Modified-live Vaccine Research Articles

Variation of abscess formation in cattle after vaccination with a modified-live Pasteurella haemolytica vaccine

Summary During the spring of the first year of a vaccine study, 57 of 238 calves (24%), in which modified-live Pasteurella haemolytica vaccine (mlv) was injected twice, developed 1 or more abscesses. Abscesses were not observed after multiple visual examinations of 437 calves given killed P haemolytica bacterin or placebo injections of similar adjuvants used in the vaccine and bacterin. Calves that developed abscesses after the second injection of mlv weighed significantly (P < 0.05) less (on the basis of body weight adjusted for weaning weight) at the second injection than did those that did not develop abscesses. Compared with calves given mlv that did not develop observable abscesses, calves developing abscesses after the second injection of mlv weighed 11.0 and 14.2 kg less, respectively, at 56 days and 112 days after injection, and they had 11.0 kg less gain at 56 days after injection. Abscess prevalence tended to be highest on certain days or at certain locations used for cattle processing, and the prevalence of abscesses increased in cattle processed later on a given day. Abscesses were not observed in 2 other groups of similarly treated calves vaccinated in the autumn or in the subsequent spring.

Recent Advances in Bovine Vaccine Technology

A description of new commercial and experimental vaccines for viral and bacterial diseases of cattle can be broadly divided into those used for both beef and dairy cows and those used predominantly in dairy cattle. For both types of cattle, newer and experimental vaccines are directed against several of the important viral (e.g., bovine herpesvirus 1, bovine viral diarrhea virus, bovine respiratory syncytial virus, parainfluenza type 3, and foot-and-mouth disease virus) and bacterial pathogens (e.g., Pasteurella spp., Haemophilus somnus). The viral vaccines include gene-deleted, modified live, subunit, and peptide antigens. Newer bacterial vaccines, particularly those for Pasteurella spp., are composed of either modified-live vaccines or bacterins supplemented with toxoid or surface antigens. Haemophilus somnus vaccine research has concentrated mainly on defining unique surface antigens. Novel dairy cow vaccines would include the lipopolysaccharide-core (J5) antigen approach, which has been used for successful immunization against coliform mastitis. Core antigen vaccines also have reduced calf mortality from Gram-negative pathogens. Staphylococcal mastitis vaccines that contain capsular antigens, toxoids, or the staphylococcal fibronectin receptor are of active research interest. Vaccines against mastitis induced by Streptococcus agalactiae and Streptococcus uberis also are areas of intensive research. Delivery of multiple subunit antigens with optimal immune response induction has led to the investigation of attenuated heterologous viral and bacterial expression vectors such as bovine herpesvirus 1, vaccinia, and Salmonella spp. This discussion also demonstrates that molecular biology is being used to advance bovine vaccine technology.

Differential Diagnostic Blocking ELISA for use in Conjunction with Modified-Live IBRV gIII-Deleted Marker Vaccine

Differential Diagnostic Blocking ELISA for use in Conjunction with Modified-Live IBRV gIII-Deleted Marker Vaccine

Recommandations pour l’utilisation de vaccins contre la peste équine dans des régions non endémiques

African horse sickness (AHS), which causes mortality up to 95%, is caused by orbiviruses and is transmitted by Culicoides. The goal of a control and eradication program for AHS is to prevent the spread of the virus via the biological vector. Control measures include slaughter of infected animals, housing of suspected infected animals in insect-proof stalls, and vaccination. Vaccination has played a key role in eradication when AHS occurred outside of Africa. Both modified live vaccines (MLV) and inactivated vaccines have been used to control AHS. An acceptable vaccine should be: safe, efficacious, and available. The vaccine should not cause disease or viremia, and the vaccine virus should not revert to a virulent virus upon backpassage in susceptible Equidae. The vaccine should protect against death and clinical signs and, most importantly, should prevent viremia in vaccinated Equidae following exposure to virulent AHS virus. The challenge inoculation system for assessing immunity to AHS is discussed. The vaccine should be readily available, implying that it is either in routine production in facilities that meet internationally accepted guidelines for biological production facilities or in a vaccine bank. Banking of cryopreserved stocks of MLV or concentrates of inactivated vaccines is a means of having AHS vaccine available for future epizootics. A recently developed diagnostic test to differentiate vaccinated from naturally infected animals provides regulatory officials with useful information for the control of AHS.

