Functional analysis of antibody responses of feedlot cattle to bovine respiratory syncytial virus following vaccination with mixed vaccines.

The antibody response of cattle to bovine respiratory syncytial virus (BRSV) immunization was investigated using 4 different commercially available mixed vaccines. Forty, 5-6 month old, beef calves, randomly assigned to groups of 10, were vaccinated on day 0 and 21 with 1 of 3 inactivated vaccines, (3 groups), or a modified live virus (MLV) vaccine. BRSV-specific antibody responses were measured prior to vaccination and on day 35 by using an enzyme linked immunosorbent assay (ELISA), virus neutralization assay (VN), a fusion inhibition assay (FI); and responses were also measured for their ability to facilitate antibody dependent, complement mediated cytotoxicity (ADCMC) of BRSV infected cells. Sera from day 35 were, in addition, analyzed by use of an IgG1, IgG2 isotype specific ELISA. All vaccines induced significant increases in BRSV specific IgG antibody as measured by ELISA, but only one inactivated and the MLV vaccine induced significant increases in VN titers. Fusion inhibiting antibody titers were low or undetected in calves vaccinated with the inactivated vaccines. Vaccination with modified live virus induced significantly higher titers of fusion inhibiting antibodies, which are considered to be most highly correlated with protection. The VN to ELISA and FI to ELISA ratio of the calves that received MLV vaccine were significantly greater than the calves receiving the 3 inactivated vaccines. Vaccination with MLV induced the highest IgG2/IgG1 ratio. This difference was small, and only significant relative to 2 of the inactivated vaccine groups, which were not significantly different from each other. The higher proportion of IgG2 isotype in the MLV sera was not associated with lower ADCMC, a function not attributed to this isotype. The VN and FI titers, but not the ELISA value of the sera, were most predictive of ADCMC. The inactivation processes apparently alter epitopes and affect the induction of functional antibodies.     

Induction of antigen-specific T-cell subset activation to bovine respiratory disease viruses by a modified-live virus vaccine

OBJECTIVE: To determine the efficacy of a modified-live virus vaccine containing bovine herpes virus 1 (BHV-1), bovine respiratory syncytial virus (BRSV), parainfluenza virus 3, and bovine viral diarrhea virus (BVDV) types 1 and 2 to induce neutralizing antibodies and cell-mediated immunity in na?ve cattle and protect against BHV-1 challenge. ANIMALS: 17 calves. PROCEDURES: 8 calves were mock-vaccinated with saline (0.9% NaCl) solution (control calves), and 9 calves were vaccinated at 15 to 16 weeks of age. All calves were challenged with BHV-1 25 weeks after vaccination. Neutralizing antibodies and T-cell responsiveness were tested on the day of vaccination and periodically after vaccination and BHV-1 challenge. Specific T-cell responses were evaluated by comparing CD25 upregulation and intracellular interferon-gamma expression by 5-color flow cytometry. Titration of BHV-1 in nasal secretions was performed daily after challenge. Results-Vaccinated calves seroconverted by week 4 after vaccination. Antigen-specific cell-mediated immune responses, by CD25 expression index, were significantly higher in vaccinated calves than control calves. Compared with control calves, antigen-specific interferon-gamma expression was significantly higher in calves during weeks 4 to 8 after vaccination, declining by week 24. After BHV-1 challenge, both neutralizing antibodies and T-cell responses of vaccinated calves had anamnestic responses to BHV-1. Vaccinated calves shed virus in nasal secretions at significantly lower titers for a shorter period and had significantly lower rectal temperatures than control calves. CONCLUSION AND CLINICAL RELEVANCE: A single dose of vaccine effectively induced humoral and cellular immune responses against BHV-1, BRSV, and BVDV types 1 and 2 and protected calves after BHV-1 challenge for 6 months after vaccination.     

