Interaction of bovine respiratory syncytial virus with bovine alveolar macrophages in vivo: effects of virus infection upon selected cell functions.

The effect of bovine respiratory syncytial virus (BRSV) upon alveolar macrophage (AM) function was investigated using an in vivo calf inoculation model. Alveolar macrophages were collected sequentially from live calves at multiple time points during the 14 day period following viral inoculation. Alveolar macrophages from bronchoalveolar lavage fluids were purified by density gradient centrifugation (> 95% AM) prior to in vitro evaluation of cell functions. There were significant but variable and inconsistent differences in the functions of AM from the BRSV inoculated calves compared to the control calves. Fc-receptor mediated phagocytosis was either increased or unchanged by BRSV inoculation. Nonopsonized phagocytosis was decreased during the early postinoculation period and later increased. There was a variable effect on AM phagosome lysosome fusion with increased fusion activity on postinoculation days 2 through 5, 7 and 12 but reduced activity on days 6 and 10. The AM respiratory burst, as measured by nitroblue tetrazolium dye reduction, was essentially unaffected with a reduction in activity on day 10 only. In this model, BRSV inoculation of calves primarily resulted in an alteration of the membrane associated phagocytic functions of the alveolar macrophages (p < 0.05).     

Effect of bovine herpesvirus-1 or parainfluenza-3 virus on immune receptor-mediated functions of bovine alveolar macrophages in the presence or absence of virus-specific serum or pulmonary lavage fluids collected after virus infection

The immune receptor-mediated functions of bovine alveolar macrophages (AM) inoculated in vitro with bovine herpesvirus-1 (BHV-1) or parainfluenza-3 (PI-3) virus were tested in the presence or absence of virus-specific antiserum or pulmonary lavage fluids collected from calves 6 days after inoculation with BHV-1 or PI-3 virus. The Fc and C3b phagocytic indices of noninoculated AM, collected from 6- to 16-week-old calves, ranged from 75 to 87 and 59 to 64, respectively, and the binding indices ranged from 5 to 8 and 22 to 28, respectively. Infection of AM with either BHV-1 or PI-3 virus had no significant effect on receptor-mediated phagocytosis or binding, with the exception of a significant (P less than 0.05) decrease, from 64 to 46, of the C3b phagocytic index of PI-3 virus-infected AM. The addition of lavage fluids, collected after BHV-1 or PI-3 virus infection, to AM infected with the respective virus caused a significant (P less than 0.05) decrease in phagocytic indices with values for the Fc and C3b indices in BHV-1-infected AM decreasing from 81 to 49 and from 47 to 8, respectively, and those for the PI-3 virus-infected AM from 79 to 51 and from 46 to 15, respectively. The binding indices of virus-infected AM increased with the addition of viral lavage fluids, but the only significant (P less than 0.05) increase was for C3b binding in PI-3 virus-infected cells, which increased from 33 to 56.(ABSTRACT TRUNCATED AT 250 WORDS)     

Differential activation of interferon regulatory factors-3 and -7 by non-cytopathogenic and cytopathogenic bovine viral diarrhoea virus

Non-cytopathogenic bovine viral diarrhoea virus (ncpBVDV) has previously been shown to inhibit the function of interferon regulatory factor-3 in cultured cells [J. Virol. 76 (2002) 8979]. In this study, we show that, like ncpBVDV, when cells were previously exposed to cytopathogenic BVDV (cpBVDV) the appearance of an IRF-3–DNA complex from nuclear extracts that can be induced by heterologous virus infection was not observed. Infection of cells with ncpBVDV or cpBVDV resulted in neither the translocation of IRF-7 from the cytoplasm to the nucleus of infected cells, nor an inhibition of its nuclear translocation in cells super-infected by Semliki Forest Virus. We conclude that cpBVDV and ncpBVDV both share the ability to inhibit the full function of IRF-3 but neither stimulate or block the nuclear uptake of IRF-7.     

