[Characterization of enterovirus type 71 isolated in Saitama Prefecture in 2000]

A novel minicircle vector based system for inhibting the replication and gene expression of enterovirus 71 and coxsackievirus A16

Enterovirus 71 (EV 71) and Coxsackievirus A16 (CA 16) are two major causative agents of hand, foot and mouth disease (HFMD). They have been associated with severe neurological and cardiological complications worldwide, and have caused significant mortalities during large-scale outbreaks in China. Currently, there are no effective treatments against EV 71 and CA 16 infections. We now describe the development of a novel minicircle vector based RNA interference (RNAi) system as a therapeutic approach to inhibiting EV 71 and CA 16 replication. Small interfering RNA (siRNA) molecules targeting the conserved regions of the 3C(pro) and 3D(pol) function gene of the EV 71 and CA 16 China strains were designed based on their nucleotide sequences available in GenBank. This RNAi system was found to effectively block the replication and gene expression of these viruses in rhabdomyosarcoma (RD) cells and virus-infected mice model. The inhibitory effects were confirmed by a corresponding decrease in viral RNA, viral protein, and progeny virus production. In addition, no significant adverse off-target silencing or cytotoxic effects were observed. These results demonstrated the potential and feasibility of this novel minicircle vector based RNAi system for antiviral therapy against EV 71 and CA 16 infection.

Partial protection against enterovirus 71 (EV71) infection in a mouse model immunized with recombinant Newcastle disease virus capsids displaying the EV71 VP1 fragment

Enterovirus 71 (EV71) infection may cause severe neurological complications, particularly in young children. Despite the risks, there are still no commercially available EV71 vaccines. Hence, a candidate vaccine construct, containing recombinant Newcastle disease virus capsids that display an EV71 VP1 fragment (NPt-VP1(1-100) ) protein, was evaluated in a mouse model of EV71 infection. Previously, it was shown that this protein construct provoked a strong immune response in vaccinated adult rabbits. That study, however, did not address the issue of its effectiveness against EV71 infection in young animals. In the present study, EV71 viral challenge in vaccinated newborn mice resulted in more than 40% increase in survival rate. Significantly, half of the surviving mice fully recovered from their paralysis. Histological analysis of all of the surviving mice revealed a complete clearance of EV71 viral antigens from their brains and spinal cords. In hind limb muscles, the amounts of the antigens detected correlated with the degrees of tissue damage and paralysis. Findings from this study provide evidence that immunization with the NPt-VP1(1-100) immunogen in a newborn mouse model confers partial protection against EV71 infection, and also highlights the importance of NPt-VP1(1-100) as a possible candidate vaccine for protection against EV71 infections.

Complete sequence analyses of enterovirus 71 strains from fatal and non-fatal cases of the hand, foot and mouth disease outbreak in Singapore (2000)

Enterovirus 71 (EV71) is a major aetiological agent of hand, foot and mouth disease (HFMD). In recent years, several outbreaks in East Asia were associated with neurological complications and numerous deaths. An outbreak in Singapore in October 2000 afflicted thousands of children, resulting in four fatal cases from three of whom EV71 was isolated. The genomes of two representative EV71 strains isolated from a fatal case and a surviving patient were completely sequenced, and their nucleotide and amino acid sequences compared with known EV71 strains. The two outbreak strains were classified under genogroup B, together with those previously isolated in Singapore, Malaysia and Japan. Comparative sequence analysis of the two Singapore strains revealed 99% nucleotide similarity, while their deduced amino acid sequences were almost identical except for residue 1506 in the 3A non-structural region. Given that the outbreak involved closely related genetic variants of EV71, the broad spectrum of disease severity may be attributed to critical factors such as varying viral inoculation doses or differing host immune responses following infection, but is less likely to be due to the emergence of EV71 strains with heightened virulence.