Response of cattle persistently infected with noncytopathic bovine viral diarrhea virus to vaccination for bovine viral diarrhea and to subsequent challenge exposure with cytopathic bovine viral diarrhea virus.

Nine steers persistently infected with noncytopathic bovine viral diarrhea (BVD) virus were allotted into 3 groups (3 cattle/group). Cattle in group A were vaccinated with a modified-live BVD virus vaccine of porcine cell origin, cattle in group B with a modified-live BVD virus vaccine of bovine cell origin, and cattle in group C with a killed BVD virus vaccine of bovine cell origin. Detrimental effects due to vaccination were not seen. Six weeks after vaccination, the steers were challenge exposed with a cytopathic BVD virus. All steers developed mucosal disease after challenge exposure, produced antibodies that neutralized various isolates of BVD virus, and remained persistently infected until death. Steers given killed virus vaccine had a minimal neutralizing-antibody response and developed mucosal disease as quickly as reported for challenge-exposed, nonvaccinated, persistently infected cattle. Steers given modified-live virus vaccines had higher neutralizing-antibody response and longer intervals from challenge exposure to development of mucosal disease. The specificity of the neutralizing-antibody response differed between groups of vaccinated cattle.

Frequency of persistent bovine viral diarrhea virus infection in selected cattle herds.

Sera and blood buffy coat samples were obtained from 3,157 cattle in 66 selected herds. Antibodies to bovine viral diarrhea (BVD) virus were detected in 89% of the serum samples by immunoprecipitation or virus-neutralization tests. Cytopathic or noncytopathic BVD viruses were isolated from blood buffy coat samples from 60 cattle in 6 herds. A second blood buffy coat sample was obtained from 54 of the 60 cattle 2 months after the initial sampling, and BVD virus was isolated again from each cow. The 54 cattle were considered persistently infected with BVD virus. The frequency of persistent infection was 1.7%.

Effects of bovine viral diarrhea virus on the percentages and absolute numbers of circulating B and T lymphocytes in cattle.

The percentage and absolute numbers of circulating B and T lymphocytes were determined for 10 healthy cattle by labeling mononuclear cells with anti-bovine immunoglobulin or peanut agglutinin. The cattle were then inoculated with a cytopathogenic isolate of bovine viral diarrhea (BVD) virus, and B- and T-lymphocyte populations were again quantitated at given intervals. Seemingly, BVD virus caused a decrease in the absolute numbers of B and T lymphocytes and in the percentage of T lymphocytes. Although these effects lasted through 7 days, all of the cattle recovered from infection and had detectable BVD virus-neutralizing antibodies in their sera 17 days after exposure.

Isolation of cytopathic and noncytopathic bovine viral diarrhea virus from the spleen of cattle acutely and chronically affected with bovine viral diarrhea.

Both cytopathic and noncytopathic bovine viral diarrhea virus (BVDV) were isolated from 16 of 17 bovine spleens representing 11 herds that had experienced acute BVD and from 12 of 21 bovine spleens from 1 herd affected with chronic BVD. It was concluded that isolation of cytopathic and noncytopathic BVDV from the same spleen probably indicates that an animal with a persistent, noncytopathic BVDV infection was superinfected with a cytopathic BVDV. The prevalence (greater than 70%) of 2 viruses in the spleen of cattle with acute or chronic BVD suggested that persistent infection with noncytopathic BVDV may be an important factor in the pathogenesis of BVD.

Severe clinical disease induced in cattle persistently infected with noncytopathic bovine viral diarrhea virus by superinfection with cytopathic bovine viral diarrhea virus.

Eight healthy cattle that were persistently infected with noncytopathic bovine viral diarrhea virus (BVDV) were inoculated with cell culture fluids that contained noncytopathic or cytopathic BVDV. A severe disease occurred after inoculation with cytopathic BVDV. The clinical signs, lesions, and immune response were consistent with those of clinical BVDV infections.

Differentiation of cytopathic and noncytopathic isolates of bovine viral diarrhea virus by virus neutralization.

Soluble antigens of cytopathic and noncytopathic isolates of bovine viral diarrhea virus were resolved by high-performance liquid gel-permeation chromatography into 4 major and 3 minor peaks. The 2 peaks with the larger molecular weights (240,000 and 140,000 daltons) were immunogenic when inoculated into rabbits. Virus neutralizing antibodies were specific for the homologous virus. The soluble antigens were determined to be greater than 100,000 daltons by filtration.

