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Abstract

Objective

To assess humoral and protective immunity in cattle vaccinated by 12 months with Brucella abortus vaccine strains RB51 and 19 under field conditions of high and low brucellosis prevalence.

Animals

450 seronegative female cattle: 330 three to eight months old (calves), and 120 ten to twelve months old (heifers).

Procedures

Ranch A had high prevalence (39%) of brucellosis, and ranch B had low prevalence (2%), as determined by results of conventional serologic testing: agar gel immunodiffusion and the ring test. Seronegative cattle were vaccinated once or twice with 5 × 109 colony-forming units of B abortus strain RB51 or once with strain 19. After vaccinating 285 cattle with strain RB51 and 165 with strain 19, 74 (26%) and 30 (18%), respectively, were bred to seropositive bulls, then were kept within the infected herd of origin.

Results

All cattle vaccinated with strain 19 seroconverted 30 days later. All 285 cattle vaccinated with strain RB51 had negative results for all serologic tests, including agar gel immunodiffusion. All RB51-vaccinated cattle that became pregnant had negative results for the ring test and for conventional serologic tests after their first calving.

Conclusions

Strain RB51 can be used as a live organism vaccine without inducing antibody titers that interfere with serodiagnosis, and induced 100% protection against field strain B abortus-induced abortion in cattle vaccinated at least 1 year before mating to an infected bull. Vaccination with strain 19 under similar conditions was less effective than vaccination with strain RB51. (Am J Vet Res 1998;59:1016–1020)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine blood protein concentration, immunoglobulin concentration, and lymphocyte profiles in equine infectious anemia virus (EIAV) seropositive, naturally infected horses without clinical signs of disease.

Animals

26 clinically normal seropositive horses, 6 febrile ponies with experimentally induced EIA, and 52 clinically normal seronegative horses and ponies.

Procedure

Serum and EDTA-anticoagulated blood were obtained from all horses and ponies, and total serum protein and albumin concentrations, immunoglobulin concentrations, and blood lymphocyte subset counts were determined.

Results

Compared with seronegative horses, EIAV seropositive inapparent carrier horses had no significant difference in serum reverse transcriptase activity, PCV, or platelet count. Inapparent carrier horses had increased plasma total solids and serum globulin concentrations and decreased serum albumin concentration and albumin-to-globulin ratio. Total serum immunoglobulin and serum IgM concentrations were increased. In-apparent carrier horses had significantly decreased percentages of CD5+ and CD4+ blood lymphocytes.

Conclusions

Serum protein and lymphocyte subset changes in EIAV-infected inapparent carrier horses are consistent with immune activation or chronic inflammation, both of which may, in part, be the result of virus-induced polyclonal B-cell activation.

Clinical Relevance

EIAV seropositive horses have immune-related abnormalities consistent with ongoing viral activity regardless of the duration they have been infected, even when the usual signs of disease (anemia, fever, weight loss) are not apparent. (Am J Vet Res 1998;59:1009–1015)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To compare recombinant transmissible gastroenteritis virus (TGEV) spike protein, (SP) R2-2, with attenuated live virus (ALV) vaccine in sows during late pregnancy.

Animals

13 TGEV-seronegative sows and their pigs.

Procedure

At prepartum weeks (PPW) 6 and 4, sows of groups 1 and 2 received ALV via the oral/intranasal (O/IN) route. At PPW 2, group-1 sows received ALV IM and group-2 sows received SPR2-2 IM. Group-3 sows received SPR2-2 IM at PPW 4 and ALV O/IN at PPW 2. Sows of group 4 (negative controls) were inoculated O/IN with mock-infected ST cell fluids at PPW 6 and 4 and IM with Sf9 cell lysates at PPW2 (n = 2), or IM with Sf9 cell lysates at PPW4 and O/IN with mock-infected ST cell fluids at PPW2 (2). Serum, colostrum, and milk samples were tested for antibody to TGEV, and a lymphoproliferative (LP) assay was done on blood mononuclear cells. Suckling pigs were challenge exposed with virulent TGEV.

Results

Sows of groups 1 and 2 had higher IgG and significantly higher antibody titers in colostrum; their pigs had significantly higher serum antibody titer. At challenge exposure of their pigs, LP responses of group-2 sows were significantly higher than those of sows in the other 3 groups. Mean pig mortality ranged from 43 (group 2) to 92% (group 4). Significant negative correlations were observed among litter mortality and sow LP response, colostral titer, and pig serum titer at time of challenge exposure.

Conclusions

In sows vaccinated twice with attenuated live TGEV, the recombinant SPR2-2 administered IM may be comparable to ALV administered IM as a booster. Vaccination failed to provide complete protection to suckling pigs after challenge exposure. (Am J Vet Res 1998;59:1002–1008)

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To determine whether clinical progression of paratuberculosis in cattle was associated with alterations in cytokine gene expression in affected tissues.

Animals

5 uninfected adult Holstein cows, 7 adult Holstein cows naturally infected with Mycobacterium paratuberculosis that did not have clinical signs of disease, and 4 adult Holstein cows naturally infected with M paratuberculosis that had progressive clinical signs of infection.

