Analysis of the antibody response to bovine respiratory syncytial virus proteins in calves

Vaccine safety and efficacy evaluation of a recombinant bovine respiratory syncytial virus (BRSV) with deletion of the SH gene and subunit vaccines based on recombinant human RSV proteins: N-nanorings, P and M2-1, in calves with maternal antibodies

The development of safe and effective vaccines against both bovine and human respiratory syncytial viruses (BRSV, HRSV) to be used in the presence of RSV-specific maternally-derived antibodies (MDA) remains a high priority in human and veterinary medicine. Herein, we present safety and efficacy results from a virulent BRSV challenge of calves with MDA, which were immunized with one of three vaccine candidates that allow serological differentiation of infected from vaccinated animals (DIVA): an SH gene-deleted recombinant BRSV (ΔSHrBRSV), and two subunit (SU) formulations based on HRSV-P, -M2-1, and -N recombinant proteins displaying BRSV-F and -G epitopes, adjuvanted by either oil emulsion (Montanide ISA71^VG, SUMont) or immunostimulating complex matrices (AbISCO-300, SUAbis). Whereas all control animals developed severe respiratory disease and shed high levels of virus following BRSV challenge, ΔSHrBRSV-immunized calves demonstrated almost complete clinical and virological protection five weeks after a single intranasal vaccination. Although mucosal vaccination with ΔSHrBRSV failed to induce a detectable immunological response, there was a rapid and strong anamnestic mucosal BRSV-specific IgA, virus neutralizing antibody and local T cell response following challenge with virulent BRSV. Calves immunized twice intramuscularly, three weeks apart with SUMont were also well protected two weeks after boost. The protection was not as pronounced as that in ΔSHrBRSV-immunized animals, but superior to those immunized twice subcutaneously three weeks apart with SUAbis. Antibody responses induced by the subunit vaccines were non-neutralizing and not directed against BRSV F or G proteins. When formulated as SUMont but not as SUAbis, the HRSV N, P and M2-1 proteins induced strong systemic cross-protective cell-mediated immune responses detectable already after priming. ΔSHrBRSV and SUMont are two promising DIVA-compatible vaccines, apparently inducing protection by different immune responses that were influenced by vaccine-composition, immunization route and regimen.

Immunogenetic responses in calves to intranasal delivery of bovine respiratory syncytial virus (BRSV) epitopes encapsulated in poly (DL-lactide-co-glycolide) microparticles

Bovine respiratory syncytial virus (BRSV) is the principal aetiological agent of the bovine respiratory disease complex. A BRSV subunit vaccine candidate consisting of two synthetic peptides representing putative protective epitopes on BRSV surface glycoproteins in soluble form or encapsulated in poly(lactide-co-glycolide) (PLG) microparticles were prepared. Calves (10 weeks old) with diminishing levels of BRSV-specific maternal antibody were intranasally administered a single dose of the different peptide formulations. Peptide-specific local immune responses (nasal secretion IgA), but not systemic humoral (serum IgG) or cellular responses (serum IFN-γ), were generated by all forms of peptide. There was a significant reduction in occurrence of respiratory disease in the animals inoculated with all peptide formulations compared to animals given PBS alone. Furthermore no adverse effects were observed in any of the animals post vaccination. These results suggest that intranasal immunisation with the peptide subunit vaccine does induce an as yet unidentified protective immune response.

Experimental infection of calves with Newcastle disease virus induces systemic and mucosal antibody responses

Calves were infected intranasally and intratracheally with Newcastle disease virus (NDV), an avian paramyxovirus. Clinical signs, viral replication, and antibody production were evaluated. This study showed that NDV replicated in calves, as evidenced by development of NDV-specific humoral and mucosal antibody responses, but was attenuated in this unnatural host. These results suggest that NDV has the potential for development as a host-range-restricted, intranasal vaccine vector for cattle that lack preexisting immunity to NDV.

Formalin-inactivated bovine RSV vaccine influences antibody levels in bronchoalveolar lavage fluid and disease outcome in experimentally infected calves

Respiratory syncytial virus (RSV) causes severe respiratory disease in calves and human infants. In response to outbreaks, formalin inactivated (FI)-RSV vaccines were developed and found to exacerbate disease following a live RSV infection. We have reproduced vaccination induced disease enhancement in calves and screened various antibody isotypes in bronchoalveolar lavage fluid (BALF) from two studies: one with disease enhancement and another where moderate protection resulted from FI-bovine RSV (BRSV) vaccination. Semi-protected vaccinated calves produced BRSV-specific BALF IgG1, but not IgA and IgG2 prior to infection; whereas, calves with enhanced disease failed to develop BRSV-specific IgG1 in BALF. Ultimately, the formulation and delivery of RSV vaccines influences protective antibody levels in respiratory secretions.

