Nucleotide sequence of the bovine parainfluenza 3 virus genome: the genes of the F and HN glycoproteins

Molecular and genetic characterization of bovine parainfluenza type 3 European field and vaccine strains

Bovine Parainfluenza Type 3 virus (BPIV-3) is an enveloped, non-segmented single-stranded, negative-sense RNA virus belonging to the Paramyxoviridae family (genus Respirovirus) with a well-known role in Bovine Respiratory Disease (BRD) onset. Being isolated for the first time in 1959, BPIV-3 currently circulates worldwide in cattle herds and is routinely tested in suspected BRD cases. Different commercial vaccines are available to prevent infection and/or to reduce the clinical signs associated with BPIV-3 infection, which are essential to prevent secondary infections. Despite years of molecular surveillance, a very limited number of complete genome sequences were made publicly available, preventing thus the understanding of the genetic diversity of the circulating strains in the field. In addition, no data about the genetic identity between field and vaccine strains is currently available. In this study, we sequenced the full-genome and genetically characterized BPIV-3 strains isolated from animals displaying respiratory illness in France and Sweden, as well as the vaccine strains contained in three different commercialized vaccines. Our results show that the sequences from France and Sweden belong to genotype C. However, a third sequence from Sweden from 2017 clustered within genotype A. The sequencing of vaccine strains revealed that two of the vaccine strains clustered within genotype C, whereas the third vaccine strain belonged to genotype A. Altogether, our findings suggest that both genotypes A and C circulate in Europe and that BPIV-3 field and vaccine strains are genetically divergent. Our sequencing results could be useful to better understand the genetic differences between the circulating field and vaccine BPIV-3 strains. This is crucial for a correct interpretation of diagnostic findings and for the assessment of BPIV-3 prevalence in cattle population.

Prevalence and Molecular Characterization of Bovine Parainfluenza Virus Type 3 in Cattle Herds in China

Bovine parainfluenza virus type 3 (BPIV3) is a common respiratory pathogen that causes respiratory illness in cattle and makes a major contribution to the bovine respiratory disease complex (BRDC); however, data on the prevalence and molecular features of BPIV3 are still scarce in China. To investigate the epidemiological characteristics of BPIV3 in China, between September 2020 and June 2022, 776 respiratory samples were received from 58 BRDC-affected farms located in 16 provinces and one municipality. Those were screened for BPIV3 using a reverse transcription insulated isothermal PCR (RT-iiPCR) assay. Meanwhile, the HN gene and complete genome sequence of strains from different provinces were amplified, sequenced, and analyzed. The tests showed that 18.17% (141/776) of samples tested were positive for BPIV3, which originated from 21 farms in 6 provinces. Moreover, 22 complete HN gene sequences and 9 nearly complete genome sequences were obtained from the positive samples. Phylogenetic analysis based on the HN gene and complete genome sequences revealed that the sequences were clustered in one large clade for all Chinese BPIV3 genotype C strains, while overseas strain sequences of BPIV3 genotype C clustered into other clades. Moving beyond the known complete genome sequences of BPIV3 in GenBank, a total of five unique amino acid mutations were found in N protein, F protein, and HN protein in Chinese BPIV3 genotype C strains. Taken together, this study reveals that BPIV3 genotype C strains, the dominant strains in China, have a broad geographical distribution and some unique genetic characteristics. These findings contribute to our understanding of the epidemiological characteristics and genetic evolution of BPIV3 in China.

First Isolation and Characteristics of Bovine Parainfluenza Virus Type 3 from Yaks

