Aerosol vaccination of calves with pasteurella haemolytica against experimental respiratory disease.

Three experiments were conducted on calves in which the efficacy of vaccination with live Pasteurella haemolytica in aerosol was tested by challenge with sequential aerosol exposure to bovine herpesvirus 1 and P. haemolytica. Neither single nor multiple aerosol vaccinations protected against the experimental disease. Macroscopically recognizable rhinitis, tonsillitis, tracheitis and pneumonia occurred in both controls and vaccinates. In one experiment as many as three aerosol vaccinations with live P. haemolytica for up to 20 minutes failed to elicit clinical signs in exposed calves. Pasteurella haemolytica was isolated less frequently from tissues of vaccinated calves than from those of nonvaccinated calves. Pasteurella haemolytica was isolated from deep nasal swabs of 4/14 vaccinated calves five and six days after viral exposure. It was concluded that although bovine herpesvirus 1 vaccination has been shown previously to prevent the experimental disease produced by bovine herpesvirus 1-P. haemolytica, live P. haemolytica vaccination by aerosol will not provide the same protection.     

The effect of dose, route and virulence of bovine herpesvirus 1 vaccine on experimental respiratory disease in cattle.

Three experiments were conducted with calves in which, following intramuscular or intranasal vaccination with virulent or attenuated bovine herpesvirus 1, calves were protected against bovine herpesvirus 1 -- Pasteurella haemolytica challenge. Calves receiving low doses of vaccine had lower levels of antibody and greater evidence of virus replication upon challenge than those receiving higher doses. In contrast 11/13 unvaccinated controls had fibrino-purulent pneumonia following challenge. The immune response developed later in younger calves and those given low doses of vaccine. Neutralizing antibodies to bovine herpes-virus 1 were not found in nasal secretions, but were present in serum seven days after vaccination. Bovine herpesvirus 1 was isolated before challenge from nasal secretions of calves vaccinated intranasally or intramuscularly with virulent virus but not those vaccinated intramuscularly with vaccine virus. It was concluded that both routes of vaccination with either virulent or attenuated bovine herpesvirus 1 provided protection from challenge with homologous or heterologous bovine herpesvirus 1 and that live vaccines should contain at least 10(3) plaque forming units/dose for effective immunization.     

Establishment of latency associated with glycoprotein E (gE) seroconversion after bovine herpesvirus 1 infection in calves with high levels of passive antibodies lacking gE antibodies

This study was conducted to investigate the glycoprotein E (gE) antibody response raised after inoculation with a low infectious dose of bovine herpesvirus 1 (BHV-1) in six calves possessing high levels of passive immunity from cows repeatedly vaccinated with gE deleted marker vaccine. Four out of the six calves developed gE antibodies 3-5 weeks after infection, whereas the two other ones remained seronegative to gE. After 5 months of infection, the six calves were treated with dexamethasone. Virus was only re-excreted by the four calves which previously seroconverted against gE. The two other calves became seronegative against BHV-1, 30-32 weeks after infection. A second dexamethasone treatment performed 11 months after infection failed to demonstrate a latent infection in these two calves. Moreover, the lack of identification of a cell-mediated immune response, after the two dexamethasone treatments, and the failure to detect BHV-1 DNA sequences in trigeminal ganglia strongly suggest that these two calves were not latently infected. In conclusion, the presence of high levels of maternal immunity lacking gE antibodies does not prevent latency after infection with a low titre of BHV-1. Moreover, latency is associated with a serological response to gE. These results confirm that the gE deletion is a good marker to identify young calves latently infected with a field virus.     

Immune response of cattle to antigens obtained from bovine herpesvirus 1-infected tissue culture.

The ability of two antigens, termed EV and CM, derived from bovine herpesvirus 1 infected cultures to produce serum-virus neutralizing antibodies has been studied in cattle. Both EV and CM when inoculated with adjuvant induced significant increases in serum-virus neutralizing antibody titers. Control groups inoculated in a similar manner failed to induce significant increases in serum-virus neutralizing antibody. Some of the animals were vaccinated, then were bred, challenged with a virulent strain of bovine herpesvirus 1 and held until calving was completed. During this 18-month period titers declined slowly in the vaccinated animals. Proportionally there were fewer live calves born to the control cattle than to the CM vaccinated group but reduction was not large enough to conclude that this vaccine had protected the cattle against the abortigenic activity of bovine herpesvirus 1. Further challenge studies should be made to determine whether the administration of these antigens can prevent the subsequent onset of the clinical signs associated with bovine herpesvirus 1.     

