Objective-To describe the prevalence of antibodies against Salmonella spp in swine marketed in Iowa. Animals-Swine marketed by 1,044 low-volume producers and 45 high-volume producers. Procedure-Samples of diaphragm muscle collected from swine carcasses were tested by an indirect ELISA based on lipopolysaccharides from Salmonella spp, in particular Salmonella serovar Typhimurium. Prevalence of positive results for antibodies against Salmonella spp for carcasses, lots, and swine for each producer was determined. Producer-level seroprevalence was used to classify swine from producers as having negligible, low, moderate, or widespread evidence of previous or historical exposure to Salmonella spp. Results-From low-volume producers, 23,609 of 25,478 (92.7%; 95% confidence interval CI, 92.4% to 92.9%) samples had negative results, and 1,863 (7.3%; 95% CI, 7.05% to 7.56%) had antibodies against Salmonella spp. Of the 6,299 lots of swine tested, 1,191 (18.9%) contained at least 1 sample with positive results. From high-volume producers, 203 of 2,486 (8.1 %; 95% CI, 6.8% to 9.3%) samples had antibodies against Salmonella spp, and 124 of 629 lots had at least 1 sample with positive results for antibodies against Salmonella spp. Conclusions and Clinical Relevance-Less than 10% of pigs marketed in Iowa are apparently exposed to Salmonella spp. Most swine marketed by low-volume producers had negligible or little evidence of exposure to Salmonella spp, whereas a higher percentage of swine marketed by high-volume producers had positive results when tested to detect antibodies against Salmonella spp.

Objective--To evaluate the immunologic response of a killed tachyzoite vaccine against Neospora caninum and its effectiveness in preventing fetal loss associated with experimentally induced neosporosis in sheep. Animals--30 Dorset ewes. Procedure--Ewes were randomly allocated to receive vaccination on days 1 and 60 of the study with a killed N caninum tachyzoite preparation in a commercially available adjuvant or a saline-adjuvant mixture. A ram was placed on pasture with the ewes from days 15 to 60. Blood was collected from ewes before primary and booster vaccinations and prior to experimental challenge with N caninum tachyzoite performed on day 90; sera were assessed via Neospora agglutination (NA) and immunofluorescence antibody (IFA) assays. Blood was collected from lambs before they suckled, and sera were tested for antibodies against N caninum. Results--Of the 14 vaccinated ewes that became pregnant, 12 gave birth to live-born lambs; in contrast, 5 of 11 pregnant control ewes gave birth to live-born lambs. Whereas vaccination improved fetal survival in pregnant ewes challenged with N caninum tachyzoites, it did not appear to have any appreciable effect on transmission of N caninum to offspring, as indicated by results of NA and IFA assays. Conclusions and Clinical Relevance--The N caninum tachyzoite vaccine used in this study appeared to provide protection against fetal loss associated with experimentally induced neosporosis in a high proportion of pregnant ewes.

A monoclonal antibody (MAB) against equine tumor necrosis factor-alpha (Eq TNF) was used to investigate the role of TNF in cytokine, eicosanoid, and metabolic responses of Miniature Horses given endotoxin. Plasma concentrations of interleukin 6 (IL-6), lactate, thromboxane A2 metabolite, and prostacyclin metabolite (6-keto-PGF(1 alpha)) were measured in 10 Miniature Horses given 0.25 micrograms of lipopolysaccharide (LPS; Escherichia coli O55:B5)/kg of body weight. Five horses were given Eq TNF MAB and 5 were given isotype-matched MAB as control. All horses were given 1.86 mg of antibody/kg by IV infusion, 5 minutes before LPS was given IV. Blood samples were taken 20 minutes before and at multiple intervals for 24 hours after LPS was given. Interleukin 6 bioactivity in plasma was measured, using IL-6-dependent cell line (B9). Eicosanoid activities were assessed by enzyme immunoassay, and plasma lactate concentration was determined enzymatically. Data were analyzed by ANOVA and Tukey's honest significant difference test for significant (P < 0.05) effect of treatment. Horses given Eq TNF MAB had significantly (P < 0.050) lower peak mean +/- SEM IL-6 (59 +/- 29 U/ml), lactate (16 +/- 2.00 mg/dl), and 6-keto-PGF(1 alpha) (254 +/- 79 pg/ml) values then did horses given control MAB (880 +/- 375 U/ml for IL-6; 26 +/- 0.04 mg/dl for lactate; and 985 +/- 290 pg/ml for 6-keto-PGF(1 alpha)). There was no effect of anti-TNF treatment on LPS-induced thromboxane A2 metabolite production. Tumor necrosis factor mediated IL-6, lactate, and prostacyclin responses, without affecting thromboxane production in horses given LPS.

