Carnivore parvoviruses in South America

ALAN RADFORD; COLIN PARRISH; MASAMI MOCHIZUKI; NICOLA DECARO; GALLO CALDERON, MARINA

Londres

Workshop; Carnivore parvovirus nomenclature Workshop.; 2012

Univserity of Liverpool

As a group, it is clear that we should maintain continued vigilance for the emergence of viruses that evade effective acquired immunity, and that should be based on continuing evidence-based analysis of the genetic variation in the viruses (particularly in known antigenic sites), cross-neutralization analysis using polyclonal antisera (ideally compared to reference sera), and field surveillance for virus infection of correctly vaccinated animals. Such analysis should be coordinated by members of the veterinary virus community, including members of this group. Hosted by the RCVS Trust and sponsored by Merial, MSD Animal Health, Pfizer and Virbac. 26th November 1-2. Round table. Overview of carnivore parvoviruses in general, evolution in different hosts including dogs and wild animals, and also an American perspective. Carnivore parvoviruses in Europe (Nicola) Carnivore parvoviruses in Asia (Masami). Carnivore parvoviruses in South America (Marina). Review of immunity (natural and vaccine induced), and vaccines licensed against carnivore parvoviruses and cross-protection in relation to observed diversity. Carnivore parvovirus nomenclature Workshop. 26th -27th November 2012. London. Summary statement. December 10, 2012 Background and the problem: The International Committee for the Taxonomy of Viruses defines a single species within the Genus Parvovirus that routinely infects hosts in the members of the Order Carnivora (carnivores), namely feline panleukopenia virus (FPV). Below this species level, further taxonomic subdivisions are the responsibility of experts in the field. As the feline panleukopenia viruses have evolved, this has led to a need to define the observed variation among parvoviruses in cats, dogs, and in other hosts. The main challenges are: • Broad host ranges and host adaptation means that these viruses (or minor variants) are frequently found in more than one species of carnivore. • Antigenic variation can be detected by particularly monoclonal antibodies or in some cases polyclonal antisera, but we lack an understanding of its significance for the epidemiology of the virus and antigenic cross-reactivity and cross-protection of animals in the field. • DNA analysis can now easily detect sequence differences between strains. However, variation in methods between laboratories and lack of follow up to identify biological differences can create differences in the interpretation of the data. Other issues: • Are mutations that result in antigenic variation more significant than others (and therefore of particular significance in describing the viruses)? • Should specific methods for describing antigenic variation be specified? • Are mutations that gain a widespread distribution (within countries, regions, or around the world) more significant than those that do not show such increased distribution? • How do we define the relationships between host-species variation and antigenic variation, particularly where those are caused by the same changes in the viruses? • How should any classification reflect the phylogeny, where below the level of the FPV-like and CPV-like viruses (see below), there is no clear support for additional sub-levels of classification? Consensus of the Issues. • It is possible at the highest level of subdivision to describe a particular virus as FPV-like or CPV-like; this is based both on clearly defined phylogenetic differences, as well as antigenicity using well defined monoclonal antibodies which are commonly available (and that will be available in the future). • Below this highest level of subdivision, the viruses from domestic dogs and cats can currently be clearly sub-divided into CPV-2 (extinct for >25 years in the field in domestic animals), and CPV-2a-like viruses, which evolved from the original CPV-like viruses. However, viruses from other carnivore hosts do not so clearly fit this pattern. • At this time the further sub-classification of CPV-2a-like viruses based on individual mutations can no longer describe the diversity among the viruses in any host. None of the single mutations that have arisen is clearly reflected in phylogenetic analyses, and in many cases they are not associated with known changes in host range or tropism. In addition, the use of the same designations for different mutations has lead to confusion in the field. • We require a method for more clearly describing the variation that is present. The current system arose through the use of monoclonal antibodies the 1980’s, when there was little variation among the viruses in dogs. However, in the past 20 years the increasingly complex combinations of mutations make that system inadequate to describe the diversity that has arisen. Suggestions. • That nomenclature should be based on a highest level sub-species classification (FPV-like and CPV-like). This level may be considered a genotype. • Along with a genotype designation, a method for uniquely identifying the virus isolate is proposed, based on: FPV or CPV/host animal of isolation/geography/local identifier/year. • This information should be included in any Genbank record so that the unique sequence properties of that virus are accessible to anyone. • The various individual mutations in the virus should be considered in a discussion of the properties of the viruses, and not included in the name of the virus. • Antigenic cross-protection remains an important issue. At present we lack a direct understanding of the association between individual or combinations of mutations and the possibility of failure of immune cross-protection – either in infected individuals or in their offspring (as delivered by maternal antibodies). There is laboratory evidence for reduced levels of antigenic cross-reactivity using polyclonal sera between virus strains in the field and in vaccines. However, it appears that licensed vaccines, irrespective of type, have had a profound effect on reducing disease in the field. • As a group, it is clear that we should maintain continued vigilance for the emergence of viruses that evade effective acquired immunity, and that should be based on continuing evidence-based analysis of the genetic variation in the viruses (particularly in known antigenic sites), cross-neutralization analysis using polyclonal antisera (ideally compared to reference sera), and field surveillance for virus infection of correctly vaccinated animals. Such analysis should be coordinated by members of the veterinary virus community, including members of this group. Dr Marina Gallo Calderón, Centro de Virologia Animal, ARGENTINA Dr Nicola Decaro, Faculty of Veterinary Medicine of Bari, ITALY Dr Prof Masami Mochizuki, Kagoshima University Veterinary School, JAPAN Prof Colin Parrish, Cornell University, USA Dr Alan Radford, University of Liverpool, UK This Workshop was kindly sponsored by Merial, MSD Animal Health, Pfizer, Virbac and the Royal College of Veterinary Surgeons Charitable Trust.