Attenuated Vaccines Can Recombine to Form Virulent Field Viruses
- Sang-Won Lee1,
- Philip F. Markham1,
- Mauricio J. C. Coppo1,
- Alistair R. Legione1,
- John F. Markham3,
- Amir H. Noormohammadi2,
- Glenn F. Browning1,
- Nino Ficorilli1,
- Carol A. Hartley1,
- Joanne M. Devlin1,*
- 1Asia-Pacific Centre for Animal Health, Faculty of Veterinary Science, The University of Melbourne, Parkville, Victoria 3010, Australia.
- 2Asia-Pacific Centre for Animal Health, Faculty of Veterinary Science, The University of Melbourne, Werribee, Victoria 3030, Australia.
- 3National ICT Australia (NICTA) Victoria Research Laboratory, Department of Electrical and Electronic Engineering, School of Engineering, The University of Melbourne, Victoria 3010, Australia.
- ↵*To whom correspondence should be addressed. E-mail: devlinj{at}unimelb.edu.au
Abstract
Recombination between herpesviruses has been seen in vitro and in vivo under experimental conditions. This has raised safety concerns about using attenuated herpesvirus vaccines in human and veterinary medicine and adds to other known concerns associated with their use, including reversion to virulence and disease arising from recurrent reactivation of lifelong chronic infection. We used high-throughput sequencing to investigate relationships between emergent field strains and vaccine strains of infectious laryngotracheitis virus (ILTV, gallid herpesvirus 1). We show that independent recombination events between distinct attenuated vaccine strains resulted in virulent recombinant viruses that became the dominant strains responsible for widespread disease in Australian commercial poultry flocks. These findings highlight the risks of using multiple different attenuated herpesvirus vaccines, or vectors, in the same populations.
- Received for publication 28 November 2011.
- Accepted for publication 26 April 2012.