Production of cattle immunotolerant to bovine viral diarrhea virus.

Inoculation of bovine virus diarrhea virus into 58 to 125 day old fetuses of bovine virus diarrhea virus seropositive pregnant cows, or inoculation of bovine virus diarrhea virus into seronegative cows 42 to 114 days pregnant, may produce clinically normal calves which are persistently infected with the specific isolate of bovine virus diarrhea virus yet seronegative to the homologous and heterologous isolates. Reinoculation of these persistently infected cattle with their homologous isolate produced no neutralizing antibody response to bovine virus diarrhea virus. These persistently infected cattle were immunocompetent as they developed neutralizing serotiters to infectious bovine rhinotracheitis, parainfluenza-3 viruses and agglutinating serotiters to Pasteurella hemolytica .

Comparison of a modified counterimmunoelectrophoresis test and a microimmunodiffusion test for detection of pseudorabies virus antibodies in porcine sera.

The correlation of a modified counterimmunoelectrophoresis (CIE) test and a microimmunodiffusion test for detecting pseudorabies virus antibodies in porcine sera was investigated, using as reference a standard virus neutralization test. The counterimmunoelectrophoresis test exhibited a sensitivity comparable to the microimmunodiffusion test but was not as sensitive as the virus neutralization test. The best feature of the modified counterimmunoelectrophoresis test is that it is a rapid test. It provides an alternative to currently used diagnostic tests for detection of pseudorabies virus antibodies in sera from field reared and experimentally reared swine exposed to pseudorabies virus.

Total protein and immunoglobulins G1, G2, and M in serum of calves persistently infected with bovine viral diarrhea virus.

Total serum protein and immunoglobulins (Ig) G1, G2, and M concentrations were investigated in 11 calves persistently infected with bovine viral diarrhea virus. These calves were allowed to suckle from their dams until weaned. A gradual increase in total protein was observed from birth to 12 months of age. There was a wide variation in Ig concentrations in pre- and postcolostrum sera. The IgG1 increased from the time of delivery of the calves to the 5th month, decreased by the 10th month, and then stabilized through the 12th month. The IgG2 increased from birth to 10 months and remained stable through 12 months. The IgM increased from birth to the 11th month, and then decreased sharply by the 12th month.

Characterization of the major structural proteins of purified bovine viral diarrhea virus.

Bovine viral diarrhea virus (BVDV) was concentrated and purified by a combination of ultrafiltration, hydroextraction using polyethylene glycol and affinity chromatography. A lectin from Crotalaria juncea that has an affinity for galactose was used in the affinity chromatography. Virions of BVDV with classic envelopes were observed by electron microscopy. Four major proteins with estimated molecular weights of 75,000, 66,000, 54,000, and 26,000 were identified in sodium dodecyl sulfate--polyacrylamide gel electrophoresis slab gels. The proteins of 75,000 and 54,000 were glycoproteins as shown by staining with dansyl hydrazine.

Effects of incubation temperatures and bovine viral diarrhea virus immune serum on bovine turbinate cells persistently infected with a noncytopathogenic isolate of bovine viral diarrhea virus.

Noncytopathogenic bovine viral diarrhea virus (BVDV) on initial inoculation in receptive cells induced a persistence in vitro at incubation temperatures of 33, 37, and 39 C. The mechanisms of this persistence were not the result of the induction of defective interfering particles or the selection of temperature-sensitive mutants, but were the result of a naturally occurring noncytopathogenic isolate of BVDV. Persistently infected cells were not freed of the infection by continuous passage in media containing homologous antibody. Persistently infected cells appeared to undergo an earlier senescence than did noninoculated cells of the same passage level and age. This phenomenon was reversed by renewal of the culture media.

Lesions in clinically healthy cattle persistently infected with the virus of bovine viral diarrhea--glomerulonephritis and encephalitis.

Four clinically healthy cattle persistently infected with the virus of bovine viral diarrhea were examined for viral antigen and lesions. Antigen was seen by direct immunofluorescence in cytoplasm of the neurons of the brain and cervical part of the spinal cord, cells and basement membrane of renal glomeruli, reticular cells of lymph nodes and spleen, epithelial cells of small intestinal crypts and renal and testicular tubules, and endothelial cells of blood vessels. Infected neurons were pyknotic and surrounded by astrocytes and macrophages. A few blood vessels in the brains were cuffed with mononuclear cells. Basement membranes of renal glomeruli were irregularly thick with eosinophilic material, and mesangial cells in the glomeruli were plentiful. The virus had a direct effect on some tissues, but was restricted in its cytopathogenicity and was not eliminated by defense mechanisms of the host. Renal glomerular lesions were believed to have an immunologic basis.