Development and validation of an enzyme-linked immunosorbent assay for human metapneumovirus serology based on a recombinant viral protein

The human metapneumovirus (hMPV) is a newly reported respiratory virus belonging to the Paramyxoviridae family that has been associated with bronchiolitis and pneumonia in young children. We developed a simple enzyme-linked immunosorbent assay (ELISA) for hMPV serological testing using the nucleoprotein (N) from group A or B (N-A or N-B) as the antigen, and we evaluated it in both children and adults. The N proteins were first used in a Western immunoblot assay to identify hMPV-negative sera, which were then used to determine the cutoff value of the ELISA test. Subsequent evaluation of the ELISA-N test revealed that the mean reciprocal antibody titer of 20 randomly selected seropositive children was 143, compared to 69 for 20 seropositive adults. In a prospective evaluation of 71 adults with acute exacerbations of chronic obstructive pulmonary disease, 58 (81.6%) had prior hMPV antibodies and 3 (4.2%) had evidence of recent hMPV infection. In testing paired sera from adults (n = 4) with recent hMPV group A infection confirmed by reverse transcriptase PCR (RT-PCR), ELISAs using the N-A or N-B proteins were able to detect hMPV seroconversion. Moreover, testing of paired sera from three adults with a recent infection by the human respiratory syncytial virus confirmed by RT-PCR and serology did not reveal any increase in hMPV antibodies over time. The ELISA-N is a simple, objective, and specific serological test useful for detecting anti-hMPV antibodies following group A or B viral infections, which should permit a better understanding of the epidemiology of this virus.

Protection against bovine respiratory syncytial virus challenge following a single dose of vaccine in young calves with maternal antibody

Twenty-one young calves with maternally derived antibody to bovine respiratory syncytial virus (BRSV) were divided into three groups of seven, each group balanced for BRSV antibody titre. The calves had no evidence of previous exposure to BRSV. The calves in one group were given a single dose of a monovalent modified live BRSV vaccine; the calves in the second group were given a single dose of an inactivated combined BRSV, parainfluenza virus type 3, Mannheimia haemolytica vaccine and the calves in the third group were left as unvaccinated controls. Three weeks after the single doses of vaccine, all the calves were challenged with BRSV. The clinical signs of disease were mild, and virus excretion was limited to two calves in the group given the inactivated vaccine, compared with six in the negative controls (P = 0.05) and five in the group given the live vaccine. The mean virus excretion titres after the challenge were not significantly different between the groups. There was little seroconversion before the challenge, but six of the seven calves in the group given the inactivated vaccine showed significant seroconversion within two weeks after the challenge, compared with only one calf in each of the other two groups (P = 0.015).

Development of a nucleoprotein-based enzyme-linked immunosorbent assay using a synthetic peptide antigen for detection of avian metapneumovirus antibodies in Turkey sera

Avian metapneumoviruses (aMPV) cause an upper respiratory tract disease with low mortality but high morbidity, primarily in commercial turkeys, that can be exacerbated by secondary infections. There are three types of aMPV, of which type C is found only in the United States. The aMPV nucleoprotein (N) amino acid sequences of serotypes A, B, and C were aligned for comparative analysis. On the basis of the predicted antigenicity of consensus sequences, five aMPV-specific N peptides were synthesized for development of a peptide antigen enzyme-linked immunosorbent assay (aMPV N peptide-based ELISA) to detect aMPV-specific antibodies among turkeys. Sera from naturally and experimentally infected turkeys were used to demonstrate the presence of antibodies reactive to the chemically synthesized aMPV N peptides. Subsequently, aMPV N peptide 1, which had the sequence 10-DLSYKHAILKESQYTIKRDV-29, with variations at only three amino acids among aMPV serotypes, was evaluated as a universal aMPV ELISA antigen. Data obtained with the peptide-based ELISA correlated positively with total aMPV viral antigen-based ELISAs, and the peptide ELISA provided higher optical density readings. The results indicated that aMPV N peptide 1 can be used as a universal ELISA antigen to detect antibodies for all aMPV serotypes.