Interferon stimulated genes, CXCR4 and immune cell responses in peripheral blood mononuclear cells infected with bovine viral diarrhea virus

Non-cytopathic bovine viral diarrhea virus (ncpBVDV) induces immune responses mediated by chemokines and interferon (IFN) stimulated genes (ISGs). Cultured bovine peripheral blood mononuclear cells (PBMC) from ncpBVDV-naïve cattle were used herein to demonstrate that BVDV infection modulates chemokine receptor 4 (CXCR4), CXCL12, IFN-I, ISGs and selected immune cell marker (CD4, CD8, CD14) mRNAs, and that these acute responses to viral infection are reflected in PBMC cultured with serum from heifers carrying fetuses persistently infected (PI) with ncpBVDV. Infection of PBMC with ncpBVDV increased IFN-β, ISG15, RIG-I, CXCR4, CXCL12, and CD8 mRNA concentrations after 32 h. Culture of PBMC with uterine vein serum from acutely infected heifers, inoculated with ncpBVDV during early gestation to generate PI fetuses, also increased the concentration of CXCR4, RIG-I and ISG15 mRNAs. In vitro PBMC treatment with ncpBVDV or uterine vein serum from acutely infected pregnant heifers activates chemokine, ISG and immune cell responses.     

A blocking ELISA for the detection of specific antibodies to bovine respiratory syncytial virus

A blocking enzyme-linked immunosorbent assay (ELISA) has been adapted to detect specific antibodies in bovine sera to respiratory syncytial virus using a horseradish peroxidase-labeled monoclonal antibody to the fusion protein of the virus. This assay plus an indirect blocking ELISA and indirect ELISA were used to detect antibodies to the bovine respiratory syncytial virus (BRSV) in 159 field-origin bovine sera. Results of these assays were compared with serum antibody titers measured by the serum neutralization (SN) test. Over a 56-day period, the mean neutralization titers and the mean delta absorbance values for the blocking ELISA, on the same sera, showed similar declines. However, the calculated correlation coefficients between mean SN titer and mean absorbance value for the blocking ELISA of the individual sera ranged from -0.2 to -0.5 depending on the source of sera. Similar values were obtained whether using crude or purified viral antigen in the assays. Corresponding calculated correlation coefficients were generally higher for the indirect blocking ELISA or indirect ELISA than for the blocking ELISA. The blocking ELISA was between 70 and 64% as sensitive as the serum neutralization test with a specificity of 100 or 90% using the crude and purified viral antigen, respectively. The indirect blocking ELISA and indirect ELISA had similar calculated sensitivities and specificities. The blocking ELISA was faster to run than either of the other ELISA's or the neutralization test. Further, nonspecific background absorbance was obviated because the blocking ELISA detects antibodies to 1 specific viral protein, the fusion protein. These studies suggest that the blocking ELISA should be useful as a serological test for BRSV antibodies.     

套式RT-PCR检测牛呼吸道合胞体病毒的研究

为了检测牛呼吸道合胞体病毒(BRSV),根据已发表的融合蛋白(F)基因序列,设计了套式RT-PCR引物,初步建立了BRSV的套式RT-PCR检测方法。对138份牛鼻腔棉拭子进行了检测,结果检测到了BRSV阳性样品54份,总的阳性检出率为39.1%。对大部分BRSV阳性样品的F基因扩增产物进行了序列测定与分析。用该套式RT-PCR对牛传染性鼻气管炎病毒、牛副流感病毒3型、牛病毒性腹泻病毒等进行了检测,结果无交叉反应,表明该检测方法具有良好的特异性。本研究首次用套式RT-PCR技术证实了我国部分省的牛群中存在BRSV感染。     

A comparison of diagnostic methods for the detection of bovine respiratory syncytial virus in experimental clinical specimens.

