The pathogenesis of the postpolio syndrome (PPS) remains unclear. In this study we looked for poliovirus (PV) persistence in the CSF of 20 patients with PPS, in a control group including 20 patients with unrelated neurological diseases, and in 7 patients with stable poliomyelitis sequelae. CSF samples and sera were examined using reverse transcriptase-polymerase chain reaction (RT-PCR) for the detection of PV or other enterovirus genomes; this assay allows the detection from as little as 1 fg viral RNA. Sequencing of amplified products from 5 patients was performed. PV genomic sequences were detected in the CSF of 11 of 20 patients with PPS and in none of the control group. Sequencing in the 5' untranslated region confirmed the presence of mutated PV sequences. These findings suggest that PPS is related to the persistence of PV in the central nervous system.
The postpolio syndrome (PPS) is characterized by new neuromuscular symptoms occurring 30 to 40 years after the acute episode of poliomyelitis paralysis. The presence of the poliovirus RNA genome in the cerebrospinal fluid from 10 patients with PPS and from 23 control patients was sought by using reverse transcription and a PCR specific for polioviruses and/or other enteroviruses. Poliovirus-specific genomic sequences in the 5 untranslated region and in the capsid region (VP1) were detected by reverse transcription PCR in 5 of 10 patients with PPS but in none of the control patients. Sequencing confirmed the presence of mutated poliovirus sequences. This finding suggests persistent viral infection in the central nervous system related to the presence of poliovirus genomes.
differed from the prototype strain in their cellular tropism. The prototype strain grew readily in five cell lines (MRC5, MA 104, Vero, BGM, and HT 29-18), while for wild strains MRC5 and HT 29-18 cells were the most sensitive and supported growth to high titers (between 4.5 and 7.4 50% tissue culture infective doses per 0.05 ml). Plaques produced by wild strains were larger (6.05 0.94 mm in diameter [mean standard deviation]) than those of the prototype strain (2.3 0.97 mm in diameter) and heterogeneous, even after cloning by three terminal dilution passages, which suggested heterogeneous virus populations. Virus neutralization with polyclonal monovalent sera showed that wild strains were significantly less neutralized by two reference immune sera than the prototype strain was. Monoclonal antibodies were raised against the echovirus type 25 JV-4 prototype strain. Nine clones with neutralizing activity were identified. Heterologous neutralizations of 14 clinical isolates revealed highly conserved, moderately conserved, and poorly conserved epitopes. The natural isolates differed from the prototype strain in two to four epitopes and can be classified into four different groups. We concluded that echovirus type 25, like coxsackieand polioviruses, consists of heterogeneous viral populations with respect to biological and antigenic properties. In terms of viral diagnosis, it may become increasingly difficult to identify recently isolated strains because of their antigenic variation.
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