Immune response to Neospora caninum in naturally infected heifers and heifers vaccinated with inactivated antigen during the second trimester of gestation

• Published in: Veterinary parasitology 2005-06, Vol.130 (1), p.29-39
• Main Authors: Moore, D.P., Leunda, M.R., Zamorano, P.I., Odeón, A.C., Romera, S.A., Cano, A., de Yaniz, G., Venturini, M.C., Campero, C.M.
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn; Antibodies, Protozoan - blood; antibody detection; antibody formation; antigens; Bovine; calves; Cattle; Cattle Diseases - immunology; Cattle Diseases - parasitology; Cattle Diseases - prevention & control; Cattle Diseases - transmission; Cell Proliferation; Coccidiosis - immunology; Coccidiosis - parasitology; Coccidiosis - prevention & control; Coccidiosis - veterinary; Enzyme-Linked Immunosorbent Assay - veterinary; Female; Fluorescent Antibody Technique, Indirect - veterinary; Immunoglobulin Isotypes - immunology; Immunology; inactivated vaccines; Infectious Disease Transmission, Vertical - prevention & control; Infectious Disease Transmission, Vertical - veterinary; Interferon-gamma - immunology; interferons; lymphocyte proliferation; Male; Neospora - immunology; Neospora caninum; neosporosis; pregnancy; Protozoan Vaccines - immunology; Protozoan Vaccines - therapeutic use; Random Allocation; seroprevalence; T-Lymphocytes - cytology; T-Lymphocytes - immunology; tachyzoites; vaccination; Vaccination - veterinary; Vaccine
• ISSN: 0304-4017; 1873-2550
• DOI: 10.1016/j.vetpar.2005.03.010

The objective of this study was to compare the immune response to Neospora caninum in naturally infected heifers and heifers inoculated with a killed whole N. caninum tachyzoite preparation during the second trimester of gestation. Nine Holstein heifers were used in this study; three naturally infected heifers were born from seropositive dams, and six seronegative heifers were born from seronegative dams. Four seronegative heifers were subcutaneously vaccinated with a killed whole N. caninum tachyzoite preparation at weeks 13, 15 and 17 of gestation. A killed whole N. caninum tachyzoite preparation containing 45 mg of protein/5 ml dose was formulated with 70% of mineral oil adjuvant (13% consisting of Arlacel C, 85% Marcol 52 and 2% Tween-80). Similarly, two seronegative heifers (negative controls) were inoculated with mock-infected bovine monocytes in oil adjuvant. Humoral immune responses were tested by using an indirect fluorescent antibody test (IFAT) and an indirect enzyme-linked immunosorbent assay (ELISA) for detecting isotype specific antibodies. Cellular immune responses were assessed by lymphocyte proliferation test (LPT) and IFN-γ production. N. caninum-specific antibody responses increased in immunized cattle by week 15 of gestation (mean reciprocal antibody titers 450 ± 252), peaked at week 23 (mean 16,000 ± 6400). Maximum antibody response in naturally infected heifers was observed at week 19 of gestation (mean: 3467 ± 2810). Mean serum IFAT titers were significantly higher in immunized heifers compared with those in naturally infected heifers from weeks 17 to 25 ( P < 0.05). Analysis of isotype specific antibodies in naturally infected heifers revealed a predominant IgG1 response in one heifer and a predominant IgG2 response in the other two. Similar titers of IgG1 and IgG2 occurred in immunized heifers. Control heifers remained seronegative throughout the study by IFAT and ELISA. Significant antigen-specific proliferation responses were only detected in naturally infected heifers in week 19 of gestation. Peripheral mononuclear blood cells (PMBC) from immunized animals produced IFN-γ in similar concentrations to those of infected animals ( P > 0.05). No abortion was seen in any experimental group; however, one calf from a vaccinated heifer died due to dystocia. All calves from vaccinated and control heifers were seronegative by IFAT at 6 months of age; in contrast, calves born from naturally infected heifers remained seropositive with titers