Virus shedding was monitored in nasal secretions of 12 calves experimentally infected with bovine respiratory syncytial virus (BRSV) using an antigen capture enzyme-linked immunosorbent assay (ELISA) detecting the nucleoprotein (NP) antigen of BRSV, by a polymerase chain reaction (PCR) amplifying the fusion protein of BRSV, and by a microisolation assay combined with immunoperoxidase staining for the F protein of BRSV. Under the conditions of this study, similar limits of detection and quantitative results were obtained from all three assays. BRSV was detected in nasal secretions of all calves for a minimum of 4 d. Virus shedding began on Day 2 after infection, peaked on Days 3-5, and was cleared in most calves by Day 8. The PCR, and to a lesser extent the ELISA, may detect virus shedding for a longer period after infection than virus isolation, possibly due to neutralization of the virus by rising mucosal antibody. Simulated environmental conditions likely to be experienced during transport of clinical field specimens markedly reduced the sensitivity of virus isolation but had a minimal effect on the results of the NP ELISA. Actual field transport conditions (overnight on ice) had minimal apparent effect on the results of the PCR assay. The less stringent specimen handling requirements, combined with low limits of detection, of both the nucleoprotein ELISA and PCR, indicate either of these assays are more suitable for diagnostic applications than virus isolation.     

Dynamics of virus infections involved in the bovine respiratory disease complex in Swedish dairy herds

The dynamics of bovine respiratory syncytial virus (BRSV), bovine parainfluenza virus 3 (PIV-3), bovine corona virus (BCoV) and bovine viral diarrhoea virus (BVDV) infections were studied in 118 dairy herds in south western Sweden. By using serology on paired samples from three approximately 7 vs. approximately 15-month-old calves per herd, the propagation of infections was investigated over about a 1-year period. The results implied that at least 74% of calves had experienced one or more of the monitored infections at the age of approximately 7 months (Sample 1, Spring); 30%, 48%, 34% and 8% were seropositive to BRSV, PIV-3, BCoV and BVDV, respectively. Seroconversions to BRSV, PIV-3, BCoV and BVDV occurred in 26%, 38%, 50% and 3% of seronegative animals and 63% had antibodies against two or more infections at approximately 15 months (Sample 2). In total, 90-97% of animals that were seropositive in Sample 1 remained positive in Sample 2. A significant association was found between BVDV and BCoV (P = 0.01). Moreover, a significantly higher proportion of herds in which no calves had a recorded history of respiratory disease (n = 15) were classified as negative to all four infections monitored when compared to herds in which disease was observed (P = 0.0002). This study showed a high infection burden in young animals and effective spread of BRSV, PIV-3 and BCoV in one area of Sweden. BVDV infections were restricted to a few herds, reflecting the effect of a voluntary control program against BVDV in Sweden.     

Experimental reproduction of respiratory tract disease with bovine respiratory syncytial virus

An experiment was conducted to reproduce respiratory tract disease with bovine respiratory syncytial virus (BRSV) in one-month-old, colostrum-fed calves. The hypothesized role of viral hypersensitivity and persistent infection in the pathogenesis of BRSV pneumonia was also investigated. For BRSV inoculation a field isolate of BRSV, at the fifth passage level in cell culture, was administered by a combined respiratory tract route (intranasal and intratracheal) for four consecutive days. Four groups of calves were utilized as follows: Group I, 6 calves sham inoculated with uninfected tissue culture fluid and necropsied 21 days after the last inoculation; Group II, 6 calves inoculated with BRSV and necropsied at the time of maximal clinical response (4-6 days after the last inoculation); Group III, 6 calves inoculated with BRSV and necropsied at 21 days after the last inoculation; Group IV, 6 calves inoculated with BRSV, rechallenged with BRSV 10 days after initial exposure, and necropsied at 21 days after the initial inoculation. Clinical response was evaluated by daily monitoring of body temperature, heart rate, respiratory rate, arterial blood gas tensions, hematocrit, total protein, white blood cell count, and fibrinogen. Calves were necropsied and pulmonary surface lesions were quantitated by computer digitization. Viral pneumonia was reporduced in each principal group. Lesions were most extensive in Group II. Disease was not apparent in Group I (controls). Significant differences (p less than 0.05) in body temperature, heart rate, respiratory rate, arterial oxygen tension, and pneumonic surface area were demonstrated between control and infected calves. Results indicate that severe disease and lesions can be induced by BRSV in one-month-old calves that were colostrum-fed and seropositive to BRSV. BRSV rechallenge had minimal effect on disease progression. Based on clinical and pathological response, results did not support viral hypersensitivity or persistent infection as pathogenetic mechanisms of BRSV pneumonia.     