Humoral immune response of the bovine fetus to in utero vaccination with attenuated bovine coronavirus

A fetal response to in utero vaccination with attenuated bovine coronavirus (9 to 49 days before parturition) was determined in 8 calves, 5 vaccinated and 3 controls. Calves were derived by hysterotomy before parturition and were maintained in a closed gnotobiotic environment. The IgA, IgM, and IgG values and coronavirus-neutralizing antibody titers were higher in the sera and intestinal loop fluid from vaccinated calves than in those from control calves. Sections of ileum and ileal lymph nodes from 1-day-old vaccinated calves, when stained with monospecific anti-bovine IgG, IgM, and IgA had numerous positively stained plasma cells. Positive fluorescence was not detected in comparable tissues from controls. When the 8 calves were given virulent coronavirus orally at 6 days of age, vaccinated calves did not become ill, whereas control calves had diarrhea in 19 to 22 hours. All calves were killed at 10 days of age. Control calves had lesions characteristic of coronavirus infection, and intestinal epithelial cells were positive by fluorescent antibody tests. In vaccinated calves, lesions of coronavirus infection were absent, and results of fluorescent antibody tests were negative. Although in utero vaccination with a coronavirus vaccine stimulated immunity in the newborn calf, the frequency of abortions (2 of 14 cows inoculated intra-amniotically) and premature births (4 of 14) precluded practical application.     

Intestinal antibody response after vaccination and infection with rotavirus of calves fed colostrum with or without rotavirus antibody

The intestinal and systemic antibody response of calves vaccinated and/or challenged with rotavirus was studied employing isotype-specific ELISAs for the detection of IgG1, IgG2, IgM and IgA antibodies to rotavirus. Monoclonal antibodies to bovine immunoglobulin isotypes of proven specificity were used as conjugated or catching antibody. Five days after oral inoculation (dpi) of a 5-day-old gnotobiotic calf with rotavirus, IgM rotavirus antibodies were excreted in faeces, followed 5 days later by IgA rotavirus antibodies. The increase in IgM rotavirus antibody titre coincided with the inability to detect further rotavirus excretion. Faeces IgM and IgA rotavirus antibody titres fell to low levels within 3 weeks post infection. IgG1 and IgG2 rotavirus antibodies were not detected in faecal samples. In serum, antibodies to rotavirus of all four isotypes were detected, starting with IgM at 5 dpi. Two SPF-calves, which were fed colostrum free of rotavirus antibodies, were vaccinated with a modified live rotavirus vaccine and challenged with virulent rotavirus 6 days later. Upon vaccination, the calves showed an antibody response similar to the response of the infected gnotobiotic calf. Intestinal IgM rotavirus antibodies were excreted before or on the day of challenge and appeared to be associated with protection against challenge infection with virulent virus and rotavirus-induced diarrhoea. In 3 control calves, which were challenged only, the antibody patterns also resembled that of the gnotobiotic calf and again the appearance of IgM rotavirus antibodies coincided with the end of the rotavirus detection period. Two other groups of 3 SPF-calves were treated similarly, but the calves were fed colostrum with rotavirus antibodies during the first 48 h of life. These calves excreted passively acquired IgG1 and IgG2 rotavirus antibodies in their faeces from 2 to 6 days after birth. After vaccination, no IgM or IgA antibody activity in serum or faeces was detectable. Upon challenge, all calves developed diarrhoea and excreted rotavirus. Seven to 10 days after challenge low levels of IgM rotavirus antibody were detected for a short period. These data indicate that the intestinal antibody response of young calves to an enteric viral infection is associated with the excretion of IgM antibodies, immediately followed by IgA antibodies. This response is absent or diminished in calves with passively acquired specific antibodies which may explain the failure to induce a protective intestinal immune response by oral vaccination with modified live rotavirus of calves fed colostrum containing rotavirus antibodies.     

Efficacy of an inactivated respiratory syncytial virus vaccine in calves.

OBJECTIVE: To determine whether an inactivated bovine respiratory syncytial virus (BRSV) vaccine would protect calves from infection with virulent BRSV. DESIGN: Randomized controlled trial. ANIMALS: 27 nine-week-old calves seronegative for BRSV exposure. PROCEDURE: Group-1 calves (n = 9) were not vaccinated. Group-2 calves (n = 9) were vaccinated on days 0 and 21 with an inactivated BRSV vaccine containing a minimum immunizing dose of antigen. Group-3 calves (n = 9) were vaccinated on days 0 and 21 with an inactivated BRSV vaccine containing an amount of antigen similar to that in a commercial vaccine. All calves were challenged with virulent BRSV on day 42. Clinical signs and immune responses were monitored for 8 days after challenge. Calves were euthanatized on day 50, and lungs were examined for lesions. RESULTS: Vaccination elicited increases in BRSV-specific IgG and virus neutralizing antibody titers and in production of interferon-gamma. Virus neutralizing antibody titers were consistently less than IgG titers. Challenge with BRSV resulted in severe respiratory tract disease and extensive pulmonary lesions in control calves, whereas vaccinated calves had less severe signs of clinical disease and less extensive pulmonary lesions. The percentage of vaccinated calves that shed virus in nasal secretions was significantly lower than the percentage of control calves that did, and peak viral titer was lower for vaccinated than for control calves. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the inactivated BRSV vaccine provided clinical protection from experimental infection with virulent virus and decreased the severity of pulmonary lesions. Efficacy was similar to that reported for modified-live BRSV vaccines.     

