A unique characteristic of the African horse sickness virus (AHSV) major core protein VP7
is that it is highly insoluble, and spontaneously forms crystalline particles in AHSV-infected cells and
when expressed in vitro. The aggregation of AHSV VP7 into these crystals presents many problems
in AHSV vaccine development, and it is unclear whether VP7 aggregation affects AHSV assembly
or contributes to AHSV pathogenesis. Here, we set out to abolish VP7 self-assembly by targeting
candidate amino acid regions on the surface of the VP7 trimer via site-directed mutagenesis. It was
found that the substitution of seven amino acids resulted in the complete disruption of AHSV VP7
self-assembly, which abolished the formation of VP7 crystalline particles and converted VP7 to a fully
soluble protein still capable of interacting with VP3 to form core-like particles. This work provides
further insight into the formation of AHSV VP7 crystalline particles and the successful development
of AHSV vaccines. It also paves the way for future research by drawing comparisons with similar
viral phenomena observed in human virology.
SUPPLEMENTARY MATERIAL : FIGURE S1: Solubility assay of modified VP7 proteins; FIGURE S2: Intracellular distribution of VP7 mutant proteins via indirect immunofluorescence microscopy; VIDEO S1: (A) and (B): Colocalisation analysis of WT VP7 with VP3.