Abstract
African swine fever (ASF) is a lethal hemorrhagic disease of swine caused by a double-stranded DNA virus, ASF virus (ASFV). There is no vaccine to prevent the disease and current control measures are limited to culling and restricting animal movement. Swine infected with attenuated strains are protected against challenge with a homologous virulent virus, but there is limited knowledge of the host immune mechanisms generating that protection. Swine infected with Pretoriuskop/96/4 (Pret4) virus develop a fatal severe disease, while a derivative strain lacking virulence-associated gene 9GL (Pret4Δ9GL virus) is completely attenuated. Swine infected with Pret4Δ9GL virus and challenged with the virulent parental virus at 7, 10, 14, 21, and 28 days post infection (dpi) showed a progressive acquisition of protection (from 40% at 7 dpi to 80% at 21 and 28 dpi). This animal model was used to associate the presence of host immune response (ASFV-specific antibody and interferon (IFN)-γ responses, or specific cytokine profiles) and protection against challenge. With the exception of ASFV-specific antibodies in survivors challenged at 21 and 28 dpi, no association between the parameters assessed and protection could be established. These results, encompassing data from 65 immunized swine, underscore the complexity of the system under study, suggesting that protection relies on the concurrence of different host immune mechanisms.
Highlights
African swine fever (ASF) is a contagious viral disease of swine
Successful experimental ASF virus (ASFV) vaccines have been exclusively based on the use of attenuated virus strains, regardless of the origin of attenuation i.e., natural, acquired by serial passages in alternative hosts or by genetic manipulation [5,7,10,11,15,21,22,23]
The host immune mechanisms mediating protection in animals infected with attenuated strains are not characterized
Summary
African swine fever (ASF) is a contagious viral disease of swine. The causative agent, ASF virus (ASFV), is a large enveloped virus containing a double-stranded (ds) DNA genome of approximately190,000 base pairs [1,2]. African swine fever (ASF) is a contagious viral disease of swine. The causative agent, ASF virus (ASFV), is a large enveloped virus containing a double-stranded (ds) DNA genome of approximately. ASFV infections in domestic pigs are often fatal and are characterized by high fever, hemorrhages, ataxia and severe depression [1,2]. The disease is endemic in sub-Saharan Africa. In Europe, ASF is endemic on the island of Sardinia (Italy), and outbreaks of ASF have been recorded in the Caucasus region since 2007, spreading to neighboring and Eastern European countries [3]. There is no vaccine available against ASF, and the only methods of control of ASF are strict quarantine and biosecurity measures, control of animal movement, and slaughter of affected and Viruses 2016, 8, 291; doi:10.3390/v8100291 www.mdpi.com/journal/viruses
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