Comparative evaluation of indirect and sandwich ELISA for the detection of antibodies to bovine respiratory syncytial virus (BRSV) in dairy cattle

Seroprevalence of bovine respiratory syncytial virus (BRSV) infection in both exotic and crossbred cattle were described. A baculovirus expressed recombinant purified nucleocapsid (N) protein was used in indirect and sandwich ELISA for screening of 499 bovine sera samples from all over the state for the presence of BRSV antibodies. The seroprevalence rate of BRSV was found to be 46.09% through indirect ELISA while it would found to be 65.33% by sandwich ELISA. The result also indicated that exotic breeds were more susceptible to BRSV infection compared to crossbred cattle. A comprehensive analysis on susceptibility to BRSV as regards to various factors like age and sex was also summarized.

The ovine respiratory syncytial virus F gene sequence and its diagnostic application

Ruminant respiratory syncytial viruses (RSVs) are classified into 2 subgroups, ovine RSV and bovine RSV. Although ovine RSV infects cattle, its contribution to bovine respiratory tract disease has not been established, which is an important issue for vaccine development in cattle. Diagnosis by virus isolation or serology has low or variable sensitivity and/or specificity and polymerase chain reaction (PCR) has been recommended as a rapid and sensitive technique for RSV detection. A simple procedure has been developed to detect and identify bovine and ovine RSVs. First, the nucleotide sequence of the ovine RSV fusion (F) gene was determined and compared with representative strains of bovine RSV and human RSV subgroups A and B. The ovine RSV F gene has 85 and 72-73% nucleotide identity with those of bovine RSV and human RSV, respectively. The predicted amino acid sequence of the ovine RSV F gene has 94 and 83-84% amino acid identity with those of bovine RSV and human RSV, respectively. Then PCR primers targeting a specific F gene fragment of bovine and ovine RSV were designed. The primers represented bases 85-103 and the complementary sequence to bases 510-493 of the ovine RSV F gene. A similar PCR product (426 bp) was obtained on agarose gel electrophoresis from bovine RSV and from ovine RSV. The products, however, were unique to the parent virus and could be distinguished by EcoRI or MspI restriction endonuclease cleavage. EcoRI cleaved the ovine product into 2 bands (285 and 141 bp) but failed to affect the bovine RSV PCR product. However, MspI cleaved the bovine product into 2 bands (229 and 197 bp) but had no effect on the ovine product. Also, this assay did not amplify any PCR product with human RSV. The reverse transcription-polymerase chain reaction (RT-PCR) followed by restriction enzyme digestion is a useful and practical approach for detection and differentiation of ruminant respiratory syncytial viruses.

Detection of antibodies to U.S. isolates of avian pneumovirus by a recombinant nucleocapsid protein-based sandwich enzyme-linked immunosorbent assay

The nucleocapsid (N) protein of subgroup C (United States-specific) avian pneumovirus (APV/US) was expressed in Escherichia coli, and antibodies to the recombinant N protein were shown to specifically recognize the approximately 47-kDa N protein of APV/US by Western immunoblot analysis. The recombinant APV/US N protein was used in a sandwich-capture enzyme-linked immunosorbent assay (ELISA), and the resulting assay was found to be more sensitive and specific than the routine indirect ELISA for the detection of APV/US antibodies in turkey sera.

Bovine respiratory syncytial virus (BRSV): a review

Bovine respiratory syncytial virus (BRSV) infection is the major cause of respiratory disease in calves during the first year of life. The study of the virus has been difficult because of its lability and very poor growth in cell culture. However, during the last decade, the introduction of new immunological and biotechnological techniques has facilitated a more extensive study of BRSV as illustrated by the increasing number of papers published. Despite this growing focus, many aspects of the pathogenesis, epidemiology, immunology etc. remain obscure. The course and outcome of the infection is very complex and unpredictable which makes the diagnosis and subsequent therapy very difficult. BRSV is closely related to human respiratory syncytial virus (HRSV) which is an important cause of respiratory disease in young children. In contrast to BRSV, the recent knowledge of HRSV is regularly extensively reviewed in several books and journals. The present paper contains an updated review on BRSV covering most aspects of the structure, molecular biology, pathogenesis, pathology, clinical features, epidemiology, diagnosis and immunology based on approximately 140 references from international research journals.