Use of a combination of an effective gE gene-deleted pseudorabies virus (PRV) vaccine with a companion diagnostic kit for PRV glycoprotein gE has proven successful in several pseudorabies-eradication programs. To produce a large quantity of functional gE protein for development of a PRV-gE diagnostic kit, an Escherichia coli expression system containing the distal region of the PRV-gE gene of a PRV strain CF was constructed. The expressed protein contained 134 amino acids of gE protein (amino acids 77-210) fused to a 19-amino acids tag containing 6 histidine residues. After induction, a truncated PRV-gE polypeptide of 18-kd was expressed to about 20% of the total E coli proteins. Results of immunoblot analysis indicated that this E coli-produced PRV-gE protein reacted specifically with serum from PRv-hyperimmunized pigs and from field PRv-infected pigs, but not with serum samples from specific-pathogen-free pigs or pigs inoculated with gE-deleted PRV vaccine. These data indicate that, although the recombinant gE protein is produced in E coli, it still retains the antigenicity of the viral gE glycoprotein. Comparison between the recombinant gE protein, using immunoblot analysis with a commercial gE ELISA containing natural PRV-gE protein, revealed comparable test performance. This finding indicated that recombinant gE protein produced by E coli can be used for development of a companion serologic assay for a PRV-gE gene-deleted vaccine.

Colostrum-deprived calves (n = 34) were fed various amounts of colostrum, colostrum substitute, or milk replacer to establish a range in titer of passively acquired viral neutralizing antibody in serum. The calves were then challenge exposed intranasally with a virulent, noncytopathic bovine viral diarrhea virus (BVDV-890). After viral challenge exposure, calves were monitored for fever, leukopenia, thrombocytopenia, and diarrhea. In addition, viral isolation and viral titration were performed on specimens of nasal secretions, buffy coat cells, and serum obtained from the calves. Fever and systemic spread of virus were detected in calves that had viral neutralizing titer of 256 or lower. Calves that had viral neutralizing titer lower than 16 developed severe clinical disease manifested by fever, leukopenia, thrombocytopenia, and diarrhea. Seventy and duration of signs of disease decreased as titers of passively acquired viral neutralizing antibody increased. These results indicate that low to intermediate titers of passively acquired viral neutralizing antibody were not sufficient to fully protect calves from virulent bovine viral diarrhea virus.

Passive protection provided by sows inoculated with the virulent Miller strain of transmissible gastroenteritis virus (TGEV), or the ISU-1 strain of porcine respiratory coronavirus (PRCV), or both was evaluated in nursing pigs challenge exposed with virulent TGEV. Four sows (group B) were inoculated with PRCV oronasally twice at 4 and 2 weeks before parturition; 1 sow (group C) was inoculated similarly, but in 2 subsequent pregnancies; and 2 sows (group D) were oronasally primed with PRCV at 4 weeks before parturition, and 2 weeks later were administered a booster inoculation of virulent TGEV. Two additional sows (group E) remained uninoculated and served as seronegative controls, and 1 sow (group A) that had been naturally infected with TGEV served as a seropositive control. The degree of passive immunity transferred by these sows to their litters was assessed by challenge exposing the pigs of sows in groups BE (only the second litter of group C) with virulent TGEV at 3 to 5 days of age. After challenge exposure, clinical signs of infection and mortality were noted and fecal and nasal shedding of virus was assessed by ELISA. The IgA, IgG, and IgM antibody titers to TGEV were quantified in colostrum and milk of the sows by use of an isotype-specific monoclonal antibody-capture ELISA, using biotinylated monoclonal antibodies against each porcine isotype as detecting reagents. A plaque-reduction assay was used to quantify neutralizing antibody titers in serum, colostrum, milk, and fractionated whey (IgG and IgA/IgM). In the sow naturally infected with TGEV (group A), there was a pronounced decrease in IgG antibody titers to TGEV in the transition from colostrum to milk, and IgA TGEV antibodies became predominant, with high titers maintained throughout lactation. The 4 group-B sows partially protected their pigs after TGEV challenge exposure; mean mortality was 67%, compared with 100% in pigs suckling the 2 TGEV seronegative control sows (group-E litters). Although IgA TGEV antibodies were detected in colostrum and milk of group-B sows, IgG TGEV antibodies were the most abundant. The sow of group C had a marked increase in IgA TGEV antibody titers in colostrum and milk after reinoculation with PRCV during the second pregnancy, before TGEV challenge exposure of the litter. Its pigs were passively protected to a high degree after TGEV challenge exposure (27% litter mortality). The sows in group D, primed with PRCV and boosted with TGEV, provided the best passive protection after TGEV challenge exposure of their pigs. Not only litter mortality (27%) but also morbidity was reduced, compared with those factors for the other challenge exposed litters, and the sows did not become ill. In these swine, the high degree of passive protection observed could not be associated with the presence of only IgA TGEV antibodies in the milk, but high IgM TGEV antibody titers also were detected in colostrum and milk. Results of this study suggest that PRCV-inoculated sows are able to partially protect their pigs from TGEV challenge exposure and, on the basis of preliminary data, the degree of protection may increase after multiple PRCV exposures or after secondary exposure to TGEV during pregnancy. Also, an IgA respiratory tract-mammary gland link may exist as evident by the low titer of IgA TGEV antibodies in the milk of PRCV-inoculated sows, but may not be as efficient in inducing lactogenic IgA immunity as is the gastrointestinal tract-mammary gland link.