Evidence for an immunocompromising effect of bovine pestivirus on bovid herpesvirus 1 vaccination

Five calves were given live intranasal vaccine against bovid herpesvirus 1 (BHV1) two days after intranasal inoculation of bovine pestivirus (BVDV). Another 5 were vaccinated in the absence of BVDV. Control unvaccinated groups were also maintained. All calves were challenged with virulent BHV1. The unvaccinated calves developed signs of infectious bovine rhinotracheitis (IBR) and both vaccinated groups showed a similar degree of clinical protection from IBR. Those given BVDV before vaccination shed up to 140 times more BHV1 (P<0.01) in the nasal mucus following challenge than those which had received BHV1 vaccine alone. The epidemiological significance of this is discussed.     

Fatal, generalized bovine herpesvirus type-1 infection associated with a modified-live infectious bovine rhinotracheitis parainfluenza-3 vaccine administered to neonatal calves.

Generalized bovine herpesvirus 1 (BHV-1) infection was diagnosed in six Salers calves from the same herd. The calves had received an intramuscular injection of modified-live infectious bovine rhinotracheitis parainfluenza-3 vaccine between birth and three days of age. The purpose of this study was to determine if the outbreak was associated with the vaccine strain of BHV-1. Analysis of epidemiological data and BHV-1 DNA for restriction fragment length polymorphism was undertaken. Multifocal necrosis in multiple organs was observed on pathological examination, and the presence of BHV-1 in tissues was confirmed by immunohistochemistry. Forty-three calves (aged birth to thirty days) were vaccinated over an 11-day interval. The 10 deaths recorded for vaccinated calves were clustered over a subsequent 14-day interval. Mortality in calves vaccinated between birth and three days of age was significantly higher than in nonvaccinated calves (chi-square test; p < or = 0.025), and this mortality was characterized by a greater age at death and duration of illness for vaccinated calves (t test; p < or = 0.001). The patterns of the restriction fragments, generated by six restriction endonucleases, of BHV-1 isolated from a necropsied calf and from the vaccine were identical, and different from that of a laboratory strain of BHV-1 (P8-2). These findings support the conclusion that newborn calves were susceptible to an intramuscularly injected vaccine strain of BHV-1, and that administration of an intramuscular modified-live infectious bovine rhinotracheitis parainfluenza-3 vaccine to neonatal calves may not be an innocuous procedure.     

Evidence for an immunocompromising effect of bovine pestivirus on bovid herpesvirus 1 vaccination

Five calves were given live intranasal vaccine against bovid herpesvirus 1 (BHV1) two days after intranasal inoculation of bovine pestivirus (BVDV). Another 5 were vaccinated in the absence of BVDV. Control unvaccinated groups were also maintained. All calves were challenged with virulent BHV1. The unvaccinated calves developed signs of infectious bovine rhinotracheitis (IBR) and both vaccinated groups showed a similar degree of clinical protection from IBR. Those given BVDV before vaccination shed up to 140 times more BHV1 (P less than 0.01) in the nasal mucus following challenge than those which had received BHV1 vaccine alone. The epidemiological significance of this is discussed.     

Enhancement of the immune response and virological protection of calves against bovine herpesvirus type 1 with an inactivated gE-deleted vaccine

Four immunisation protocols based on inactivated and attenuated commercially available marker vaccines for bovine herpesvirus type 1 (BHV-1) were compared. The first group of calves were vaccinated with an attenuated vaccine administered intranasally and an inactivated vaccine injected subcutaneously, four weeks apart; the second group were vaccinated twice with the attenuated vaccine, first intranasally and then intramuscularly; the third group were vaccinated twice subcutaneously with the inactivated vaccine; and the fourth group were vaccinated twice intramuscularly with the attenuated vaccine. A control group of calves were not vaccinated. The cellular and humoral immune responses were highest in the two groups which received at least one injection of the inactivated vaccine. Virological protection was observed in all the vaccinated groups after a challenge infection and reactivation by treatment with dexamethasone, but the calves which received one dose of the inactivated vaccine as a booster or two doses of the inactivated vaccine excreted significantly less of the challenge virus than the calves which were vaccinated only with the attenuated preparation.     

Induction of immunity against pneumonic pasteurellosis following experimental infection in calves.

