An outbreak of type 26 Echovirus infection with exanthem in an infant home near Tokyo

Replication of echo virus type 25 JV-4 reference strain and wild type strains in MRC5 cells compared with that of poliovirus type 1

In echo virus type 25/JV-4 the shut off of host cell protein synthesis took significantly longer and the kinetics of the synthesis of viral proteins and viral RNA occurred much later than in the poliovirus. However, these characteristics impaired neither polyprotein processing nor virus production in the JV-4 strain. In contrast the two wild strains M.1262 and Th.222 had a lower virus yield than strain JV-4. The presence of a high Mr protein in the pattern of viral proteins of wild strains suggested that a defect in the polyprotein processing was responsible for the decreased virus yield. The infectious cycle of strain Th.222 differed from that of strains JV-4 and M.1262 in the rapid inhibition of host cell translation and the extent of viral protein synthesis. The sensitivity to actinomycin D was also investigated. Strain M.1262 was found to be insensitive. The virus yield of strains JV-4 and Th.222 was three- and fourfold lower respectively in the presence of actinomycin D. This sensitivity to the antibiotic was observed during viral RNA synthesis in strain JV-4 and during viral protein synthesis in strain Th.222. These results suggest that cellular factors are involved in the replication of echo virus type 25 strains in MRC5 cells.

Impact on routine diagnosis of echovirus infections of intratypic differentiation and antigenic variation in echovirus type 25 studied by using monoclonal antibodies

We studied the biological and antigenic properties of wild strains of echovirus type 25 isolated in France between 1982 and 1987 and compared them with the JV-4 prototype strains isolated in 1957. The wild strains 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 titres (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 coxsackie- and polioviruses, consists of heterogeneous viral populations with respect to biological and antigenic properties. In term of viral diagnosis, it may become increasingly difficult to identify recently isolated strains because of their antigenic variation.

An outbreak of skin rash by echovirus 25 in an infant home

In September 1980 an outbreak of a skin eruption occurring in an infant home in Milan involved 15 children (aged five to 22 months) out of a total of 25. All of them showed a pink maculopapular rash, three had slight fever and eight mild gastroenteric symptoms (diarrhoea). The exanthem lasted three to four days and was distributed over the trunk and the face and only affected the limbs partially. Mild gastroenteric symptoms (abdominal pain or diarrhoea) were reported also by five subjects out of 13 of the staff. Specimens of stools from the 15 affected children and from the five nurses were submitted for virological examination. A strain of echovirus 25 was isolated on primary monkey kidney cells from the stools of eight children and from one adult.

Entérovirus et infections respiratoires

The importance of enteroviruses in upper and lower respiratory infections is reviewed. Occasionaly summer epidemics of upper respiratory infections seem due to an enterovirus : on the other hand, the lower respiratory injections rarely seem due to these viruses.The relationship between the enteroviruses and respiratory infections remains to be proved.