Analysis of glycoprotein I (gI) negative and aberrant pseudorabies viral diagnostic isolates

Summary Glycoprotein I (gI) phenotypes and genotypes of 4 pseudorabies viral diagnostic isolates were evaluted by use of in vitro dna amplification, monoclonal antibody binding, gI-specific serodiagnostic responses, and in vivo virulence approaches. Three viruses were avirulent and did not elicit gI-specific serologic responses, react with gI-specific monoclonal antibodies, or contain gI epitope-encoding dna sequences. The fourth virus was virulent and did elicit a gI-specific serodiagnostic response. Compared with reference virulent Pseudorabies viruses, however, the fourth isoslate had reduced reactivity with a group of gI monoclonal antibodies and had a single nucleotide sequence substitution with a corresponding putative amino acid change in the epitopically dominant portion of the gI molecule. Presumably, the first 3 isolates represented diagnostic recoveries of viruses derived from gI-deleted modified-live Pseudorabies viral vaccines, whereas the fourth isolate was a virulent but gI-aberrant wild-type virus. Thoroughly assessing the gI status of pseudorabies viral diagnostic isolates was considered to be essential in evaluating the epidemiologic importance of these viruses and in monitoring the validity of gI-based vaccine companion tests now used worldwide in Pseudorabies control and eradication programs.

Bovine respiratory syncytial virus-specific immune responses in cattle following immunization with modified-live and inactivated vaccines. Analysis of the specificity and activity of serum antibodies

Cattle were immunized with vaccines containing modified-live or inactivated bovine respiratory syncytial virus (BRSV) and serum antibody responses were analyzed. Compared with preinculation values, at Day 14 after two biweekly immunizations with modified-live or inactivated vaccines there were significant increases in BRSV-specific titers in the sera of cattle that received both types of vaccines, as determined by a whole cell ELISA. Using a blocking ELISA and radioimmune precipitation it was determined that there was recognition of the fusion (F) protein by antibodies from cattle that received both types of BRSV antigens: however, virus neutralization assays revealed that only cattle that received modified live virus, either in monovalent or polyvalent vaccines, developed neutralizing antibodies to BRSV after two immunizations. These results indicate that inactivation of BRSV can lead to a dissociation between serological recognition of the F protein and virus neutralization in vaccinated cattle.

Bovine respiratory syncytial virus-specific immune responses in cattle following immunization with modified-live and inactivated vaccines. Analysis of proliferation and secretion of lymphokines by leukocytes in vitro

Cattle were immunized with vaccines containing modified-live or inactivated bovine respiratory syncytial virus (BRSV) and lymphocyte proliferative responses and cytokine secretion were monitored sequentially. Compared to pre-inoculated values, significant increases in proliferative responses to modified-live BRSV were detectable by Day 7 after the primary immunization with the vaccine containing inactivated BRSV, and by 7 days after the second immunization with modified-live virus. After a third immunization with the respective vaccines, proliferative responses to live BRSV were significantly higher in the group that received modified-live vaccine compared to the group that received inactivated vaccine. Proliferative responses to live BRSV corresponded with the presence of interleukin-2 (IL-2) in the supernatants from BRSV-stimulated leukocyte cultures and there were significantly higher levels of IL-2 in cultures from the group that received modified-live BRSV. An interferon species with the characteristics of interferon-α was also present in the supernatants from leukocyte cultures and there were no significant differences between the groups of vaccines. The predominant phenotype of proliferating cells in BRSV-stimulated leukocyte cultures derived from both groups of bovine vaccines was a BoCD4+ T-lymphocyte. These in vitro data suggest that both types of vaccines are capable of stimulating cell-mediated immune responses to BRSV in cattle.