The yaks belong to the genus Bos within the family Bovidae that live in the Tibet Plateau and is an indispensable economic resource for the local herders. Respiratory tract infections are common diseases in yaks caused by various pathogens; however, there have been no reports of bovine parainfluenza virus type 3 (BPIV3) infection. This study was conducted to investigate the pathogens and analyze their characteristics from the four yak lung samples with severe respiratory tract infection symptoms in the yak farm. Results showed that out of four lung samples, three were identified as BPIV3-positive by RT-PCR. A BPIV3 strain (10^6.5 TCID₅₀/mL) was successfully isolated from the BPIV3-positive lung samples using Madin–Darby bovine kidney cells. The isolate caused systemic infection in the BALB/c mice and induced pathological changes in the lungs. Moreover, three complete BPIV3 genomes were amplified from the clinical samples. Phylogenetic trees based on the complete genomes, hemagglutinin-neuraminidase protein (HN), phosphoprotein (P), and large polymerase subunit protein (L) amino acid sequences showed that the complete BPIV3 genomes belonged to BPIV3 genotype C, and clustered into a large branch with the Chinese strains, although the three yak BPIV3 strains were clustered into a small branch. Compared to known BPIV3 genotype C strains in GenBank, the three genomes of yak BPIV3 showed four identical amino acid mutations in the HN, P and L proteins, suggesting a unique genetic evolution of BPIV3 in yaks. This study first isolated and characterized the BPIV3 from yaks, which contributed to the understanding of the infection and evolution of BPIV3 in yaks in the Tibet Plateau.

Homologous recombination as a mechanism of genetic changes in bovine parainfluenza-3 virus

Bovine parainfluenza-3 virus (BPIV-3) is one of the main viruses associated with bovine respiratory disease complex (BRDC) worldwide. BPIV-3 infect the bovine respiratory tract causing from subclinical infections to severe pneumonia with significant economic losses in the cattle industry. BPIV-3 is a RNA virus with high genetic variability, nevertheless, the contribution of recombination events to its variability has not been assessed so far. In this study the 25 complete genome sequences (CGS) reported so far and 215 partial sequences of different viral genes of BPIV-3 were analyzed to determine their genotypes and subgenotypes, distribution, and the existence of potential recombination events. Based on the analysis of the HN, M, N, and P genes one hypothetical subgenotype was found (subgenotype A4). Four recombination events between sequences of swine and cattle were detected by RDP4 analysis in conjunction with phylogenetic incongruences in the L gene. In addition, 9 sequences reported from Argentina were found to be miss-classified. These results reveal that homologous recombination events have a relevant role in the evolution of BPIV-3 and highlight the importance of implement advanced molecular characterization to better understand the variability and evolution of BPIV-3 as a component of BRDC.

Complete genome sequence of the first isolate of genotype C bovine parainfluenza virus type 3 in Japan

Bovine parainfluenza virus type 3 (BPIV3) isolates are classified into three genotypes (BPIV3a to -c). Here, we report the complete genome sequence of the BPIV3c isolate for the first time in Japan. Our results indicate that new primer sets will be required to detect all genotypes of BPIV3 strains.

Adenovirus-mediated gene therapy enhances parainfluenza virus 3 infection in neonatal lambs

Parainfluenza viruses are a common cause of seasonal respiratory disease, but in high-risk individuals (e.g., young children) these viruses can cause severe clinical manifestations that require hospitalization. Beta-defensins are a subclass of antimicrobial peptides with antiviral activity. Use of adenovirus-mediated beta-defensin gene expression has been proposed as therapy for chronic bacterial infections commonly seen in cystic fibrosis patients; however, its use during parainfluenza virus 3 (PIV3) infection has not been evaluated. The hypothesis in this experiment was that adenovirus expression of human beta-defensin 6 (HBD6) would diminish concurrent PIV3 infection in neonatal lambs. The group infected with adenovirus HBD6 and PIV3 had increased levels of pulmonary neutrophil recruitment compared to those for the group infected with PIV3 or PIV3 and adenovirus, with an increased respiration rate and body temperature late in the course of the PIV3-adenovirus HBD6 infection. Interestingly, the adenovirus-treated groups had higher levels of immunohistochemical staining for PIV3 and syncytial cell formation than the group infected with PIV3, suggesting that treatment with the adenovirus vector, regardless of whether it was carrying a target gene, exacerbated the PIV3 infection. The levels of expression of mRNA for antimicrobial surfactant proteins A and D and sheep beta-defensin 1 were increased by PIV3 and adenovirus treatment, and the increased levels of expression roughly corresponded to the degree of inflammation. While pulmonary administration of a high-dose adenovirus vector has been associated with undesirable inflammation, this is the first study to show that it can exacerbate concurrent viral infection, a concern that needs to be addressed for future studies of adenovirus in the lung. Additionally, this study showed that adenovirus-mediated HBD6 expression increases neutrophil recruitment, a recently described attribute of beta-defensins, with mild accentuation of PIV3 activity and inflammation.