Generation of bovine respiratory syncytial virus (BRSV) from cDNA: BRSV NS2 is not essential for virus replication in tissue culture, and the human RSV leader region acts as a functional BRSV genome promoter

In order to generate recombinant bovine respiratory syncytial virus (BRSV), the genome of BRSV strain A51908, variant ATue51908, was cloned as cDNA. We provide here the sequence of the BRSV genome ends and of the entire L gene. This completes the sequence of the BRSV genome, which comprises a total of 15,140 nucleotides. To establish a vaccinia virus-free recovery system, a BHK-derived cell line stably expressing T7 RNA polymerase was generated (BSR T7/5). Recombinant BRSV was reproducibly recovered from cDNA constructs after T7 RNA polymerase-driven expression of antigenome sense RNA and of BRSV N, P, M2, and L proteins from transfected plasmids. Chimeric viruses in which the BRSV leader region was replaced by the human respiratory syncytial virus (HRSV) leader region replicated in cell culture as efficiently as their nonchimeric counterparts, demonstrating that all cis-acting sequences of the HRSV promoter are faithfully recognized by the BRSV polymerase complex. In addition, we report the successful recovery of a BRSV mutant lacking the complete NS2 gene, which encodes a nonstructural protein of unknown function. The NS2-deficient BRSV replicated autonomously and could be passaged, demonstrating that NS2 is not essential for virus replication in cell culture. However, growth of the mutant was considerably slower than and final infectious titers were reduced by a factor of at least 10 compared to wild-type BRSV, indicating that NS2 provides a supporting factor required for full replication capacity.

Subgrouping of bovine respiratory syncytial virus strains detected in lung tissue

Bovine respiratory syncytial virus is an important respiratory pathogen in cattle. Recently, subgroups of BRSV have been identified, based on antigenic differences. However, little is known about subgroups of BRSV that circulate in the cattle population. Therefore, we determined the reactivity of monoclonal antibodies (mAbs), directed against the G, F, or P protein of BRSV, with lung tissue from 47 calves, that suffered from severe respiratory disease. Fourteen animals (30%) proved to be infected with BRSV, because they all reacted with mAbs against the P or F protein, as detected by fluorescent antibody tests. Monoclonal antibodies against the G protein were able to discriminate between the BRSV-positive specimens: 7 strains were identified as subgroup A strains, and 5 strains as subgroup AB, which is introduced as BRSV subgroup in this paper. Two strains could not be identified unambiguously. It is concluded that BRSV subgroup A and AB were associated with severe respiratory disease, and that strains belonging to either subgroup circulated concurrently in the cattle population in the Netherlands.

Antibody responses against the G and F proteins of bovine respiratory syncytial virus after experimental and natural infections

Antibodies against the two major surface glycoproteins of bovine respiratory syncytial virus (BRSV), G and F, play a role in protection against BRSV-associated disease, but only the antibody response against the F protein has been well described. Therefore, we used a novel peptide-based enzyme-linked immunosorbent assay (G peptide-ELISA) to compare immunoglobulin G (IgG) and IgG subclass antibody responses against the G protein with the antibody response against the F protein, as measured by a conventional BRSV ELISA (F-ELISA). Experimental infection of cattle induced significantly lower antibody titers than did natural infection. After natural primary infection, G peptide-specific antibodies declined more rapidly and to lower levels than the F protein-specific antibodies. As a consequence, the G peptide-ELISA detected more reinfections than did the F-ELISA. Ratios of G- and F-specific IgG1/IgG2 antibody titers did not differ markedly after infection or vaccination. Interestingly, after natural infection calves did not develop an IgG2 response to the complete G protein. In contrast, adult cattle had high IgG2 titers against this protein. Vaccination with a live vaccine induced low antibody titers, similar to the titers after experimental infection, whereas vaccination with an inactivated vaccine induced high titers. The results indicate that the kinetics of the G- and F-specific antibody responses differ. Furthermore, the IgG subclass response against the unglycosylated central region of the G protein is similar to the IgG subclass response to the F protein, but the IgG subclass response differs from the response to the complete G protein.

