The application of the lytic domain of endolysin from Staphylococcus aureus bacteriophage in milk.

Staphylococcus aureus is a widespread foodborne pathogen that threatens human health. In particular, multidrug-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) are emerging problems in modern health care, food safety, and animal health, which require the development of new antimicrobials to replace overused conventional antibiotics. Dairy products can potentially act as vehicles for the transmission of S. aureus and other antibiotic-resistant strains from the farm into the general human population, and should be controlled during the production and storage process. Recently, bacteriophage endolysins, which degrade the cell wall that is indispensable for bacteria, have been deemed promising antimicrobial agents. In this study, one endolysin, LysGH15, demonstrated prominent antimicrobial efficacy against S. aureus, as did its catalytic domain, cysteine, histidine-dependent amidohydrolase/peptidases (CHAP)LysGH15 alone. The LysGH15 and CHAPLysGH15 exhibited different characteristics in one MRSA strain (MRSA 2701), reaching the highest activity under different conditions (35°C and pH 6.0 for LysGH15, 40°C and pH 9.0 for CHAPLysGH15). A difference in the sensitivity of LysGH15 and CHAPLysGH15 to NaCl concentration was found, where the lytic activity of LysGH15 depends strongly on its binding domain's binding capacity, which is positively correlated with the NaCl concentration, whereas the CHAPLysGH15 activity showed a negative correlation with the NaCl concentration. When the NaCl concentration was 450 mM, the lytic activity of LysGH15 reached its peak, whereas the lytic activity of CHAPLysGH15 was the highest in the absence of NaCl. The difference in NaCl sensitivity between LysGH15 and CHAPLysGH15 may be due to the sensitivity of the SH3b binding protein of LysGH15 to NaCl. The CHAPLysGH15 was tested as a biopreservative in whole and skim milk and exerted effective control against S. aureus (declined by approximately 2.5 log10 cfu/mL when incubated at 4°C for 8 h), which suggests promise for application in dairy products.

Impact of inactivated vaccines on decrease of viral RNA levels in individuals with the SARS-CoV-2 Omicron (BA.2) variant: A retrospective cohort study in Shanghai, China.

Background: SARS-CoV-2 Omicron (BA.2) has stronger infectivity and more vaccine breakthrough capability than previous variants. Few studies have examined the impact of inactivated vaccines on the decrease of viral RNA levels in individuals with the Omicron variant, based on individuals' continuous daily cycle threshold (Ct) values and associated medical information from the infection to hospital discharge on a large population. Methods: We extracted 39,811 individuals from 174,371 Omicron-infected individuals according to data inclusion and exclusion criteria. We performed the survival data analysis and Generalized Estimating Equation to calculate the adjusted relative risk (aRR) to assess the effect of inactivated vaccines on the decrease of viral RNA levels. Results: Negative conversion was achieved in 54.7 and 94.3% of all infected individuals after one and 2 weeks, respectively. aRRs were shown weak effects on turning negative associated with vaccinations in asymptomatic infections and a little effect in mild diseases. Vaccinations had a protective effect on persistent positivity over 2 and 3 weeks. aRRs, attributed to full and booster vaccinations, were both around 0.7 and had no statistical significance in asymptomatic infections, but were both around 0.6 with statistical significance in mild diseases, respectively. Trends of viral RNA levels among vaccination groups were not significant in asymptomatic infections, but were significant between unvaccinated group and three vaccination groups in mild diseases. Conclusion: Inactivated vaccines accelerate the decrease of viral RNA levels in asymptomatic and mild Omicron-infected individuals. Vaccinated individuals have lower viral RNA levels, faster negative conversion, and fewer persisting positive proportions than unvaccinated individuals. The effects are more evident and significant in mild diseases than in asymptomatic infections.

HCV Core protein represses DKK3 expression via epigenetic silencing and activates the Wnt/ß-catenin signaling pathway during the progression of HCC.

The Wnt/ß-catenin signaling pathway is frequently activated in hepatocellular carcinoma (HCC). A number of studies have focused on the aberrant hypermethylation of the DKK family proteins and its role in regulating the activation of specific signaling pathways. However, the exact way by which DKK regulates the signaling pathway caused by Core protein of HCV has not been reported. In the present study, we evaluated the expression level of DKK and its aberrant promoter methylation to investigate the involvement of epigenetic regulation in hepatoma cell lines. The transcription and protein expression of DKK1 was significantly increased, whereas the transcription and protein expression levels of DKK2, DKK3, and DKK4 were significantly decreased following overexpression of Core protein. Pyrosequencing indicated that hypermethylation of DKK3 was increased. This was associated with increased expression of Dnmt1. The investigation of the molecular mechanism indicated that HCV Core protein interacted with Dnmt1, which combined with the promoter of DKK3, leading to methylation of DKK3. Functional studies indicated that Core protein promoted the growth, migration and invasion of cancer cells. However, upregulation of the expression of DKK3 and/or the knockdown of the expression of Dnmt1 inhibited the growth, migration and invasion of cancer cells. Taken together, the data indicated that epigenetic silencing of DKK3 caused by Dnmt1 activated the Wnt/ß-catenin pathway in HCV Core-mediated HCC. Therefore, DKK3 may be a potential diagnostic and therapeutic target for HCC.