Bovine viral diarrhea virus quasispecies during persistent infection

Analysis of viral genome sequences from two calves persistently infected wi th bovine viral diarrhea virus revealed a quasispecies distribution. The se quences encoding the glycoprotein E2 were variable, translating to a number of changes in predicted amino acid sequences. the NS3 region was found to be highly conserved in both animals, the number of E2 clones showing varian t amino acids increased with the age of the animal and comparison of the co nsensus sequences at the different time points confirmed differences in the predicted E2 sequences over time. The immune tolerance that allows the lif elong persistence of this viral infection is highly specific. It is likely that some of the variant viruses generated within these animals will differ antigenically from the persisting virus and be recognized by the immune sy stem. Evidence of an immune response to persisting virus infection was gath ered from a larger sample of cattle. Serum neutralizing antibodies were fou nd in 4 of 21 persistently infected animals. Accumulations of viral RNA in the lymph nodes of all animals examined, particularly in the germinal cente r light zone, may represent antigenic variants held in the form of immune c omplexes on the processes of follicular dendritic cells. (C) 1999 Academic Press.