Effect of vaccination with live or killed Pasteurella haemolytica on resistance to experimental bovine pneumonic pasteurellosis

Using 6- to 8-month-old beef calves, 3 experiments were conducted to compare the effect of vaccination with live or killed Pasteurella haemolytica on resistance to a transthoracic challenge exposure with the organism and to correlate serum antibody response with resistance. In each experiment, calves were vaccinated twice at 1-week intervals and were challenge exposed 21 days after the first inoculation. Lung lesions were evaluated by a system, such that higher scores indicated the more severe lesions. In each experiment, calves immunized with live P haemolytica had lower lesion scores than calves vaccinated with saline solution or bacterin. In 2 of the experiments, the differences were significant (P less than 0.05). In all experiments, calves vaccinated parenterally with a commercial P haemolytica/P multocida bacterin or with a formalin-killed P haemolytica bacterin had lesion scores that were not significantly different (P greater than 0.05) than for control calves vaccinated with saline solution. Live and killed bacterial preparations induced a significant serum antibody response to P haemolytica as measured by a quantitative fluorometric immunoassay. The antibody response to vaccination was not affected by preexisting titers to P haemolytica. Serum antibody titers were not consistently as high for calves vaccinated with bacterins as for calves vaccinated with live organisms. Although high antibody titers correlated with low lesion scores when calves vaccinated with saline solution or live organisms were analyzed collectively, there was not a significant correlation between the 2 variables when calves, vaccinated with saline solution or with bacterin, were analyzed collectively. These data indicate that, although bacterins may induce a detectable serum antibody response, they do not induce protection against transthoracic challenge exposure to P haemolytica.     

The influence of colostral antibodies on the postvaccinale humorale immune response in neonatal calves

The aim of this study was to evaluate the efficiency of vaccination of young calves and to see whether maternal antibodies may influence the immunological response in calves. For this project 20 matched-pairs of cows and their offspring were selected. Of each pair, one cow received a placebo 8 and 4 weeks before term (group A) and the other was vaccinated against Feline Leucose Virus, FeLV, with Leucogen? (group B). All calves received colostrum from their respective mother shortly after birth and all calves were vaccinated with Leucogen? 10 days after birth. Blood samples from the cows and calves were taken during the whole study period (till four weeks after calf vaccination). An ELISA test was done in the lab to define the FeLV antibody concentration. 30 % of the vaccinated cows showed a seroconversion, 13 out of 20 vaccinated cows passed the antibodies onto their calves. 11 calves of group B did not convert in comparation of only 4 of group A. All seroconverted calves had low antibody concentration before their vaccination. Calves of group B with a low passive antibody level at the beginning showed a higher seroconversion as compared to calves with higher antibody concentrations of the same group. Two thirds of the calves without maternal antibodies reacted adequately to the vaccination. Therefore, an early vaccination of calves can be recommended.     

Effects of various vaccination protocols on passive and active immunity to Pasteurella haemolytica and Haemophilus somnus in beef calves.

