Blocking ELISA using recombinant NcSRS2 protein for diagnosing bovine neosporosis

Indirect ELISAs with sucrose subcellular fractions of Neospora caninum as antigens for diagnosis of neosporosis in cattle

Neosporosis is one of the major causes of abortion in cattle, and it is responsible for significant economic losses in those animals. Thus, this study aimed to evaluate indirect ELISA using subcellular fractions of Neospora caninum obtained via sucrose gradient separation. Eighty-five sera from dairy cattle previously tested using indirect immunofluorescence assay (IFA) were used. Three distinct bands were separated at 1.0 M, 1.4 M, 1.6 M, and the pellet at 1.8 M, which were identified as fractions one (F1), two (F2), three (F3), and four (F4), respectively. These fractions showed parasite membranes in the F1, rhoptry and conoids in the F2, mitochondria in the F3, and tachyzoite ghosts remain in F4. Indirect ELISAs for IgM, and IgG were performed. Additionally, sensitivity, specificity, and kappa values were defined considering the IFA as the gold standard. The highest and lowest specificities were observed for F1 (76 %) and F3 (16 %), respectively. F2 and F4 showed the highest sensitivity (93.3 %), kappa agreement (0.46), and Negative Preventive Value (NPV) (73 %) respectively. It was possible to standardize indirect ELISAs using whole soluble antigen and subcellular fractions of N. caninum, and F2 and F4 showed higher sensitivity (93.3 %), kappa (0.41), and NPV values (75 %) than F1, and F3, which could be used for epidemiology studies such as screening.

Chimeric Protein Designed by Genome-Scale Immunoinformatics Enhances Serodiagnosis of Bovine Neosporosis

Neosporosis has become a concern since it is associated with abortion in cattle. Currently, in situ diagnosis is determined through anamnesis, evaluation of the history, and perception of the clinical signs of the herd. There is no practical and noninvasive test adapted to a large number of samples, which represents a gap for the use of new approaches that provide information about infections and the risks of herds. Here, we performed a search in the Neospora caninum genome by linear B-cell epitopes using immunoinformatic tools aiming to develop a chimeric protein with high potential to bind specifically to antibodies from infected cattle samples. An enzyme-linked immunosorbent assay with the new chimeric antigen was developed and tested with sera from natural field N. caninum-infected bovines. The cross-reactivity of the new antigen was also evaluated using sera from bovines infected by other abortive pathogens, including Trypanosoma vivax, Leptospira sp., Mycobacterium bovis, and Brucella abortus, and enzootic bovine leucosis caused by bovine leukemia virus, as well as with samples of animals infected with Toxoplasma gondii The assay using the chimeric protein showed 96.6% ± 3.4% of sensitivity in comparison to healthy animal sera. Meanwhile, in relation to false-positive results provided by cross-reactivity with others pathogens, the specificity value was 97.0% ± 2.9%. In conclusion, immunoinformatic tools provide an efficient platform to build an accurate protein to diagnose bovine neosporosis based on serum samples.

From Signaling Pathways to Distinct Immune Responses: Key Factors for Establishing or Combating Neospora caninum Infection in Different Susceptible Hosts

: Neospora caninum is an intracellular protozoan parasite affecting numerous animal species. It induces significant economic losses because of abortion and neonatal abnormalities in cattle. In case of infection, the parasite secretes numerous arsenals to establish a successful infection in the host cell. In the same context but for a different purpose, the host resorts to different strategies to eliminate the invading parasite. During this battle, numerous key factors from both parasite and host sides are produced and interact for the maintaining and vanishing of the infection, respectively. Although several reviews have highlighted the role of different compartments of the immune system against N. caninum infection, each one of them has mostly targeted specific points related to the immune component and animal host. Thus, in the current review, we will focus on effector molecules derived from the host cell or the parasite using a comprehensive survey method from previous reports. According to our knowledge, this is the first review that highlights and discusses immune response at the host cell-parasite molecular interface against N. caninum infection in different susceptible hosts.

An indirect ELISA for Neosporosis: Associating recombinant Neospora caninum proteins NcSRS2 and NcSAG1

Neosporosis is caused by infection with the protozoa Neospora caninum. It manifests as various neurological symptoms and is considered as one of the main causes of abortion in cattle, and induces uncommon congenital infection in sheep. The standard diagnosis is based on indirect immunofluorescence (IFI); however, cross-reactivity with other protozoa proteins is common. Aiming a more specific diagnosis, recombinant antigens have been tested in several immunoassays; of these, NcSAG1 (surface antigen-1) and NcSRS2 (SAG1-related sequence 2) were the most promising. In this context, we developed an indirect ELISA with recombinant NcSRS2 (ELISA-rNcSRS2) and NcSAG1 (ELISA-rNcSAG1) proteins alone and in association (ELISA-rNcSRS2/rNcSAG1) for the diagnosis of cattle and ovine neosporosis. A total of 216 samples from cattle and 154 samples from sheep were used to evaluate the ELISAs. The sensitivity and specificity results of the ELISA-rNcSRS2 were 91.5 % and 96.4 % for cattle, and 89.6 % and 96.3 % for sheep, respectively. For the ELISA-rNcSAG1, the sensitivity and specificity were 84.9 % and 97.3 % for cattle, and 89.6 % and 92.6 % for sheep, respectively. The sensitivity and specificity of the ELISA-rNcSRS2/rNcSAG1 was 98.1 % and 99.1 % for cattle, 100 % and 97.2 % for sheep, respectively. These results indicated that indirect ELISA using the rNcSRS2 and rNcSAG1 proteins are a highly sensitive and specific method, especially when used in association, for detecting antibodies in cattle and ovine populations infected with N. caninum.