Étude des déterminants de l’induction et de la sensibilité à l’interféron chez le réovirus de mammifères
Mammalian reovirus is currently under study as an oncolytic virus that can preferentially kill cancer cells. Although the viral and cellular determinants responsible are poorly understood, the interferon-related signaling pathways are probably involved. Two viral isolates differing in their sensitivity to interferon were previously obtained and their nucleotide sequence was determined. In order to establish the importance of the differences between these two viruses (T3DK and VeroAV) and the wild-type virus (T3DS), the plasmids carrying each of the corresponding viral genes were mutated. Viruses carrying different combinations of T3DK or VeroAV genes in a T3DS genetic background were then recovered by transfection of cells using the "reverse genetics" technique. T3DK virus is not only more sensitive to interferon than T3DS, but it also induces much more interferon production. We were able to show that the sensitivity phenotype is solely due to the presence of the T3DK μ2 and λ2 proteins, whereas its ability to induce the interferon-related pathways is rather associated with the combination of its μ2 and λ1 proteins. On the other hand, the VeroAV virus is also more sensitive to interferon than the T3DS virus, without however inducing more interferon. The sensitivity phenotype is, in this case, due to a single point mutation in the virus S1 gene. This mutation modifies both the σ1 and σ1s protein of VeroAV, but it seems that it is its impact on the non-structural protein σ1s that is responsible for the observed sensitivity phenotype. The results thus demonstrated that phenotypes of induction and sensitivity to interferon are partially genetically dissociable properties and that they may be dependent on multiple viral determinants. The selection of interferon-sensitive mutants followed by their characterization with the reverse genetics approach will certainly contribute to a better understanding of the mechanisms involved in the mammalian reovirus oncotropism.
Reovirus Interferon Reverse genetics