Effect of vaccination of cattle with the low virulence Nc-Spain 1H isolate of Neospora caninum against a heterologous challenge in early and mid-gestation

Abstract

Live vaccines have emerged as one of the most potentially cost-effective measures for the control of bovine neosporosis. Previous studies have shown that Nc-Spain 1H is a naturally attenuated isolate of Neospora caninum and that immunisation with live Nc-Spain 1H tachyzoites generated a protective immune response in mice. The aim of this study was to evaluate the safety and efficacy of immunisation in cattle. N. caninum-seronegative heifers were immunised subcutaneously twice with 107 live Nc-Spain 1H tachyzoites prior to artificial insemination. No adverse reactions or negative effects on reproductive parameters were recorded following immunisation. In immunised and non-challenged heifers, no foetal deaths were observed, and none of the calves was congenitally infected. The efficacy against N. caninum-associated foetal death and vertical transmission was determined after challenge with high doses of the Nc-1 isolate at 70 and 135 days of gestation, respectively. After the challenge in early gestation, the immunisation induced a protection of 50% against foetal death. In addition, the microsatellite analysis performed in PCR-positive tissue samples from foetuses that died after challenge infection showed that the profiles corresponded to the challenge isolate Nc-1. A degree of protection against vertical transmission was observed after challenge at mid-gestation; calves from immunised heifers showed significantly lower pre-colostral Neospora-specific antibody titres than calves from the non-immunised/challenge group (P < 0.05). Strong antibody and interferon gamma responses were induced in the immunised heifers. This study indicates that the immunisation before pregnancy with the Nc-Spain 1H vaccine isolate appeared to be safe and reduced the occurrence of N. caninum-associated abortion and vertical transmission in experimentally infected cattle. In light of these encouraging results, the next step for testing this live attenuated candidate should be the assessment of its efficacy and safety in naturally infected cattle.

Influence of the gestational stage on the clinical course, lesional development and parasite distribution in experimental ovine neosporosis

“…Finally, the inoculation dose, 10 6 tachyzoites, was a 1:10 dilution of that commonly used in cattle (i.e. 10 7 tachyzoites) [ 30 - 33 ], considering the weight difference between cattle and sheep (aprox. 10:1).…”

The effect of a live Neospora caninum tachyzoite vaccine in naturally infected pregnant dairy cows

“…However, in the mid-term gestation a significant decrease of the cell proliferation and IFN-␥ response occurred due to the initiation of typical physiological immunomodulation during pregnancy (Innes et al, 2001). In cows vaccinated with live tachyzoites before pregnancy, a challenge at mid-gestation induced strong and long-lasting specific IFN-␥ responses, sufficient to protect the fetus and prevent abortion (Innes et al, 2001;Williams et al, 2007;Rojo-Montejo et al, 2013).…”

“…It has been considered that an effective vaccine against neosporosis should either be aimed to prevent infection in uninfected animals, or to prevent abortion or vertical transmission in infected animals (Innes et al, 2002). Previous studies demonstrated that vaccination of naïve cows with live tachyzoites was protective against experimental challenge (Williams et al, 2007;Rojo-Montejo et al, 2013;Weber et al, 2013;Hecker et al, 2013;Reichel et al, 2014;Monney and Hemphill, 2014). The Israeli N. caninum NcIs491 isolate, obtained from brain tissue of an aborted fetus, can be easily grown in culture and is suggested to be of low pathogenicity to laboratory animals including gerbils (Fish et al, 2007) and mice (unpublished results), in comparison with the NC-1 strain (Lindsay et al, 1995;Rettigner et al, 2004).…”

Markers related to the diagnosis and to the risk of abortion in bovine neosporosis

“…Such patterns could be important in the pathogenesis of the infection and/or abortion. Finally, in experimentally infected heifers, strong IFN-γ responses were registered in immunized heifers with reduced occurrence of Neosporaassociated abortion and vertical transmission (Bacigalupe et al, 2013;Rojo-Montejo et al, 2013).…”