Research Fdn for Microbial Diseases of Osaka University

As one aspect of its campaign to eradicate poliomyelitis, the World Health Organization (WHO) has encouraged development of the inactivated polio vaccine (IPV) derived from the Sabin strains (sIPV) as an option for an affordable polio vaccine, especially in low-income countries. The Japan Poliomyelitis Research Institute (JPRI) inactivated three serotypes of the Sabin strains and made sIPV preparations, including serotypes 1, 2 and 3 D-antigens in the ratio of 3:100:100. The National Institute of Infectious Diseases, Japan, assessed the immunogenic stability of these sIPV preparations in a rat potency test, according to an evaluation method recommended by the WHO. The immunogenicity of the three serotypes was maintained for at least 4 years when properly stored under -70°C. Based on these data, the sIPV preparations made by JPRI have been approved as national reference vaccines by the Japanese national control authority and used for the quality control of the tetracomponent sIPV-containing diphtheria-tetanus-acellular pertussis combination vaccines that were licensed for a routine polio immunization in Japan.

Enterovirus 71 (EV71) is a picornavirus that causes outbreaks of hand, foot, and mouth disease (HFMD), primarily in the Asia-Pacific area. Unlike coxsackievirus A16, which also causes HFMD, EV71 induces severe neuropathology leading to high fatalities, especially among children under the age of 6 years. Currently, no established vaccines or treatments are available against EV71 infection. The monoclonal antibody MA28-7 neutralizes only specific strains of EV71 that have a conserved glycine at amino acid VP1-145, a surface-exposed residue that maps to the 5-fold vertex and that has been implicated in receptor binding. The cryo-electron microscopy structure of a complex between EV71 and the Fab fragment of MA28-7 shows that only one Fab fragment occupies each 5-fold vertex. A positively charged patch, which has also been implicated in receptor binding, lies within the Fab footprint. We identify the strain-specific epitope of EV71 and discuss the possible neutralization mechanisms of the antibody.

Poliovirus (PV) 2A pro has been considered important for PV replication and is known to be toxic to host cells. A 2A pro -deficient PV would potentially be less toxic and ideal as a vector. To examine whether 2A pro is needed to form progeny virus, a full-length cDNA of dicistronic ( dc ) PV with (pOME) or without (pOMEΔ2A) 2A pro was constructed in the strain PV1(M)OM. RNAs of both pOME and pOMEΔ2A were capable of forming progeny viruses, called OME and OMEΔ2A, respectively. In their ability to induce a cytopathic effect (CPE), the strains ranked as OMEΔ2A < OME ≒ PV1(M)OM. These results suggest that 2A pro is not essential for full-length dc PV to form progeny virus and that it contributes to the efficient viral replication and/or induction of a CPE. To clarify whether 2A pro is essential for P1-null (lacking the entire coding sequence for capsid proteins) PV, the RNA replication activity of P1-null PV (pOMΔP1) or P1-null PV without 2A pro (pOMΔP1Δ2A) or without both 2A pro and 2B (pOMΔP1Δ2AΔ2B) was examined. The RNAs of pOMΔP1 and pOMΔP1Δ2A could replicate and form progeny viruses under a trans supply of P1 protein, whereas the RNA of pOMΔP1Δ2AΔ2B could not. These results suggest that 2A pro is not needed for the replication of P1-null PV, although it is important for PV RNA replication and inducing a CPE. To know whether a 2A pro -deficient PV can be used as a vector, a P1-null PV containing the enhanced green fluorescent protein (EGFP) coding sequence with or without 2A pro was examined. It expressed fluorescent protein. This result suggests that 2A pro -deficient PV can express foreign genes.