Sequence determination and molecular analysis of two strains of bovine parainfluenza virus type 3 that are attenuated for primates

The Kansas/15626/84 (Ka) and Shipping Fever (SF) strains of bovine parainfluenza virus type 3 (BPIV3) replicate less efficiently than human PIV3 (HPIV3) in the upper and lower respiratory tract of rhesus monkeys, and BPIV3 Ka is also highly attenuated in humans and is in clinical trials as a candidate vaccine against HPIV3. To initiate an investigation of the genetic basis of the observed attenuation phenotype of BPIV3 in primates, the complete genomic sequences of Ka and SF genomes were determined and compared to those of BPIV3 strain 910N and two HPIV3 strains, JS and Wash/47885/57. There is a high degree of identity between the five PIV3 viruses in their 55 nucleotide (nt) leader (83.6%) and 44 nt trailer (93.2%) sequences. The five viruses display amino acid sequence identity ranging from 58.6% for the phosphoprotein to 89.7% for the matrix protein. Interestingly, the majority of amino acid residues found to be variable at a given position in a five-way protein alignment are nonetheless identical within the viruses of either host species (BPIV3 or HPIV3). These host-specific residues might be products of distinct selective pressures on BPIV3 and HPIV3 during evolution in their respective hosts. These host-specific sequences likely include ones which are responsible for the host range differences, such as the efficient growth of BPIV3 in bovines compared to its restricted growth in primates. It should now be possible using the techniques of reverse genetics to import sequences from BPIV3 into HPIV3 and identify those nt or protein sequences which attenuate HPIV3 for primates. This information should be useful in understanding virus-host interactions and in the development of vaccines to protect against HPIV3-induced disease.

Cytoplasmic domain of Sendai virus HN protein contains a specific sequence required for its incorporation into virions

In the assembly of paramyxoviruses, interactions between viral proteins are presumed to be specific. The focus of this study is to elucidate the protein-protein interactions during the final stage of viral assembly that result in the incorporation of the viral envelope proteins into virions. To this end, we examined the specificity of HN incorporation into progeny virions by transiently transfecting HN cDNA genes into Sendai virus (SV)-infected cells. SV HN expressed from cDNA was efficiently incorporated into progeny Sendai virions, whereas Newcastle disease virus (NDV) HN was not. This observation supports the theory of a selective mechanism for HN incorporation. To identify the region on HN responsible for the selective incorporation, we constructed chimeric SV and NDV HN cDNAs and evaluated the incorporation of expressed proteins into progeny virions. Chimera HN that contained the SV cytoplasmic domain fused to the transmembrane and external domains of the NDV HN was incorporated to SV particles, indicating that amino acids in the cytoplasmic domain are responsible for the observed specificity. Additional experiments using the chimeric HNs showed that 14 N-terminal amino acids are sufficient for the specificity. Further analysis identified five consecutive amino acids (residues 10 to 14) that were required for the specific incorporation of HN into SV. These residues are conserved among all strains of SV as well as those of its counterpart, human parainfluenza virus type 1. These results suggest that this region near the N terminus of HN interacts with another viral protein(s) to lead to the specific incorporation of HN into progeny virions.

Genetic characterization of parainfluenza virus 3 derived from guinea pigs

To understand the relationship between novel parainfluenza virus 3 (PIV-3), which has recently been isolated from the lungs of guinea pigs, and other PIV-3 strains, we determined the complete nucleotide sequence of the novel PIV-3 (GPv) genome. A comparison of the nucleotide sequence among PIV-3s, including bovine PIV-3, revealed that GPv is closely related to human PIV-3. The results of the phylogenetic analysis clearly showed that GPv is a lineage of human PIV-3, suggesting that GPv has probably been introduced into guinea pig colonies via infected humans.