Investigation of causative agents of bovine respiratory tract disease in a beef cow-calf herd with an early weaning program.

Serum samples were collected from early weaned fall calves shortly after the onset of respiratory tract disease. Antibody titers to infectious bovine rhinotracheitis (IBR) virus, parainfluenza type 3 (PI-3) virus, bovine viral diarrhea (BVD) virus, bovine adenovirus type 3 (BAV-3), and bovine respiratory syncytial virus (BRSV) were determined on paired (acute and convalescent) serums. Seroconversion rate (a fourfold or greater rise in antibody titer) for IBR virus was 4.3%, PI-3 virus--16.3%, BVD virus--9.6%, and BAV-3--2.2%. Seroconversion for BRSV was 45.4%. An increased rate of seroconversion for IBR, PI-3, and BVD viruses and BAV-3 was observed in the presence of BRSV seroconversion. These results suggest that BRSV may facilitate infection by other viruses. Results of virus isolation procedures from these calves were negative.     

Ribavirin inhibits proliferation of bovine respiratory syncytial virus in vitro

Bovine respiratory syncytial virus (BRSV) is an important pathogen in bovine respiratory diseases in the United States. Proliferation of the disease can reach epidemic proportions with mortality reaching as high as 20%. In vitro work shown here suggests that the antiviral compound Ribavirin will be effective in the treatment of infected animals. Treatment at three dose levels with Ribavirin have shown significant inhibition of BRSV proliferation. Bovine turbinate cells were host cells for this study. Tissue culture specimens, infected and noninfected, were carried for 10 days. Presence of BRSV was verified with the use of monoclonal antibody. In addition, the infection with BRSV and consequential treatment with Ribavirin of calves demonstrated a noticeable reduction in viral symptom but no apparent systemic reaction to drug therapy.     

Study on the etiologic role of bovine respiratory syncytial virus in pneumonia of dairy calves

Bovine respiratory syncytial virus (BRSV) was the viral agent most commonly identified in 14 epizootics of pneumonia in dairy calves. A microtiter serum-virus neutralization test proved to be the best means of identifying involvement of BRSV; seroconversion (fourfold or greater rise in titer) was demonstrated in 10 of the 14 epizootics. Only limited involvement of bovine viral diarrhea virus, infectious bovine rhinotracheitis virus, parainfluenza 3 virus, and bovine adenovirus type 3 was recognized. Pasteurella multocida was isolated in 12 of 14 epizootics, and Pasteurella haemolytica in 4 of 14 epizootics. Mycoplasmal and ureaplasmal agents were isolated in all 14 epizootics.     

Immunology of bovine respiratory syncytial virus infection of cattle

Bovine respiratory syncytial virus (BRSV) is a respiratory pathogen of cattle that causes severe disease in calves alone and as one of several viruses and bacteria that cause bovine respiratory disease complex. Like human RSV this virus modulates the immune response to avoid stimulation of a vibrant CD8+ T cytotoxic cell response and instead promotes a Th2 response. The Th2 skew sometimes results in the production of IgE antibodies and depresses production of the Th1 cytokine interferon γ. Innate immune cells have a pivotal role in guiding the adaptive response to BRSV, with selective secretion of cytokines by pulmonary dendritic cells. Here we review some of the pertinent observations on immune responses to BRSV infection and vaccination and illustrate how experimental infection models have been used to elucidate the immunopathogenesis of BRSV infection. Recent experiments using intranasal vaccination and/or immune modulation with DNA based adjuvants show promise for effective vaccination by the stimulation of Th1 T cell responses.     

