[Inactivation of EV71 by Exposure to Heat and Ultraviolet Light].

Enterovirus 71 (EV71) is a major agent of hand, foot and mouth disease that can cause a severe burden of disease to children. To identify an effective method for the control and prevention of EV71, we studied the effect of exposure to heat and ultraviolet (UV) light upon EV71 inactivation. We found that exposure to 50 degrees C could not inactivate the infectivity of EV71. However, exposure to 60 degrees C and 70 degrees C could inactivate EV71 effectively. EV71 could be inactivated after exposure to UV light at a distance between the sample and a lamp of 30 cm for 30 min or 60 min because viral genomic RNA was destroyed. However, fetal bovine serum (FBS) could attenuate the inactivation proffered by heat and UV light. Attenuation effects of FBS were correlated positively with FBS concentration. Hence, EV71 can be inactivated by exposure to heat and UV light, and our results could provide guidance on prevention of the spread of EV71.

MEK1-ERKs signal cascade is required for the replication of Enterovirus 71 (EV71).

The role of the MEK1-ERK signaling cascade in the replication cycle of Enterovirus 71 (EV71), the primary cause of hand, foot and mouth disease (HFMD), has been analyzed. In vitro infection with EV71 induced a biphasic activation of ERK. The two phases of activation appeared to be triggered by different mechanisms, with the first phase being activated by the binding of viral particles to the membrane receptor of host cells and the second probably being in response to the production of new virus particles. Inhibition of ERK activation by U0126 was found to severely impair virus production. A similar reduction in EV71 replication was also observed when MEK1 expression was subject to knockdown using specific siRNAs. By contrast knockdown of MEK2 expression showed that it was dispensable for virus replication cycle, despite both MEK isoforms being activated and translocated to the nucleus equally well in response to virus infection. Overall, this study suggests distinct functions of the two isoforms of MEK in EV71 replication cycle, with an essential role for MEK1 in stimulating the ERK signaling cascade to promote virus replication. Taken together with our previous work on herpes simplex virus type 2 (HSV2) this study highlights MEK1 as a potential broad antiviral molecular target.

Methylene blue-mediated photodynamic inactivation as a novel disinfectant of enterovirus 71.

OBJECTIVES: We tested whether methylene blue, an inexpensive and safe photosensitizer, is feasible for photodynamic inactivation of enterovirus 71 (EV71) in the environment. METHODS: By escalating light doses and photosensitizer concentrations, photoinactivation of EV71 and other enteroviruses was examined in vitro. Viral transmission in the environment was simulated with a neonatal mouse model in vivo. Possible mechanisms were analysed with alterations of viral DNA and proteins after treatments. RESULTS: Photodynamic inactivation of EV71 in suspensions occurred in a dose-dependent manner. The optimal condition for photoinactivating EV71 required a light dose of 200 J/cm(2) in the presence of methylene blue. This photodynamic condition was also able to inactivate other enteroviruses, including poliovirus 1 and coxsackieviruses A2, A3, A16 and B3. In an imitation environment, EV71 spread on a solid surface was inactivated by methylene blue-mediated photodynamic inactivation and prevented EV71 transmission to mice. Western blot and RT-PCR analysis indicated that both the viral proteins and the genome were disrupted after photodynamic inactivation. CONCLUSIONS: Methylene blue-mediated photodynamic inactivation may provide a novel way to eliminate environmentally contaminated sources of EV71 to prevent infection.

Viral protein synthesis is required for Enterovirus 71 to induce apoptosis in human glioblastoma cells.

Human glioblastoma cells (SF268) develop apoptosis, as characterized by DNA fragmentation and caspase activation, upon infection with Enterovirus 71 (EV71). To determine the step in virus replication that triggers apoptosis, the authors used ultraviolet (UV)-inactivated virus, inhibitors of protein and viral RNA synthesis, and chloroquine to block virus uncoating. Activation of caspase-3 was detected 24 h after infection with EV71 but not with UV-inactivated EV71. Apoptosis was inhibited when EV71-infected cells were treated with chloroquine, guanidine HCl, or cycloheximide. In summary, the authors studied the event(s) required to induce apoptosis in EV71-infected human glioblastoma cells, a subject much less studied than the possible role of viral proapoptotic genes, concluding that EV71 induces apoptosis in the infected SF268 cell in the presence of viral protein synthesis and virus replication, whereas virus adsorption, internalization, entry, uncoating, and viral RNA replication are all not required to trigger the apoptosis.