Impact of the Coronavirus Disease 2019 Pandemic on Medical Practices in Awaji Island.

Introduction: Since the first confirmed case of coronavirus disease 2019 (COVID-19) in China, COVID-19 continues to be a global threat and exerts a significant impact on medical practices. This study aims to investigate the impact of the COVID-19 pandemic on medical practices in Awaji Island, a remote island in Japan. Methods: First, we conducted a survey on the epidemiological characteristics of COVID-19 on Awaji Island before and during the pandemic. Next, using a questionnaire, we conducted a survey with doctors working full time at Hyogo Prefectural Awaji Medical Center, which is the only designated infectious disease hospital on Awaji Island. Results: The COVID-19 infection rate of Awaji Island was lower than that of Hyogo Prefecture and of Japan as a whole, although the peaks occurred simultaneously. Outpatient visits as well as hospitalized patients, i.e., inpatients, decreased during the pandemic as a result of restrictions on surgeries and hospitalizations, with no changes in the disease composition ratio. The results of the questionnaire show that during the pandemic, doctors working full time at our hospital worked less and slept more. Furthermore, data obtained from the Medical Affairs Department showed a decrease in overtime hours worked and an increase in the number of days of paid holidays taken. Conclusions: Epidemiologically, the impact of the COVID-19 pandemic on Awaji Island showed a similar trend to that in Japan, but the results of the survey questionnaire indicated that doctors working full time at our hospital were not necessarily adversely affected.

IL-12 regulates the expansion, phenotype, and function of murine NK cells activated by IL-15 and IL-18.

NK cells, which are composed of phenotypically and functionally heterogeneous subpopulations, play critical roles in immunity against cancer. The mechanism of generation of distinct subsets such as the effector and regulatory subtypes is unclear. Here, we show that this process comprises several steps, including generation of proliferating, highly cytotoxic cells activated by IL-15/IL-18 and differentiation into distinct cell populations induced with IL-12. Freshly prepared murine splenic NK cells expressed IL-15Rs and IL-18Rs and rapidly began to proliferate following stimulation with IL-15/IL-18. The proliferating NK cells highly expressed various activation markers such as B220, CD49b (DX5), lysosome-associated membrane glycoprotein 1 (LAMP-1), DNAX accessory molecule 1, perforin, and granzyme B and showed reduced expression of natural killer cell p46-related protein (NKp46) and IL-18Rα. These cells exerted strong cytotoxicity against YAC-1 cells, but did not secrete cytokines. IL-12 rapidly activated STAT4 in these cells, induced IFN-γ production, and then upregulated p21 and p27, leading to withdrawal from the cell cycle. In parallel, IL-12-stimulated cells gradually reduced cytotoxicity, decreased expression of activation markers, and instead increased expression of Sca-1, CD25, CD49a, and NKp46. Some IL-15/IL-18-induced cells strongly expressed PD-1, whereas NK cells induced with IL-15/IL-18 and IL-12 expressed high levels of T cell immunoglobulin mucin-3, LAG-3, and natural killer group 2 A. Furthermore, these cells spontaneously secreted IL-10 and TGF-ß following prolonged incubation. Thus, IL-12 regulates expansion of NK cells activated with IL-15/IL-18, influences the population size of highly cytotoxic cells, and induces differentiation to unique cells sharing some phenotypes of ILCs.

Frontline Science: IL-18 primes murine NK cells for proliferation by promoting protein synthesis, survival, and autophagy.

Combined stimulation by IL-2 and IL-18 effectively promotes proliferation of NK cells, whereas singular stimulation does not. In this study, synergistic effects of these cytokines on NK cells proliferation was analyzed, focusing on the roles of IL-18. In splenic resting NK cells from IL-18KO mice, IL-18 rapidly activated NF-κB independently of IL-2, and activated or up-regulated various molecules downstream of PI3K/AKT and mTOR, including S6, Bcl-XL, ATG5, and LC3II, accompanying increases in cell growth and survival. Thus, IL-18 alone was revealed to augment various cellular processes (gene transcription, protein synthesis, survival) in the absence or presence of IL-2. Notably, combined IL-18 and IL-2 promoted autophagosome formation. In addition, priming NK cells with IL-18 augmented IL-2R, especially CD25, and enabled cells to respond to IL-2, resulting in activation of STAT3 and STAT5, followed by increase of cyclin B1 leading to proliferation. However, IL-2 alone failed to activate STAT3 or STAT5 in resting IL18KO NK cells. These results clarify the distinct roles of IL-2 and IL-18 in NK cell proliferation, and the intrinsic roles of IL-18 in various cellular processes, suggesting a range of functions of IL-18 expressed in an array of nonhematopoietic cells.