Effect of respiratory infections caused by bovine herpesvirus-1 or parainfluenza-3 virus on bovine alveolar macrophage functions

Calves, 90 to 130 days old, were inoculated with bovine herpesvirus-1 (BHV-1) or parainfluenza-3 (PI-3) virus. Pulmonary lavage specimens obtained from calves before virus inoculation contained 98% alveolar macrophages (AM) and 1% neutrophils. Six days after inoculation, the mean percentage of neutrophils in lavage specimens had significantly increased to 7.9 +/- 6.0% in BHV-1-inoculated calves and to 18.3 +/- 9.9% in PI-3 virus-inoculated calves, reflecting viral-induced pulmonary inflammation that was confirmed histologically. Approximately 75% of AM obtained before virus inoculation had Fc surface receptors, and 60% had C3b receptors. Six days after inoculation, the percentage of AM with Fc and C3b receptors was significantly reduced to 69.7 +/- 8.6% and 27.1 +/- 19.8%, respectively, in BHV-1-inoculated calves and to 67.8 +/- 15.4% and 38.8 +/- 23.2%, respectively, in PI-3 virus-inoculated calves. Alveolar macrophages obtained after virus inoculation were significantly impaired in their ability to phagocytize opsonized Staphylococcus epidermidis, but were able to kill ingested bacteria. Alveolar macrophage dysfunctions caused by BHV-1 or PI-3 respiratory infection did not differ appreciably.     

Comparison of levels and duration of detection of antibodies to bovine viral diarrhea virus 1, bovine viral diarrhea virus 2, bovine respiratory syncytial virus,bovine herpesvirus 1, and bovine parainfluenza virus 3 in calves fed maternal colostrum or a colostrum-replacement product

Colostrum-replacement products are an alternative to provide passive immunity to neonatal calves; however, their ability to provide adequate levels of antibodies recognizing respiratory viruses has not been described. The objective of this study was to compare the serum levels of IgG at 2 d of age and the duration of detection of antibodies to bovine viral diarrhea virus 1 (BVDV-1), bovine viral diarrhea virus 2 (BVDV-2), bovine respiratory syncytial virus (BRSV), bovine herpesvirus 1 (BHV-1), and bovine parainfluenza virus 3 (BPIV-3) in calves fed maternal colostrum (MC) or a colostrum replacement (CR) at birth. Forty newborn male Holstein calves were assigned to the CR or the MC group. Group CR (n = 20) received 2 packets of colostrum replacement (100 g of IgG per 470-g packet), while group MC (n = 20) received 3.8 L of maternal colostrum. Blood samples for detection of IgG and virus antibodies were collected from each calf at birth, at 2 and 7 d, and monthly until the calves became seronegative. Calves in the MC group had greater IgG concentrations at 2 d of age. The apparent efficiency of absorption of IgG was greater in the MC group than in the CR group, although the difference was not significant. Calves in the CR group had greater concentrations of BVDV neutralizing antibodies during the first 4 mo of life. The levels of antibodies to BRSV, BHV-1, and BPIV-3 were similar in the 2 groups. The mean time to seronegativity was similar for each virus in the 2 groups; however, greater variation was observed in the antibody levels and in the duration of detection of immunity in the MC group than in the CR group. Thus, the CR product provided calves with more uniform levels and duration of antibodies to common bovine respiratory viruses.     