The bovine parainfluenza virus type-3 (BPIV-3) hemagglutinin/neuraminidase glycoprotein expressed in baculovirus protects calves against experimental BPIV-3 challenge

Despite the availability of numerous vaccine schedules, "shipping fever", an acute bronchopneumonia brought on in part by a complex of bovine respiratory viruses, remains a major source of economic loss in the beef and dairy industries. We are exploring new strategies of bovine vaccine design which we hope may provide more effective and more cost-efficient control of these pathogens. In this report, we examined the possible use of subunit vaccines, using as an example the hemagglutinin/neuraminidase (HN) protein of bovine parainfluenza virus type-3 (BPIV-3) expressed in the baculovirus expression system. We showed that the protein was expressed at high levels, and was modified to a similar, but not identical size as the native HN protein expressed from BPIV-3 infected bovine cells. We further demonstrated antigenicity and biological activity of the expressed HN protein. Finally, we vaccinated colostrum deprived sera-negative calves with the baculo HN recombinant protein and challenged with BPIV-3. Vaccination induced excellent serum neutralizing antibody responses, and surprisingly, good mucosal antibody responses, even though the vaccine was administered parenterally. The vaccinated animals were well protected against challenge.

Comparisons of the F and HN gene sequences of different strains of bovine parainfluenza virus type 3: relationship to phenotype and pathogenicity

The genes for the F and HN glycoprotein of a pathogenic field isolate of bovine parainfluenza virus type 3 (BPIV3) were isolated, converted to cDNA, and sequenced using dideoxynucleotides. The resulting nucleotide sequences were converted to protein sequence and were compared to previously sequenced glycoprotein genes with amino acid differences in the glycoproteins of isolates expressing different phenotypes. The HN glycoprotein, involved in the attachment and release of the virus, and the F glycoprotein, involved in penetration and spread of the virus, have been shown to affect pathogenicity of the virus and are the immunodominant proteins of the virus. Both the F and HN proteins have been shown to be required for syncytium formation. Our results suggest that BPIV3 viruses that exhibit greater syncytium-inducing activity in vitro have greater pathogenicity in vivo. By determining which epitopes are involved in syncytium formation and comparing the sequences and enzymatic activities of different strains of virus, it may be possible to design subunit vaccines that protect against disease.

Peptide motif of a cattle MHC class I molecule

A consensus motif for a bovine major histocompatibility complex (MHC) class I molecule, A20, was derived from parainfluenza type-3 (PI-3) virus-infected muscle-derived fibroblast cells and peripheral blood leukocytes by extraction of the naturally processed peptides from MHC class I molecules by treatment with TFA and peptide sequencing of the complex mixture. The results showed that the majority of peptides were 9 amino acids long with position 2 occupied by lysine and position 9 occupied by arginine. The arginine at position 9 suggests that cattle, like humans, but unlike the mouse have permissive TAP transporter molecules accepting peptides with positively charged amino acids at their C-terminus. This is the first report of a MHC ligand motif in cattle.

Proteolytic cleavage of wild type and mutants of the F protein of human parainfluenza virus type 3 by two subtilisin-like endoproteases, furin and Kex2

The fusion (F) protein of human parainfluenza virus type 3 contains the tribasic cleavage site R-T-K-R, which was altered by site-directed mutagenesis. Wild-type F protein and various mutants were expressed by recombinant vaccinia viruses. The endogenous endoprotease present in CV-1 cells cleaves F variants containing the furin recognition motif R-X-K/R-R but not variants containing the dibasic site K-R or a single R at the cleavage site. A similar cleavage pattern was obtained when the subtilisin-like endoproteases Kex2 and furin were coexpressed with the wild type and mutants of the F protein. Peptidylchloromethylketone inhibitors mimicking basic cleavage sites prevent cleavage of the precursor Fo by the endogenous protease only when the furin-specific motif is present in the peptidyl portion. The data support the concept that furin is a cellular protease responsible for the activation of the F protein of human parainfluenza virus type 3.