A simple, specific, and highly sensitive blocking enzyme-linked immunosorbent assay for detection of antibodies to bovine herpesvirus 1

By using a monoclonal antibody directed against an epitope located on glycoprotein B of bovine herpesvirus 1 (BHV1), a simple, convenient blocking enzyme-linked immunosorbent assay (ELISA) which combines a high sensitivity with a low false-positive rate has been developed. The test can be performed at low variance on undiluted bovine serum samples. The epitope on glycoprotein B appears to be conserved, because it could be detected by immunostaining in all of 160 BHV1 isolates originating from 10 countries. In testing 215 anti-BHV1 antibody-negative and 179 anti-BHV1 antibody-positive serum samples, specificity and sensitivity were 0.96 and 0.99, respectively. This blocking ELISA is superior to a commercially available indirect ELISA and to the 24-h virus neutralization test in detecting low antibody levels in serum. In addition, this blocking ELISA is able to detect specific antibodies in serum as early as 7 days postinfection. To minimize any risk of introducing latent BHV1 carriers among noninfected cattle, this blocking ELISA would be, in our opinion, the test of choice.

Reliable confirmation of antibodies to bovine respiratory syncytial virus (BRSV) by enzyme-linked immunosorbent assay using BRSV nucleocapsid protein expressed in insect cells

The nucleocapsid (N) protein of bovine respiratory syncytial virus (BRSV) in the baculovirus expression system was evaluated as a source of antigen in an enzyme-linked immunosorbent assay (ELISA) for the detection of respiratory syncytial virus (RSV) antibodies. The recombinant N protein was purified from infected-cell extracts by sucrose gradient centrifugation and used in the ELISA for the detection of antibodies to various RSV strains. The ELISA was compared with the virus neutralization (VN) test for determining BRSV antibodies in 10 consecutive serum samples from four calves vaccinated with a live modified BRSV vaccine and from two nonvaccinated control calves. The ELISA compared favorably with the VN test for detecting serological responses. All serum samples which were positive in the VN test were also positive in the ELISA. None of the serum samples collected from the two nonvaccinated calves reacted in the ELISA. To determine the usefulness of the ELISA for epidemiological studies, 58 cattle serum samples were tested in the ELISA and the VN test. Approximately 94% (42 of 45) of field serum samples which were positive in the ELISA were also positive in the VN test. No case was found in which the ELISA result was negative and the VN test result was positive. Thirteen of the serum samples were negative in both methods. Our results indicate that the ELISA with the baculovirus-expressed N protein as an antigen is an efficient, sensitive, and specific method for detecting serum antibodies to RSV.

Antigenic diversity of respiratory syncytial viruses and its implication for immunoprophylaxis in ruminants

Bovine respiratory syncytial virus (BRSV) is a very important pathogen of cattle and perhaps other ruminants. It is a major contributor to the incidence of respiratory tract disease in nursing beef and feedlot and dairy calves. The genome of respiratory syncytial viruses encodes 10 proteins translated from 10 unique mRNAs. The major glycoprotein (G), fusion protein (F), 1A protein and the 22K protein are components of the viral envelope. The nucleocapsid contains the nucleocapsid protein (N), the phosphoprotein (P), and the large protein (L). The matrix protein (M) forms a structural layer between the envelope and the nucleocapsid. Antibodies to all the structural proteins develop in convalescent calves. However, evidence suggests that immunity develops primarily as a result of the antigenic stimulus by the major glycoprotein G and the fusion glycoprotein F. It is known also that activated cytotoxic T cells interact with N and F protein antigens and helper T cells interact with N, F, and 1A protein antigens. With the exception of the major glycoprotein, the respective proteins of various respiratory syncytial viruses share major antigenic domains. Based on antigenic differences of the major glycoprotein, at least 3 subgroups of RSV are recognized; human A, human B, and bovine RSV. Indirect evidence suggests that a second subgroup of BRSV exists. However, we have identified only one BRSV subgroup based on our work with RNase mismatch cleavage analysis of the G protein gene from a limited number of strains. Furthermore, our data indicated that a caprine RSV isolate is closely related to the bovine strains, but an ovine isolate is not. The latter may constitute yet another subgroup of RSV. These data affect decisions on optimization of immunoprophylaxis since evidence suggests that protection against a homologous RSV subgroup virus is superior to that against a heterologous strain in immune subjects.