Serological studies of parainfluenza type 3 virus, bovine adenovirus type 3 and bovine respiratory syncytial virus infection in beef calves

Six serum samples were taken at monthly intervals from birth to weaning from each of 41 newborn calves in the autumn and spring calf crops of a beef cow--calf herd. The serum hemagglutination-inhibition (HI) antibody titres to parainfluenza type 3 virus (PIV-3), virus-neutralization (VN) antibody titres to bovine adenovirus type 3 (BAV-3) and bovine respiratory syncytial virus (BRSV) were determined using microtitration techniques. There was serological evidence of a significantly higher incidence of infection with BAV-3 in the fall calves than in the spring calves. Serological responses to BAV-3 were not detected in calves with VN titres of greater than 1/256. Serological evidence of subclinical infection with PIV-3 occurred mainly in late February or early March during a period of marked environmental temperature fluctuations. Serological evidence of a high incidence of infection with BRSV was obtained for both the fall and spring calf crops. Serum antibody appeared to be unable to prevent infection with BRSV. An association between infection with BRSV and clinical pneumonia was found in 3 out of 9 calves. BAV-3 infection was related to pneumonia in only 1 instance; however, there was simultaneous evidence of BRSV infection in this calf. PIV-3 infection was found to be related to pneumonia in only 1 instance. There was serological evidence of infection with BAV-3 in association with the occurrence of diarrhea in 3 calves.     

Effect of infection with bovine respiratory syncytial virus on pulmonary clearance of an inhaled antigen in calves

OBJECTIVE: To evaluate the effect of infection with bovine respiratory syncytial virus (BRSV) on clearance of inhaled antigens from the lungs of calves. ANIMALS: Eleven 6- to 8-week-old Holstein bull calves. PROCEDURES: Aerosolized (99m)technetium ((99m)Tc)-labeled diethylene triamine pentacetate (DTPA; 3 calves), commonly used to measure integrity of the pulmonary epithelium, and (99m)Tc-labeled ovalbumin (OA; 8 calves), commonly used as a prototype allergen, were used to evaluate pulmonary clearance before, during, and after experimentally induced infection with BRSV or sham inoculation with BRSV. Uptake in plasma (6 calves) and lung-efferent lymph (1 calf) was examined. RESULTS: Clearance of (99m)Tc-DTPA was significantly increased during BRSV infection; clearance of (99m)Tc-OA was decreased on day 7 after inoculation. Clearance time was correlated with severity of clinical disease, and amounts of (99m)Tc-OA in plasma and lymph were inversely correlated with clearance time. Minimum amounts of (99m)Tc-OA were detected at time points when pulmonary clearance of (99m)Tc-OA was most delayed. CONCLUSIONS AND CLINICAL RELEVANCE: BRSV caused infection of the respiratory tract with peak signs of clinical disease at 7 or 8 days after inoculation. Concurrently, there was a diminished ability to move inhaled protein antigen out of the lungs. Prolonged exposure to inhaled antigens during BRSV infection may enhance antigen presentation with consequent allergic sensitization and development of chronic inflammatory lung disease. IMPACT FOR HUMAN MEDICINE: Infection of humans with respiratory syncytial virus early after birth is associated with subsequent development of allergic asthma. Results for BRSV infection in these calves suggested a supportive mechanism for this scenario.     

Effect of "in vitro" exposure of bovine alveolar macrophages to different strains of bovine respiratory syncytial virus.

A vaccine strain of respiratory syncytial (RS) virus and an isolate from pneumonic calves (AC2) were inoculated onto cultures of bovine alveolar macrophages recovered by lung lavage, and the functional properties of the cells observed over a period of 10 days. In most cultures no infectious virus was produced although immunofluorescence indicated the presence of virus antigens in some cells. No significant difference was noted between infected and control macrophage cultures in their capacity to phagocytose latex particles (neutral phagocytosis), although the ability to phagocytose complement-coated Candida krusei cells was affected, particularly with the AC2 strain after 6 days. Killing of C. krusei cells was slightly affected by infection of macrophages with the vaccine strain and was dramatically affected by infection with strain AC2. C3b and Fc receptor expression was adversely affected by both virus strains. Production of neutrophil chemotactic factors was increased in cultures infected with both strains, but was greater with AC2, suggesting that some properties of the cells were activated.     