An update on approaches to the development of respiratory syncytial virus (RSV) and parainfluenza virus type 3 (PIV3) vaccines

RSV and PIV3 are responsible for about 30% of severe viral respiratory tract disease leading to hospitalization of infants and children. For this reason, there is a need to develop vaccines effective against these viruses. Since these viruses cause severe disease in early infancy, vaccines must be effective in the presence of maternal antibody. Currently, several strategies for immunization against these viruses are being explored including peptide vaccines, subunit vaccines, vectored vaccines (e.g., vaccinia-RSV or adenovirus-RSV recombinants), and live attenuated virus vaccines. The current status of these approaches is reviewed. In addition, the immunologic basis for the disease potentiation seen in vaccinees immunized with formalin-inactivated RSV during subsequent RSV infection is reviewed. The efficacy of immunization in the presence of maternal antibody is discussed. Much progress for a RSV and PIV3 vaccine has been made and successful immunization against each of these pathogens should be achieved within this decade.

Gene expression of nonsegmented negative strand RNA viruses

Nonsegmented negative strand RNA viruses comprise major human and animal pathogens in nature. This class of viruses is ubiquitous and infects vertebrates, invertebrates, and plants. Our laboratory has been working on the gene expression of two prototype nonsegmented negative strand RNA viruses, vesicular stomatitis virus (a rhabdovirus) and human parainfluenza virus 3 (a paramyxovirus). An RNA-dependent RNA polymerase (L and P protein) is packaged within the virion which faithfully copies the genome RNA in vitro and in vivo; this enzyme complex, in association with the nucleocapsid protein (N), is also involved in the replication process. In this review, we have presented up-to-date information of the structure and function of the RNA polymerases of these two viruses, the mechanisms of transcription and replication, and the role of host proteins in the life-cycle of the viruses. These detailed studies have led us to a better understanding of the roles of viral and cellular proteins in the viral gene expression.

Molecular cloning and sequence analysis of human parainfluenza type 4A virus HN gene: its irregularities on structure and activities

We cloned the cDNA of human parainfluenza type 4A virus (PIV-4A) HN gene by reverse-transcription of virus-specific mRNAs and genomic RNA, and determined the complete nucleotide sequence of the HN gene. The predicted HN protein sequence of PIV-4A showed significant relatedness with those of other paramyxoviruses, SV5, NDV, MuV, PIV-3, BPIV-3, indicating a common ancestor. The homologies between the viruses suggested that PIV-4A is more closely related to NDV, SV5, and MuV than to the parainfluenza viruses, PIV-3, bovine parainfluenza type 3 virus (BPIV-3), and Sendai virus (SV). Sixty amino acids were commonly conserved among the viruses, other than PIV-4A. Two of these amino acids were substituted in PIV-4A HN and are predicted to be located near the active site of the neuraminidase. The analysis of neuraminidase of PIV-4 revealed that the activity is hardly detectable, suggesting the significant effect of the substituted amino acid sites on neuraminidase activity.

Sequence determination of the hemagglutinin-neuraminidase (HN) gene of human parainfluenza type 2 virus and the construction of a phylogenetic tree for HN proteins of all the paramyxoviruses that are infectious to humans

The nucleotide sequence of the hemagglutinin-neuraminidase (HN) gene of human parainfluenza type 2 virus (PIV-2) was determined. The PIV-2 HN gene was 2112 nucleotides excluding poly(A) tail. There was a single large open reading frame in the mRNA which encoded a protein of 571 amino acids with a calculated molecular weight of 63,262. Analysis of the deduced amino acid sequence revealed that there were fourteen potential glycosylation sites and a major hydrophobic region near the N-terminus, which would anchor the protein in the viral membrane. Comparisons of the HN protein sequences of PIV-2 with those of Simian virus 5 (SV5), Sendai virus (SV, parainfluenza virus type 1), human parainfluenza virus type 3 (PIV-3), type 4 (PIV-4), bovine parainfluenza virus type 3 (BPIV-3), mumps virus (MuV), and Newcastle disease virus (NDV) showed definite amino acid sequence relatedness, indicating a common ancestor for these viruses. Furthermore, statistical analysis of the protein sequences suggested a possible evolutionary relatedness among the paramyxoviruses. This is the first time that a phylogenetic tree has been constructed for all the parainfluenza viruses and mumps virus which are infectious to humans. In addition, amino acid sequences involved in hemagglutinating and neuraminidase activities of paramyxovirus were discussed.