Response of pups with maternal derived antibody to modified-live canine parvovirus vaccine

The AA reports the results of vaccination against canine parvovirus (CPV) of pups with maternal antibody, utilizing a modified-live virus (MLV) CPV vaccine having a titer of 10 7 TCID 50/dose. This vaccine was shown to be effective also when HI antibody titers of pups were ≤ 1:80.

An experimental contribution to the study of the pathogenesis of bovine viral diarrhea virus infection

This presentation summarizes the results of a study on the pathogenesis of bovine viral diarrhea (BVDV) infection. The cytopathic (CP) strain TVM-2 of BVDV induced in calves an overt clinical disease which is usually recorded as the acute primary BVDV infection observed under natural conditions. In contrast the non-cytopathic (NCP) strain New York-1 of BVDV did not cause any significant signs of disease. However, when the calves were immunosuppressed by treatment with dexamethasone (DMS) the biotype of BVDV involved did not seem to be as important as it appeared to be in an immunologically normal animal. This was shown in this study by the NCP BVDV which caused a fatal disease in calves treated with DMS. A mixed infection given to calves by injecting them with both CP and NCP BVDV, did not result in any particularly serious disease. So, the potential immunosuppressive activity of BVDV itself for the host has not been proven under the experimental procedures used in this experiment. Finally, a modified-live CP BVDV vaccine was unable to cause clinical disease when injected into calves that had been infected previously with strain New York-1 of BVDV.

Antibody response to canine distemper vaccine in African wild dogs.

Antibody levels against canine distemper virus were measured by means of an immunofluorescent antibody test prior to, and after, administration of a modified-live virus booster vaccine to seven African wild dogs (Lycaon pictus). Positive seroconversion with no harmful side-effects was seen in all the animals.

Genotypic screening of pseudorabies virus strains for thymidine kinase deletions by use of the polymerase chain reaction

Summary Genetic recombination between field strains and vaccine strains of pseudorabies virus (prv) has been suggested as a scenario that might arise from use of deletion-mutant modified-live vaccine strains, particularly those strains attenuated by deletions within the thymidine kinase (tk-) gene locus. To address this hypothesis experimentally, it is necessary to screen large numbers of prv isolates for their tk genotype. Techniques to detect the native tk genotype are routinely used in molecular virology laboratories, but are time-consuming. We adapted the polymerase chain reaction to define the genotypic status of prv isolates with regard to the presence or absence of deletions in the tk gene locus. Used in tandem with the existing glycoprotein-specific elisa that discriminate between prv-vaccinated and field strain-infected swine populations, the described technique may help to clarify whether vaccine-derived recombinants are generated under natural conditions and after normal vaccine usage.

Variation amongst the neutralizing epitopes of bluetongue viruses isolated in the United States in 1979–1981

Neutralizing epitopes present on field isolates of bluetongue virus (BTV) serotypes 10, 11, 13 and 17 were evaluated with a panel of polyclonal and neutralizing monoclonal antibodies (MAbs). A total of 91 field isolates were evaluated, including 15 isolates of BTV-10, 29 isolates of BTV-11, 26 isolates of BTV-13, and 21 isolates of BTV-17. The viruses were isolated from cattle, goats, sheep, elk and deer in Idaho, Louisiana, Nebraska and, predominantly, California, in the years 1979, 1980 and 1981. The isolates were analyzed and compared using a panel of neutralizing MAbs which included five MAbs raised against BTV-2, seven against BTV-10, five against BTV-13, and six against BTV-17. Neutralization patterns obtained with the MAb panel and individual field isolates were compared to those obtained with prototype viruses of each serotype. All field isolates were neutralized by at least some of the MAbs raised against the prototype virus of the same serotype. All field isolates of BTV-10 were neutralized by the seven MAbs raised to BTV-10, whereas the field isolates of BTV-11, BTV-13 and BTV-17 were not consistently neutralized by all of the MAbs raised against the prototype virus of the same serotype. Variation in neutralizing epitopes recognized by the MAb panel was most pronounced amongst the field isolates of BTV-17. A one-way cross neutralization was evident between BTV-10 and BTV-17 as all field isolats of BTV-17 were neutralized by four of the MAbs raised against BTV-10. In contrast, no BTV-10 isolates were neutralized by the MAbs raised against BTV-17. Differences in the MAb neutralization patterns of field isolates of BTV-11, BTV-13 and BTV-17 suggest that the immunogenic domain responsible for their neutralization is plastic, such that individual epitopes within the domain may vary in their significance to the neutralization of different viruses, even of the same serotype. The apparent conservation of neutralizing epitopes on field isolates of BTV-10 suggests that the field isolates may be derived from the modified-live vaccine strain of BTV-10.