Effects of allergen challenge on plasma concentrations of prostaglandins, thromboxane B2, and histamine in calves infected with bovine respiratory syncytial virus.

To examine the influence of allergen-induced type-1 hypersensitivity on the pathogenesis of bovine respiratory syncytial virus (BRSV) infection, we sensitized calves by aerosol to Micropolyspora faeni (MF) and challenge exposed them during infection with BRSV. The development of MF-specific IgE serum concentrations was confirmed by ELISA. The dynamics of arachidonic acid metabolism and histamine release during a type-1 hypersensitivity reaction in the bovine lung were studied by quantitating the concentrations of prostaglandin (PG)E2, PGF2 alpha, PGI2 as 6-keto-PGF1 alpha, thromboxane (TX) A2 as TXB2, and histamine in plasma of BRSV-infected and/or MF-sensitized/challenge-exposed calves. Four treatment groups were established: (1) BRSV infection only, (2) aerosol sensitization to MF followed by BRSV infection and aerosol challenge exposure to MF, (3) MF aerosol sensitization and challenge exposure without BRSV infection, and (4) aerosol sensitization to MF followed by BRSV infection without MF challenge exposure. Significantly increased concentrations of PGI2 were associated with MF aerosol exposure, particularly when combined with BRSV infection in group 2. After MF challenge exposure, TXB2 concentrations were significantly greater in the virus and MF challenge-exposed group 2. Individual calf data for the change in MF-specific IgE concentration between the first and second MF challenge exposures and the change in PGE2 concentration 30 minutes after the second MF challenge exposure had a highly significant direct correlation. Histamine concentrations were significantly greater in calves infected with BRSV than in uninfected controls regardless of MF exposure. These data further substantiate the thesis that implicates type-1 hypersensitivity as a pathogenic mechanism in BRSV-related disease.     

Response of calves to challenge exposure with virulent bovine respiratory syncytial virus following intranasal administration of vaccines formulated for parenteral administration

OBJECTIVE: To determine whether single-fraction and combination modified-live bovine respiratory syncytial virus (BRSV) vaccines commercially licensed for parenteral administration could stimulate protective immunity in calves after intranasal administration. DESIGN: Randomized controlled trial. ANIMALS: 39 calves. PROCEDURES: Calves were separated from dams at birth, fed colostrum with a minimal concentration of antibodies against BRSV, and maintained in isolation. In 2 preliminary experiments, 9-week-old calves received 1 (n = 3) or 2 (3) doses of a single-component, modified-live BRSV vaccine or no vaccine (8 control calves in each experiment), and were challenged with BRSV 21 days after vaccination. In a third experiment, 2-week-old calves received combination modified-live virus (MLV) vaccines with or without BRSV and calves were challenged with BRSV 8 days later. Calves were euthanized, and lung lesions were measured. Immune responses, including serum and nasal antibody and nasal interferon-alpha concentrations, were assessed. RESULTS: BRSV challenge induced signs of severe clinical respiratory tract disease, including death and pulmonary lesions in unvaccinated calves and in calves that received a combination viral vaccine without BRSV. Pulmonary lesions were significantly less severe in BRSV-challenged calves that received single or combination BRSV vaccines. The proportion of calves that shed virus and the peak virus titer was decreased, compared with control calves. Protection was associated with mucosal IgA antibody responses after challenge. CONCLUSIONS AND CLINICAL RELEVANCE: Single and combination BRSV vaccines administered intranasally provided clinical protection and sparing of pulmonary tissue similar to that detected in response to parenteral delivery of combination MLV and inactivated BRSV vaccines previously assessed in the same challenge model.