Procedure

Samples of ileum and cecal lymph nodes were obtained from each animal at the time of slaughter. A reverse transcriptase-competitive polymerase chain reaction assay was used to determine mRNA expression of interferon-γ (IFN-γ) and interleukin 4 in each sample.

Results

Interferon-γ gene expression was significantly higher in ileum and cecal lymph node samples from subclinically infected cows than from clinically infected cows.

Conclusions and Clinical Relevance

Progression of paratuberculosis to clinical stages is associated with reduced expression of IFN-γ at site of infection. If immune response to M paratuberculosis can be manipulated so that IFN-γ expression is increased, resistance to infection in cattle might be enhanced. (Am J Vet Res 1998;59:842–847)

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To determine the duration for cross-neutralizing antibodies stimulated by administration of a single dose of a modified-live vaccine against bovine viral diarrhea virus (BVDV) to seronegative cattle.

Animals

23 Angus cows seronegative to BVDV.

Procedure

Cows were randomly assigned to control (unvaccinated) or test (vaccinated) groups. Eighteen BVDV-seronegative Angus cattle were vaccinated via IM injection with a modified-live BVDV (NADL strain) vaccine and commingled with 5 unvaccinated seronegative cows. Serum was obtained from the cows before vaccination, on the day of vaccination, and 1.5, 3, 6, 9, 12, and 18 months after vaccination. Serum neutralizing antibody tests were performed on samples obtained at each point after vaccination, using a panel of 12 strains of BVDV that, on the basis of reactivity with monoclonal antibodies, were identified as heterologous.

Results

Antibodies against all 12 strains of BVDV (which we tested) were detected by use of viral neutralization testing in samples obtained from vaccinated cattle 18 months after vaccination; however, concentration of antibody for some of the strains was low. Nonvaccinated cattle remained seronegative throughout the 18-month study period.

Clinical Implications

Analysis of these data indicated that modified-live BVDV vaccines could stimulate an antibody response in seronegative cows that was detectable for at least 18 months after vaccination. These antibodies were able to cross neutralize 12 antigenically diverse strains of BVDV. (Am J Vet Res 1998;59:848–850)

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To investigate the potential allergenic role of the yeast Malassezia pachydermatis in dogs with clinical diagnosis of atopic dermatitis.

Animals

5 clinically normal nonatopic dogs, 10 atopic dogs with cytologic evidence of Malassezia dermatitis, and 12 atopic dogs without cytologic evidence of Malassezia dermatitis.

Procedure

A crude yeast extract was produced by disrupting the cell wall of M pachydermatis. The crude extract and 8 of its fractions, which were generated by fractionation in a high-performance liquid chromatography column, were injected along with 46 commercial allergens for intradermal allergy testing of normal and atopic sample populations. Significant difference between atopic populations was evaluated, using a threshold concentration of crude yeast extract that failed to induce wheal-and-flare responses in normal nonatopic dogs.

Results

Atopic dogs with cytologic evidence of Malassezia dermatitis had significantly greater wheal-and-flare reactions to intradermal injection of crude extract of M pachydermatis than did atopic dogs without cytologic evidence of Malassezia dermatitis.

Conclusions

It is concluded that M pachydermatis is capable of promoting type-1 hypersensitivity reactions in dogs with an atopic dermatitis phenotype.

Clinical Relevance

Currently, Malassezia dermatitis is principally managed by use of antifungal chemotherapy. Because the yeast appears to be a contributing allergen in dogs with atopic dermatitis, hyposensitization with M pachydermatis extracts may offer a future alternative to extended or repeated episodic administration of antifungals for extended control of recurrent infections. (Am J Vet Res 1998;59:836–841)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine whether differences exist in induction and quantity of tumor necrosis factor α (TNF-α), interleukin (IL)1ß, and IL-10 mRNA transcripts when mouse J774A.1 macrophages are infected with Listeria monocytogenes, including 2 isolates originating from channel catfish, the wild-type virulent (EGD) strain, and a nonhemolytic strain (ATCC 15313).

Samples

Listeria monocytogenes isolates from kidneys or fillets of channel catfish were used to stimulate cytokine production from mouse macrophages. The RNA from the infected macrophages was collected.

Procedure

Four hours after infection with L monocytogenes, total cellular RNA was extracted from the J774A.1 cells and reversed transcribed to cDNA, which was amplified, using specific primers for TNF- α, IL-1ß, or IL-10. The specific amplified DNA fragments were detected on polyacrylamide gels and quantified, using a reverse transcription polymerase chain reaction (PCR)-mediated ELISA.

Results

The wild-type hemolytic EGD strain and the 2 hemolytic catfish isolates of L monocytogenes induced higher amounts of TNF-α-, IL-1ß-, and IL-10- specific mRNA in J774A.1 cells than did the nonhemolytic strain.

