Rapid and accurate diagnostic tests are essential for controlling the ongoing Covid-19 pandemic. Although the current standard involves testing of nasopharyngeal swab specimens by quantitative reverse-transcriptase polymerase chain reaction (RT-qPCR) to detect SARS-CoV-2, saliva specimens may be an alternative diagnostic sample.^1-4 Rigorous evaluation is needed to determine how saliva specimens compare with nasopharyngeal swab specimens with respect to sensitivity in detection of SARS-CoV-2 during the course of infection.

Toll-like receptors (TLRs) are important sensors of microbial pathogens and mediators of innate immune responses. Although the signal transduction of TLRs is well elucidated, their basal regulation is largely unexplored. Here we show that the tumor suppressor p53 positively regulates the transcription of TLR3, a receptor for viral double-stranded RNA and poly(I-C), by binding to the p53 site in the TLR3 promoter. TLR3 expression was lower in HCT116 p53^−/− cells than in HCT116 p53^+/+ cells. Activation of p53 by 5-fluorouracil increased the TLR3 mRNA in epithelial cell lines with wild-type p53 but not in cell lines harboring mutant p53. Knockdown of p53 by small interfering RNA decreased the TLR3 expression. TLR3 mRNA was also lower in liver and intestine of p53^−/− mice than in p53^+/+ mice. Furthermore, the poly(I-C)-induced phosphorylation of IκB-α, nuclear translocation of NF-κB, and phosphorylation of interferon regulatory transcription factor 3, were drastically reduced in HCT116 p53^−/− cells, indicating a dysregulation of the two signaling pathways governed by TLR3. Consequently, induction of interleukin-8 and beta interferon after poly(I-C) stimulation was impaired in HCT116 p53^−/− cells. These results suggest that p53 influences TLR3 expression and function and highlight a role of p53 in innate immune response in epithelial cells.

Immunodeficient mice are becoming invaluable tools in human stem cell and tumor research. In this study, we generated Rag‐2/Jak3 double‐deficient (Rag‐2^−/−Jak3^−/−) mice with a C57/BL6 and Balb/c genetic background and compared the human lymphohematopoietic cell engraftment rate. Human cord blood‐derived CD34⁺ hematopoietic stem cells were successfully engrafted into Balb/c Rag‐2^−/−Jak3^−/− mice; however, the engraftment rate was far lower in C57/BL6 Rag‐2^−/−Jak3^−/− mice. Transplantation of human peripheral blood mononuclear cells resulted in the same tendency. Thus, a Balb/c background offers superior engraftment capacity than a C57/BL6 background and provides an attractive model for human hematopoietic cell engraftment.