, it is necessary to distinguish the CRE patterns of analytes. Additionally, MET and GLB were analyzed with the developed TLC-SERS method and confirmed by another validated method using high-performance liquid chromatography. Four herbal products collected on the market were found to be adulterated with GLB or/and MET; among those, one product was adulterated with both MET and GLB, and two products were adulterated with GLB at a higher concentration than the usual GLB prescription dose. The TLC-SERS method provided a useful tool for the simultaneous detection of adulterated anti-diabetic herbal products, and the comparison of the SCRE and DCRE provided more evidence to predict CRE patterns in TLC-SERS.

A New Ceanothane-Type Triterpenoid Saponin Isolated from Gouania leptostachya DC. var. tonkinensis Pit. and Its Underlying Anti-Inflammatory Effects.

Metabolites from medicinal plants continue to hold significant value in the exploration and advancement of novel pharmaceuticals. In the search for plants containing compounds with anti-inflammatory effects, we observed that the ethanol (EtOH) extract obtained from the aerial components of Gouania leptostachya DC. var. tonkinensis Pit. exhibited substantial suppression of nitric oxide (NO) in vitro. In a phytochemical study on an EtOH extract of G. leptostachya, 11 compounds were purified, including one unreported compound namely gouanioside A (1). Their chemical structures were unambiguously determined through the use of various spectroscopic techniques, such as 1 and 2D NMR, IR, and HR-ESI-MS, and by producing derivatives via chemical reactions. The EtOH extract, fractions, and a new compound exerted inflammatory effects by altering NO synthesis in murine RAW264.7 macrophage cells stimulated with lipopolysaccharide. The underlying inflammatory mechanism of the new compound 1 was also explored through various in vitro experiments. The results of this study indicate the potential usefulness of new compound 1 from G. leptostachya as a treatment for inflammatory diseases.

Optimization of Ultrasonic-Assisted Extraction of α-Glucosidase Inhibitors from Dryopteris crassirhizoma Using Artificial Neural Network and Response Surface Methodology.

Dryopteris crassirhizoma Nakai is a plant with significant medicinal properties, such as anticancer, antioxidant, and anti-inflammatory activities, making it an attractive research target. Our study describes the isolation of major metabolites from D. crassirhizoma, and their inhibitory activities on α-glucosidase were evaluated for the first time. The results revealed that nortrisflavaspidic acid ABB (2) is the most potent α-glucosidase inhibitor, with an IC50 of 34.0 ± 0.14 µM. In addition, artificial neural network (ANN) and response surface methodology (RSM) were used in this study to optimize the extraction conditions and evaluate the independent and interactive effects of ultrasonic-assisted extraction parameters. The optimal extraction conditions are extraction time of 103.03 min, sonication power of 342.69 W, and solvent-to-material ratio of 94.00 mL/g. The agreement between the predicted models of ANN and RSM and the experimental values was notably high, with a percentage of 97.51% and 97.15%, respectively, indicating that both models have the potential to be utilized for optimizing the industrial extraction process of active metabolites from D. crassirhizoma. Our results could provide relevant information for producing high-quality extracts from D. crassirhizoma for functional foods, nutraceuticals, and pharmaceutical industries.

Spatiotemporal Evolution of SARS-CoV-2 Alpha and Delta Variants during Large Nationwide Outbreak of COVID-19, Vietnam, 2021.

We analyzed 1,303 SARS-CoV-2 whole-genome sequences from Vietnam, and found the Alpha and Delta variants were responsible for a large nationwide outbreak of COVID-19 in 2021. The Delta variant was confined to the AY.57 lineage and caused >1.7 million infections and >32,000 deaths. Viral transmission was strongly affected by nonpharmaceutical interventions.

Spectroscopic analysis, kinetic mechanism, computational docking, and molecular dynamics of active metabolites from the aerial parts of Astragalus membranaceusBunge as tyrosinase inhibitors.

A new isoflavane derivative (2), a new natural isoflavane (6), four new oleanane-type triterpenoid saponins (23, 25, 28, and 29), and twenty three known secondary metabolites (1, 3-5, 7-22, 24, 26, and 27) were isolated from the aerial parts of Astragalus membranaceus Bunge. The chemical structures of these compounds were elucidated through spectroscopic analysis and compared with those identified in previous studies. Tyrosinase inhibition ability of isolated compounds (1-29) was evaluated. Of these, compounds 3, 4, 6, and 14 exhibited inhibitory effects, with IC50 values ranging from 24.6 to 59.2 µM. According to kinetic analysis, compounds 3 and 4 were non-competitive inhibitors of tyrosinase, whereas compounds 6 and 14 inhibited tyrosinase in uncompetitive and competitive modes, respectively. Molecular docking analysis identified that compounds 3, 4, and 6 could bind to allosteric sites and compound 14 could bind to the catalytic site of tyrosinase, which is consistent with the results of kinetic studies. Molecular dynamics behaviors of the active compounds in complex with tyrosinase were investigated via 60 ns simulation which demonstrated their high stability. These findings indicate that the aerial parts of A. membranaceus are a potential source of natural tyrosinase inhibitors.

