Progressive multifocal leukoencephalopathy (PML) is a devastating demyelinating disease caused by JC virus (JCV), predominantly affecting patients with impaired cellular immunity. PML is a non-reportable disease with a few exceptions, making national surveillance difficult. In Japan, polymerase chain reaction (PCR) testing for JCV in the cerebrospinal fluid (CSF) is performed at the National Institute of Infectious Diseases to support PML diagnosis. To clarify the overall profile of PML in Japan, patient data provided at the time of CSF-JCV testing over 10 years (FY2011–2020) were analyzed. PCR testing for 1537 new suspected PML cases was conducted, and 288 (18.7%) patients tested positive for CSF-JCV. An analysis of the clinical information on all individuals tested revealed characteristics of PML cases, including the geographic distribution, age and sex patterns, and CSF-JCV-positivity rates among the study subjects for each type of underlying condition. During the last five years of the study period, a surveillance system utilizing ultrasensitive PCR testing and widespread clinical attention to PML led to the detection of CSF-JCV in the earlier stages of the disease. The results of this study will provide valuable information not only for PML diagnosis, but also for the treatment of PML-predisposing conditions.

Zika virus (ZIKV) infection during pregnancy causes a wide spectrum of congenital abnormalities and postnatal developmental sequelae such as fetal loss, intrauterine growth restriction (IUGR), microcephaly, or motor and neurodevelopmental disorders. Here, we investigated whether a mouse pregnancy model recapitulated a wide range of symptoms after congenital ZIKV infection, and whether the embryonic age of congenital infection changed the fetal or postnatal outcomes. Infection with ZIKV strain PRVABC59 from embryonic day 6.5 (E6.5) to E8.5, corresponding to the mid-first trimester in humans, caused fetal death, fetal resorption, or severe IUGR, whereas infection from E9.5 to E14.5, corresponding to the late-first to second trimester in humans, caused stillbirth, neonatal death, microcephaly, and postnatal growth deficiency. Furthermore, 4-week-old offspring born to dams infected at E12.5 showed abnormalities in neuropsychiatric state, motor behavior, autonomic function, or reflex and sensory function. Thus, our model recapitulated the multiple symptoms seen in human cases, and the embryonic age of congenital infection was one of the determinant factors of offspring outcomes in mice. Furthermore, maternal neutralizing antibodies protected the offspring from neonatal death after congenital infection at E9.5, suggesting that neonatal death in our model could serve as criteria for screening of vaccine candidates.

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease caused by the JC polyomavirus (JCPyV). Based on the clinical criteria, PML is diagnosed via polymerase chain reaction (PCR) detection of JCPyV DNA in cerebrospinal fluid (CSF) in combination with neurological and imaging findings. Although the utility of CSF JCPyV testing using ultrasensitive PCR assays has been suggested, its potential requires further evaluation. This study retrospectively analyzed the detection performance of ultrasensitive PCR for CSF JCPyV in patients who underwent brain tissue examination based on the pathological diagnostic criteria for PML. Of the 110 patients with pathologically confirmed definite PML or not PML, standard and ultrasensitive CSF testing was performed for 36 and 74 patients, respectively. The sensitivity of ultrasensitive CSF JCPyV testing of the initial specimens was 85%. With the addition of the follow-up testing, this figure increased to 95%. The specificity and false-positive rate of ultrasensitive CSF JCPyV testing, including follow-up, were 100% and 0%, respectively. No statistically significant correlation was observed between CSF and brain JCPyV levels. The results of this study demonstrate the high sensitivity and accuracy of ultrasensitive CSF JCPyV testing and provide essential information for the clinical diagnosis of PML.