Two field trials were conducted in a beef cow herd in Saskatchewan to determine the effectiveness of a combined Pasteurella haemolytica and Haemophilus somnus vaccine in increasing passively and actively acquired antibodies in beef calves. Vaccination of dams at 4 and/or 7 weeks prepartum was associated with increased antibody titers to P. haemolytica and H. somnus in their serum (P < 0.05), colostrum (P < 0.05), and serum of their calves at 3 days and 1 month of age (P < 0.05). There was no significant (P > 0.05) difference in antibody titers in the colostrum and serum of calves from single or double vaccinated dams. Calves vaccinated at 1 and 2 months of age in the face of maternal antibodies to P. haemolytica and H. somnus had significantly (P < 0.05) higher antibodies to P. haemolytica and H. somnus at 4 and 6 months of age than did unvaccinated calves. Calves vaccinated at 3 and 4 months of age in the face of low levels of preexisting antibodies had significantly (P < 0.05) higher antibodies to P. haemolytica at 5 months of age and to H. somnus at 5 and 6 months of age than did unvaccinated calves. Calves vaccinated once at 4 months of age had significantly (P < 0.05) higher antibody titers to P. haemolytica and H. somnus at 4.5 months of age than did unvaccinated calves, but this difference was not apparent at 6 months of age.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sequential titration of bovine lung and serum antibodies after parenteral or pulmonary inoculation with Pasteurella haemolytica

Calves were vaccinated by intrabronchial or subcutaneous injection of formalinized Pasteurella haemolytica. Antibody in serum, nasal washings, and bronchoalveolar washings was titrated sequentially before and after calves were vaccinated and then challenge exposed with live homologous bacteria. Bronchoalveolar washings were collected by fiberoptics bronchoscopy, and antibody was titrated by indirect (antiglobulin) bacterial agglutination. Responsiveness to vaccination was related in initial serum antibody concentrations. Calves with serum antibody titers of 1:20 or more were nonresponsive, whereas with few exceptions, calves having titers of less than 1:20 responded to vaccination. Results indicated that serum and lung antibody were induced by subcutaneous or by intrabronchial inoculation of formalinized P haemolytica. By either route of immunization, serum antibody was more persistent than was lung antibody, and pulmonary challenge exposure with live P haemolytica did not alter existing titers.     

Comparative serological response in calves to eight commercial vaccines against infectious bovine rhinotracheitis, parainfluenza-3, bovine respiratory syncytial, and bovine viral diarrhea viruses

A field trial was conducted to compare the serological responses in calves to eight commercial vaccines against infectious bovine rhinotracheitis virus (IBRV), parainfluenza-3 virus (PI3V), bovine respiratory syncytial virus (BRSV), and/or bovine viral diarrhea virus (BVDV). Calves given IBRV, P13V, BRSV, and BVDV vaccines had significantly higher antibodies to these viruses than unvaccinated controls; however, serological responses to killed BVDV vaccines were low. Calves with preexisting antibodies to IBRV, PI3V, BRSV, and the Singer strain of BVDV had lower seroconversion rates following vaccination than calves that were seronegative initially.

Serological responses in calves to IBRV, PI3V, BRSV, and BVDV differed among various commercial vaccines. Antibody titers to IBRV were higher in calves vaccinated with modified-live IBRV vaccines than in those vaccinated with killed IBRV vaccines. Following double vaccination with modified-live IBRV and PI3V vaccines, seroconversion rates and antibody titers to IBRV and PI3V were higher in calves vaccinated intramuscularly than in those vaccinated intranasally. Calves given Cattlemaster 4 had significantly higher titers to BRSV and PI3V, and lower titers to BVDV, than calves given Cattlemaster 3, suggesting that the addition of BRSV to Cattlemaster 4 caused some interaction among antigens.

     

Evaluation of efficacy of an inactivated vaccine against bovine respiratory syncytial virus in calves with maternal antibodies

OBJECTIVE: To assess short- and long-term efficacy of an inactivated bovine respiratory syncytial virus (BRSV) vaccine administered i.m. to calves with maternally derived antibodies. ANIMALS: 28 two-week-old calves with neutralizing, maternally derived antibodies against BRSV. PROCEDURE: For evaluation of short-term efficacy, 6 calves were vaccinated i.m. at 2 and 6 weeks of age and challenged intranasally and intratracheally along with a matched group of 4 unvaccinated control calves at 10 weeks of age. For evaluation of long-term efficacy, 2 groups of 6 calves each were vaccinated i.m. at 2, 6, and 18 weeks of age or 14 and 18 weeks of age; these calves were challenged intranasally and intratracheally along with 6 matched unvaccinated control calves at 43 weeks of age. Serum virus neutralizing antibody titer, clinical reactions, and virus shedding in nasal mucus and lung washings were assessed. RESULTS: None of the vaccination regimens resulted in a significant increase in serum virus neutralizing antibody titer. As judged by virus shedding in nasal mucus and lung washings, vaccinated calves were protected against challenge, compared with unvaccinated control groups. Clinical signs attributable to challenge were coughing (short-term efficacy study) and tachypnea and dyspnea (long-term efficacy study). The severity and incidence of disease were significantly lower in the vaccinated groups, compared with that in the unvaccinated groups. CONCLUSIONS AND CLINICAL RELEVANCE: Through vaccination, it is possible to protect vulnerable calves with maternal antibodies against BRSV infection and reduce respiratory tract disease.     

