Constitutive proteins of lumpy skin disease virion assessed by next-generation proteomics

Lumpy skin disease (LSD) virus, a ruminant poxvirus of the Capripoxvirus genus, is the etiologic agent of an economically important cattle disease categorized as a notifiable disease by the World Organisation for Animal Health. The large and complex enveloped LSD virus (LSDV) particle encloses a double-stranded linear DNA genome of 151 kbp, comprising 156 predicted ORFs, together with a variety of proteins that are not yet identified. In parallel with a recent widespread expansion of LSD, many LSDV whole genomes have been sequenced, but knowledge on protein composition of the LSDV particle remains missing. In this study, LSD mature virions (MV) from strain KSGP-0240 were purified through a multistep ultracentrifugation process. The protein composition of LSD virions was then analyzed using label-free shotgun proteomics, based upon nano-liquid chromatography (LC) and tandem mass spectrometry. This procedure resulted in the identification of a total of 111 LSDV proteins. Considering that this first MV proteome extended beyond packaged proteins into the field of contaminants, an analytical methodology was developed and made it possible to select 66 viral proteins as candidates for packaging into MV. These viral proteins were analyzed comparatively with proteins previously demonstrated to be constitutive of the vaccinia virus MV particle. Offering for the first time a comprehensive proteomic analysis of an LSDV strain, this study contributes to our understanding of the structural features of infectious LSDV MV particles and paves the way for further systematic proteomic characterization of other LSDV strains. IMPORTANCE: Lumpy skin disease virus (LSDV) is the causative agent of an economically important cattle disease which is notifiable to the World Organisation for Animal Health. Over the past decades, the disease has spread at an alarming rate throughout the African continent, the Middle East, Eastern Europe, the Russian Federation, and many Asian countries. While multiple LDSV whole genomes have made further genetic comparative analyses possible, knowledge on the protein composition of the LSDV particle remains lacking. This study provides for the first time a comprehensive proteomic analysis of an infectious LSDV particle, prompting new efforts toward further proteomic LSDV strain characterization. Furthermore, this first incursion within the capripoxvirus proteome represents one of very few proteomic studies beyond the sole Orthopoxvirus genus, for which most of the proteomics studies have been performed. Providing new information about other chordopoxviruses may contribute to shedding new light on protein composition within the Poxviridae family.