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A 78 kDa host cell invasion protein of Neospora caninum as a potential vaccine candidate
Qiang Lv1, Shenyang Xing2, Pengtao Gong3
1College of Veterinary Medicine of Jilin University, 5333 Xian Road, Changchun 130062, China; Key Laboratory of Polymer Ecomaterials, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China.
Abstract:
Neosporosis is an intracellular protozoan disease caused by Neospora caninum. Until now, there is no effective vaccine to prevent neosporosis. The host cell binding protein has the potential as neosporosis vaccine. In the present study, a T7 phage display library was constructed and screened using Vero cells to obtain host cell binding protein of N. caninum. Two host cell binding proteins, a hypothetical protein of 78 kDa (named as NcP78) homologous to the acylglycerol lipase of Toxoplasma gondii ME49 (XP_002370319.1) and NcGRA7 (known as a dense granules protein that is involved in the invasion of N. caninum to the host cells), were identified. Immune responses induced by recombinant NcP78 and NcGRA7 proteins and their protective efficacies against homologous challenge in BALB/c mice were evaluated respectively. Results showed that recombinant NcP78 and NcGRA7 could elicit both Th1 and Th2 immune responses (with the elevated levels of IgG1 and IgG2a antibody), but predominately a Th2 immune response with a high level of IgG1. The ani-NcP78 and anti-NcGRA7 serum also had inhibitory effects on N. caninum invasion to Vero cells in vitro, which indicated that both NcP78 and NcGRA7 proteins were involved in host cell invasion. Recombinant NcP78 and NcGRA7 could not prolong the survival times and improve the survival rates of dams, but could prolong the survival times and improve the survival rates of offspring significantly. Moreover, the recombinant NcP78 and NcGRA7 could reduce the brain parasite load of dams and offspring. Though these protein vaccines could not effectively alleviate the symptom of abortion, they could increase the number of born offspring significantly, indicating that Nc78 and NcGRA7 recombinant proteins could provide a partial protection against N. caninum infection in mice.
Insights
Developing a Neospora caninum vaccine is crucial as no effective prevention exists. Host cell binding proteins, NcP78 and NcGRA7, show potential, improving offspring survival and reducing parasite load in mice.
Area of Science:
- Veterinary immunology
- Parasitology
- Vaccine development
Background:
- Neosporosis, caused by Neospora caninum, lacks effective vaccines.
- Host cell binding proteins are potential candidates for a Neospora caninum vaccine.
Purpose of the Study:
- To identify and evaluate host cell binding proteins of N. caninum as vaccine candidates.
- To assess the immunogenicity and protective efficacy of recombinant NcP78 and NcGRA7 proteins in a mouse model.
Main Methods:
- Construction and screening of a T7 phage display library to identify N. caninum host cell binding proteins.
- Expression and purification of recombinant NcP78 and NcGRA7 proteins.
- Evaluation of immune responses (antibody levels, Th1/Th2) and protective effects against N. caninum challenge in BALB/c mice.
Main Results:
- Two host cell binding proteins, NcP78 and NcGRA7, were identified and involved in N. caninum invasion.
- Recombinant NcP78 and NcGRA7 elicited Th1/Th2 immune responses, predominantly Th2 (IgG1).
- Vaccination improved offspring survival rates, reduced brain parasite load, and increased offspring numbers, but did not prevent abortion.
Conclusions:
- Recombinant NcP78 and NcGRA7 proteins demonstrate partial protective efficacy against Neospora caninum infection in mice.
- These proteins represent promising candidates for developing a Neospora caninum vaccine, particularly for improving offspring outcomes.