Effects of vaccination of calves against induced Haemophilus somnus pneumonia

The efficacy of a killed whole-cell Haemophilus somnus bacterin against induced H somnus pneumonia was examined in 10-week-old male calves. Twenty calves were assigned to 1 of the 3 following groups: group 1, nonvaccinated controls (n = 4); group 2, vaccinated once (n = 8); and group 3, vaccinated twice 14 days apart (n = 8). The serum antibody response to vaccination and challenge exposure was evaluated by the bacterial agglutination test and solid-phase immunoassay (SPIA). Vaccinating calves twice, 14 days apart, significantly (P less than 0.05) reduced the severity of clinical signs of pneumonia and gross lesions. Deaths occurred in 1 of 4 nonvaccinated controls, 1 calf vaccinated once, and none of the calves vaccinated twice, 14 days apart. Postvaccination bacterial agglutination titers measured 14 days after the final vaccination were not significantly different between groups 2 and 3, but SPIA titers were significantly (P less than 0.05) higher in groups 2 and 3, compared with those in group 1. The less severe clinical signs of pneumonia observed in group-3 calves, compared with those in calves in groups 1 and 2, were significantly (P less than 0.01) correlated to higher SPIA titers, indicating the protective value of vaccinating twice.     

Effects of gastrointestinal parasites on parasite burden, rectal temperature, and antibody titer responses to vaccination and infectious bovine rhinotracheitis virus challenge

Thirty-three colostrum-deprived Holstein bull calves (initial BW of 131 ± 4 kg) were used to determine the effect of timing of anthelmintic administration relative to vaccination on antibody titer response to vaccine component antigens. When calves were at least 3 mo of age, they were sorted randomly into individual pens and assigned to 1 of 3 treatment groups, treatments consisted of 1) dewormed 2 wk before vaccination (DPV), 2) dewormed at the time of vaccination (DV), or 3) control, vaccinated but not dewormed (CONT). All calves were inoculated with infective larvae of brown stomach worms (Ostertagia ostertagi) and intestinal worms (Cooperia spp.) on d 1, 7, 10, 14, and 18 for a total dose of 235,710 infective larvae per calf. Calves (DPV and DV) were dewormed on d 21 or 35 with a 10% fenbendazole suspension at 5 mg/kg of BW. On d 35, all calves were vaccinated with a modified-live virus respiratory vaccine containing IBRV (infectious bovine rhinotracheitis virus), BVDV-1 (bovine viral diarrhea virus genotype 1), BVDV-2 (BVDV genotype 2), PI-3 (parainfluenza-3), and BRSV (bovine respiratory syncytial virus). During the 103-d experiment, weekly fecal egg counts, blood, and rectal temperatures were collected and health status was recorded daily. Blood samples were obtained weekly to determine serum neutralizing (SN) antibody titers to IBRV, BVDV-1, BVDV-2, and PI-3 and cytokine levels for IL-4, IL-6, TNF-α (tumor necrosis factor-α), and IFN-γ (interferon-gamma). There was a tendency (P < 0.09) for CONT calves to have greater IL-4 concentrations. By design, control calves had greater (P < 0.01) fecal egg counts during the experiment. All calves developed antibody titers to IBRV, BVDV-1, BVDV-2, and PI-3 by d 15 postvaccination. On d 88, all calves were challenged with IBRV and blood samples were obtained on d 88, 89, 90, 93, 95, 98, 99, and 103. All calves had increased rectal temperatures during the final 7 d of the IBRV challenge. However, the CONT group had greater (P < 0.01) rectal temperatures on each sampling day except d 90 compared with the DPV and DV treatments. Therefore, deworming before or at vaccination reduced parasite burden and decreased rectal temperature increase after an IBRV challenge. Deworming strategy had no effect on antibody response to vaccination or IBRV challenge.     

