Oligomannose-coated liposome-entrapped dense granule protein 7 induces protective immune response to Neospora caninum in cattle

Neospora caninum is an intracellular protozoan parasite that causes abortion in cows. Vaccination is an important strategy for control of neosporosis, and a safe and effective vaccine suitable for cattle is required. Dense granule protein 7 of N. caninum (NcGRA7) is a secretory protein with high antigenicity in hosts. We demonstrated previously that NcGRA7 entrapped in liposomes coated with mannotriose (M3-NcGRA7) could induce a parasite-specific T-helper type 1 immune response and produce humoral antibodies that resulted in increased offspring survival and decreased infection in the brains of mice dams. In the present study, the efficacy of M3-NcGRA7 as a vaccine candidate against N. caninum has been evaluated in cattle (n = 12). Cattle were immunized with M3-NcGRA7 containing 50 mu g (n = 4) or 200 mu g NcGRA7 (n = 4) subcutaneously twice with a 4-week interval and all cattle including the non-immunized controls (n = 4) were inoculated with 10(7) tachyzoites of Nc-1 strain 27 days after the second immunization and euthanized at 85-87 days post infection (dpi). In immunized cattle, NcGRA7-specific antibody production and IFN-gamma production in PBMC was induced before challenge. At 3 dpi, body temperature and concentration of serum IFN-gamma tended to be higher in control cattle than in the immunized cattle. Furthermore, the parasite load in the brain significantly decreased in cattle immunized with 50 mu g M3-NcGRA7 compared with controls. These results suggest that M3-NcGRA7 can induce protective immune responses to N. caninum tachyzoites in cattle, which could lead to practical application of safe and effective subunit vaccines. (c) 2013 Elsevier Ltd. All rights reserved.