Development of pneumonia in desert bighorn sheep after exposure to a flock of exotic wild and domestic sheep

Summary From 1986 to 1989, 5 desert bighorn sheep (3 Ovis canadensis mexicana and 2 O c nelsoni), ranging in age from 2 to 3 years, were exposed to a flock of exotic wild and domestic sheep to potentially achieve naturally acquired pneumonia. Pasturella multocida was isolated from nasal samples from 4 of 6 sheep randomly sampled from the flock. Bighorn sheep were exposed individually and each exposure period was a trial. Treatment before and after exposure varied and included combinations of α interferon, antibiotics, anti-inflammatory drugs, and vaccines. Treatments were chosen on the basis of recommendations of others for treating pneumonia in desert bighorn sheep as well as our own experience in sheep and cattle. Regardless of treatment used, bighorn sheep in trials 1 to 4 developed signs of pneumonia within 10 to 14 days of exposure. Bighorn sheep in trials 1 to 3 died within 11 to 17 days of initial exposure. In trial 4, the bighorn sheep was isolated from the carrier sheep for treatment of pneumonia on day 14 and died on day 30. Pasteurella multocida was isolated from lung tissue in 3 of the 4 bighorn sheep. On the basis of results of trials 1 to 4, a more in depth clinical study was conducted in trial 5. Nasal and blood specimens were collected prior to and during trial 5 for bacteriologic culturing and serologic testing for bovine viral diarrhea virus, infectious bovine rhinotracheitis, parainfluenza-3 virus, and respiratory syncytial virus. The bighorn sheep was vaccinated with a modified-live Pasteurella haemolytica vaccine and allowed to habituate to its new facilities for 133 days before it was exposed to the carrier sheep. Body temperature of this bighorn sheep was monitored every hour with radiotelemetry. Pneumonia was diagnosed on day 30 of exposure to the carrier sheep. Treatment consisting of long-acting oxytetracycline, sulfadimethoxine, long-acting sulfamethazine bolus, dexamethasone, and flunixin meglumine was given for 8 days and clinical improvement was detected. Acute pneumonia was again diagnosed on day 53. The bighorn sheep was removed from contact with the carrier sheep and put in isolation for a second treatment regimen. The bighorn sheep died on day 99. Pasteurella multocida was isolated from a tracheal flush and a nasal specimen obtained during the second bout of pneumonia and from lung tissue and sinuses at necropsy. Viruses were not isolated from the tracheal flush or from tissue samples collected at necropsy. None of the carrier sheep had clinical signs of pneumonia during the trials. Bacteriologic culturing and serologic testing in the bighorn sheep and ewes prior to and during the study suggested that carrier ewes were the source of P multocida infection in the bighorn sheep. Viruses were not a predisposing factor. Chronic sinusitis following initial pneumonia was suspected to play a role in the recurrence of pneumonia in the bighorn sheep of trial 5.

Antibody response to modified-live canine adenovirus vaccine in African hunting dogs (Lycaon pictus).

Nine hunting dogs were bled pre and post vaccination with modified-live virus vaccine. Their antibody responses to canine adenovirus type 1 was measured by an indirect immunofluorescent antibody test. The vaccine proved to be both effective and safe.