Antibody Response in Calves Following Administration of Attenuated Infectious Bovine Rhinotracheitis (IBR) Vaccines

The serum antibody response of calves vaccinated against infectious bovine rhinotracheitis by the intramuscular route was compared to calves vaccinated subcutaneously. Immunological response in the calves as determined by serum neutralization tests was highly variable; however, a significantly greater percentage (87.5%) of the calves inoculated subcutaneously responded to vaccination by producing a four-week post-vaccinal serum titer of two or higher as compared to only 47.8% of the calves that were vaccinated intramuscularly. Of those calves that were vaccinated a second time, all maintained or had produced titers of two or higher within four weeks after the second immunization. However, the existing circulating serum antibody titers resulting from the first vaccination of nine of 22 calves were lowered by repeat vaccination.     

Effect of age at the time of vaccination on antibody titers and feedlot performance in beef calves

OBJECTIVE: To compare antibody responses, feedlot morbidity and mortality rates, feedlot performance, and carcass value for calves vaccinated with 1 of 2 vaccination strategies and for unvaccinated control calves. DESIGN: Randomized controlled clinical trial. ANIMALS: 451 beef steers and heifers. PROCEDURES: Calves were vaccinated with a modified-live infectious bovine rhinotracheitis virus (IBRV), bovine viral diarrhea virus types 1 (BVDV1) and 2 (BVDV2), parainfluenza type 3 virus, and bovine respiratory syncytial virus vaccine and Mannheimia haemolytica and Pasteurella multocida bacterin-toxoid at approximately 67 and 190 days of age (group 1; n = 151) or at approximately 167 and 190 days of age (group 2; 150) or were not vaccinated (control; 150). Serum antibody titers were measured at approximately 2, 67, 167, 190, and 232 days of age. Morbidity and mortality rates, feedlot performance, and carcass value were recorded for 361 calves shipped to feedlots. RESULTS: Percentages of calves seroconverting to IBRV, BVDV1, and BVDV2 were significantly higher for groups 1 and 2 than for the control group. Mean treatment costs were significantly lower for vaccinated than for control calves, and mean mortality rate was significantly higher for control calves than for group 1 calves. Feedlot performance and carcass value did not vary significantly among groups. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that vaccination of beef calves with a 5-antigen modified-live virus vaccine at 67 and 190 days of age was as effective in terms of immunologic responses as was vaccination at 167 and 190 days of age.     

Q fever (Coxiella burnetii) investigations in dairy cattle: persistence of antibodies after vaccination.

The immune response and persistence of antibodies were investigated in dairy cattle vaccinated with formalin-inactivated phase (ph) I Coxiella burnetii vaccine agglutinating antibody geometric mean titer (GMT) of 193.2 at 1 month after vaccination compared to a GMT of 2.0 for nonvaccinated calves. The agglutinating antibodies gradually decreased in vaccinated cattle, but the GMT remained approximately 4 times higher than that for the nonvaccinated group for at least 20 months. Results of serotests at 2 months after revaccination indicated a rapid increase in the GMT to 177.0 with agglutinating titers between 1:64 and 1:512.     

Production of Brucella abortus-specific protein A-reactive antibodies (IgG2) in infected and vaccinated cattle

The IgG2 anti-Brucella antibody response of cattle to Brucella vaccination and infection was measured. Three groups of animals were studied; Group 1 contained 11 non-vaccinated cows, Group 2, 17 cows vaccinated with a low dose of Strain 19 vaccine and Group 3, 17 cows vaccinated with a high dose of Strain 19 vaccine. All animals were challenged at Week 33 with an infectious isolate of B. abortus (Strain 2308). Studies of the IgG2 antibodies response indicated an absolute correlation between anti-Brucella IgG2 levels and infection of the animal. All animals showing reciprocal titers of greater than or equal to 3000 (16 of 45 tested) were found to be positive for the challenge organism at slaughter. Animals with reciprocal IgG2 titers less than or equal to 1000 (29 of 45 tested) were found to be negative for the challenge organism at the time of slaughter. The predictive value of IgG2 antibody levels for infection held for animals in all three groups and consequently this suggests that monitoring of specific IgG2 anti-Brucella antibody levels may be of value in detection of Brucella-infected cattle.     

