Inhibition of priming for bovine respiratory syncytial virus-specific protective immune responses following parenteral vaccination of passively immune calves.

The effect of maternal antibodies (MatAb) on immunological priming by neonatal parenteral vaccination for bovine respiratory syncytial virus (BRSV) was addressed for the first time in experimental infection in 34 Holstein calves. Both vaccinated and control calves developed moderate to severe respiratory disease characteristic of acute BRSV infection. There were no differences in clinical signs, BRSV shed, arterial oxygen concentrations, or mortality between vaccinated and control calves after BRSV challenge approximately 11 wk after vaccination. There were no anamnestic antibody or cytokine responses in the vaccinates after challenge. Lung lesions were extensive in both groups, and although there was a statistically significant (P = 0.05) difference between groups, this difference was considered not biologically significant. These data indicate that stimulation of protective immune responses was inhibited by maternal antibodies when a combination modified-live BRSV vaccine was administered parenterally to young passively immune calves. Alternate routes of administration or different vaccine formulations should be used to successfully immunize young calves with good passive antibody transfer.

Inhibition de l'amorçage pour les réponses immunitaires protectrices spécifiques pour le virus respiratoire syncytial bovin après la vaccination parentérale des veaux ayant une immunité passive. L'effet des anticorps maternels sur l'amorçage immunologique par une vaccination parentérale néonatale pour le virus respiratoire syncytial bovin (VRS) a été abordé pour la première fois dans une infection expérimentale chez 34 veaux Holstein. Les veaux vaccinés et témoins ont développé une maladie respiratoire de modérée à grave présentant les caractéristiques d'une infection aiguë au VRS. Il n'y avait pas de différences au niveau des signes cliniques, de l'excrétion du VRS, des concentrations d'oxygène artérielle ou de la mortalité entre les veaux vaccinés et témoins après un test de provocation de VRS, environ 11 semaines après le vaccin. Il n'y avait aucune réponse d'anticorps ou de cytokines anamnestiques chez les veaux vaccinés après le test de provocation. Les lésions aux poumons étaient importantes dans les deux groupes et, même s'il y avait une différence statistiquement significative (P = 0,05) entre ces groupes, cette différence n'était pas considérée significative sur le plan biologique. Ces données indiquent que la stimulation des réponses immunitaires protectrices a été inhibée par les anticorps maternels lors de l'administration parentérale d'une combinaison de vaccin à VRS vivant modifié aux jeunes veaux ayant une immunité passive. D'autres voies d'administration ou différentes formulations de vaccins devraient être utilisées pour immuniser avec succès les jeunes veaux ayant un bon transfert passif.(Traduit par Isabelle Vallières).

Effect of calf age and administration route of initial multivalent modified-live virus vaccine on humoral and cell-mediated immune responses following subsequent administration of a booster vaccination at weaning in beef calves.

OBJECTIVE: To compare immune responses following modified-live virus (MLV) vaccination at weaning after intranasal or SC administration of an MLV vaccine to beef calves at 2 or 70 days of age. ANIMALS: 184 calves. PROCEDURES: Calves were allocated to 1 of 5 groups. The IN2 (n = 37) and IN70 (37) groups received an MLV vaccine containing bovine herpesvirus 1 (BHV1), bovine viral diarrhea virus (BVDV) types 1 and 2, bovine respiratory syncytial virus (BRSV), and parainfluenza 3 virus intranasally and a Mannheimia haemolytica and Pasteurella multocida bacterin SC at median ages of 2 and 70 days, respectively. The SC2 (n = 36) and SC70 (37) groups received a 7-way MLV vaccine containing BHV1, BVDV1, BVDV2, BRSV, parainfluenza 3 virus, M haemolytica, and P multocida SC at median ages of 2 and 70 days, respectively; the control group (37) remained unvaccinated until weaning. All calves received the 7-way MLV vaccine SC at median ages of 217 (weaning) and 231 days. Serum neutralizing antibody (SNA) titers against BHV1, BVDV1, and BRSV and intranasal IgA concentrations were determined at median ages of 2, 70, 140, 217, and 262 days. Cell-mediated immunity (CMI) against BHV1, BRSV, BVDV1, and P multocida was determined for 16 calves/group. RESULTS: At median ages of 140 and 217 days, BVDV1 SNA titers were significantly higher for the SC70 group than those for the other groups. Intranasal IgA concentrations and CMI increased over time for all groups. Vaccination at weaning increased SNA titers and CMI in all groups. CONCLUSIONS AND CLINICAL RELEVANCE: SC administration of an MLV vaccine to 70-day-old calves significantly increased BVDV1 antibody titers before weaning.

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 naïve 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.