Lindsay D S, Lenz S D, Dykstra C C, Blagburn B L, Dubey J P
Department of Pathology, College of Veterinary Medicine, Auburn University, Alabama 36849-5519, USA.
J Parasitol. 1998 Apr;84(2):311-5.
Neospora caninum is a protozoan parasite that can cause severe disease in mammals. Two experiments were conducted to examine the effects of subcutaneous (s.c.) vaccination with Hank's balanced salt solution (HBSS), 1 x 10(5) N. caninum NC-1 strain tachyzoites or 1 x 10(5) Toxoplasma gondii TS-4 strain tachyzoites on challenge oral infections in mice with sporulated VEG strain T. gondii oocysts (1 X 10(3) oocysts exp. 1 and 5 x 10(3) oocysts exp. 2). An additional study, experiment 3, evaluated s.c. challenge with 2.5 X 10(3) tachyzoites of the highly virulent RH strain of T. gondii after vaccination with HBSS, NC-1 tachyzoites, or TS-4 tachyzoites. Mice vaccinated with NC-1 strain tachyzoites survived significantly (P < 0.05) longer than mice given HBSS in experiment 1, but not in experiments 2 and 3. Mice vaccinated with TS-4 strain tachyzoites survived significantly longer than HBSS-vaccinated mice in experiments 1, 2, and 3 and significantly longer than mice vaccinated with the NC-1 strain in experiments 2 and 3. Toxoplasma gondii tissue cyst numbers were significantly lower for mice vaccinated with TS-4 strain tachyzoites than mice vaccinated with HBSS or the NC-1 strain tachyzoites in experiment 1. No difference was observed in tissue cyst numbers in mice vaccinated with HBSS or NC-1 strain tachyzoites in experiment 1. No HBSS-vaccinated mice survived experiment 2, and the numbers of T. gondii tissue cysts were significantly lower for mice vaccinated with the TS-4 strain tachyzoites compared to NC-1 strain tachyzoites. No HBSS- or NC-1-vaccinated mice survived RH strain challenge in experiment 3. Results of these experiments indicate that infection with N. caninum provides some protection against fatal oral infection with T gondii oocysts of a moderately pathogenic strain but not tachyzoites of a highly pathogenic strain. The protection provided by N. caninum is much less than that provided by previous exposure to T. gondii, and the numbers of tissue cysts in the brains of mice are not significantly (P > 00.5) lowered.
犬新孢子虫是一种可在哺乳动物中引发严重疾病的原生动物寄生虫。开展了两项实验，以研究皮下接种汉克平衡盐溶液（HBSS）、1×10⁵个犬新孢子虫NC - 1株速殖子或1×10⁵个刚地弓形虫TS - 4株速殖子，对经口感染孢子化的刚地弓形虫VEG株卵囊（实验1为1×10³个卵囊，实验2为5×10³个卵囊）的小鼠所产生的影响。另一项研究，即实验3，评估了在接种HBSS、NC - 1速殖子或TS - 4速殖子后，用2.5×10³个刚地弓形虫高毒力RH株速殖子进行皮下攻击的情况。在实验1中，接种NC - 1株速殖子的小鼠存活时间显著（P < 0.05）长于接种HBSS的小鼠，但在实验2和实验3中并非如此。在实验1、2和3中，接种TS - 4株速殖子的小鼠存活时间显著长于接种HBSS的小鼠，且在实验2和3中显著长于接种NC - 1株的小鼠。在实验1中，接种TS - 4株速殖子的小鼠脑中的刚地弓形虫组织囊肿数量显著低于接种HBSS或NC - 1株速殖子的小鼠。在实验1中，接种HBSS或NC - 1株速殖子的小鼠的组织囊肿数量未观察到差异。在实验2中，接种HBSS的小鼠无一存活，接种TS - 4株速殖子的小鼠的刚地弓形虫组织囊肿数量显著低于接种NC - 1株速殖子的小鼠。在实验3中，接种HBSS或NC - 1的小鼠在RH株攻击后无一存活。这些实验结果表明，感染犬新孢子虫可对中等致病力株的刚地弓形虫卵囊经口致命感染提供一定保护，但对高致病力株的速殖子感染则无保护作用。犬新孢子虫提供的保护远小于先前感染刚地弓形虫所提供的保护，且小鼠脑中组织囊肿的数量并未显著（P > 0.05）减少。
