No abstract

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 allcis-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.

The global burden of disease caused by respiratory syncytial virus (RSV) is increasingly recognised, not only in infants, but also in older adults (aged ≥65 years). Advances in knowledge of the structural biology of the RSV surface fusion glycoprotein have revolutionised RSV vaccine development by providing a new target for preventive interventions. The RSV vaccine landscape has rapidly expanded to include 19 vaccine candidates and monoclonal antibodies (mAbs) in clinical trials, reflecting the urgency of reducing this global health problem and hence the prioritisation of RSV vaccine development. The candidates include mAbs and vaccines using four approaches: (1) particle-based, (2) live-attenuated or chimeric, (3) subunit, (4) vector-based. Late-phase RSV vaccine trial failures highlight gaps in knowledge regarding immunological protection and provide lessons for future development. In this Review, we highlight promising new approaches for RSV vaccine design and provide a comprehensive overview of RSV vaccine candidates and mAbs in clinical development to prevent one of the most common and severe infectious diseases in young children and older adults worldwide.

A vectored mucosal vaccine expressing the SARS-coronavirus S protein alone may be highly effective in a single-dose format for the prevention of SARS.

Complete consensus nucleotide sequences were determined for human metapneumovirus (HMPV) isolates CAN97-83 and CAN98-75, representing the two proposed genotypes or genetic subgroups of HMPV. The overall level of genome nucleotide sequence identity and aggregate proteome amino acid sequence identity between the two HMPV subgroups were 80 and 90%, respectively, similar to the respective values of 81 and 88% between the two antigenic subgroups of human respiratory syncytial virus (HRSV). The diversity between HMPV subgroups was greatest for the SH and G proteins (59 and 37% identity, respectively), which were even more divergent than their HRSV counterparts (72 and 55% cross-subgroup identity, respectively). It is reasonable to anticipate that the two genetic subgroups of HMPV represent antigenic subgroups approximately comparable to those of HRSV.

Human metapneumovirus (HMPV) has recently been identified as a significant cause of serious respiratory tract disease in humans. In particular, the emerging information on the contribution of HMPV to pediatric respiratory tract disease suggests that it will be important to develop a vaccine against this virus for use in conjunction with those being developed for human respiratory syncytial virus and the human parainfluenza viruses. A recently described reverse genetic system (S. Biacchesi, M. H. Skiadopoulos, K. C. Tran, B. R. Murphy, P. L. Collins, and U. J. Buchholz, Virology 321:247-259, 2004) was used to generate recombinant HMPVs (rHMPVs) that lack the G gene, the SH gene, or both. The DeltaSH, DeltaG, and DeltaSH/G deletion mutants were readily recovered and were found to replicate efficiently during multicycle growth in cell culture. Thus, the SH and G proteins are not essential for growth in cell culture. Apart from the absence of the deleted protein(s), the virions produced by the gene deletion mutants were similar by protein yield and gel electrophoresis protein profile to wild-type HMPV. When administered intranasally to hamsters, the DeltaG and DeltaSH/G mutants replicated in both the upper and lower respiratory tracts, showing that HMPV containing F as the sole viral surface protein is competent for replication in vivo. However, both viruses were at least 40-fold and 600-fold restricted in replication in the lower and upper respiratory tract, respectively, compared to wild-type rHMPV. They also induced high titers of HMPV-neutralizing serum antibodies and conferred complete protection against replication of wild-type HMPV challenge virus in the lungs. Surprisingly, G is dispensable for protection, and the DeltaG and DeltaSH/G viruses represent promising vaccine candidates. In contrast, DeltaSH replicated somewhat more efficiently in hamster lungs compared to wild-type rHMPV (20-fold increase on day 5 postinfection). This indicates that SH is completely dispensable in vivo and that its deletion does not confer an attenuating effect, at least in this rodent model.

Respiratory syncytial virus (RSV) is

Bovine respiratory syncytial virus (BRSV) is a major etiological agent of respiratory tract disease in calves and results in substantial economic loss (40,45). The immune response and pathology in calves mimic symptoms caused by human respiratory syncytial virus (HRSV), which remains the leading cause of serious bronchiolitis and pneumonia in infants and young children throughout the world (9). Molecular cloning has confirmed a very close relationship between BRSV and HRSV and has revealed substantial differences from other members of the Paramyxoviridae family, leading to the establishment of the Pneumovirus genus within the Paramyxoviridae family (36, 37).As with all members of the order Mononegavirales, the 15-kb genomic RNA of RSV is contained in a ribonucleoprotein (RNP) complex which serves as a template for sequential transcription of genes (25, 49). Eleven proteins are expressed from 10 transcription units, which are arranged in the order 3Ј-NS1-NS2-N-P-M-SH-G-F-M2-L-5Ј (5, 9, 30, 31). The proteins encoded include five RNP-associated proteins, namely, the nucleoprotein N, the phosphoprotein P, the large catalytic subunit L of the RNA polymerase, and a transcription elongation factor (M2-1) encoded by the first of two overlapping open reading frames of the M2 gene (8,17,27,38). The second open reading frame of the M2 transcription unit (M2-2) was reported to encode a nonessential protein (1) which is probably involved in the regulation of RNA synthesis (4, 28). Three viral proteins are associated with the viral envelope, namely, the fusion protein F, the putative attachment protein G, and a small hydrophobic protein SH.The presence of two nonstructural protein genes, NS1 and NS2, at the 3Ј-terminal position of the genome distinguishes pneumoviruses from all other members of the Mononegavirales. Due to the 3Ј-proximal location, the NS genes are abundantly transcribed. The encoded proteins have been demonstrated in infected cells (10,16). The BRSV NS1 and NS2 genes encode polypeptides of 136 and 124 amino acids, respectively. Comparison with NS proteins of HRSV subgroup A and B proteins revealed amino acid identities of 69 and 68% for NS1 proteins and 84 and 83%, for NS2 proteins, respectively (5, 34). The deduced sequences, however, did not provide obvious clues to the function of NS proteins in the virus life cycle. The HRSV NS1 protein was reported to be associated with the M protein, while the NS2 protein did not show any detectable association with RSV structural proteins, indicating distinct functions of NS1 and NS2 (16,47). An inhibitory function of NS1 in virus RNA transcription and RNP replication was recently suggested by experiments in which artificial HRSV minigenomes were grown in the absence or presence of NS1. In the same study, an inhibitory but far less pronounced effect was also observed for NS2 (3).Recently established protocols for recovery of infectious minus-strand RNA viruses from cDNA (11) have allowed the generation of recombinant HRSV (8, 29) and BRSV (5) and allowed researchers to...