title: Immune response to Neospora caninum in naturally infected heifers and heifers vaccinated with inactivated antigen during the second trimester of gestation.
abstract: 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-gamma 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-gamma 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 > or = 200. Killed vaccine induced similar immune responses to those found in chronically, naturally infected cattle which did not abort; however, different immune pathways may be followed in vaccinated and natural infected heifers with differences in degree of protective immunity.
authors.affiliation: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina. pmoore@uoguelph.ca
authors.forename: D P
authors.initials: DP
authors.lastname: Moore
authors.forename: M R
authors.initials: MR
authors.lastname: Leunda
authors.forename: P I
authors.initials: PI
authors.lastname: Zamorano
authors.forename: A C
authors.initials: AC
authors.lastname: Odeón
authors.forename: S A
authors.initials: SA
authors.lastname: Romera
authors.forename: A
authors.initials: A
authors.lastname: Cano
authors.forename: G
authors.initials: G
authors.lastname: de Yaniz
authors.forename: M C
authors.initials: MC
authors.lastname: Venturini
authors.forename: C M
authors.initials: CM
authors.lastname: Campero
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000913:Antibodies, Protozoan / Q000097:blood; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology* / Q000469:parasitology* / Q000517:prevention & control / Q000635:transmission; D049109:Cell Proliferation; D003048:Coccidiosis / Q000276:immunology / Q000469:parasitology / Q000517:prevention & control / Q000662:veterinary*; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect / Q000662:veterinary; D007132:Immunoglobulin Isotypes / Q000276:immunology; D018445:Infectious Disease Transmission, Vertical / Q000517:prevention & control / Q000662:veterinary*; D007371:Interferon-gamma / Q000276:immunology; D008297:Male; D018688:Neospora / Q000276:immunology*; D016052:Protozoan Vaccines / Q000276:immunology* / Q000627:therapeutic use; D011897:Random Allocation; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology; D014611:Vaccination / Q000662:veterinary*
chemical_list: D000913:Antibodies, Protozoan; D007132:Immunoglobulin Isotypes; D016052:Protozoan Vaccines; D007371:Interferon-gamma