Bartley P M, Wright S, Sales J, Chianini F, Buxton D, Innes E A
Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik EH26 0PZ, Scotland, UK.
Parasitology. 2006 Oct;133(Pt 4):421-32. doi: 10.1017/S0031182006000539. Epub 2006 Jun 9.
To determine whether prolonged in vitro passage would result in attenuation of virulence in vivo, Neospora caninum tachyzoites were passaged for different lengths of time in vitro and compared for their ability to cause disease in mice. Groups of Balb/c mice were inoculated intraperitoneally with 5 x 10(6) or 1 x 10(7) of low-passage or high-passage N. caninum tachyzoites. The mice were monitored for changes in their demeanour and body weight, and were culled when severe clinical symptoms of murine neosporosis were observed. Mice inoculated with the high-passage parasites survived longer (P<0.05), and showed fewer clinical symptoms of murine neosporosis, compared to the mice receiving the low-passage parasites. The parasite was detected in the brains of inoculated mice using immunohistochemistry and ITS1 PCR. Tissue cysts containing parasites were seen in mice inoculated with both low-passage and high-passage parasites. When the in vitro growth rates of the parasites were compared, the high-passage parasites initially multiplied more rapidly (P<0.001) than the low-passage parasites, suggesting that the high-passage parasites had become more adapted to tissue culture. These results would suggest that it is possible to attenuate the virulence of N. caninum tachyzoites in mice through prolonged in vitro passage.
为了确定体外长时间传代是否会导致体内毒力减弱，将犬新孢子虫速殖子在体外传代不同时间，并比较它们在小鼠体内引发疾病的能力。将Balb/c小鼠分组，腹腔注射5×10(6)或1×10(7)个低代或高代犬新孢子虫速殖子。监测小鼠的行为和体重变化，当观察到小鼠新孢子虫病的严重临床症状时将其扑杀。与接受低代寄生虫的小鼠相比，接种高代寄生虫的小鼠存活时间更长（P<0.05），且小鼠新孢子虫病的临床症状更少。使用免疫组织化学和ITS1 PCR在接种小鼠的脑中检测到寄生虫。在接种低代和高代寄生虫的小鼠中均可见到含有寄生虫的组织囊肿。比较寄生虫的体外生长速率时，高代寄生虫最初比低代寄生虫繁殖得更快（P<0.001），这表明高代寄生虫对组织培养的适应性更强。这些结果表明，通过体外长时间传代有可能减弱犬新孢子虫速殖子在小鼠体内的毒力。