Immunity against pneumonic pasteurellosis was studied in calves after recovery from experimental respiratory disease with Pasteurella haemolytica. Nine calves were exposed to aerosols of parainfluenza-3 virus and Pasteurella haemolytica A1 six days apart to produce respiratory disease. After recovery from the disease, these nine principal and four control calves were challenged with aerosols of bovine herpesvirus 1 and P. haemolytica A1 four days apart. With this viral-bacterial challenge, the nine principal animals failed to develop clinical responses to this bacterial challenge and their lungs did not show the growth of P. haemolytica on cultures, whereas two of four control calves had elevated temperatures and developed necropurulent pneumonia with the isolation of P. haemolytica from the lungs. The principal calves had developed high levels of cytotoxin neutralizing antibodies in their sera following parainfluenza-3 virus-P. haemolytica infection. This demonstrated that immunity against pneumonic pasteurellosis can be achieved, with a suggestion that further search for an effective vaccine for P. haemolytica is warranted.     

A comparison in calves of the antigenicity of three strains of bovid herpesvirus 2.

Three strains of bovid herpesvirus 2, viz. Allerton, bovine mammillitis and 69/1LO were used to infect calves intradermally. Twenty-eight days later the immunity of the calves was challenged by intravenous injection of a homologous or heterologous strain. Challenge control calves developed a fever (greater than 40 degrees C) lasting several days and widespread skin lesions which varied with the strain. Homologous challenge of the primary infection produced neither skin lesions nor febrile response, except in one calf in which fever was noted on one day. Heterologous challenge did not cause skin lesions but fever occurred in 8/12 calves. In particular Allerton virus failed to protect completely against heterologous challenge. Despite minor differences evident in these experiments, it is recommended that these isolates should be considered as strains of the same virus--bovid herpesvirus 2.     

Impact of meloxicam on respiratory virus titers and health outcomes when administered concurrently with a modified live respiratory vaccine in abruptly weaned beef steers

Abruptly weaned crossbred steer calves (N = 271) were used in a randomized, blinded 2-arm clinical trial to assess the impact of a long-acting non-steroidal anti-inflammatory drug on bovine herpesvirus type 1, bovine respiratory syncytial virus, parainfluenza virus type 3, and coronavirus titers and health outcomes when administered concurrently with a modified live respiratory vaccine upon arrival at a feedlot. Treatment groups included a control (saline; n = 135) and an experimental group (injectable meloxicam; n = 136). Viral antibody titers and body weight were measured on arrival, day 7, and day 21, along with a final weight on day 45. Body weight and antibody titers for all viruses increased over time (P < 0.001); however, there were no differences by treatment group or a significant group × time interaction when evaluated using repeated measures analysis of variance. Interestingly, the use of meloxicam was associated with increased treatment risk (P < 0.05). In conclusion, the administration of meloxicam may adversely affect health; however, a decreased vaccine response is likely not a contributing factor.     

Antibody response to glycoprotein E after bovine herpesvirus type 1 infection in passively immunised, glycoprotein E-negative calves

This study was conducted to determine whether young calves with maternal antibodies against bovine herpesvirus type 1 (BHV-1) but without antibodies against glycoprotein E (gE) can produce an active antibody response to gE after a BHV-1 infection. Five calves received at birth colostrum from gE-seronegative cows which had been vaccinated two or three times with an inactivated BHV-1, gE-deleted marker vaccine. After inoculation with a wild-type virulent strain of BHV-1, all the passively immunised gE-negative calves shed virus in large amounts in their nasal secretions. All the calves seroconverted to gE within two to four weeks after inoculation and then had high levels of gE antibodies for at least four months. The development of an active cell-mediated immune response was also detected by in vitro BHV-1-specific interferon-gamma assays. All the calves were latently infected, because one of them re-excreted the virus spontaneously and the other four did so after being treated with dexamethasone. The results showed that under the conditions of this work the gE-negative marker could also distinguish between passively immunised and latently infected calves.     

Protective effects against abortion and fetal infection following exposure to bovine viral diarrhea virus and bovine herpesvirus 1 during pregnancy in beef heifers that received two doses of a multivalent modified-live virus vaccine prior to breeding