Longevity of protective immunity to experimental bovine herpesvirus-1 infection following inoculation with a combination modified-live virus vaccine in beef calves

OBJECTIVE: To determine whether a combination viral vaccine containing modified-live bovine herpesvirus-1 (BHV-1) would protect calves from infection with a recent field isolate of BHV-1. DESIGN: Randomized controlled trial. ANIMALS: Sixty 4- to 6-month-old beef calves. PROCEDURE: Calves were inoculated with a placebo 42 and 20 days prior to challenge (group 1; n = 10) or with the combination vaccine 42 and 20 days prior to challenge (group 2; 10), 146 and 126 days prior to challenge (group 3; 10), 117 and 96 days prior to challenge (group 4; 10), 86 and 65 days prior to challenge (group 5; 10), or 126 days prior to challenge (group 6; 10). All calves were challenged with BHV-1 via aerosol. Clinical signs, immune responses, and nasal shedding of virus were monitored for 14 days after challenge. RESULTS: Vaccination elicited increases in BHV-1-specific IgG antibody titers. Challenge with BHV-1 resulted in mild respiratory tract disease in all groups, but vaccinated calves had less severe signs of clinical disease. Extent and duration of nasal BHV-1 shedding following challenge was significantly lower in vaccinated calves than in control calves. In calves that received 2 doses of the vaccine, the degree of protection varied with the interval between the last vaccination and challenge, as evidenced by increases in risk of clinical signs and extent and duration of viral shedding. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that this combination vaccine provided protection from infection with virulent BHV-1 and significantly reduced nasal shedding of the virus for at least 126 days after vaccination.     

Efficacy of swine influenza A virus vaccines against an H3N2 virus variant

We compared the efficacy of 3 commercial vaccines against swine influenza A virus (SIV) and an experimental homologous vaccine in young pigs that were subsequently challenged with a variant H3N2 SIV, A/Swine/Colorado/00294/2004, selected from a repository of serologically and genetically characterized H3N2 SIV isolates obtained from recent cases of swine respiratory disease. The experimental vaccine was prepared from the challenge virus. Four groups of 8 pigs each were vaccinated intramuscularly at both 4 and 6 wk of age with commercial or homologous vaccine. Two weeks after the 2nd vaccination, those 32 pigs and 8 nonvaccinated pigs were inoculated with the challenge virus by the deep intranasal route. Another 4 pigs served as nonvaccinated, nonchallenged controls. The serum antibody responses differed markedly between groups. After the 1st vaccination, the recipients of the homologous vaccine had hemagglutination inhibition (HI) titers of 1:640 to 1:2560 against the challenge (homologous) virus. In contrast, even after 2nd vaccination, the commercial-vaccine recipients had low titers or no detectable antibody against the challenge (heterologous) virus. After the 2nd vaccination, all the groups had high titers of antibody to the reference H3N2 virus A/Swine/Texas/4199-2/98. Vaccination reduced clinical signs and lung lesion scores; however, virus was isolated 1 to 5 d after challenge from the nasal swabs of most of the pigs vaccinated with a commercial product but from none of the pigs vaccinated with the experimental product. The efficacy of the commercial vaccines may need to be improved to provide sufficient protection against emerging H3N2 variants.     

The influence of maternal antibody and age of calves on effective vaccination against Leptospira interrogans serovar hardjo

Twelve seronegative cows were vaccinated with an experimental bivalent Leptospira interrogans serovars hardjo and pomona vaccine late in their first pregnancy. Calves born of these dams were divided into 4 equal groups that received this vaccine at 4, 6, 10 and 18 weeks of age, respectively. Before vaccination the group geometric mean titres of maternally-derived circulating antibodies ranged from 2 to 25 for the microscopic agglutination (MA) test and 3 to 35 for enzyme-linked immunosorbent assay (ELISA) using a serovar hardjo outer envelope antigen. Post-vaccination peak titres were 645 to 1612 for MA and 562 to 1037 for ELISA, respectively. Calves vaccinated at the youngest age, had the highest pre-vaccination circulating maternal antibody titres, but showed the smallest rise in post-vaccination antibody titres. Circulating maternal antibody was detected in calves up to 13 weeks of age. All immunised calves were protected against a virulent challenge with serovar hardjo type Hardjobovis, regardless of their age or maternally-derived antibody titres. These findings indicate that calves as young as 4 weeks old, vaccinated in the presence of maternally-derived antibody, can be fully protected against homologous virulent challenge.