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Poliomyelitis is the inflammation of the spinal cord due to infection with poliovirus, and is characterized by fever, sore throat, headache, vomiting, and neck and back stiffness. This condition has been virtually eliminated in the United States since 1972 due to the use of a poliovirus vaccine. This vaccine consists of the live poliovirus, which is attenuated or has diminished infective ability. The live attenuated poliovirus vaccine is given by mouth. However, despite widespread immunization with oral poliovirus vaccine (OPV), 5 to 10 cases of poliovirus occur each year in the United States. It is thought that the attenuated poliovirus may revert (change) to a virulent, or infective, form during passage through the gut. The incidence of reversion is not known, but most cases of poliomyelitis occur after the first dose of OPV. The enhanced-potency inactivated poliovirus vaccine (EIPV) is a more powerful or effective vaccine with a noninfective poliovirus and is given parenterally, or directly into the circulation. The initial use of EIPV with or without subsequent use of OPV may prevent the production of virulent revertant virus. The types of poliovirus detected in the feces of infants vaccinated with EIPV or OPV were assessed. Revertant virus was recovered from the feces of infants who were initially vaccinated with EIPV, and later with OPV. The transmission of virulent revertant virus requires further study. However, the combined use of EIPV and OPV enhances the production of antibody, or immune protein directed against poliovirus. (Consumer Summary produced by Reliance Medical Information, Inc.)

ABSTRACTThe isolation of a capsid intertypic poliovirus recombinant from a child with vaccine-associated paralytic poliomyelitis is described. Virus 31043 had a Sabin-derived type 3-type 2-type 1 recombinant genome with a 5'-end crossover point within the capsid coding region. The result was a poliovirus chimera containing the entire coding sequence for antigenic site 3a derived from the Sabin type 2 strain. The recombinant virus showed altered antigenic properties but did not acquire type 2 antigenic characteristics. The significance of the presence in nature of such poliovirus chimeras and the consequences for the current efforts to detect potentially dangerous vaccine-derived poliovirus strains are discussed in the context of the global polio eradication initiative.

ABSTRACTCHAT and Cox type 1 live-attenuated poliovirus strains were developed in the 1950s to be used as vaccines for humans. This paper describes their characterization with respect to virulence, sensitivity for growth at high temperatures, and complete nucleotide and amino acid sequences. The results are compared to those for their common parental wild virus, the Mahoney strain, and to those for two other poliovirus strains derived from Mahoney, the Sabin 1 vaccine strain and the mouse-adapted LS-a virus. Analysis of four isolates from cases of vaccine-associated paralytic poliomyelitis related to the CHAT vaccine revealed genetic and phenotypic properties of the CHAT strain following replication in the human gut. CHAT-VAPP strain 134 contained a genome highly evolved from that of CHAT (1.1% nucleotide differences), suggesting long-term circulation of a vaccine-derived strain in the human population. The molecular mechanisms of attenuation and evolution of poliovirus in humans are discussed in the context of the global polio eradication initiative.

ABSTRACTA 20-year-old female hypogammaglobulinemic patient received monotypic Sabin 3 vaccine in 1962. The patient excreted type 3 poliovirus for a period of 637 days without developing any symptoms of poliomyelitis, after which excretion appeared to have ceased spontaneously. The evolution of Sabin 3 throughout the entire period of virus excretion was studied by characterization of seven sequential isolates from the patient. The isolates were analyzed in terms of their antigenic properties, virulence, sensitivity for growth at high temperatures, and differences in nucleotide sequence from the Sabin type 3 vaccine. The isolates followed a main lineage of evolution with a rate of nucleotide substitution that was very similar to that estimated for wild-type poliovirus during person-to-person transmission. There was a delay in the appearance of antigenic variants compared to sequential type 3 isolates from healthy vaccines, which could be one of the possible explanations for the long-term excretion of virus from the patient. The distribution of mutations in the isolates identified regions of the virus possibly involved in adaptation for growth in the human gut and virus persistence. None of the isolates showed a full reversion of the attenuated and temperature-sensitive phenotypes of Sabin 3. Information of this sort will help in the assessment of the risk of spread of virulent polioviruses from long-term excretors and in the design of therapies to stop long-term excretion. This will make an important contribution to the decision-making process on when to stop vaccination once wild poliovirus has been eradicated.