To date, there is no effective vaccine to prevent abortion or vertical transmission associated with neosporosis in cattle. In the present study, the efficacy of a live experimental vaccine of Neospora caninum attenuated (NCa) by long-term serial passages on a murine macrophage cell line was evaluated in the prevention of vertical transmission and abortion in the mouse model. Forty non-pregnant mice were randomly divided into four equal groups including non-immunized/challenged (injected with PBS); positive control (inoculated with un-attenuated NC-1 tachyzoites); immunized/challenged (inoculated with NCa attenuated strain) and immunized/non-challenged or vaccinated (inoculated with NCa) groups. Following pregnancy synchronization, both the immunized and control mice were challenged with virulent live NC-1 tachyzoites (2.5 × 10⁶) in the mid-pregnancy stage. The number of abortions and post-natal pup mortalities was recorded. Serological, molecular, and histopathologic examinations were employed to evaluate the efficacy of the vaccine and the vertical transmission rates. Results indicated that the live attenuated N. caninum strain (NCa) could significantly reduce the risk of abnormal parturitions and fetal mortality in the vaccinated group (20 %) compared to the non-immunized/challenged group (80 %). Also, the NCa strain reduced the lesion score in the brain of the offspring (0.3 vs 1.9) compared to the non-immunized/challenged group (P < 0.05). The molecular assay showed a decrease in the parasite DNA detection rates from 83 % and 77 % in the non-immunized/challenged group to 27 % and 0 % in the vaccine group in the brain and liver tissues, respectively. While in the immunized/non-challenged group no parasite DNA was detected in the brain tissue samples of the pups. Serological analyses showed that NCa strain was able to stimulate the humoral immunity and create effective protection against neosporosis with a moderate systemic IFN-γ response. In conclusion, the NCa strain could significantly (P < 0.05) reduce the risk of vertical transmission and proved to be a safe vaccine while conferring significant levels of protection in the laboratory mice.

迄今为止，还没有有效的疫苗来预防牛新孢子虫病引起的流产或垂直传播。在本研究中，犬新孢子虫活实验疫苗的功效通过在小鼠巨噬细胞系上长期连续传代的减毒（NCa）进行评估，以预防小鼠模型中的垂直传播和流产。将四十只未怀孕的小鼠随机分为四个相等的组，包括未免疫/激发的（注射PBS）；未注射的小鼠。阳性对照（接种未减毒的NC-1速殖子）；免疫/激发（接种NCa减毒株）和免疫/非激发或接种（NCa接种）组。妊娠同步后，免疫和对照小鼠均受到有毒的活NC-1速殖子（2.5×10 ⁶）处于怀孕中期。记录堕胎次数和产后幼仔死亡率。进行了血清学，分子和组织病理学检查，以评估疫苗的功效和垂直传播率。结果表明，活减毒犬链与未免疫/挑战组（80％）相比，接种疫苗组（NCa）可显着降低接种组（20％）的异常分娩和胎儿死亡率的风险。而且，与未免疫/激发组相比，NCa菌株降低了后代大脑的病变评分（0.3对1.9）（P <0.05）。分子测定法显示，脑和肝组织中的寄生虫DNA检测率分别从未免疫/激发组的83％和77％降低到疫苗组的27％和0％。而在免疫/非激发组中，幼犬的脑组织样本中未检测到寄生虫DNA。血清学分析表明，NCa菌株能够刺激体液免疫，并以中等程度的全身性IFN-γ应答有效防御新孢子虫病。结论，