A bovine respiratory syncytial virus strain with mutations in subgroup-specific antigenic domains of the G protein induces partial heterologous protection in cattle

Amino Acid Variations of The Immuno-Dominant Domain of Respiratory Syncytial Virus Attachment Glycoprotein (G) Affect the Antibody Responses In BALB/c Mice

Respiratory syncytial virus (RSV) is the leading cause of respiratory illness in ruminants and infants. The G glycoprotein of RSV serves as the viral attachment ligand. Despite currently available vaccines, RSV immunity is insufficient, and re-infections occur. Vaccine studies employing the G-protein's 174-187 amino acids, representing the immunodominant domain, have protected mice and calves against infections. To investigate the causes of vaccination failure, we designed four synthetic peptides for the ruminant RSV isolates (391-2, Maryland-BRSV, European-BRSV, and ORSV) using the immune-dominant sequence and vaccinated mice groups with them. The produced antibodies targeting each peptide were evaluated using ELISA and flow cytometry to determine their reactivity against the linear antigen and the native form of the G protein, respectively. Antibodies responded to homologous and heterologous peptides as determined by ELISA. Using flow cytometry-analysis targeting the natively folded protein, most generated antibodies reacted only with their homologous strain. However, antibodies raised to 391-2 peptide reacted with homologous and heterologous Maryland-BRSV viral epitopes. Accordingly, inadequate immunity and recurring RSV infections might be attributed to variations of antibodies targeting the immunodominant region of the G-protein.

Genetic analysis of bovine respiratory syncytial virus in Croatia

Bovine respiratory syncytial virus (BRSV) represents an important causative agent of respiratory tract disease in cattle. This study describes the genetic diversity of BRSV strains detected in beef cattle herds in Croatia during four consecutive years, from the end of 2011 to April 2016. Genetic diversity of circulating Croatian strains is reflected in their clustering within three different genetic subgroups. Analysis of representative BRSV G gene sequences revealed that infections in Croatia were caused by BRSV strains belonging to two new subgroups (VII and VIII identified herein for the first time). In 2014-2016, the subgroup VII strains were replaced with BRSV strains clustered in the previously unidentified subgroup VIII. Furthermore, co-circulation of subgroup II and new subgroup VIII strains in Croatia was recorded in the same time period. Sequences of Croatian BRSV strains within subgroups II and VII revealed unique mutations within an essential immunodominant region, demonstrating continuous evolution of viral mechanisms for immune escape.

Phylogenetic relationships of Brazilian bovine respiratory syncytial virus isolates and molecular homology modeling of attachment glycoprotein

Bovine respiratory syncytial virus (BRSV) causes lower respiratory tract disease in young cattle. Recently, it was possible to determine the sequence of the G protein gene, which plays a role in the attachment of BRSV particles to the cells, from three distinct Brazilian isolates. The phylogenetic analysis conducted here using those sequences compared to other worldwide distributed isolates of BRSV allow us to allocate Brazilian strains within the subgroup B, which was no longer found in the world since the 1970s. One of the Brazilian strains has a major mutation between amino acid residues 173 and 178, within the central hydrophobic conserved region, exactly on the site of two of the four cysteine-noose forming cysteine residues. Homology modeling with the previously determined NMR structure of this protein domain was made to check whether these mutations altered the three-dimensional conformation of this immunodominant region. Possible consequences on the biological effects induced by such mutation on the G protein are discussed.

Genetic and Antigenic Analyses of Bovine Respiratory Syncytial Virus Detected in Japan

Genetic and antigenic analyses of bovine respiratory syncytial virus were conducted on 12 field strains from Tohoku and Hokuriku districts in Japan during from 2002 to 2004. On the phylogenetic tree of the nucleotide sequences of the glycoprotein region, the examined strains fell in the same cluster as the strain isolated in Nebraska and were classified as the subgroup III. The examined strains were subdivided into 2 lineages (A, B). Isoleucine 200 of the epitope domain was replaced by threonine as a feature of the lineage B strains. The examined strains showed the nucleotide sequence homologies of 88.3-93.3% with the known Japanese strains classified as the subgroup II and of 86.1-96.6% with those in the subgroup III. No significant difference was found on the neutralization index between the examined strain and the 52-163-13 phylogenetically similar to the Japanese vaccine one. The results suggest that the subgroup III strains have existed in Japan and that epidemics of the strains could be protected due to the present vaccination.

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.

Evolution of bovine respiratory syncytial virus

Until now, the analysis of the genetic diversity of bovine respiratory syncytial virus (BRSV) has been based on small numbers of field isolates. In this report, we determined the nucleotide and deduced amino acid sequences of regions of the nucleoprotein (N protein), fusion protein (F protein), and glycoprotein (G protein) of 54 European and North American isolates and compared them with the sequences of 33 isolates of BRSV obtained from the databases, together with those of 2 human respiratory syncytial viruses and 1 ovine respiratory syncytial virus. A clustering of BRSV sequences according to geographical origin was observed. We also set out to show that a continuous evolution of the sequences of the N, G, and F proteins of BRSV has been occurring in isolates since 1967 in countries where vaccination was widely used. The exertion of a strong positive selective pressure on the mucin-like region of the G protein and on particular sites of the N and F proteins is also demonstrated. Furthermore, mutations which are located in the conserved central hydrophobic part of the ectodomain of the G protein and which result in the loss of four Cys residues and in the suppression of two disulfide bridges and an alpha helix critical to the three-dimensional structure of the G protein have been detected in some recent French BRSV isolates. This conserved central region, which is immunodominant in BRSV G protein, thus has been modified in recent isolates. This work demonstrates that the evolution of BRSV should be taken into account in the rational development of future vaccines.

Airborne transmission of BHV1, BRSV, and BVDV among cattle is possible under experimental conditions

To control the diseases caused by bovine herpesvirus 1 (BHV1), bovine respiratory syncytial virus (BRSV), and bovine virus diarrhoea virus (BVDV), it is crucial to know their modes of transmission. The purpose of this study was to determine whether these viruses can be transmitted by air to a substantial extent. Calves were housed in two separate isolation stables in which a unidirectional airflow was maintained through a tube in the wall. In one stable, three of the five calves were experimentally infected with BHV1 and later with BRSV. In the BVDV experiment, two calves persistently infected with BVDV (PI-calves) instead of experimentally infected calves, were used as the source of the virus. In all the calves infections were monitored using virus and antibody detection. Results showed that all the three viruses were transmitted by air. BHV1 spread to sentinel calves in the adjacent stable within three days, and BRSV within nine days, and BVDV spread to sentinel calves probably within one week. Although airborne transmission is possibly not the main route of transmission, these findings will have consequences for disease prevention and regulations in control programmes.