Submitted to: Journal of Virology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/12/2005
Publication Date: 9/15/2005
Citation: Risatti, G.R., Holinka, L.G., Lu, Z., Kutish, G.F., Tulman, E.R., French, R.A., Sur, J.H., Rock, D.L., Borca, M.V. 2005 Mutation of E1 Glycoprotein of Classical Swine Fever Virus Affects Viral Virulence in Swine. Journal of Virology 343: 116-127. Interpretive Summary: In this manuscript it is described, for the first time, a role of a structural glycoprotein (E1) of CSFV in virulence in pigs. Transponson insertion mutagenesis, a methodology that allows the in frame insertion of DNA fragments encoding, in this particular case, nineteen foreign amino acid residues was used to disrupt the E1 gene in the Brescia infectious clone. The produced virus, named C22-RB, presented a significantly attenuated phenotype when inoculated in pigs by the oronasal route. C22-RB transiently replicates in target organs (tonsils, lymph nodes and spleen) with titers 100-10000 times lower when compared with the virulent parental Brecia virus. Interestingly, C22-RB virus, besides to be attenuated, was able to induce protection against the challenge with Brescia as early as 3 days after infection with C22-RB. Thus, C22-RB could be considered as an experimental vaccine strain.
Technical Abstract: Transposon linker insertion mutagenesis (TLIM) is a technique that allows the random insertion of DNA fragments into a target DNA causing an in frame disruption of the DNA target sequence. The insertion of the transponson could lead to the functional disruption of the targeted gene. We used TLIM to mutate the infectious clone of the virulent strain Brescia obtaining a library of mutated CSFV harboring, each one of them, a randomly located single transposon insertion. Some of these mutated viruses were tested in their virulence in vivo. One of these mutants, C22, resulted completely attenuated in swine. C22 replicated less efficiently than the parental Brescia virus in all lymphatic organs. Virus shedding is also lower than with the wild type. Interestingly, animls infected with C22 resist the challenge with the virulent Brescia since the 3rd day post-infection with C22. C22 vaccinated animals remained completely asymptomatic after the challenge. This is the first report demonstrating that glycoprotein E1 is involved in virulence during the infection in swine.