Objective-To determine whether administration of 2 doses of a multivalent, modified-live virus vaccine prior to breeding of heifers would provide protection against abortion and fetal infection following exposure of pregnant heifers to cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) and cattle with acute bovine herpesvirus 1 (BHV1) infection. Design-Randomized controlled clinical trial. Animals-33 crossbred beef heifers, 3 steers, 6 bulls, and 25 calves. Procedures-20 of 22 vaccinated and 10 of 11 unvaccinated heifers became pregnant and were commingled with 3 steers PI with BVDV type 1a, 1b, or 2 for 56 days beginning 102 days after the second vaccination (administered 30 days after the first vaccination). Eighty days following removal of BVDV-PI steers, heifers were commingled with 3 bulls with acute BHV1 infection for 14 days. Results-After BVDV exposure, 1 fetus (not evaluated) was aborted by a vaccinated heifer; BVDV was detected in 0 of 19 calves from vaccinated heifers and in all 4 fetuses (aborted after BHV1 exposure) and 6 calves from unvaccinated heifers. Bovine herpesvirus 1 was not detected in any fetus or calf and associated fetal membranes in either treatment group. Vaccinated heifers had longer gestation periods and calves with greater birth weights, weaning weights, average daily gains, and market value at weaning, compared with those for calves born to unvaccinated heifers. Conclusions and Clinical Relevance-Prebreeding administration of a modified-live virus vaccine to heifers resulted in fewer abortions and BVDV-PI offspring and improved growth and increased market value of weaned calves.     

The effect of subunit or modified live bovine herpesvirus-1 vaccines on the efficacy of a recombinant Pasteurella haemolytica vaccine for the prevention of respiratory disease in feedlot calves

The efficacy of a Pasteurella haemolytica vaccine (PhV) administered once to calves within 24 hours of arrival at a feedlot was tested for the ability to prevent morbidity and mortality from all bovine respiratory disease (BRD) and specifically from fibrinous pneumonia mortality. The PhV consisted of two immunizing ingredients: outer membrane proteins extracted from P. haemolytica, plus genetically attenuated leukotoxin produced by recombinant DNA technology. This double blind study was conducted at a large Saskatchewan feedlot using 2,324 high-risk calves purchased at auction markets and kept under typical commercial feedlot conditions. The trial design included four vaccine test groups: 1) PhV and a bovine herpesvirus type-1 (BHV-1) subunit vaccine comprised only of the virus glycoprotein IV (gIV); 2) PhV and a commercial modified live vaccine (MLV) containing BHV-1 and parainfluenza-3 viruses; 3) gIV alone; and 4) MLV alone. Calves were assigned to vaccine groups in a random systematic manner, individually identified, and monitored for 90 days after vaccination. The vaccines were given once, on arrival, to reflect common feedlot practice, although vaccination prior to expected risk would be more appropriate.

The PhV in combination with gIV reduced BRD morbidity by 20% (p < 0.05) compared to gIV alone and 24% (p < 0.05) compared to MLV alone, and reduced BRD mortality by 88% (p < 0.05) and fibrinous pneumonia mortality by 100% (p < 0.05) when compared to either gIV or MLV alone. Vaccination with PhV in combination with MLV significantly reduced the efficacy of the PhV in preventing BRD morbidity, BRD mortality, and fibrinous pneumonia mortality and also reduced the antibody response to P. haemolytica leukotoxin. These results suggest that the MLV interfered with the protective capacity of the PhV.

     

Vaccination of calves with contaminated batches of bovine herpes virus 1 vaccines did not result in infection with bovine virus diarrhea virus

The aim of the experiment was to study whether bovine herpesvirus 1 (BHV1) marker vaccine batches known to be contaminated with bovine virus diarrhoea virus (BVDV) type 1 could cause BVD in cattle. For this purpose, four groups of cattle were used. The first group (n = 4 calves, the positive control group), was vaccinated with vaccine from a batch contaminated with BVDV type 2. The second group (n = 4 calves, the negative control group), was vaccinated with vaccine from a batch that was not contaminated with BVDV. The third group (n = 39 calves), was vaccinated with a vaccine from one of four batches contaminated with BVDV type 1 (seronegative experimental group). The fourth group (n = 6 seropositive heifers), was vaccinated with a vaccine from one of three batches known to be contaminated with BVDV type 1. All cattle were vaccinated with an overdose of the BHV1 marker vaccine. At the start of the experiment, all calves except those from group 4 were seronegative for BVDV and BHV1. The calves from group 4 had antibodies against BVDV, were BVDV-free and seronegative to BHV1. After vaccination, the positive control calves became severely ill, had fever for several days, and BVDV was isolated from nasal swabs and white blood cells. In addition, these calves produced antibodies to BVDV and BHV1. No difference in clinical scores of the other groups was seen, nor were BVDV or BVDV-specific antibody responses detected in these calves; however, they did produce antibodies against BHV1. The remainder of each vaccine vial used was examined for the presence of infectious BVDV in cell culture. From none of the vials was BVDV isolated after three subsequent passages. This indicates that BVDV was either absent from the vials or was present in too low an amount to be isolated. Thus vaccination of calves with vaccines from BHV1 marker vaccine batches contaminated with BVDV type 1 did not result in BVDV infections.     

