Global incidence of resistance to current antimicrobial drugs is on the rise, highlighting the urgent need to develop novel antimicrobials. Antimicrobials currently in use typically target pathogen encoded proteins or pathways, leading to selective pressure to acquire resistance. Resistance mechanisms, both acquired and innate, are generally elicited by the cellular stress response. A recent approach targets host factors that the invading microbes rely on for their spread, virulence or survival. It is proposed this approach will produce antimicrobials that are much less likely to select for resistance. This study uses vaccinia virus (VACV) to model the development of resistance to host targeted antimicrobial imatinib, which inhibits the release of enveloped virus.

Previous work has isolated a putative imatinib resistance allele through culturing virus in the presence of imatinib. A mutation in this isolate was identified in the outer envelope viral protein A34. This study aims to characterise the novel A34 mutation (A34^K111T) as well as another published mutation in A34 (A34^K151E), both leading to higher virus release from cells than the parental WR strain. Results show that the two alleles in A34 resist imatinib treatment to a differing extent, and potentially represent different modes of resistance. This study has also amplified and cloned the A34^K111T point mutation into a plasmid vector, and used homologous recombination to insert the mutation back into the parental background, laying the foundation for creation of a recombinant virus to further characterise the allele. A putative recombinant awaits sequencing and characterisation. As well as in vitro characterisation of the viral strains mice will be used for in vivo studies. Mice infected with a fatal dose of VACV survive when treated with imatinib. In vivo studies will establish whether these mutations in A34 restore fatality in infected mice when treated with imatinib.