Identification of amino acid residues important to the neuraminidase activity of the HN glycoprotein of Newcastle disease virus

Monoclonal antibodies (MAbs) to three overlapping antigenic sites (designated 12, 2, and 23) on the hemagglutinin-neuraminidase glycoprotein (HN) of Newcastle disease virus (NDV) were previously shown to inhibit neuraminidase activity (NA) on neuraminlactose (R. M. Iorio and M. A. Bratt, 1984a, J. Immunol. 133, 2215-2219; R. M. Iorio et al., 1989, Virus Res. 13, 245-262). However, a competitive inhibitor of NA blocks the binding of only MAbs to site 23, suggesting that the domain they recognize may be closely related to the NA site. Antigenic variants selected with site 23 MAbs have single amino acid substitutions at HN residues 192, 193, or 200. Virions of variants, which have a substitution at residue 193 or 200, have alterations in NA which are not attributable to a commensurate change in HN content. A revertant of a temperature-sensitive mutant, which has markedly diminished NA relative to the wild type, has an amino acid substitution at residue 175. A second step revertant having partially restored NA has an additional substitution at residue 192 identical to that in one of the site 23 variants, which, in turn, also makes the revertant resistant to neutralization by site 23 MAbs. Thus, an amino acid substitution at residue 175, 193, or 200 of the HN of NDV can have marked effects on the NA of the protein. The amino acids in the region around residue 175 are highly conserved between the HNs of NDV and other paramyxoviruses, suggesting that this domain is important to the integrity of the NA site in this group of viruses.

Syncytium formation by recombinant vaccinia viruses carrying bovine parainfluenza 3 virus envelope protein genes

The highly syncytium-inducing M strain and the weakly syncytium-inducing SC strain of bovine parainfluenza 3 virus differ by a single amino acid substitution in each of the hemagglutinin-neuraminidase (HN) and membrane (M) proteins, while their fusion (F) proteins are identical (T. Shioda, S. Wakao, S. Suzu, and H. Shibuta, Virology 162:388-396, 1988). We constructed recombinant vaccinia viruses which express separately the M virus HN (Vac-MHN), SC virus HN (Vac-SCHN), M virus M (Vac-MM), SC virus M (Vac-SCM), and common F (Vac-F) proteins. CV-1 cells were infected with the recombinants, singly or in combination, and implanted onto indicator MDBK cells for syncytium formation. Combinations of Vac-MHN plus Vac-F and Vac-SCHN plus Vac-F induced extensive and weak syncytium formation, respectively. Vac-F alone did not induce syncytium formation, and both Vac-MM and Vac-SCM had no effect on syncytium formation. These findings indicated that the syncytium formation by bovine parainfluenza 3 virus requires both the F and HN proteins and that the extensive syncytium formation by the M virus is due to the M virus HN protein. MSC, another weakly syncytium-inducing virus variant, newly isolated from the M virus, was identical to the M virus in the primary structure of the HN and M proteins but differed from the M virus by a single amino acid residue in the F protein. The combination of the recombinant vaccinia virus expressing the MSC virus F protein and Vac-MHN resulted in weak syncytium formation.

Newcastle disease virus evolution. II. Lack of gene recombination in generating virulent and avirulent strains

Sequence analysis and comparison of the fusion glycoprotein genes of 11 Newcastle disease virus (NDV) isolates indicated a high degree of functional and structural constraint exerted on the change of the glycoprotein. However, synonymous nucleotide substitutions occurred frequently throughout the coding region. Facilitated by an analysis of synonymous difference (Ks) in pairwise strain comparison, we defined the branching orders of the strains and identified three distinct evolutionary lineages correlating with the virulence as expressed by mean death time (MDT) for chick embryo. The typically virulent strains with MDT of about 50 hr were associated with one lineage, while the typically nonvirulent strains with MDT of infinity were of another lineage. The third lineage consisted of both virulent and avirulent strains whose MDTs lay on a continuum from 50 to 120 hr. Synonymous substitutions were found to occur with almost the same rates in the adjacent hemagglutinin-neuraminidase and membrane protein genes as in the fusion protein gene, and the branching orders based upon the Ks for these genes were essentially identical to those derived from the fusion protein gene. Therefore, no gene exchange by recombination seems to have occurred to generate the strains of distinct lineages. Rather, the different strains appear to have evolved through various degrees of accumulation of point mutations. Besides these evolutionary features, the present study strongly supports the importance of the previously identified signals for gene expression and for the proteolytic activation of the gene product.