Nucleotide sequence analysis of the bovine respiratory syncytial virus fusion protein mRNA and expression from a recombinant vaccinia virus

Bovine respiratory syncytial (BRS) virus is an important cause of serious respiratory illness in calves. The disease caused in calves is similar to that caused by human respiratory syncytial (HRS) virus in children. The two viruses, however, have distinct host ranges and the attachment glycoproteins, G, have no antigenic cross-reactivity. The fusion glycoproteins, F, of the HRS and BRS viruses, however, have some antigenic cross-reactivity. To further compare the BRS virus and HRS virus fusion proteins, we determined the nucleotide sequence of cDNA clones to the BRS virus F protein mRNA, deduced the amino acid sequence, and compared these sequences with the HRS virus F protein sequences. The BRS virus F mRNA was 1899 nucleotides in length and had a single major open reading frame which could code for a polypeptide of 574 amino acids with an estimated molecular weight of 63.8 kDa. Structural features predicted from the amino acid sequence included an NH2-terminal signal sequence (residues 1-26), a site for proteolytic cleavage (residues 131-136) to generate the disulfide-linked F1 and F2 subunits, and a hydrophobic transmembrane anchor sequence (residues 522-549). The nucleic acid identity between the BRS virus and the HRS virus F mRNA sequences was 71.5%. The predicted BRS virus F protein shared 80.5% overall amino acid identity with the HRS virus F protein with 89% identity in the F1 polypeptide but only 68% identity in the F2 polypeptide. The position and number of the cysteine residues in the F1 and F2 polypeptides were conserved among all F proteins. However, BRS virus F protein had only three potential N-linked carbohydrate acceptor sites in comparison to four or five for the HRS viruses. A difference in the extent of glycosylation between the BRS and HRS virus F2 polypeptides was shown to be responsible for differences observed in the electrophoretic mobility of these proteins. A cDNA containing the complete open reading frame of the BRS virus F mRNA was inserted into the thymidine kinase gene of vaccinia virus and following homologous recombination, a recombinant virus containing the BRS virus F gene was isolated. The BRS virus F protein was expressed in recombinant virus infected cells as demonstrated by immunoprecipitation and was transported to and expressed on the surface of infected cells as shown by indirect immunofluorescence.

Nucleotide sequence analysis and expression from recombinant vectors demonstrate that the attachment protein G of bovine respiratory syncytial virus is distinct from that of human respiratory syncytial virus

Bovine respiratory syncytial (BRS) virus causes a severe lower respiratory tract disease in calves similar to the disease in children caused by human respiratory syncytial (HRS) virus. While there is antigenic cross-reactivity among the other major viral structural proteins, the major glycoprotein, G, of BRS virus and that of HRS virus are antigenically distinct. The G glycoprotein has been implicated as the attachment protein for HRS virus. We have carried out a molecular comparison of the glycoprotein G of BRS virus with the HRS virus counterparts. cDNA clones corresponding to the BRS virus G glycoprotein mRNA were isolated and analyzed by dideoxynucleotide sequencing. The BRS virus G mRNA contained 838 nucleotides exclusive of poly(A) and had a major open reading frame coding for a polypeptide of 257 amino acid residues. The deduced amino acid sequence of the BRS virus G polypeptide showed only 29 to 30% amino acid identity with the G protein of either the subgroup A or B HRS virus. However, despite this low level of identity, there were strong similarities in the predicted hydropathy profiles of the BRS virus and HRS virus G proteins. A cDNA molecule containing the complete BRS virus G major open reading frame was inserted into the thymidine kinase gene of vaccinia virus by homologous recombination, and a recombinant virus containing the BRS virus G protein gene was isolated. This recombinant virus expressed the BRS virus G protein, as demonstrated by Western immunoblot analysis and immunofluorescence of infected cells. The BRS virus G protein expressed from the recombinant vector was transported to and expressed on the surface of infected cells. Antisera to the BRS virus G protein made by using the recombinant vector to immunize animals recognized the BRS virus attachment protein but not the HRS virus G protein and vice versa, confirming the lack of antigenic cross-reactivity between the BRS and HRS virus attachment proteins. On the basis of the data presented here, we conclude that BRS virus should be classified within the genus Pneumovirus in a group separate from HRS virus and that it is no more closely related to HRS virus subgroup A than it is to HRS virus subgroup B.