Conclusions

Hemolysin-associated induction of TNF-α, IL-1ß, and IL-10 cytokines may be related to survival and replication of L monocytogenes in macrophages. It also suggests that the PCR-mediated ELISA procedure is a sensitive test to quantify cytokines from cell cultures. (Am J Vet Res 1998;59:717-721)

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To quantitate numbers of immunoglobulin (Ig)-containing cells (IgA, IgG, and IgM) and T cells (CD3+, CD4+, and CD8+) in the colonic mucosa of healthy dogs, and to determine whether mean cell numbers differ among colonic regions.

Animals

10 clinically normal young adult mixed-breed dogs.

Procedure

Endoscopically obtained specimens of ascending, transverse, and descending colonic mucosa were stained specifically for IgA, IgG, and IgM heavy chains and T-cell antigens, CD3+, CD4+, and CD8+, using immunoperoxidase techniques. Morphometric analysis, performed by light microscopy, was used to quantitate numbers in these standardized areas of colonic mucosa. Data analysis allowed determination of mean cell numbers in each colonic region, as well as comparison of mean cell numbers among colonic regions.

Results

The CD3+ and CD8+ T cells were the predominant immune cell types in all colonic regions. In the mucosa, CD3+ T cells were significantly (P < 0.05) more numerous than CD8+ T cells, and CD8+ T cells were significantly (P < 0.05) more numerous than CD4+ T cells. The IgA-containing cells were significantly (P < 0.05) more numerous than IgG-containing cells, whereas IgM-containing cells were least numerous (P < 0.05). Differences in mean cell counts among colonic regions were not significant for Ig-containing cells or T cells.

Conclusions

Mean numbers of immune cells did not differ significantly among colonic regions in healthy dogs, although differences existed in mean populations of T cells and Ig-containing cells. The CD3+ and CD8+ T cells were the most numerous immune cell types in colonic mucosa.

Clinical Relevance

These quantitative data provide a basis for study of alterations in populations of mucosal immune cells and their possible contribution to the pathogenesis of gastrointestinal tract disease. (Am J Vet Res 1998;59:552–556)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To evaluate live attenuated Brucella abortus RB51, killed B suis cells, O-polysaccharide (OPS) from B abortus 1119-3 and OPS from B suis 1330, for protection of swine against B suis challenge exposure under farm conditions.

Animals

10 infected boars, 160 unvaccinated control sows and their 1,040 progeny, and 610 vaccinated sows and their 6,600 progeny.

Procedure

Gilts (45 to 65 days or 4 to 6 months old) were vaccinated or not vaccinated. For the latter gilts, additional variables studied were dose, number of doses, and delivery route. Mature gilts were mated with 4 infected boars, then serologic reaction to Brucella spp, results of bacteriologic culture of vaginal secretions, presence of abortion, and litter size were assessed. Various tissues obtained from aborted fetuses were obtained for culture of Brucella spp.

Results

About 40% of unvaccinated control gilts seroconverted to Brucella spp, 27% were positive for OPS precipitation by use of agar gel immunodiffusion, 23% aborted their fetuses, and the remaining gilts had litters of 5 to 8 pigs. Killed B suis cells provided the following protection: 25% of vaccinates were seropositive, 5% had positive results of agar gel immunodiffusion, 5% aborted, and the remaining gilts had litters of 7 to 8 pigs. Gilts that received live RB51 or OPS vaccine were protected. Serologic reactions were always negative, abortion did not occur (ie, 100% were protected), and litter size was 10 to 12 pigs.

Conclusions

Live attenuated B abortus RB51 or purified OPS was effective in protecting gilts against B suis infections. Dose (106 to 109 cells, 100 to 500 μg, respectively), number of doses (1 or 3), or route (IM or PO) made little difference. Further research is required to determine why these 2 vaccine candidates are similar in protection effectiveness and whether they can be used after infection as a treatment. (Am J Vet Res 1998;59:546–551)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To investigate whether the procedure used to snare and restrain pigs during collection of blood samples would alter in vitro functional capacity of leukocytes in the samples.

Animals

8 gilts.

Procedure

Catheters were surgically inserted into the jugular vein of gilts to enable blood sample collection without restraint. After collection of a control sample, gilts were restrained by use of a snare and samples were collected at 0.5, 3.5, and 6.5 minutes after start of restraint (0 minutes). At each time point, plasma β-endorphin and cortisol concentrations as well as WBC counts were recorded, and functional capacity of leukocytes in cultures of whole blood was assessed by means of mitogen-induced proliferation and interleukin-2 activity, virus-induced interferon-α concentration, and phagocytosis of zymosan particles.

Results

Concentrations of plasma β-endorphin and cortisol were increased at 3.5 and 6.5 minutes after start of restraint. At these times, virus-induced interferon-α concentration was decreased, whereas proliferative response to Concanavalin A and phytohemagglutinin increased in samples collected at 6.5 minutes.

Conclusion and Clinical Relevance

It was possible to snare pigs for the purpose of collecting blood samples and restrain them without causing excessive stress that would affect immunologic variables, provided that the collection procedure was completed within a few minutes. (Am J Vet Res 1998;59:421–425)

Free access
in American Journal of Veterinary Research