Analysis of the relationship between cleavability of a paramyxovirus fusion protein and length of the connecting peptide

The relationship between the length of the connecting peptide in a paramyxovirus F0 protein and cleavage of F0 into the F1 and F2 subunits has been examined by constructing a series of mutant F proteins via site-directed mutagenesis of a cDNA clone encoding the simian virus 5 F protein. The mutant F proteins had one to five arginine residues deleted from the connecting peptide. The minimum number of arginine residues required for cleavage-activation of the simian virus 5 F0 protein by host cell proteases was found to be four. F proteins with two or three arginine residues in the connecting peptide were not cleaved by host cell proteases but could be cleaved by exogenously added trypsin. The mutant F protein possessing a connecting peptide consisting of one arginine residue was not cleaved by trypsin. The altered F proteins were all transported to the infected-cell plasma membrane as shown by cell surface immunofluorescence or cell surface trypsinization. However, the only mutant F protein found to be biologically active as detected by syncytium formation was the F protein which has four arginine residues at the cleavage site. The results presented here suggest that in the paramyxovirus F protein the number of basic amino acid residues in the connecting peptide is important for cleavage of the precursor protein by host cell proteases but is not the only structural feature involved. In addition, the data indicate that cleavage of F0 into F1 and F2 does not necessarily result in biological activity and that the connecting peptide may affect the local conformation of the F polypeptide.

Identification of amino acids relevant to three antigenic determinants on the fusion protein of Newcastle disease virus that are involved in fusion inhibition and neutralization

Nucleotide sequence analysis of F protein antigenic variants of Newcastle disease virus mapped three distinct antigenic determinants to positions 343, 72, and 161 on the protein. The high fusion-inhibiting and neutralizing capacities of all of the monoclonal antibodies used for selection suggested close functional and structural relationships of the three positions with the fusion-inducing N-terminal region of the F1 subunit. The former two positions were located at the cysteine cluster domain near the C terminus of the F1 subunit and at the major hydrophilic domain in the F2 subunit, respectively, and both domains appeared to represent the major antigenic determinants of paramyxovirus F protein.

Identification of amino acids involved in the sialidase activity of the mumps virus hemagglutinin-neuraminadase protein

We previously described sialidase-deficient variants of the O'Take strain of mumps virus obtained by growth under the selective pressure of the competitive sialidase inhibitor 2-deoxy-2,3-dehydro-N-acetylneuraminic acid (DANA). In this report, we describe the production of a sialidase-deficient variant of the RW strain of mumps virus using an identical selection protocol. The biologic activities of the RW variant, RW(DANA)v1, were identical to those described for O'Take-(DANA)v1 and included a lack of detectable sialidase activity, unchanged hemagglutination activity, and expression of cell-to-cell fusion in infected cell monolayers. Analysis of the structural proteins of each virus by both two-dimensional tryptic peptide mapping and monoclonal antibody binding assays suggested that limited changes occurred in the hemagglutinin-neuraminidase (HN) proteins and that only the HN proteins were altered. The complete nucleotide sequence of the RW(DANA)v1 HN was determined and compared to the HN sequence of the RW parent. Two nucleotide differences accounting for two nonconservative amino acid differences were noted; an lle to a Thr at amino acid 181 and a Gln to Lys at amino acid 261 from RW to RW(DANA)v1, respectively. By comparing the data presented here with those reported for several other paramyxoviruses, we tentatively identify amino acid 181 as a critical residue in the active site of the mumps virus sialidase enzyme.

