A study of orf virus isolates from sheep in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy in Virology and Immunology at Massey University
A preliminary study of various orf virus isolates in New Zealand is presented. A method of isolating and purifying the virus from scab material is described. Thirteen orf virus isolates were compared by DNA restriction endonuclease analysis. There was extensive heterogeneity in the EcoR1 restriction patterns, however, two of the isolates were similar. Propagation of the virus in in vitro was also attempted. Five of the isolates were successfully adapted to growth in lamb testis cells and two of these were plaque-purified twice. The characteristic cytopathic effect of cell-adapted virus is early rounding and clumping together of infected cells. This cell rounding could be seen as early as two hours post-infection and could be inhibited by cyclohexamide. There were two types of plaques exhibited by the isolates in lamb testis cell monolayers, the "open" and "closed" types. Inclusion bodies were also seen in stained infected monolayers. 32 P-labelling of a plaque-purified isolate was successfully performed. Low passage (23 passages) in cell culture of plaque-purified isolate No. 2 did not alter the EcoR1, Bam H-I or Hind III patterns of the DNA when compared with the original viral DNA from scab material.