Evolution of pseudorabies virions containing genomes with an invertible long component after repeated passage in chicken embryo fibroblasts

B. Lomniczi, A. Gielkens, I. Csobai, T. Ben-Porat

Research output: Contribution to journalArticle

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Abstract

The genome of pseudorabies virus consists of two components, short (S) and long (L). Only the S component is bracketed by inverted repeats, and only the S component inverts itself relative to the L component, giving rise to two isomeric forms of the genome. An attenuated vaccine strain of pseudorabies virus (Norden), however, has a genome which is found in four isomeric forms (B. Lomniczi, M.L. Blankenship, and T. Ben-Porat, J. Virol. 49:970-979, 1984). To determine the basis for the atypical structure of the genome of the Norden strain, we examined more than 40 field isolates of pseudorabies virus; all contained genomes in which the L component was fixed in only one orientation relative to the S component. Several independently generated vaccine strains which have been passaged extensively in chicken embryos and chicken embryo fibroblast (CEF) cell cultures were also analyzed; they possessed an invertible L component. Furthermore, emergence of pseudorabies virus variants with an invertible L component was observed after passage of the virus in CEF, but not in rabbit kidney or pig kidney, cells. The invertibility of the L component was associated consistently with a translocation of sequences from the left end of the genome to a position next to the inverted repeat sequence of the S component. Three observations indicate that genomes with an invertible L component (and the translocation) have a selective growth advantage over standard pseudorabies virus when grown in CEF. (i) The proportion of virions with such genomes does not increase linearly as would be expected if the translocation events occurred repeatedly, most genomes eventually experiencing the translocation. Instead, after a lag, the proportion of such virions in the population increases relatively rapidly. (ii) The genome structures that are generated upon independent passage in CEF of each virion population were relatively homogeneous. Some heterogeneity was observed at relatively early stages of the emergence of the genomes carrying the translocation; at later stages, virions with genomes with a specific size translocation predominated in the virus population. (iii) Parallel passages in CEF of the same pseudorabies virus resulted in the emergence of populations of virions with genomes with different size translocations. However, in each of the passaged populations of virions the majority of virions had genomes with the same size translocation. The most likely interpretation of these results is that virions with genomes carrying the translocations that emerge upon passage of the virus in CEF have a selective advantage when grown in these cells.

Original languageEnglish
Pages (from-to)1772-1780
Number of pages9
JournalJournal of Virology
Volume61
Issue number6
Publication statusPublished - 1987

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Pseudorabies
Aujeszky disease
virion
Virion
fibroblasts
Chickens
embryo (animal)
Embryonic Structures
Fibroblasts
Genome
chickens
genome
Suid Herpesvirus 1
Suid herpesvirus 1
Population
Viruses
viruses
Inverted Repeat Sequences
Kidney
Attenuated Vaccines

ASJC Scopus subject areas

  • Immunology

Cite this

Evolution of pseudorabies virions containing genomes with an invertible long component after repeated passage in chicken embryo fibroblasts. / Lomniczi, B.; Gielkens, A.; Csobai, I.; Ben-Porat, T.

In: Journal of Virology, Vol. 61, No. 6, 1987, p. 1772-1780.

Research output: Contribution to journalArticle

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