A correlation between capsid protein VP2 and the plaque morphology of African horse sickness virus in cell culture

Abstract

The attenuated live virus vaccine that is used in South Africa to protect against African horse sickness infection was developed more than 50 years ago. With the selection of the vaccine strains by cell culture passage, a correlation between the size of plaques formed in monolayer Vero cultures and attenuation of virus virulence in horses was found. The large plaque phenotype was used as an indication of cell culture adaptation and strongly correlated with attenuation of virulence in horses. There was never any investigation into the genetic causes of either the variation in plaque size, or the loss of virulence. An understanding of the underlying mechanisms of attenuation would benefit the production of a safer AHSV vaccine. To this end, the genomes of different strains of two African horse sickness isolates, producing varying plaque sizes, were compared and the differences between them identified. This comparison suggested that proteins VP2, VP3, VP5 and NS3 were most likely involved in the determination of the plaque phenotype. Comparison between genome sequences (obtained from GenBank) of low and high passage strains from two additional serotypes indicated that VP2 was the only protein with amino acid substitutions in all four serotypes. The amino acid substitutions all occurred within the same hydrophilic area, resulting in increased hydrophilicity of VP2 in the large plaque strains.

Characterization of Plaque Variants and the Involvement of Quasi-Species in a Population of EV-A71

“…Recently, a study characterised three isolates of Zika Virus (ZIKV) which exhibited three plaque sizes, namely: big, small and medium plaques [ 39 ]. Additionally, an African horse sickness virus (AFHS) population was characterised and was also shown to harbour three distinct plaque size variants [ 40 ]. As such, it is very likely that the EV-A71/WT population could be harbouring a variant of medium plaque size.…”

Cell culture propagation of foot-and-mouth disease virus: adaptive amino acid substitutions in structural proteins and their functional implications

“…Commonly, these FMD vaccines are produced by propagation of FMDV in BHK-21 cells [7]. It is known for many viruses, however, that cultivation outside the natural host, for instance during the course of adaptation to a permanent cell line, can result in alterations to the amino acid sequence of viral proteins [9][10][11][12][13]. Especially RNA viruses, such as FMDV, consist of viral populations without a defined genomic sequence but of distributions of related but non-identical genomes (quasispecies).…”

ViralPlaque: a Fiji macro for automated assessment of viral plaque statistics

“…Indeed, plaque statistics (size, clarity, border definition and distribution) can provide important information on the replication kinetics and virulence factors of a virus. Morphology of plaques has been reported to help distinguish viral isolates and is currently used as an indicator of virus attenuation (Tajima et al, 2010; Goh et al, 2016; Kato et al, 2017; Fan et al, 2018; Moser et al, 2018; Schade-Weskott, Van Schalkwyk & Koekemoer, 2018).…”