Immune response and antigen recognition in non-pregnant ewes experimentally infected with Neospora caninum tachyzoites.

The cellular and humoral responses as well as the antigen recognition during the acute stage of a Neospora caninum (NC) infection were investigated in non-pregnant ewes. The experimentally infected ewes developed specific lymphoproliferative and humoral responses within 2 weeks post-infection (PI). The magnitude of the cellular response showed large variations between animals. A significant decrease in the proliferative response to Con A mitogen and N. caninum, Toxoplasma gondii (TG) antigens was recorded on day 21 post-infection (PI). The humoral response and the pattern of antigen recognition were similar among infected ewes. Proteins of 44, 42, 40, 39 and 28 kDa were intensively recognized by the infected animals during the experiment. The 42 and 28 kDa antigens should be considered as useful for the diagnostic of N. caninum infection, as the intensity of recognition infection of the other antigens had decreased markedly 8 weeks post-infection. For some antigens a sequential recognition was recorded. The 59, 54 and 38-37 kDa proteins were frequently recognized by infected sera during the first weeks of the infection, but recognition of these antigens was absent or rare at the end of the experiment. These antigens could be related to the acute stage of the infection

Use of a serum-free medium to produce in vitro Neospora caninum and Toxoplasma gondii tachyzoites on Vero cells

Neospora caninum and Toxoplasma gondii are cyst-forming coccidian parasites of human and veterinary clinical relevance. In vitro cultivation of the protozoans using Vero cells is usually performed in order to produce antigenic materials. Quantitative and qualitative comparisons of Vero cells grown in RPMI medium supplemented either with foetal calf serum (FCS), horse serum (HS) or a specific serum-free additive (DefCell) were performed. A serum-free cell culture system used to propagate N. caninum (NC-1 isolate) and T. gondii tachyzoites (Rh stain) were compared with the other two cell culture systems. FCS supplemented media was found to be more effective than the others in promoting Vero cells and N. caninum tachyzoites. However, it was found unable to support adequate T. gondii tachyzoite proliferation. Vero cells, T. gondii and N. caninum tachyzoite production gave similar growth patterns with either HS or DefCell supplemented media. Defcell was considered as a good alternative to supplement culture medium.Utilisation d'un milieu sans sérum pour la production in vitro de tachyzoites de Neospora caninum et Toxoplasma gondii sur cellules Vero. Neospora caninum et Toxoplasma gondii sont deux sporozoaires présentant un intérêt en médecine humaine et vétérinaire. La culture in vitro utilisant, entre autres, les cellules Vero comme support de la multiplication des deux parasites, est généralement employée en vue de l'obtention de tachyzoïtes. Au cours de cette étude, une évaluation quantitative et qualitative de la production de cellules Vero dans un milieu complémenté en sérum de veau foetal, de cheval ou bien avec un additif (DefCell) exempt de sérum, a été réalisée. Les trois types de milieu de culture ont également été employés et comparés dans le cadre de la production sur cellules Vero de tachyzoïtes de T. gondii (souche RH) et de N. caninum (isolat NC-1). Le milieu complémenté en sérum de veau fœtal s'est révélé être le plus adéquat pour la croissance de cellules Vero et la production de tachyzoïtes de N. caninum. Cependant, ce milieu s'est avéré incapable d'assurer une production optimale de tachyzoïtes de T. gondii. La production de cellules Vero, ainsi que de tachyzoïtes de T. gondii et de N. caninum, a présenté des caractéristiques communes en milieu complémenté en sérum de cheval et en DefCell. Ce dernier s'est révélé être une bonne alternative au sérum de veau foetal et de cheval pour complémenter les milieux de culture. L'absence de protéines animales dans ce milieu présente un certain nombre d'avantages qui sont discutés