Change of specific T cells in an emerging neonatal infectious disease induced by a bacterial superantigen

A new epidemic, NTED, has recently occurred in Japan. The cause of NTED is a bacterial superantigen, TSST-1. The aim of the present study was to analyze the change in Vbeta2(+) T cells reactive to TSST-1 in NTED in order to establish T-cell-targeted diagnostic criteria for NTED. Blood samples from 75 patients with clinically diagnosed NTED were collected from 13 neonatal intensive care units throughout Japan. We investigated the percentages of Vbeta2(+), Vbeta3(+) and Vbeta12(+) T cells and their CD45RO expressions in the samples using flow cytometry. In 18 of the 75 patients, we conducted multiple examinations of the T cells and monitored serial changes. The Vbeta2(+) T-cell population rapidly changed over three phases of the disease. Whereas the percentage of Vbeta2(+) T cells was widely distributed over the entire control range, CD45RO expression on Vbeta2(+) T cells in CD4(+) in all 75 patients was consistently higher than the control range. Patients cannot necessarily be diagnosed as having NTED based on expansion of Vbeta2(+) T cells alone in the early acute phase. Instead, CD45RO expression on specific Vbeta2(+) cells is a potential diagnostic marker for a rapid diagnosis of NTED. We present three diagnostic categories of NTED. Fifty patients (66.7%) were included in the category 'definitive NTED'. It is important to demonstrate an increase of Vbeta2(+) T cells in the following phase in cases of 'probable NTED' or 'possible NTED'.