Reproductive performance of apparently healthy cattle persistently infected with bovine viral diarrhea virus.

A Holstein-Friesian bull and three Holstein-Friesian cows were seronegative for bovine viral diarrhea (BVD) virus but were persistently infected with the virus. Virus was isolated from buffy coat cells and nasal and lacrimal secretions during their lifetime, and they remained free of clinical signs of BVD. The three cows were pregnant when purchased, and they gave birth to full-term calves. One calf lived only a few hours, one calf became ill and died within a few days, and one calf became ill and was euthanatized within a few weeks. One cow was then bred and became pregnant but aborted a 7-month fetus. A second cow was bred approximately 5 months after parturition but did not conceive. The third cow was necropsied 6 weeks after calving, because of loss of weight. Although the bull's semen contained BVD virus when seropositive cows were bred, normal calves were born. When seronegative heifers were bred, they became seropositive to BVD virus within two weeks, with higher titers in six weeks. On heifer conceived after one service but aborted a 6-month fetus. Three others continued to have estrous cycles until their titers rose to 1:128, then they conceived and gave birth to normal calves. Another heifer conceived on the first service, had a titer of 1:128 two weeks after breeding, and gave birth to a normal calf.

Isolation of bovine adenovirus type 1 without an adenovirus-associated virus.

This report describes the isolation and identification of a strain of bovine adenovirus type 1 from a cow in a herd that had undergone an episode of diarrhea and abortions. This strain of bovine adenovirus type 1 did not agglutinate either guinea pig or human 0 erythrocytes, and no 20-nm virus particles were evident by electron microscopy, further indicating that it was not contaminated by adenovirus-associated virus.

Isolation and identification of a bovine adenovirus type 3 with an adenovirus-associated virus.

A bovine adenovirus with agglutinating activity was isolated from feedlot calves and classified as serotype 3. The agglutinating activity was shown to be the property of an adenovirus-associated virus (AAV). The AAV was isolated from the bovine adenovirus by isopycnic centrifugation in CsCl; the AAV had a density of 1.4 g/cm2. This AAV is serologically related to bovine AAV-TR-15, but is distinct from bovine parvovirus-1 and primate AAV types 1 to 4, using counterimmunoelectrophoresis and hemagglutination-inhibition.

Duration of active and colostrum-derived passive antibodies to bovine viral diarrhea virus in calves.

Duration of active and colostrum-derived passive antibodies to bovine viral diarrhea virus was studied in 14 calves. Five calves born with actively induced antibodies to bovine viral diarrhea virus retained high titers during the year of observation. Colostrum-derived antibodies to bovine viral diarrhea virus in nine calves declined at an expected rate for the first four to six months of age. However, titers of six of these calves increased at five to eight months of age and either remained constant or increased through one year of age. Bovine viral diarrhea virus antibody titers of the other three calves declined at a constant rate to less than 1:4 by nine to 12 months of age.

Selected isolates of bovine viral diarrhea (BVD) virus propagated on bovine turbinate cells: virus titer and soluble antigen production as factors in immunogenicity of killed BVD virus.

Soluble antigen production in a bovine turbinate cell line by 17 isolates of bovine viral diarrhea virus was studied. We showed that the quantity of soluble antigen produced may vary considerably between isolates. Further, the isolate producing the greatest quantity of soluble antigen produced a higher antibody titer in calves than an isolate producing only half as much soluble antigen.

Response of congenitally immune chicks to viscerotropic velogenic Newcastle disease virus.

Separate groups of chicks of hen hyperimmune to viscerotropic velogenic Newcastle disease virus (VVNDV) were challenge-exposed to VVNDV by intraocular route at 1 day and 34 days old. Their response was evaluated by clinical symptoms, hemagglutination-inhibition (HI) titers, and virus isolations. Chicks exposed at 1 day old excreted VVNDV from the vent for up to 60 days; their active mean HI titers remained low (10-40); and deaths from VVNDV occurred early (5-16 days) and late (28-55 days). Chicks challenge-exposed at 34 days old excreted virus from the vent for 10 days; active HI titers developed quickly and remained high (891-1177); and deaths and signs of VVNDV occurred early (5-13 days).