Current approaches to the development of vaccines effective against parainfluenza and respiratory syncytial viruses

Vaccines against parainfluenza (PIV) and respiratory syncytial viruses (RSV) that are currently being developed include both live and subunit vaccines. Candidate live PIV vaccines that have been found to be attenuated and efficacious in rodents or primate models are (1) cold-adapted, temperature-sensitive mutants of PIV-type 3 that have been serially passaged at low temperature (20 degrees C) in simian kidney tissue culture; (2) protease-activation mutants (PIV-1-Sendai), which have mutations that decrease the cleavability of their F glycoprotein by host cell protease; (3) an animal virus, bovine PIV-3 virus, which is antigenically related to the human PIV-3 virus, and (4) vaccinia recombinant viruses bearing RSV or PIV-3 glycoproteins. Subunit RSV and PIV-3 viruses are being produced and evaluated as immunogens. A major concern with these vaccines is the possibility of disease potentiation following virus infection as occurred previously with formalin-inactivated measles and RSV vaccines. Studies indicate that PIV-3 and RSV glycoprotein vaccines are immunogenic and efficacious in animals but insufficient data exist to estimate their capacity to potentiate disease. However, since a cotton rat model is available to detect potentiated disease resulting from infection of cotton rats previously immunized with formalin-inactivated RSV vaccine, it is now possible to systematically evaluate new vaccines in experimental animals for disease potentiation before studies are initiated in humans. It is likely within the next several years that one or more of these PIV or RSV vaccines will be tested in humans for safety and immunogenicity.

Fusion glycoprotein (F) of rinderpest virus: entire nucleotide sequence of the F mRNA, and several features of the F protein

The full-length cDNA corresponding to the mRNA for the fusion protein of rinderpest virus (RV) was cloned and its complete nucleotide sequence was determined. The mRNA for the F protein was composed of 2359 nucleotides and contained a single large open reading frame which was capable of encoding 566 amino acids with a molecular weight (MW) of 58,929. The RV-F mRNA had a long noncoding region at the 5' end (586 bases) which was C-rich like the measles virus (MV)-F mRNA but they did not appear to be homologous with each other. Their secondary structure with long G-C stems suggested that they are easily folded. The coding region of RV-F mRNA was significantly homologous with that of MV-F; 74% of the nucleotides and 79.0% [corrected] of the amino acids were identical. The predicted RV-F protein had a basic amino acid region (104-108) which may be cleaved by protease to yield an activated form of F1,2. Three regions (1-19, 109-133, 418-513) were highly hydrophobic, and the N-terminal hydrophobic region of F1 or the positions of cysteines were significantly conserved compared with those of the other paramyxovirus F proteins. Three potential sites for glycosylation existed only in the F2 protein. Several features of the predicted RV-F protein were confirmed in polyacrylamide gel electrophoresis.

Live viral vaccines for respiratory and enteric tract diseases

In its programme for accelerated development of vaccines for viral respiratory and enteric tract diseases the WHO has assigned a very high priority to respiratory syncytial virus (RSV), parainfluenza viruses and rotaviruses. There is also some interest in alternative approaches to immunization against influenza viruses because of the failure of inactivated vaccines to provide complete and reasonably durable immunity. Current attempts to develop satisfactorily attenuated viruses for use in prevention of disease caused by the above viral pathogens are described.

Differences in bovine parainfluenza 3 virus variants studied by sequencing of the genes of viral envelope proteins

By determining gene nucleotide sequences we compared the primary structures of the membrane (M), fusion (F), and hemagglutinin-neuraminidase (HN) proteins of bovine parainfluenza 3 virus strains, M, SC, and MR which are substrains derived from a wild strain YN. The M and SC viruses are indistinguishable in having very weak hemagglutination (HA) and neuraminidase (NA) activities, but M virus' syncytium-inducing (SI) activity is considerably higher than that of the SC virus. However, the results showed that the amino acid sequence of the F protein was identical in M and SC viruses, demonstrating that M virus' high SI activity was not due to alteration of its F protein. Two differences in M and SC viruses' other proteins then seemed to be important, although their significance in the SI activity is not clear at present; the first being the 70th amino acid residue of the M protein, which was Asp in the M virus and Gly in the SC virus, and the other being the 539th residue of the HN protein, which was Tyr in the M virus and His in the SC virus. The nucleocapsid proteins of both M and SC viruses were identical. The MR virus, which is a variant derived from the M virus and has high HA and NA activities but very weak SI activity, was different from the M virus at only one site throughout the M, F, and HN proteins; the 193rd amino acid residue of the HN protein was Leu in the MR virus and Phe in the M virus. This result strongly suggested that the substitution of Leu with Phe at this particular site was closely linked to the drastic reduction in both HA and NA activities.