Immune response of neonatal lambs to a modified live Pasteurella haemolytica vaccine

Pregnant cross-bred ewes in the last month of gestation were either inoculated once intradermally with 0.5 ml of a modified-live Pasteurella haemolytica vaccine ( n=26) or kept as non-vaccinated controls ( n=24). Serum was collected at that time and 2 weeks later for evaluation of P. haemolytica antibodies. Vaccinated ewes were reinoculated at 2 week intervals until lambing. Vaccinated ewes responded 2 weeks after a single inoculation with a small but statistically significant increase in direct bacterial agglutination (DBA) log 2 titer (4.9 to 5.3). Control ewe titers did not increase. Lambs born to all ewes in the study received colostrum from their dams. Approximately equal number of randomly selected lambs from both ewe groups were serologically evaluated for P. haemolytica DBA and leukotoxin serum antibody titers on day 2 of life. Lambs from vaccinated ewes showed no significant increase in DBA titers (4.5 vs 3.9) but had significantly elevated anti-leukotoxin titers (3.5 vs 2.2) compared to lambs from control ewes. These same lambs were then assigned to either a vaccination or a non-vaccination group. Vaccination group lambs were inoculated intradermally on days 2 and 16 of life with 0.25 ml of the same vaccine given the ewes. Lambs were bled on days 16, 23, 30, 37, and 60, and sera were assayed for DBA and leukotoxin antibody titers. In addition, randomly selected sera from bleeding days 2, 16, 23, and 30 were screened for antibody against a carbohydrate-protein subunit of P. haemolytica using ELISA. Vaccination of lambs from both ewe groups resulted in increased DBA titers on days 23 and 30 compared to controls. Thereafter, titers increased in all groups, and there were no differences between them on day 60. Vaccination of lambs did not affect leukotoxin antibody. Lambs from vaccinated ewes, however, had significantly lower anti-leukotoxin titers than lambs from non-vaccinated ewes by day 60. There was no effect of lamb vaccination on carbohydrate-protein subunit antibody. This study did not assess efficacy of the vaccine against challenge; however, based on serological responses, vaccination of lambs with a modified-live Pasteurella haemolytica vaccine does not appear to be an efficacious preventative strategy for ovine enzootic pneumonia.

The vaccination and challenge with bovine viral diarrhea virus (BVDV) of calves previously infected with a non-cytopathic BVDV

Four calves were infected with noncytopathic (NCP) New York-1 strain of bovine viral diarrhea virus (BVDV). During the observation period of one month the calves remained clinically normal but the virus was repeatedly recovered from their pharyngeal swabbings and blood. Thirty days following infection the four calves were vaccinated, together with two uninfected calves, with a modified-live vaccine containing cytopathic (CP) BVDV, infectious bovine rhinotracheitis virus and parainfluenza-3 virus. No detrimental effects were observed after vaccination. Forty-three days after vaccination the calves were challenged by exposure either with the CP TVM-2 strain or the NCP New York-1 strain of BVDV. The vaccinated calves remained healthy throughout the 60-day observation period.

Antibodies to Aujeszky's disease virus in pigs immunized with purified virus glycoproteins

Antibodies to Aujeszky's disease virus (ADV) glycoproteins gII, gIII, and gp50 were compared using four in vitro tests. Antibodies generated by vaccination with a modified-live vaccine (MLV) were also compared. The serological assays employed were: serum neutralization test (SNT), complement facilitated serum neutralization test (C'SNT), complement-mediated cytolysis and antibody dependent cellular cytotoxicity (ADCC). Pigs were immunized with single glycoproteins twice 14 days apart, or once with the modified-live vaccine. Fourteen days after the second immunization, sera were collected. Virus neutralizing activity (SNT) was demonstrated in the sera from all pigs immunized with gp50 and in one out of three immunized with gIII. Sera from the MLV group all had neutralization titers higher than animals immunized with single glycoproteins. Addition of guinea pig complement to the serum neutralization test (i.e., C'SNT) produced an enhancement of antibody titers in all groups except the pigs immunized with gIII. The complement-mediated cytolysis test rendered antibody titers similar in magnitude for all pigs immunized with single glycoproteins, but slightly lower than values for MLV vaccinated pigs. ADCC activity was clearly displayed in sera from pigs immunized with gIII or vaccinated with MLV, whereas sera from pigs immunized with gII or gp50 had a minimal response. The results indicate that the relative efficiency of antibodies against ADV glycoproteins in protection should be considered for selecting or producing gene-deleted strains for use in vaccine production.

