Omicron variant susceptibility to neutralizing antibodies induced in children by natural SARS-CoV-2 infection or COVID-19 vaccine

The novel SARS-CoV-2 Omicron variant may increase the risk of re-infection and vaccine breakthrough infections as it possesses key mutations in the spike protein that affect neutralizing antibody response. Most studies on neutralization susceptibility were conducted using specimens from adult COVID-19 patients or vaccine recipients. However, since the paediatric population has an antibody response to SARS-CoV-2 infection that is distinct from the adult population, it is critical to assess the neutralization susceptibility of pediatric serum specimens. This study compared the neutralization susceptibility of serum specimens collected from 49 individuals of <18 years old, including 34 adolescent BNT162b2 (Pfizer-BioNTech) vaccine recipients, and 15 recovered COVID-19 patients aged between 2 and 17. We demonstrated that only 38.2% of BNT162b2 vaccine recipients and 26.7% of recovered COVID-19 patients had their serum neutralization titre at or above the detection threshold in our live virus microneutralization assay. Furthermore, the neutralizing antibody titer against the Omicron variant was substantially lower than those against the ancestral virus or the Beta variant. Our results suggest that vaccine recipients and COVID-19 patients in the pediatric age group will likely be more susceptible to vaccine breakthrough infections or reinfections due to the Omicron variant than previous variants

Targeting DNA-PKcs and ATM with miR-101 Sensitizes Tumors to Radiation

Radiotherapy kills tumor-cells by inducing DNA double strand breaks (DSBs). However, the efficient repair of tumors frequently prevents successful treatment. Therefore, identifying new practical sensitizers is an essential step towards successful radiotherapy. In this study, we tested the new hypothesis: identifying the miRNAs to target DNA DSB repair genes could be a new way for sensitizing tumors to ionizing radiation.HERE, WE CHOSE TWO GENES: DNA-PKcs (an essential factor for non-homologous end-joining repair) and ATM (an important checkpoint regulator for promoting homologous recombination repair) as the targets to search their regulating miRNAs. By combining the database search and the bench work, we picked out miR-101. We identified that miR-101 could efficiently target DNA-PKcs and ATM via binding to the 3'- UTR of DNA-PKcs or ATM mRNA. Up-regulating miR-101 efficiently reduced the protein levels of DNA-PKcs and ATM in these tumor cells and most importantly, sensitized the tumor cells to radiation in vitro and in vivo.These data demonstrate for the first time that miRNAs could be used to target DNA repair genes and thus sensitize tumors to radiation. These results provide a new way for improving tumor radiotherapy

Creating localized DNA double-strand breaks with microirradiation.

We describe a protocol for creating localized DNA double-strand breaks (DSBs) with minimal requirements that can be applied in cell biology and molecular biology. This protocol is based on the combination of 5-bromo-2\u27-deoxyuridine (BrdU) labeling and ultraviolet C (UVC) irradiation through porous membranes. Cells are labeled with 10 μM BrdU for 48-72 h, washed with Ca(2+)- and Mg(2+)-free PBS(-), covered by polycarbonate membranes with micropores and exposed to UVC light. With this protocol, localized DSBs are created within subnuclear areas, irrespective of the cell cycle phase. Recruitment of proteins involved in DNA repair, DNA damage response, chromatin remodeling and histone modifications can be visualized without any specialized equipment. The quality is the same as that obtained by laser microirradiation or by any other focal irradiation. DSBs become visible within 30 min of UVC irradiation.without figure