Urinary catecholamine excretion, cardiovascular variability, and outcomes in tetanus.

Severe tetanus is characterized by muscle spasm and cardiovascular system disturbance. The pathophysiology of muscle spasm is relatively well understood and involves inhibition of central inhibitory synapses by tetanus toxin. That of cardiovascular disturbance is less clear, but is believed to relate to disinhibition of the autonomic nervous system. The clinical syndrome of autonomic nervous system dysfunction (ANSD) seen in severe tetanus is characterized principally by changes in heart rate and blood pressure which have been linked to increased circulating catecholamines. Previous studies have described varying relationships between catecholamines and signs of ANSD in tetanus, but are limited by confounders and assays used. In this study, we aimed to perform detailed characterization of the relationship between catecholamines (adrenaline and noradrenaline), cardiovascular parameters (heart rate and blood pressure) and clinical outcomes (ANSD, mechanical ventilation required, and length of intensive care unit stay) in adults with tetanus, as well as examine whether intrathecal antitoxin administration affected subsequent catecholamine excretion. Noradrenaline and adrenaline were measured by ELISA from 24-h urine collections taken on day 5 of hospitalization in 272 patients enrolled in a 2 × 2 factorial-blinded randomized controlled trial in a Vietnamese hospital. Catecholamine results measured from 263 patients were available for analysis. After adjustment for potential confounders (i.e., age, sex, intervention treatment, and medications), there were indications of non-linear relationships between urinary catecholamines and heart rate. Adrenaline and noradrenaline were associated with subsequent development of ANSD, and length of ICU stay.

Isolation, structural elucidation and molecular docking studies against SARS-CoV-2 main protease of new stigmastane-type steroidal glucosides isolated from the whole plants of Vernonia gratiosa.

Phytochemical investigation of the whole plants of Vernonia gratiosa Hance. led in the isolation and identification of two new stigmastane-type steroidal glucosides (1-2), namely vernogratiosides A (1), and B (2). Their chemical structures were fully elucidated based on 1 D/2D NMR spectroscopic, HR-ESI-MS data analyses, and by producing derivatives by chemical reactions. The binding potential of the isolated compounds to replicase protein - main protease of SARS-CoV-2 were examined using the molecular docking simulations. Our results show that the isolated steroidal glucosides (1-2) bind to the substrate-binding site of SARS-CoV-2 main protease with binding affinities of -7.2 and -7.6 kcal/mol, respectively, as well as binding abilities equivalent to N3 inhibitor that has already been reported (-7.5 kcal/mol).

Kinetics of Neutralizing Antibodies against Omicron Variant in Vietnamese Healthcare Workers after Primary Immunization with ChAdOx1-S and Booster Immunization with BNT162b2.

We studied the development and persistence of neutralizing antibodies against SARS-CoV-2 ancestral strain, and Delta and Omicron (BA.1 and BA.2) variants in Vietnamese healthcare workers (HCWs) up to 15 weeks after booster vaccination. We included 47 HCWs, including group 1 (G1, N = 21) and group 2 (G2; N = 26) without and with breakthrough Delta variant infection before booster immunization, respectively). The study participants had completed primary immunization with ChAdOx1-S and booster vaccination with BNT162b2. Neutralizing antibodies were measured using a surrogate virus neutralization assay. Of the 21 study participants in G1, neutralizing antibodies against ancestral strain, Delta variant, BA.1, and BA.2 were (almost) abolished at month 8 after the second dose, but all had detectable neutralizing antibodies to the study viruses at week 2 post booster dose. Of the 26 study participants in G2, neutralizing antibody levels to BA.1 and BA.2 were significantly higher than those to the corresponding viruses measured at week 2 post breakthrough infection and before the booster dose. At week 15 post booster vaccination, neutralizing antibodies to BA.1 and BA.2 dropped significantly, with more profound changes observed in those without breakthrough Delta variant infection. Booster vaccination enhanced neutralizing activities against ancestral strain and Delta variant compared with those induced by primary vaccination. These responses were maintained at high levels for at least 15 weeks. Our findings emphasize the importance of the first booster dose in producing cross-neutralizing antibodies against Omicron variant. A second booster to maintain long-term vaccine effectiveness against the currently circulating variants merits further research.