東本 祐紀

Varicella-zoster virus (VZV) causes varicella in children, establishes lifelong latency and reactivates to cause herpes zoster later in life. Implementation of routine varicella vaccination in Japan since 2014 has reduced varicella cases, however, breakthrough varicella still occurs. This study aimed to clarify the current distribution of VZV clade among pediatric varicella patients and adults with VZV-associated central nervous system (CNS) infections in Japan. Skin swabs were collected from varicella patients (< 15 years) in Aichi Prefecture (September 2015-August 2017). Cerebrospinal fluid (CSF) samples were obtained from adult patients (> 15 years) with VZV-associated CNS infections (November 2014-June 2023). VZV DNA was detected by PCR, and its clade was determined by sequencing open reading frame (ORF) 22 and ORF37 regions. Wild-type and Oka vaccine strains were distinguished by loop-mediated isothermal amplification (LAMP) method. Of 124 pediatric swab samples and 62 adult CSF samples 94.4% belonged to clade 2 and 4.8% clade 1. No clade 1 samples were detected in CSF samples. No vaccine strain was detected. Clinical characteristics did not differ significantly among clades. Clade 2 VZV predominates in both pediatric varicella and adult VZV-related CNS infections in Japan with sporadic clade 1 varicella cases.

Objectives: To establish a point-of-care test for coronavirus disease 2019 (COVID-19), we developed a dry loop-mediated isothermal amplification (LAMP) method to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA. Methods: We carried out reverse transcription (RT)-LAMP using the Loopamp SARS-CoV-2 Detection kit (Eiken Chemical, Tokyo, Japan). The entire mixture, except for the primers, is dried and immobilized inside the tube lid. Results: To determine the specificity of the kit, 22 viruses associated with respiratory infections, including SARS-CoV-2, were tested. The sensitivity of this assay, determined by either a real-time turbidity assay or colorimetric change of the reaction mixture, as evaluated by the naked eye or under illumination with ultraviolet light, was 10 copies/reaction. No LAMP product was detected in reactions performed with RNA from any pathogens other than SARS-CoV-2. After completing an initial validation analysis, we analyzed 24 nasopharyngeal swab specimens collected from patients suspected to have COVID-19. Of the 24 samples, 19 (79.2%) were determined by real-time RT-PCR analysis as being positive for SARS-CoV-2 RNA. Using the Loopamp SARS-CoV-2 Detection kit, we detected SARS-CoV-2 RNA in 15 (62.5%) of the 24 samples. Thus, the sensitivity, specificity, positive predictive value, and negative predictive values of the Loopamp 2019-CoV-2 detection reagent kit were 78.9%, 100%, 100%, and 55.6%, respectively. Conclusions: The dry LAMP method for detecting SARS-CoV-2 RNA is fast and easy to use, and its reagents can be stored at 4°C, solving the cold chain problem; thus, it represents a promising tool for COVID-19 diagnosis in developing countries.

In the era of universal varicella vaccination, diagnosis of varicella is challenging, especially for breakthrough cases. We sought to clarify the reliability of direct varicella-zoster virus (VZV) loop-mediated isothermal amplification (LAMP) and DermaQuick® VZV using the immunochromatography technique as rapid diagnostic tests for varicella. In addition, the usefulness of saliva as a sample type for direct LAMP was investigated. Among the 46 enrolled patients with suspected VZV infection, 31 patients (67.3%) were positive for the nucleic acid test based on real-time PCR from skin swab samples. Direct LAMP of skin swabs was positive in 29 (63.0%) of 46 patients. DermaQuick® VZV was positive in 25 (54.3%) of 46 patients. VZV DNA was detected in only 48.4% of oral swabs with the direct LAMP method. With real-time polymerase chain reaction (PCR) as the standard for diagnosing varicella, the sensitivity and specificity of DermaQuick® VZV were 80.7% and 100%, respectively. The sensitivity and specificity of direct LAMP from skin swabs were 93.6% and 100%, respectively. The sensitivity and specificity of real-time PCR for DNA extracted from oral swabs were 74.2% and 93.3%, respectively. Thus, oral swab samples are not suitable for breakthrough varicella diagnosis. Although DermaQuick® VZV is considered the most convenient point-of-care test for varicella, its sensitivity and specificity were lower than those of direct VZV LAMP.

We analyzed serially collected serum samples from healthy adults who underwent BNT162b2 vaccination to elucidate the association between spike (S)-IgG antibody titers determined by ELISA using the WHO international standard (NIBSC code 20/136) and neutralizing antibody titers against three live SARS-CoV-2 variants. This study included 53 health care workers who received two doses of the BNT162b2 vaccine. S-IgG and nucleocapsid (N)-IgG antibody titers were measured by ELISA. Neutralizing (NT) antibody responses against three variants (Wuhan D614 G: KUH003, Alpha, and Delta) were evaluated before and after the first and second vaccination. N-IgG were not detected in any serum samples. S-IgG antibody titers remarkably increased after two BNT162b2 vaccine doses in all participants. S-IgG antibody titers were strongly correlated with NT titers against three variants of live viruses: KUH003 (r = 0.86), Alpha (r = 0.72), and Delta (r = 0.84). Serum samples from participants after one dose of BNT162b2 neutralized Alpha efficiently (median titer, 113.0), but median NT titers against KUH003 and Delta variants were lower, 57.0 and 28.0, respectively (p < .01). Two doses of the BNT162b2 vaccine elicited a strong immune response in this study. The second dose was required for induction of a strong booster effect. Serum collected from BNT162b2 vaccine recipients contained significantly lower neutralizing activity against Delta than that of against KUH003 (p < .0001) and Alpha (p < .0001). If a new variant emerges, live virus-based NT titers should be examined in serum obtained from vaccine recipients to evaluate vaccine efficacy for protection against infection.