Coinfection with a rhabdovirus: vesicular stomatitis virus of Indiana and New-Jersey serotypes.

Coinfection of cells with vesicular stomatitis virus (VSV) of Indiana and New-Jersey serotypes were performed. Thermosensitive mutants (ts) of VSV Indiana and the wild type strain (+) of New-Jersey were used. Harvests and titrations were made at permissive(PT) and nonpermissive (NPT) temperatures. It was shown that the harvest was mainly composed of one parental-like infectious particles. The dominance of one serotype over the other was shown to be a function of the relative multiplicity of the two viruses; the presence of a thermosensitive lesion imparts a disadvantage to the corresponding serotype. Non parental-like particles were also detected. As expected, these particles were detected only in two conditions. 1) Harvest performed at NPT and titrations allowed at PT.- Most of the infectious particles (i.e. twin particles) resistant to anti-Nj serum developped a plaque (i.e. mixed-plaque)containing virions of both serotypes: Indiana (ts) and New-Jersey (+). After sonication or EDTA treatment of the harvest, prior to titrations, no more mixed-plaques were formed. Examination of the harvest by electron microscopy showed that 7-17 % of the particles formed aggregates; therefore, it is likely that the twin-particles are in fact aggregates. 2) Harvest performed at PT and titrations allowed at NPT.-It has been shown that 1 % of the wild type infectious particles was resistant to anti-Nj serum even though being of Nj genotype. It was inactivated by a mixture of anti-Nj and anti-In sera and therfore behave as pseudotypes. But since twin particles, when plated at Nt, would give rise to an homogenous progeny from New-Jersey (+), they could be confused with pseudotypes. Under those conditions there is no absolute evidence that phenotypic mixing really occurs between VSV of Indiana and New-Jersey serotypes.