To study
genetic changes underlying
myxoma virus evolution in its new host, the European rabbit (
Oryctolagus cuniculus), we
sequenced selected genomic regions of nine recent
virulent field strains and a live
attenuated vaccine strain ("MAV", Germany).
DNA was extracted from
cell culture passaged
myxoma virus. A total of 4863 bp (approximately 3% of the genome) of 10 regions spanning 12 genes of the
myxoma viruses was
sequenced and compared to the original
virulent strain "Lausanne" and its
attenuated field derivative strain "6918". The field strains displayed a maximum of three (strains C43, C95) and a minimum of one (strains CD01, CD05)
nucleotide substitutions. These were distributed through all analysed
coding regions, except gene M022L (major envelope protein), where all strains were identical to "Lausanne" and "6918". Two new single
nucleotide insertions were observed in some of the field strains: within the
intergenic region M014L/M015L and within gene M009L, where it leads to a
frameshift. These insertions were located after
homopolymeric regions. The
vaccine strain displayed 37
nucleotide substitutions, predominantly (95%) located in genes M022L and M036L. Interestingly, regions M009L and M014L/M015L of the
vaccine were not amplified successfully, suggesting major genomic changes that could account for its
attenuated phenotype. Our results support a high degree of
genetic stability of
myxoma virus over the past five decades. None of the analysed genome regions by its own seems sufficient for the
genetic characterisation of field strains.