Molecular biology of bovine virus diarrhoea virus

Our understanding of the molecular biology of bovine virus diarrhoea virus (BVDV) has greatly increased over the past several years. The development of monoclonal antibodies (MAB's) has identified a key antigen of BVDV while at the same time providing evidence for considerable variation in this protein. MAB's, particularly those directed against the p80 protein, can be developed for use in diagnostic tests while others may be useful in molecular epidemiological studies of BVDV. The successful cloning of BVDV and hog cholera virus can provide nucleic acid probes for use in routine diagnostic testing, for use in pathogenesis studies and for the detection of BVDV contamination in biological materials. With the identification of the key antigens of BVDV and its molecular cloning, the future holds the promise of vectored vaccines which can provide the efficacy of modified-live vaccines with the safety of killed vaccines. However, much work still must be done to define the significance of the antigenic variation of BVDV as it relates to providing protection for the developing fetus.

Vaccine‐associated Canine Distemper Infection in a Litter of African Hunting Dogs (Lycaon pictus)

Four, 57 days old, African hunting dog puppies (Lycaon pictus) from one litter died within three weeks following vaccination with modified-live canine distemper virus (CDV) and killed canine adenovirus type 1, canine parvovirus and Leptospira icterohemorrhagiae and canicola. 18 days post vaccination, the animals developed neurologic disease characterized by episodes of grand mal seizures and circling. Macroscopic, histological and immunohistochemical studies revealed acute systemic CDV infection with acute encephalopathy. Virus isolation attempts using primary dog kidney cells, lung macrophages and Vero cells were negative. Therefore, the question whether the infection was the result of vaccination or natural infection remains open. The benefits and risks regarding the use of modified-live CDV vaccines and killed canine distemper vaccines in exotic carnivores are briefly discussed.

Bovine recombinant interleukin-2 augments immunity and resistance to bovine herpesvirus infection

The in vivo administration of bovine recombinant interleukin-2 (rIL-2) was evaluated in calves vaccinated and then challenged with bovine herpesvirus-1 (BHV-1). In Experiment 1, 24 calves were allotted to four groups: control; bovine rIL-2; BHV-1 vaccine (modified-live); and bovine rIL-2+BHV-1 vaccine. Serum neutralizing antibody titers to BHV-1 were increased sixfold, and virus shedding was fourfold less in calves vaccinated and treated with rIL-2 (25 μg/kg, intramuscularly) when compared to calves that received vaccine only. Treatment with rIL-2 induced lymphokine-activated killer activity that was eliminated by pretreating effector cells with complement and a monoclonal antibody (B26A) specific for the sheep red blood cell receptor. The rIL-2 treatment in BHV-1-vaccinated calves increased the calves' ability to withstand a BHV-1 challenge. However, during treatment with rIL-2, calves developed diarrhea and mild fever that abated after IL-2 treatment was stopped. A second experiment was then conducted to determine a dose of rIL-2 that would enhance immunity to BHV-1 without causing adverse side effects. Twenty-five calves were allotted to five groups that received injections of rIL-2 at 0.0, 25.0, 2.5, 0.25, or 0.025 μg kg −1 day −1 for 5 days. All calves received a modified-live BHV-1 vaccine. Calves treated with 25.0 μg kg −1 day −1 showed similar adverse side effects as in the first experiment but all other calves were normal. Compared to control calves, those treated with 25.0, 2.5, and 0.25 μg kg −1 day −1 of rIL-2 had higher ( P<0.05) serum antibody titers to BHV-1 and following challenge lower ( P<0.05) BHV-1 titers in nasal secretions; additionally, clinical disease as evidenced by nasal and ocular discharge was less severe ( P<0.05). In vitro cytotoxic responses against BHV-1-infected bovine kidney cells were increased ( P<0.05) in calves treated with rIL-2 in a dose dependent manner. These data suggest that bovine rIL-2 at 2.5 to 0.25 μg/kg may be an effective adjuvant to immunization.