Effects of hypervaccination with bovine herpesvirus type 1 gE-deleted marker vaccines on the serological response and virological status of calves challenged with wild-type virus

Twenty-four calves were immunised four times with gE-deleted infectious bovine rhinotracheitis marker vaccines before being challenged with small doses of wild-type bovine herpesvirus type 1 (BHV-1). The repeated vaccinations induced strong immunity that prevented detectable virus replication and gE-seroconversion after the challenge infection in most of the calves. The hypervaccinated calves that shed virus after the challenge infection showed no delay in gE-seroconversion compared with unvaccinated control calves. Using a sensitive nested PCR, BHV-1 gE sequences could be detected in the trigeminal ganglia of several of the gE-seronegative, challenge-infected calves, possibly indicating the presence of wild-type BHV-1 DNA.     

No effect of bovine interferon-tau for control of calf diarrhea and immunomodulation in calves

Newborn calves received a low dose of bovine interferon-tau (boIFN-tau) orally for 4 weeks and calves that had developed diarrhea received a low dose of boIFN-tau orally for 5 days. No effects of boIFN-tau were seen in the duration of the diarrhea, or in daily weight gain. Calves received a high dose of boIFN-tau subcutaneously 3 times and they were then stimulated with bovine herpesvirus type 1 vaccine. No adverse effects were observed after the administration of boIFN-tau and lymphocyte subsets from calves did not change after the stimulation. Our results suggest that boIFN-tau does not seem protecting for preventing calves from diarrhea, recovering the health of calves with diarrhea or immunomodulation, although the treatment itself is not toxic.     

Identification of immune response correlates for protection against bovine tuberculosis

Identification of an immune response correlate for protection against bovine tuberculosis would greatly facilitate the rational development of an effective vaccine. However, finding such a correlate has been a daunting task. Vaccination/challenge studies in cattle provide an ideal platform to compare induction of immune response parameters following vaccination and challenge, and assess the correlation of these parameters with protection. Protection against tuberculosis requires a Th 1-type cell-mediated immune response and induction of an antigen-specific interferon-gamma (IFN-gamma) response was the logical first choice in an investigation to identify an immune response correlate for protection. Calf vaccination studies showed that the subcutaneous injection of BCG vaccine induced significant protection against experimental challenge with Mycobacterium bovis. This protection was associated with strong whole blood IFN-gamma responses to bovine PPD 2-4 weeks after vaccination, but within the BCG-vaccinated groups, these responses were not correlated with protection. Use of a variety of vaccination strategies has shown that IFN-gamma responses in isolation were not necessarily associated with protection and concurrent IL-4 mRNA expression or antibody responses could also be induced. Collation of an immunological profile may be more informative than a study of individual cytokines. An indication of vaccine efficacy can be provided by the study of immune responses following challenge of the calves with M. bovis. IFN-gamma responses to ESAT-6, antibody responses following tuberculin skin testing and antigen-specific IL-4 mRNA expression all correlated with the severity of disease and indirectly provided an indication of protection. Future studies should be directed towards obtaining immunological profiles of calves following vaccination using techniques such as DNA microarray analysis, measurement of cytokine mRNA expression by real-time PCR, protein profiling by SELDI-TOF mass spectrometry as well as determining cytokine production by specific T cell sub-sets in individual protected animals.     

Encephalitis induced by bovine herpesvirus 5 and protection by prior vaccination or infection with bovine herpesvirus 1.

Calves were intranasally challenged with bovine herpesvirus 5 (BHV5) and followed for the development of viral infection, clinical encephalitis, histologic lesions in the brain, and viral sequences in the trigeminal ganglia. Calves that were previously vaccinated with bovine herepesvirus 1 (BHV1, n = 4) or previously infected with BHV1 (n = 5) or that had not been exposed to either virus (n = 4) were compared. No calf developed signs of encephalitis, although all calves developed an infection as indicated by nasal secretion of BHV5 and seroconversion to the virus. Histologic lesions of encephalitis consisting of multifocal gliosis and perivascular cuffs of lymphocytes were observed in calves not previously exposed to BHV1. BHV5 sequences were amplified from the trigeminal ganglia of calves previously vaccinated and from calves not previously exposed to BHV1; calves sequentially challenged with BHV1 and later BHV5 had exclusively BHV1 sequences in their trigeminal ganglia. Administration of dexamethasone 28 days after BHV5 challenge did not influence clinical disease or histologic lesions in either previously unexposed calves (n = 2) or previously immunized calves (n = 2), although it did cause recrudescence of BHV5, as detected by nasal virus secretion.