African swine fever (ASF) is an acute viral hemorrhagic disease in domestic swine with mortality rates approaching 100%. Devastating ASF disease outbreaks and the continuing disease epidemic in the Caucasus region and Russia (2007 – to date) highlight the significance of this disease as arguably the most significant emerging disease threat for the swine industry worldwide. There is no vaccine for ASF available; however, it is clear that vaccination is possible since protection against homologous reinfection has been definitively demonstrated. Vaccine progress is hindered by lack of knowledge concerning the extent of ASFV strain variation and the viral antigens responsible for protective immunity. To date, eight ASFV serogroups have been identified although more likely exist. Notably and of great significance with respect to vaccine design and development, viruses within serogroups provide cross-protection from challenge with viruses within the serogroup. Unlike other viruses currently challenging the swine industry, such as PRRS, ASFV is a DNA virus and thus much less variable over time. Once the viral diversity currently circulating in natural reservoirs has been determined, a set of vaccines could be developed to be effective against relevant ASFV strains.
Here, we have used a collection of serologically-grouped ASFV isolates and a large and diverse collection of ASF viruses to identify genetic signature(s) for ASFV serologic group specificity and to further define ASFV strain variability. We have demonstrated through gene sequencing and comparative analysis of ASFV strains a correlation between the genotype of the ASFV CD2v gene and virus grouping based on serospecificity. Overall, the concordance between CD2v region phylogenetic data and serogroup-specific typing provides predictive value of CD2v locus genotyping in predicting serologic, and potentially cross protective, virus groups.
Results outlined here will have broad impact on vaccine-orientated approaches for ASF disease control thus reducing the threat posed by this high consequence viral disease. Knowledge of ASFV strain diversity and the breath of strain variation in nature as well as rapid genotyping methods to serotype viruses and to predict efficacy of a given vaccine to provide cross protection for a newly identified field isolate will facilitate vaccine design, development and emergency use. (For additional information contact D. L. Rock – [email protected])