Immunity to human and bovine respiratory syncytial virus

Human and bovine respiratory syncytial viruses resemble each other closely. During annual winter outbreaks, they cause similar respiratory tract disease in infants and calves. The disease is most severe in children and calves between 1 and 3 months old, when maternal antibodies against the virus are usually present. Reinfections, which are common, are accompanied by progressively milder illnesses in children, but are symptomless in calves. Because maternal antibodies suppress serum and mucosal antibody responses of all isotypes, the development of a vaccine that is effective in young children and calves with high levels of maternal antibodies has been severely hampered. Although virus administered intranasally to young calves with maternal antibodies does not evoke antibody responses, it can prime these calves for a protective memory response upon reinfection. Protection appears to be associated with the capacity to mount a mucosal memory IgA response. There are several indications that one or more immunopathologic mechanisms contribute to the disease. An Arthus reaction (type III) may have a role in the pathogenesis, because activated complement may cause most of the pathologic lesions, including edema and emphysema in uninfected parts of the lung. Lungs from calves with severe or fatal disease have depositions of complement component C3 and a low histamine content. The most immunogenic and protective antigen of the virus is the fusion (F) glycoprotein, which evokes a strong antibody response and is a target for cytotoxic T cells. On the F protein, epitopes that induce neutralizing and non-neutralizing antibodies, both of which may enhance complement activation, were identified. Immunity to the F protein may have beneficial and harmful effects.

Antibodies elicited by a biosynthetic peptide related to a major immunogenic area of FMDV A12

Foot-and-mouth disease virus (FMDV) capsid contains 60 copies each of four structural proteins, virus proteins 1-4. Virus protein 1 (VP1) plays an important immunogenic role, being the only VP that is immunogenic as an isolated protein. Even peptides representing a partial amino acid (AA) sequence of VP1 can induce protective immunity in experimental hosts. A 32 AA residue, in a tandem repeat configuration (32dimer), of sero/subtype A-12 Lp ab VP1 (AA 132-168) was highly immunogenic for its homologous subtype and partially protective for FMDV serotype A strain A24. This cross-reactivity was further demonstrable in the ELISA and mouse protection tests. Three different antibody populations were isolated by affinity chromatography (AFC) from the serum of a steer immunized with the 32dimer. Each population seems to recognize a different epitope on the 32dimer peptide since each fraction was defined as unique by its reactivity with different subtypes of FMDV virus in RIA, ELISA, neutralization and competition assays. Considering the neutralizing activity of each of the antibody populations the pattern of neutralization of the 32dimer elicited antiserum can be described. Two of the three epitopes were mapped by competition assays using synthetic peptides.

Priming for local and systemic antibody memory responses to bovine respiratory syncytial virus: effect of amount of virus, virus replication, route of administration and maternal antibodies

We studied the conditions under which calves can be primed for mucosal and serum antibody memory responses against bovine respiratory syncytial virus (BRSV), and the relationship between such responses and protection against the virus. Calves were primed via the respiratory tract with a low or high amount of live virus, with killed virus, or intramuscularly with live virus. Calves were challenged via the respiratory tract. Priming with live virus via the respiratory tract induced primary antibody responses in serum and on the mucosae, which were identical after the low and the high amount of virus. These responses were suppressed by maternal antibodies. Intramuscular priming of seronegative calves induced serum IgG1 and sometimes serum IgM and IgG2 responses, but no responses were detected on the mucosae. Sera of calves primed by the intramuscular or the respiratory route recognized the same viral proteins. No responses were observed after priming with killed virus, or after intramuscular priming of calves with maternal antibodies. After challenge, mucosal and serum antibody memory responses developed in calves that had been primed via the respiratory tract with live virus, whether they had maternal antibodies or not. One colostrum-fed calf showed a mucosal memory response, although serum responses were still suppressed by maternal antibodies. None of the calves thus primed shed virus after challenge. Intramuscular priming also primed for mucosal and serum memory responses after challenge, which however started perhaps slightly later and were not associated with protection against virus shedding. Priming with killed virus, or with live virus intramuscularly in the presence of maternal antibodies proved least effective in inducing memory and protection against virus shedding. Thus, protection against virus shedding was afforded by priming with live virus via the respiratory tract, both in calves with an without maternal antibodies. Protection was associated with a strong and rapid mucosal antibody memory response, but the reverse was not necessarily true. Protection against virus excretion had no relationship to titers of serum neutralizing or serum IgG1 or nasal IgA antibodies at the time of challenge.