ARS | Publication request: Genetic change in BVDV occurs more rapidly during acute infections in pregnant rather than nonpregnant cattle

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 16, 2011
Publication Date: September 25, 2011
Citation: Neill, J.D., Newcomer, B., Marley, S., Ridpath, J.F., Givens, D. 2011. Genetic change in BVDV occurs more rapidly during acute infections in pregnant rather than nonpregnant cattle [abstract]. In: Proceedings of the International Pestivirus Symposium of the European Society for Veterinary Virology, September 25-28, 2011, Hannover, Germany. p. 136.

Technical Abstract: BVDV strains show significant sequence variation, so much so that they have been divided into 2 species and the BVDV-1 species into at least 12 subgenotypes. The source of variation is the rather sloppy RNA-dependent RNA polymerase. The mechanism behind selection that results in new BVDV strains with altered characteristics is unclear. Recently, we showed that at least equivalent numbers of nucleotide changes were introduced during establishment of a single persistent infection (PI; 17 to 48) than during a series of acute outbreaks over a large geographic area by a single BVDV strain (4 to 33). Additionally, some changes in PI viruses resulted in antigenic shift based on monoclonal antibody reactivity. We next sequenced the acute phase viruses isolated from the dams of the PI animals used above. This revealed that the majority of the nucleotide changes found in the virus from the PI calf were already in place six days post-infection, before infection of the fetus. In all viruses, an additional two to three nucleotide changes were introduced in the fetus. This was compared to viruses isolated from three acutely infected, nonpregnant animals that were infected by exposure to PI calves. These viruses had six to eight nucleotide changes per genome. A final comparison was made of viruses from a PI cow and its PI calf. These viruses showed 22 nucleotide differences. These results demonstrate that genetic change is introduced more rapidly into the BVDV genome during the infection of pregnant animals. The mechanism driving this change is unknown.