A Proteomic Atlas of the African Swine Fever Virus Particle

Abstract

African swine fever virus (ASFV) is a large and complex DNA virus that causes a highly lethal swine disease for which there is no vaccine available. The ASFV particle, with an icosahedral multilayered structure, contains multiple polypeptides whose identity is largely unknown. Here, we analyzed by mass spectroscopy the protein composition of highly purified extracellular ASFV particles and performed immunoelectron microscopy to localize several of the detected proteins. The proteomic analysis identified 68 viral proteins, which account for 39% of the genome coding capacity. The ASFV proteome includes essentially all the previously described virion proteins and, interestingly, 44 newly identified virus-packaged polypeptides, half of which have an unknown function. A great proportion of the virion proteins are committed to the virus architecture, including two newly identified structural proteins, p5 and p8, which are derived from the core polyproteins pp220 and pp62, respectively. In addition, the virion contains a full complement of enzymes and factors involved in viral transcription, various enzymes implicated in DNA repair and protein modification, and some proteins concerned with virus entry and host defense evasion. Finally, 21 host proteins, many of them localized at the cell surface and related to the cortical actin cytoskeleton, were reproducibly detected in the ASFV particle. Immunoelectron microscopy strongly supports the suggestion that these host membrane-associated proteins are recruited during virus budding at actin-dependent membrane protrusions. Altogether, the results of this study provide a comprehensive model of the ASFV architecture that integrates both compositional and structural information. African swine fever virus causes a highly contagious and lethal disease of swine that currently affects many countries of sub-Saharan Africa, the Caucasus, the Russian Federation, and Eastern Europe and has very recently spread to China. Despite extensive research, effective vaccines or antiviral strategies are still lacking, and many basic questions on the molecular mechanisms underlying the infective cycle remain. One such gap regards the composition and structure of the infectious virus particle. In the study described in this report, we identified the set of viral and host proteins that compose the virion and determined or inferred the localization of many of them. This information significantly increases our understanding of the biological and structural features of an infectious African swine fever virus particle and will help direct future research efforts.

Current status and evolving approaches to African swine fever vaccine development

“…The difficulty in developing ASF vaccines is undoubtedly due to multifactorial processes including limited virus–host interaction understanding and complex nature of the virus (Tulman et al, ). ASFV encodes more than 80 structural proteins (Alejo, Matamoros, Guerra, & Andrés, ), which play crucial roles in virus attachment, entry and replication (Gómez‐Puertas et al, ; Jia, Ou, Pejsak, Zhang, & Zhang, ). Moreover, the diversity of ASFV isolates with varied virulence has complicated the task of defining immune protection determinants and remains a major gap in ASFV research (Dixon et al, ; Rowlands et al, ).…”

“…Broadly, more than fifty immunogenic ASFV proteins have been identified, and recently 44 virus‐packaged polypeptides have been reported. Nevertheless, the immunogenicity of the newly identified proteins remains unknown (Alejo et al, ; Jankovich et al, ). To develop ASF subunit vaccine platform, the pertinent ASFV protective antigens and the existing virus strain diversity need to be explored (Rock, ).…”

“…ASFV encodes more than 80 structural proteins (Alejo, Matamoros, Guerra, & Andrés, 2018), which play crucial roles in virus attachment, entry and replication (Gómez-Puertas et al, 1998;Jia, Ou, Pejsak, Zhang, & Zhang, 2017). Moreover, the diversity of ASFV isolates with varied virulence has complicated the task of defining immune protection determinants and remains a major gap in ASFV research Rowlands et al, 2008).…”

Homologous recombination shapes the genetic diversity of African swine fever viruses

“…The names of the blast best hits were used to infer the name of the protein group (Table S3). The functions of the protein groups were adapted from Dixon's (Dixon et al, 2013) and Alejo's work (Alejo et al, 2018) (Table S3).…”

“…The large genetic diversity of ASFVs, which was supposed to hinder the development of effective vaccines or drugs against the virus (Sanchez-Cordon et al, 2018;Escribano et al, 2013;Arabyan et al, 2018), has been investigated in many studies. The ASFV genome encodes over 150 proteins, including viral enzymes, viral transcription and replication-related proteins, structural proteins, other proteins involved in the virus assembly, the evading of host defence systems and the modulation of host cell function, etc (Dixon et al, 2013;Alejo et al, 2018;Kessler et al, 2018). For example, the transcription of the virus is independent on the host RNA polymerase because the virus contains relevant enzymes and factors (Dixon et al, 2013).…”