Sequential histologic, immunologic, and virologic features of herpesvirus-induced keratitis were studied in 18 experimentally infected cats. Histologic changes were assessed by use of light microscopy, and the presence of viral antigen, B lymphocytes, and T lymphocytes was verified immunohistochemically. Flow cytometry was used to monitor changes in blood T lymphocytes (CD4 and CD8 homologues) and B lymphocytes. Cellular immunity was assessed by use of the lymphocyte proliferation assay. Development of stromal keratitis was preceded by prolonged absence of corneal epithelium, decreased numbers of circulating lymphocyte subsets, decreased mitogen responses, and acquisition of viral antigen by the corneal stroma. Return to normal of circulating lymphocyte numbers and function was temporally associated with the arrival of neutrophils and B and T lymphocytes in the corneal stroma. Sequelae to stromal inflammation were fibrosis and scarring. Findings suggest that suppression of local immune responses allows virus access to the corneal stroma, and that subsequent keratitis is mediated by an immune response to viral antigen.

Fifty serum samples from dogs with clinical signs of hypothyroidism and autoantibodies (AA) to thyroglobulin (Tg), thyroxine, or triiodothyronine were screened for AA to thyroid peroxidase (TPO). Thyroid peroxidase is the antigen against which microsomal AA are formed in human beings with lymphocytic thyroiditis. The TPO was isolated from canine thyroid tissue, using a modification of the procedure for purifying porcine TPO. The enzyme was solubilized from the membrane, using a deoxycholate-trypsin solution, followed by ammonium sulfate precipitation and diethylaminoethyl Sephadex chromatography. Activity of TPO was determined, using an iodide oxidation assay and a guaiacol assay. A monoclonal antibody to canine Tg, coupled to an immunoaffinity column, was used to eliminate the contaminating Tg from the TPO preparation. Using the TPO preparation as an antigen, an ELISA was performed on 10 serum samples and immunoblot assays were performed on 50 canine sera. Autoantibodies to TPO were not found in any of the sera. Assays also were performed, using purified porcine and human TPO and evidence of cross-reactivity with canine TPO was not identified. The absence of AA to TPO in dogs suggests a different pathogenesis for autoimmune thyroid disease in dogs than that hypothesized for lymphocytic thyroiditis in human beings.

Receptors for opsonins, such as complement component C3b (CR1) and immunoglobulins, Fc receptors, interact with adhesion glycoproteins in mediating immune functions. Defects in expression of the adhesion glycoproteins CD11/CD18 results in severely hampered in vitro and in vivo adherence-related functions of leukocytes. Little is known regarding the effect of leukocyte adhesion deficiency (LAD) on ligand binding and receptor expression. We investigated the binding and expression of CR1 and Fc receptors by bovine neutrophils isolated from dairy calves suffering from LAD, compared with clinically normal (hereafter referred to as normal) age-matched calves. Neutrophils were also assayed for endogenously bound IgG and IgM and for exogenous binding of C3b, IgG1, IgG2, IgM, and aggregated IgG (aIgG), using flow cytometry. Luminol-enhanced chemiluminescence (CL) production in response to IgG2 opsonized zymosan was studied, and specific inhibition of CL was used to determine the specificity of IgG2 binding. Activation of protein kinase C with phorbol myristate acetate was used to determine the effect of cellular activation on expression of CR1. A greater percentage of neutrophils from normal calves bound C3b than did neutrophils from LAD-affected calves. Receptor expression was similar. Activation with phorbol myristate acetate resulted in increased expression of CR1 on neutrophils from normal and LAD-affected calves, but expression was almost twofold greater on neutrophils from normal calves. There was no difference between LAD-affected and normal calves in percentage of neutrophils that bound endogenous IgG and IgM. A greater percentage of neutrophils from normal calves bound exogenous IgM than did neutrophils from LAD-affected calves. Receptor expression for aIgG was greater on neutrophils from LAD-affected calves than on those from normal calves. Luminol-enhanced CL of neutrophils in response to IgG2 opsonized zymosan was not different between LAD-affected and normal calves. Results indicate increased binding and expression of Fc receptors for aIgG and decreased binding and expression for C3b and IgM on neutrophils from calves with LAD. Leukocyte adhesion deficiency may be compounded by added defects in the expression and binding of receptors for opsonins, such as C3b and IgM.

We investigated the ability of an antibody-specific, O antigen-based ELISA to document Salmonella typhimurium herd infections by screening of milk samples. Three cattle populations, 20 herds with no history of salmonellosis, 8 herds with history of S. typhimurium episodes within the previous 7 months, and 220 herds of unknown disease status, were tested. A herd was considered ELISA positive if at least 5% of the cows had OD values > 0.3. Among the 20 herds without history of salmonellosis, only 2 herds were ELISA positive, whereas all 8 herds with a known history of salmonellosis were ELISA positive (herd specificity, 0.9 and herd sensitivity, 1.0). A significant correlation (P < 0.001) was found between the OD values of serum and milk samples from cows in the herds with a history of salmonellosis. It was concluded that ELISA testing of individual milk samples can be used for surveillance of herds for S. typhimurium infections, but further modifications are needed to test bulk tank milk samples.