Seroprevalence of antibodies to SARS-CoV-2 in healthcare workers in a nonepidemic region, Japan: A hospital-based study on May, 2020.

The polymerase chain reaction (PCR) testing rate is low in our local area and the true rate of coronavirus disease 2019 (COVID-19) infection may include many asymptomatic individuals. We conducted a serosurveillance using antibody testing in an area where official report of COVID-19 infection is not done yet. Blood samples were obtained from 1404 healthcare workers (41 ± 11 years) in our hospital on May 29-31, 2020. First, the potential infection frequency was confirmed using two quantitative antibody tests. In addition, the usefulness of rapid antibody kit testing for COVID-19 serosurveillance was examined. A COVID-19-indected case was defined as showing positive results in both quantitative tests. None of 1404 samples had positive results from the two quantitative tests. The false positive rates were 0.36% and 0.07%, whereas those in rapid antibody kits were 3.3% and 3.0%. In conclusion, as of May, 2020, potential spread mainly by asymptomatic individuals infected with COVID-19 was not found in our local area where there was no official report of COVID-19, even if the PCR testing rate was low. Rapid antibody kits might not be useful due to the high false positive rate in an area with a low incidence of COVID-19 infected individuals.

Orthogonal antibody testing for COVID-19 among healthcare workers in a non-epidemic place and time:Japan's Iwate Prefecture, May 18-31, 2020.

Of the 47 prefectures in Japan, Iwate had the fewest cases of coronavirus disease 2019 (COVID-19), with the first diagnosis officially confirmed on July 28, 2020. A baseline serological survey of COVID-19 antibodies is essential to accurately evaluate an epidemic outbreak. The primary purpose of this study was to determine pre-epidemic prevalence of COVID-19 antibodies among healthcare workers, using two laboratory-based quantitative tests. In addition, a point-of-care (POC) qualitative test, rapid, simple, and convenient for primary care clinics, was compared with the laboratory-based tests. All antibody tests were performed on serum from 1,000 healthcare workers (mean age, 40 ± 11 years) in Iwate Prefectural Central Hospital, May 29-31, 2020. A COVID-19 case was defined as showing positive results in both laboratory-based quantitative tests. None of 1,000 samples had positive results in both of the laboratory immunoassays. The POC test showed positive results in 33 of 1,000 samples (3.3%) (95% confidence interval:2.19-4.41), but no samples were simultaneously positive in both laboratory-based tests. In conclusion, COVID-19 cases were not serologically confirmed by a baseline control study of healthcare workers at our hospital in late May, 2020. Moreover, the POC qualitative test may offer no advantage in areas with very low prevalence of COVID-19, due to higher false-positive reactions compared with laboratory-based quantitative immunoassays.

[Role of lysophosphatidic acid as a mechanosensitizer].

The mechanotransduction mechanisms play an important role in regulation of specific cellular response or maintenance of cellular homeostasis in a wide variety of cell types. Increase in intracellular free Ca(2+) concentration ([Ca(2+)](i)) is an important signal in the first step of mechanotransduction. Mechanosensitive (MS) cation channels are thought to be a putative pathway of Ca(2+) entry; however, the molecular mechanisms remain unclear. We have previously demonstrated that lysophosphatidic acid (LPA), a bioactive phospholipid present in human plasma, sensitizes the response of [Ca(2+)](i) to mechanical stress in cultured smooth muscle cells, cultured lung epithelial cells, and cultured lens epithelial cells. Using real-time confocal microscopy, local increases in [Ca(2+)](i) in several regions within the cell subjected to mechanical stress were clearly visualized in cultured bovine lens epithelial cells and cultured vascular endothelial cells in the presence of LPA. We called the phenomenon "Ca(2+) spots". Pharmacological studies revealed that the Ca(2+) spot is an elementary Ca(2+)-influx event through MS channels. In this review, possible physiological and pathophysiological roles of LPA as a mechanosensitizer are discussed.