Coxsackievirus B (CVB) is one of the major pathogens of aseptic meningitis and meningioencephalitis, particularly in newborn infants. To analyze the influence of neural maturation on susceptibility to CVB infection, we prepared immature and mature neurons from 16-day-old BALB/c embryonic cortex. In contrast to immature neurons, mature neurons were less susceptible to CVB5 infection, as indicated by the decrease of cytopathic features. In mature neurons, progeny virus production was significantly hindered, and virus capsid protein VP1 synthesis and virus genome amplification were concomitantly reduced. In addition, the expression of coxsackievirus and adenovirus receptor (CAR), the major receptor of CVB5, was down-regulated in mature neurons. The antibody treatment specific to CAR significantly attenuated CVB5 susceptibility of immature neurons. These findings demonstrate that mature neurons become less susceptible to CVB by the decrease of CAR level. Thus, the data strongly support the idea that the level of virus receptor in neurons is one of the crucial determinants in the age-dependency of CVB virulence in central nervous system.

Coxsackievirus B (CVB) is often associated with aseptic meningitis and encephalitis, but the six serotypes of CVB vary in their relative disease severity. To elucidate the detailed mechanisms of CVB-induced cytopathological effects, the morphological and biochemical characteristics caused by the CVB serotypes in mouse primary cortical neuronal cells were investigated. By 24 h post-infection, all CVB serotypes except CVB2 induced severe cytotoxic alterations, including a loss of neurites. Both fluorescence and transmission electron microscopy revealed CVB-induced morphological changes indicative of apoptosis, including heavily condensed nuclei, subsequent chromatin condensation into the periphery of the nuclei and oligonucleosomal DNA fragmentation. It was also found that infection with all six CVB serotypes led to productive virus replication, which was completed prior to an apoptotic signal. The caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone significantly inhibited nuclear changes associated with virus-induced apoptosis, but had less effect on virus-associated cytopathic effects and no effect on virus production. In contrast, the transcription inhibitor actinomycin D profoundly inhibited all three virus-induced events. Taken together, these findings demonstrate that all six CVB serotypes can efficiently replicate in mouse cortical neuronal cells and that productive replication of these CVBs, except for CVB2, induces multiple cytopathological effects, including apoptotic alterations.