Cloning and expression of Neospora caninum dense-granule 7 in E. coli

Immunogenicity, safety and dual DIVA-like character of a recombinant candidate vaccine against neosporosis in cattle

Neosporosis is the major infectious cause of abortion and reproductive losses in cattle worldwide; however, there are no available vaccines or drugs to control this disease. Recently, a dual (positive and negative) DIVA-like (Differentiation of Infected from Vaccinated Animals) vaccine was evaluated in a pregnant mouse model of neosporosis, showing promising immunogenic and protective results. The current report aimed to study the safety, the dose-dependent immunogenicity and the dual DIVA-like character of a recombinant subunit vaccine composed of the major surface antigen from Neospora caninum (rNcSAG1) and the carrier/adjuvant Heat shock protein 81.2 from Arabidopsis thaliana (rAtHsp81.2) in cattle. Healthy heifers were separated and assigned to experimental groups A-F and subcutaneously immunized with 2 doses of vaccine formulations 30 days apart as follows: A (n = 4): 50 μg rNcSAG1 + 150 μg rAtHsp81.2; B (n = 4): 200 μg rNcSAG1 + 600 μg rAtHsp81.2; C (n = 4): 500 μg rNcSAG1 + 1,500 μg rAtHsp81.2; D (n = 3): 150 μg rAtHsp81.2; E (n = 3):1,500 μg rAtHsp81.2, and F (n = 3) 2 ml of sterile PBS. The immunization of heifers with the different vaccine or adjuvant doses (groups A-E) was demonstrated to be safe and did not modify the mean value of the evaluated serum biomarkers of metabolic function (GOT/ASP, GPT/ALT, UREA, Glucose and total proteins). The kinetics and magnitude of the immune responses were dose-dependent. The higher dose of the vaccine formulation (group C) stimulated a broad and potent humoral and cellular immune response, characterized by an IgG1/IgG2 isotype profile and IFN-γ secretion. In addition, this was the first time that dual DIVA-like character of a vaccine against neosporosis was demonstrated, allowing us to differentiate vaccinated from infected heifers by two different DIVA compliant test approaches. These results encourage us to evaluate its protective efficacy in infected pregnant cattle in the future.

Gene cloning, expression, and enzyme kinetics analysis of Eimeria tenella 2- methylcitrate synthase

In prokaryotes and lower eukaryotes, 2-methylcitrate cycle (2-MCC) is the main pathway for propionate decomposition and transformation, but little is known about the 2-MCC pathway of Eimeria tenella. The analysis of genomic data found that the coding gene of 2- methylcitrate synthase (EC 2.3.3.5, PrpC) exists in E. tenella, which is a key enzyme of 2-MCC pathway. Through the search analysis of the database (ToxoDB), it was found that ETH_ 00026655 contains the complete putative sequence of EtprpC. In this study, we amplified the ORF sequence of EtprpC based on putative sequence. Then, prokaryotic expression, enzyme activity and kinetic analysis was performed. The results showed that the EtprpC ORF sequence was 1272 bp, encoding a 46.3 kDa protein comprising 424 amino acids. Enzyme activity assays demonstrate linearity between the initial reaction rate (OD/min) and EtPrpC concentration (ranging from 1.5 to 9 µg/reaction), with optimal enzyme activity observed at 41°C and pH 8.0. The results of enzymatic kinetic analysis showed that the Km of EtPrpC for propionyl-CoA, oxaloacetic acid, and acetyl-CoA was 5.239 ± 0.17 mM, 1.102 ± 0.08 μM, and 5.999 ± 1.24 μM, respectively. The Vmax was 191.11 ± 19.1 nmol/min/mg, 225.48 ± 14.4 nmol/min/mg, and 370.02 ± 25.8 nmol/min/mg when EtPrpC concentration at 4, 6, and 8 μg, respectively. Although the ability of EtPrpC to catalyze acetyl-CoA is only 0.11% of its ability to catalyze propionyl-CoA, it indicates that the 2-MCC pathway in E. tenella is similar to that in bacteria and may have a bypass function in the TCA cycle. This study can provide the theoretical foundation for the new drug targets and the development of new anticoccidial drugs.

Identification of the antigenic region of Neospora caninum dense granule protein 7 using ELISA

Dense granule protein 7 (NcGRA7) is a potent diagnostic antigen of Neospora caninum. Some studies have reported on the difficult expression, low yield, and variable degree of solubility of recombinant NcGRA7. We aimed to unravel the possible causes for these issues and tested NcGRA7 antigenicity in enzyme linked immunosorbent assays (ELISAs). The NcGRA7 coding sequence (217 amino acids) was split into five amino acid regions: NcGRA7m (27-217), NcGRA7m3 (27-160), NcGRA7m4 (27-135), NcGRA7m5 (161-190), and NcGRA7m6 (188-217). Three fragments, NcGRA7m, NcGRA7m3 and NcGRA7m4, exhibited high antigenic properties when tested against experimentally-infected mice and dog sera by ELISA. High levels of IgG2 antibodies against NcGRA7m3 were observed in field dog sera. In experimentally and naturally-infected cattle, the N. caninum-specific sera only reacted with NcGRA7m, indicating that this antigenic region differs among the three animal species. This study presents valuable information about the antigenic properties and topology of NcGRA7, and highlights its suitability for diagnostic purposes.